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Talk:Simple machine
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- 1 Untitled
- 2 hydraulics
- 3 Another Unlisted Simple Machine
- 4 Number of Simple Machines
- 5 Citations for the number of simple machines
- 6 One more machine?
- 7 Adding to the variations list
- 8 Simple Machine or simple machine
- 9 Rolamite
- 10 Definition of Simple Machine
- 11 Request for images
- 12 About the Wedge
- 13 editing talk pages
- 14 How many simple machines?
- 15 The Blade as a simple machine
- 16 Hydraulics
- 17 Machines are not studied as combinations of simple machines
- 18 800 Simple Machines
- 19 Did identification of simple machines end in the Renaissance?
- 20 No word from Chetvorno as yet.
- 21 I will try again
- 22 Compound machines
- 23 Alternate definitions
- 24 Frictionless analysis
- 25 Friction and self-locking
- 26 Egyptians and the Great Wall
- 27 Machine elements v. Simple machines
- 28 Improvements
- 29 2 Classes ????
- 30 There really should only be Two Simple Machines
- 31 Protection
- 32 Semi-protected edit request on 7 February 2017
Does anyone know exactly what a simple machine is?
Should it say "In mechanical engineering" instead of "In physics"? Also, can anyone explain how it is known that there are just these six and no others? Is it just engineering experience, or is a something like a mathematical theorem? Michael Hardy 18:45, 24 Mar 2005 (UTC)
A simple machine is the most basic possible machine that operates on a specific mechanical principle. The pulley, for example, is the simplest way to change the direction of a pulling force without wasting it all (as occurs when you simply pull a rope around a corner). Adaptations of a simple machine are not different machines in themselves, even if they can do things that the basic mechanism does not inherehtly do. A block and tacke, for instance, is an application of the pulley that produces a mechanical advantage although the basic pulley does not. The number of simple machines is defined by the number of known unique mechanical principles.
Despite what so many "experts" say, there are not six principles, which would allow six simple machines. There are four or, if you count Rolamite, five. The four are the inclined plane, lever, pulley, and wheel and axle. Both the screw and the wedge are applications of the inclined plane; and, in fact, the Wikipedia articles on them both so state. Because an application of a simple machine is not a different simple machine, the number is really four. Rolamite, which I include as a fifth simple machine, operates on a principle unlike those of the other four simple machines, and some experts consider it to be a fifth simple machine.
Richard Binder • Pens That Write Right! 23:54, 7 January 2007 (UTC)
- Well, you're partly right. The concept of simple machines is intended to identify the lowest common denominators for the transformation of forces. ("Wasting" has nothing to do with it - pulling the rope around a corner is actually an example of an inefficient class 1 pulley.) Inclined planes, levers and pulleys tranform the direction and magnitude of a force. The wheel-and-axle transforms a rotational force into a lateral force and vice versa. The screw also transforms a rotational force but this time into a longitudinal force. Is that sufficient to earn its own "class" as a simple machine? That's an interesting question but neither of our opinions are relevant to the article. Historically, there have been 6 classes of simple machines. The article already notes that some scholars have tried to revise the count but six is still the most commonly accepted list.
- Your example of the rolamite is new to me, but on first glance it appears to be in implementation of the wheel-and-axle. The potential applications look fascinating but, Popular Science notwithstanding, I think the jury's still out on whether this will be seen as another simple machine. Rossami (talk) 03:47, 8 January 2007 (UTC)
- I think arguing about the number of simple machines is somewhat of a moot point. As was stated above, the designation simple machines arises from engineering, not physics. There is not any "law" in physics that defines a simple machine, but through experience we have developed tools that can easily be utilized to change forces, direction of motion, etc. From reading several articles on wikipedia I've begin to notice how the line between what is science and what is engineering is often blurred, I assume because it in general it encourages education in both areas. Still, I think it is very important to distinguish whether something is a scientific concept or an application of science. I don't know if we need to change physics to mechanical engineering in the article, but I hope people can see the difference. Arsawyer84 16:33, 21 July 2007 (UTC)
- Can I suggest that if the 6 examples are indeed a 'classic' list, then we find some references for this, eg physics text books etc. And then the second part of the article can elaborate on how some of them use the same principles. I can't help thinking that the list of the simple machines must rooted quite deep in history, as this would explain why '2pistons+hydraulic coupling' is not included in the list. Jimbowley 13:14, 22 August 2007 (UTC)
Is a hydraulic system a simple machine, independent of the others?
- reversed statement on hydraulics because link supplied [1] did not support the statement. My statement may be a bit strong, but I suspect it is a better representation than the previous statement. Hmmmmm. Even if they were included in a few lists somewhere, the inclusion would be 'wrong' so I'm not even sure whether the hydraulics thing should be mentioned at all? Jimbowley (talk) 13:56, 12 December 2007 (UTC)
Hydraulics is the science and the hydraulic press is the simplest possible application of the science in a machine.
- The hydraulic press was invented by Blaise Pascal around 1645, and is the latest invention to be potentially included in the list of simple machines. All the other members on the list are thousands of years old.
For a hydraulic press to be a Simple Machine the following must be proved to be true :
- a) requires a single force to work
- b) performs force transformation (change direction, multiply/reduce force/speed)
- c) is not a compound machine (cannot be broken down into simpler Simple Machines)
- d) is not a variation on an existing Simple Machine
- e) no overzealous application of d) is used (similar to making the Six Simple Machines into only 2 - see main article).
a) and b) are easily true according to most articles on the subject.
c) while a hydraulic Jack is broken into a lever for the handle and a hydraulic press, the hydraulic press itself is typically not broken further down into simple machines.
d) and e) are the tricky requirements.
References for hydraulic press being a kind of Pulley [2]
References for hydraulic press being a kind of lever [3], [4]
References for hydraulic press being a unique Simple Machine [5], [6], [7], [8], [9], [10], [11]
Ambivalent references that mention hydraulic press along with simple machines, but at the same time claim it is not one of the six classical machines. [12], [13], [14]
If the list of 6 classical machines is collapsed into only 2 simple machines [15] then the hydraulic press would belong in the group: lever together with pulley and wheel.
But if we consider the mental leap necessary for jumping from pulley or wheel to lever, then the jump from hydraulic press is of of equal proportion. This would make the hydraulic press a Simple Machine, on the same level as Wheel and Pulley.
Conclusion : The current six Simple Machines are the classical list of Simple Machines, with the hydraulic press being a Simple Machine but not a classical Simple Machine, it being a added in modern time.
Please point out flaws in my (non-original) research, assumptions and conclusions. Jesper Jurcenoks (talk) 04:05, 2 April 2008 (UTC)
Another Unlisted Simple Machine[edit]
I suppose that a spring could be regarded as another simple machine, if attachments were made at different points along the spring. Such a spring would convert a small force applied at the end through a large distance, to a larger force applied through a smaller distance at one of the attachments. Some conveyor belts use such a transformation of force of a spring, to avoid shocks in loading.
--Joseph D. Rudmin 18:27, 11 January 2007
- What you have described does not actually transform the forces. Springs store and release energy. During release, they apply force identically-opposite to the force applied during storage. The distance over which the force is applied is unchanged. Rossami (talk)
A machine ought to be able to multiply force - "mechanical advantage". A spring is able to multiple Power, that is the energy is released much faster than it is accumulated. A little out of the scope of Basic mechanics, though. Good observation.Pete318 (talk) 23:08, 9 April 2008 (UTC)
Number of Simple Machines[edit]
There really are only four simple machines. Look at the articles for the wedge, screw, and the incline plane. Essentially, the goals of these three machines are the same and thus they are the same machine. Please note that the screw in itself to be an incline plane but rather the threading around the screw that lets it enter an object. Read the articles on each of these three machines. —Preceding unsigned comment added by 22.214.171.124 (talk) 03:08, 9 September 2007 (UTC)
- Many have argued that (and the article already says so). The classic list, however, is of six based on differences in the interpretation of how forces are transformed. For example, you could interpret a screw as a helical inclined plane or you could say that the inclined plane transforms a horizontal force into a vertical force while the screw transforms a rotational force into a longitudinal force. Rossami (talk) 04:44, 9 September 2007 (UTC)
- I suppose that this is true. I guess my main quarrel with this article was how it seemed to state that very few people believed there to be only four simple machines. I had believed that the idea should be given a bit more thought. Yet I admit that this annoyance I have is not really all that big. —Preceding unsigned comment added by 22.214.171.124 (talk) 9 September 2007
Citations for the number of simple machines[edit]
As has already been discussed extensively above, there is no magic answer for the definitive number of simple machines. However, the classic texts generally list the six shown in the current version of the article. Here are a few quick citations of publications with notes on their counts. Most of these are teacher-support sites aimed at elementary or middle school students and their teachers. I don't consider any of the ones I found to be ideal cites. Better references are requested from anyone who can find them. Rossami (talk) 05:14, 24 October 2007 (UTC)
- The Franklin Institute - 6
- The Science Learning Network - 6
- Scholastic books - 6
- Utah State Office of Education - 6
- Henry County Public Schools, GA - 6
- NASA Glenn Research Center -6
- GSU Physics/Astronomy Dept - 6
- MiKids.com - 6
- Teacher resource cite hosted from Univ of Houston - 6
- EdHeads.org - 7 (includes the gear)
- Boston Museum of Science - 5 (omits the inclined plane)
Note: None of these cites verify the mnemonics that were added to the article back in July 2005. If the mnemonics can't be independently sourced, we should probably pull them out. Rossami (talk)
Thanks for your efforts Rossami, I think we have the same view. We still need a good citation for the 'classic list of six' to prove that there is such a thing. Within the above citations there is plenty of misunderstanding especially on wheel and axle (a wheel on a wagon is not a 'wheel and axle' in the simple machine sense) this is someting I am making my mission to bring clarity to. And the use of a woodscrew as an example of the screw is pretty much 99% missing the point, a car jack (of the vertical screw type)would be a perfect example. Jimbowley 12:43, 24 October 2007 (UTC)
- While there is certainly plenty of misunderstanding on this topic, I don't think your two examples are quite it. A wheel on a wagon is still an example of a wheel-and-axle because it is converting the magnitude of force needed to overcome friction at the point of attachment. Consider that without the wheel, the bed of the wagon must be pushed along the floor and will require a certain force (exerted over a given distance) to overcome the friction. With the wheel, the point of friction is moved to the connection between the axle and the wagon (or the axle and wheel hub in the more conventional design). The force you use to push the wagon is increased by the ratio of the radii of the wheel and axle (and the distance moved at the point of connection correspondingly reduced).
On your second point, a bolt would be a better example than a woodscrew because a "normal" woodscrew is simultaneously a simple screw and a wedge. The woodscrew (like the car jack screw) converts a rotational force into a longitudinal force while it is being inserted. That longitudinal force powers the wedge which causes the wood fibers to separate and then to provide friction against the screw. But the difference between a woodscrew and a bolt is not that great to a third grader - and that was the apparent target audience of most of these sites. Rossami (talk) 23:15, 24 October 2007 (UTC)
- In reverse order. My example 2, Yes a bolt is better than a screw as an example, but the car jack is much better because lifting a car is understandable to a layman as 'work' where as after doing up a bolt the 'work achieved' is harder to understand (mainly because you can't normally see it).
On whether a wheel on wagon is an example of a simple machine, I can see that I should first persuade you before I tackle the world. This is a little difficult because the wiki pages for simple machine and wheel-and-axle share some of the wrong ideas. anyway, here goes:
- In reverse order. My example 2, Yes a bolt is better than a screw as an example, but the car jack is much better because lifting a car is understandable to a layman as 'work' where as after doing up a bolt the 'work achieved' is harder to understand (mainly because you can't normally see it).
Why a wheel is not a machine.[edit]
I like to consider lifting objects when thinking about simple machines, in fact I think a useful definition of a simple machine would be that it can help you lift something heavy. However for the purpose of this argument I will use the task of getting a heavy rock from A to B (separated horizontally).
A) We could drag the rock from A to B. This would require considrable effort to be expended.
B) We could attach pulleys to the rock and to a handy tree. The mechanical advantage of this machine means you need to pull the rope less hard (but further) to drag the rock. The same effort is expended.
C) We could spread super slick grease (mu=0.0) along the floor. This would reduce the effort required to a negligible amount.
D) We could attach wheels to rock. This would reduce the effort required to a negligible amount.
The point of these illustrations is that the wheel is like the grease, not like the pulley. The wheel removes the friction that is causing the effort to be expended, it does not give you a mechanical advantage over it.
An important concept is that no 'useful work' has been done in the example above. If we return to the subject of lifting things, we can see that the pulley can help us, but the grease and the wheel are not helpful.
I await comments. I'm sure I can improve my argument if this does not convince. regards. Jimbowley 15:42, 31 October 2007 (UTC)
- Your A-D are a great way to explain this. But the wheel is more like a pulley than like grease because, contrary to intuition, the wheel does not remove any friction - it just moves it to a different point and trades distance for force. Friction is a function only of μ, the coefficient of friction (which is an empirical property of the contacting materials) and Fn, the normal force exerted between the surfaces. If you put the rock in a wooden wagon bed, make your wheel, axle and floor all from the same wood with exactly equal smoothness, etc, the coefficient of friction is the same whether between the wagon bed and the floor or between the wagon bed and the axle. And the mass of the rock is unchanged, so the normal force between the wagon and the floor is the same as the normal force between the wagon and the axle. Thus, the force of friction is equal in either scenario. (Now, you can grease the axle and thereby affect μ but for the purposes of this discussion, that would be cheating. Let's continue to assume identical materials. Let's also assume for simplicity that this is a very rudimentary wagon with the wheels fixed to the axle and the axle free to spin within some sort of bracket attached to the underside of the wagon bed.)
- To drag the rock from A to B, you must do work equal the force necessary to overcome the friction times the distance travelled - μ Fn (B-A) - because the entire wagonbed travels from A to B, scaping along the floor the whole way.
- When you add wheels, the force you apply on the wagon is balanced by the force of the floor on the bottom of the wheel. The force at the bottom of the wheel is transferred into a force applied between the bed of the wagon and the exterior surface of the axle. In doing so, the force is increased in magnitude by the ratio of the radii of the wheel and the axle but is applied over a shorter distance in the same ratio. Since we only have to overcome μ Fn of frictional force at the point of connection, we can use much less input force on the back of the wagon to do so.
- Another way to think about it is to consider what would change if you attached a log to the bottom of the wagon instead of a wheel and axle - that is, what if the radii of the wheel and axle were the same? If you nail the log to the bed, you've got wood-to-wood friction (because you're still on the wood floor). If you allow the log to spin within the bracket, you've got wood-to-wood friction of exactly the same magnitude.
- Having said all that to defend the "wagon wheel" example, I think that winching the bucket up from the waterwell is a more intuitive example and is much better suited for most classes. Rossami (talk) 20:38, 31 October 2007 (UTC)
- On Wheel-and-axle, I added a picture of a waterwell some weeks ago, but used the wrong licence declaration so it got pulled. It may not be the best example anyway because on a waterwell the 'wheel' is usually just a handle and hence does not look like a wheel. I've tried to find an illustration of the wheel and axle that I suspect were used to raise the drawbridge, or raise the portcullis, in a castle. Or maybe I can find an example on a trebuchet.
- I see that I need to apply some further argument to persuade you that a wheel is not a machine. I do this not for the sake of winning the argument or to save you from your misconception but to clear the way for me to correct the articles.
- Your argument above is based on saying that the wheel does not remove friction but just moves it to a different place. But that is wrong for any example other than your specific wheel/axle/road made of the same material. How does your argument stand up if the wheel has frictionless bearings? Is that a machine still? You said yourself right at the top of this page that 'wasting effort' has nothing to do with it, yet your argument now relies on frictional waste to argue that the wheel is a machine.
- Perhaps this confusion is all arising becasue we don't have an agreed definition of 'simple machine' rather we have a historical list but don't know the concept behind the list. For me, a simple machine gives you a mechanical advantage so you can lift stuff, but I'm not sure what makes it 'simple'. Jimbowley 13:46, 1 November 2007 (UTC)
- If the wheel, axle or road are made of different materials or if you add bearings, then you are correct that the wheel has the additional effect of changing μ. That does not invalidate the observation that the wheel and axle also transforms forces as a simple machine (though you could argue that if you are simultaneously changing μ that it is now a slightly complex machine).
- I think you're right that we disagree over the definition of a simple machine. You are framing it solely in terms of lift. Enabling lifting is a pretty good example but not complete. In classical mechanics, a "machine" is anything which can transform a force in either magnitude or direction. A lever can change the magnitude and/or the direction of a force, whether that force is used to lift a rock up or press a bullet down into a casing or simply to crack a walnut shell (neither up nor down). Likewise, the pulley changes magnitude and direction of a force whether it is vertical (lifting a rock) or horizontal (pulling a ship out to sea). The inclined plane and wedge transform horizontal forces into a vertical forces and vice versa. A screw transforms rotational force into a longitudinal force and vice versa. A wheel and axle transforms a rotational force into a lateral force and back.
- The "simple" part is what has always been problematic. In theory, these are the six "simple" machines because they were thought to represent the lowest common denominators - that all other machines could be composed of combinations and variations on these. As the article already says, many people believe that some of the six are not in fact the lowest common denominator - that, for example, the wedge is a variation on the inclined plane. Nevertheless, these are the classic six. Rossami (talk) 05:45, 2 November 2007 (UTC)
- I am not saying all machines are lifting devices, just that thinking about lifting is useful when determining whether something is a machine. All the 'simple machines' can be used to help you lift something. Similarly, all the simple machines could be used to help get your bullet into its casing. But a wheel will not help you get a bullet into its casing.
- You did not answer my challenge to your argument. What if the wheel has a frictionless bearing? Where is the transformation of forces, that your defintion of machine relies on? (note that this does not imply that I accept your definition of machine, I am simply taking your argumant apart).Jimbowley 14:05, 2 November 2007 (UTC)
- As I said above, a wheel with any kind of bearing (frictionless or not) is more than a simple machine. Changing μ is outside the scope of a classic simple machine. It reduces the need for a force, it does not change any force.
- A wheel and axle can be used to lift something (or press the bullet into the casing). If you attach a cam to the axle, you can convert a small (rotational) force applied over a longish distance to a much larger force applied over a shorter distance to press the bullet into the casing. And if you attach a rope to the axle, you can winch up the water bucket.
- I think that the way you are defining the problem, you are prelimiting yourself to scenarios which require a longitudinal force. That's not how the wheel and axle works. It transforms rotational forces. By the way, this is not "my" definition of a simple machine. That's the standard definition used in classical mechanics texts. Rossami (talk) 15:02, 2 November 2007 (UTC)
- All the above info about 'wheel and axle' is irrelevant. We are discussing a wheel, and the example we are using is a wheel on a wagon which. You stated it was a machine because it transforms forces.
- When I say 'your definition' that means the definition that you are using in your argument, it does not mean you invented it, and it does not imply that I either agree or disagreee with it.
- So please, give me a definition of a simple machine and show how a wheel with a frictionless bearing meets that definition. Or better still, having had plenty of time now to think it through, agree that a wheel is not a machine.Jimbowley 17:25, 3 November 2007 (UTC)
One more machine?[edit]
I am curious about why the vector mechanics devices are often ignored. True, the topic of simple machines is usually restricted to undergraduate and even elementary science courses, however the bowstring (in an archer's bow) is both ancient and basic.
Further, an number of (web)sites and articles confuse mechanical efficiency (work out/work in [which should be 1.00 for an ideal machine]) with mechanical advantage, i.e. force out/force in.
184.108.40.206 (talk) 18:25, 11 December 2007 (UTC)(peter)
- See the discussion on springs above. A bowstring stores and then releases energy but does not convert the force applied. Rossami (talk) 21:37, 11 December 2007 (UTC)
I should be more specific. The BOW itself (a cantilever spring)stores the energy, the bowstring [a taut cord] bends the bow and stores very little energy itself. When the deflection is minimal a small horzontal force requires large vertical forces in the string to maintain equilibrium.
The crankshaft mechanism at TDC (and BDC) of a crank and slider(piston) assembly exhibits a similar nonlinear mechanical advantage.
With respect to the section on springs:
The helical spring is primarily an energy storage device..... however each coil displays a lever mechanism. A spring with a few coils with a large spring constant is difficult to deflect, however increasing the number of identical coils lowers the spring constant allowing a a greater deflection for the same force. True, it maybe a "stretch"(sorry!) but in that sense it displays the attributes of multple simple machines.
One additional note on simple machines that is also often overlooked is that of the block and tackle. Pulleys are not necessary for mechanical advantage to be achieved - only rings or bars with a low coefficient of friction between the rings and rope. The mechanical advantage is achieved by the number of passes of a constant tension cable.
184.108.40.206 (talk) 22:48, 11 December 2007 (UTC)Peter
- You are right. But in the bow application it is just part of a process which may explain why it was not considered worthy. I am currently trying to think of an example where the principle is used to lift something or do some other work as an end result! Jimbowley (talk) 14:05, 12 December 2007 (UTC)
You make a good point - the bowstring mechanical advantage is only part of the mechanism.
If still curious, though, there is a technique used to tighten rigging on ships - mostly tall ships now. The rope in a block and tackle assembly is wrapped around a pin or rail to maintain tension. Then one crew member pulls on one of the pulley ropes as one would with an archer's bow. The blocks are pulled together easier than pulling directly (axially) on the rope. As the rigger releases the bowed cable the other riggers pull in the slack.
Modern riggers now use a gear winch with a rachet mechanism to trim large sails.
A rare application now, but if one scans tall ship videos one is bound to see the technique.
Still, the bow string better displays ( I think) the vector technique than does the variations of the inclined plane.
The application of this technique in compression(as opposed to tension in the bow string) is common in crank and slider designs in manufacting processes such as stamping and pressing.220.127.116.11 (talk) 20:04, 12 December 2007 (UTC)Peter
- What you describe I would call a general rigging technique, but there isn't a machine there. For some reason this got me wondering how many people go through life without ever using ropes and knots. Jimbowley (talk) 11:03, 13 December 2007 (UTC)
This tall ship video almost shows this technique: Youtube Video on Barque James Craig added Feb3/07 by "betobatres" 6:56min see frames between 1:40 and 2:00 minutes. [16]Pete318 (talk) 18:30, 10 April 2008 (UTC)
- There current discussions about salvaging of the Costa Cocordia often mentions the concept of "parbuckling". The mechanical advantage of traditional parbuckling is discussed in the Wiki article "Parbuckle Salvage" [17].
- However in the more generic sense of the term there is a technique used by sailors to pull a vessel into dock against a strong wind. From this source[18] it appears that the mechanical advantage of the Bow String (vector mechanics) that I have noted - is used. ("Bow" as in "bow and arrow" not to be confused with "bow" as the front of a boat.)
- "…..If ever you find yourself with a heavy boat tied to a dock or wall, blowing off so that no amount of heaving will bring her in, you can always use the simple principle of parbuckling on your docklines. Dig out a stout rope of reasonable length. Make one end fast to the dock, somewhere between your two docklines. Now pass it around a bight in your bow line, bringing the working part back to where the bitter end is secured, and haul away. The bow line will take on a V-shape, and your boat will march in toward the dock in defiance of all the natural forces acting upon her. Once she's alongside, you can either rig another bow line to replace the one you've parbuckled, or you can smartly release your parbuckling line and have the crew snatch in the slack on the existing bow line. …"
Adding to the variations list[edit]
Could we consider adding the Gear as an item under the variations list? I have found several sources (including wikipeida's own article on gear) that define it aas a simple machine.--Cpkondas (talk) 19:44, 29 January 2008 (UTC)
- Wikipedia's article is, ironically, not a reliable source for the verification of other Wikipedia content. You could add it to the variations list if you have other reliable sources. I only found a single reference (in the list above that mentioned the gear as a simple machine. That one reference didn't seem strong enough to me. Rossami (talk) 23:59, 30 January 2008 (UTC)
- Here is one external source: http://www.mos.org/sln/Leonardo/InventorsToolbox.html Do you need a definite number to add to the variations list? --Cpkondas (talk) 18:07, 31 January 2008 (UTC)
- There's no magic number. It's a qualitative assessment made by the consensus of editors who choose to discuss it here.
Your source is the same Boston Museum of Science reference we found above. It doesn't really call a gear a simple machine. It lists gears in the section titled "Other Elements of Machines", a heading at the same level as the section titled "Simple Machines". (I must also admit that my confidence in that reference is reduced by their unexplained omission of the inclined plane from the list of simple machines.) Rossami (talk) 23:20, 31 January 2008 (UTC)
- I agree. A gear is a special application of a simple machine such as a wheel. In fact, it's simply a wheel that needs a lot of "friction", the way a tire on your car needs some friction against the road. Look at a Gear#Rack_and_pinion, which is clearly a gear. Now squint and pretend the pinion is smooth instead of toothed, like the rubber roller that feeds paper through a printer. Pretend the rack is also smooth (like the paper). Is there any difference in the mechanical action of a rack-and-pinion vs a rubber roller and paper? Each is converting rotational force into lateral force. Depending on the magnitude of the torque and the material you need to move, you simply vary the surface of the pinion, perhaps smooth like rubber, or as rough as sandpaper, or even so rough that it's toothed to match a toothed rack. A worm gear is a special application of the inclined plane. Seems like it's a helically shaped inclined plane that transfers rotational movement to longitudinal (not lateral) movement. Petershank (talk) 23:45, 4 January 2011 (UTC)
- There's no magic number. It's a qualitative assessment made by the consensus of editors who choose to discuss it here.
- Here is one external source: http://www.mos.org/sln/Leonardo/InventorsToolbox.html Do you need a definite number to add to the variations list? --Cpkondas (talk) 18:07, 31 January 2008 (UTC)
Simple Machine or simple machine[edit]
I think that any machine that is simple could be called a "simple machine" but that only the 6 (or 4,5,7 ect) "simple machines" discussed on this page falls under the category of "Simple Machine" (notice caps). This way we indicate that we a talking about the result of classical mechanical reductionism and not just of any machine that is simple. Jesper Jurcenoks (talk) 23:42, 1 April 2008 (UTC)
summary of previous discussion: Rolamite is a bearing, not a machine.
Definition of Simple Machine[edit]
Does anyone know exactly what a simple machine is [?] Richard Binder • Pens That Write Right! 23:54, 7 January 2007 (UTC)
This article needs a good simple non-ambiguous definition of a Simple Machine. So that anybody can take a given machine and see if it falls under the definition of a Simple Machine. Definitions like : a Simple Machine is one of the following X machines - Lever, Pulley, ...." will not do, as the definition needs to shows why these X machines are Simple Machines, not just be an arbitrary selection.
I propose the following definition of a Simple Machine :
For a given machine to be a Simple Machine the following must be proved to be true :
- a) requires a single force to work (no stored energy see discussion on springs)
- b) performs force transformation (change direction, multiply/reduce force/speed)
- c) is not a compound machine (cannot be broken down into simpler Simple Machines)
- d) is not a variation on an existing Simple Machine
- e) no overzealous application of d) is used (similar to making the 6 Simple Machines into only 2 - see main article).
Jesper Jurcenoks (talk) 04:06, 2 April 2008 (UTC)
- While certainly a reasonable definition, it is not one that I have ever seen written down anywhere else. It would therefore seem to fall afoul of WP:NOR. Can you cite that definition in some other reliable source? Rossami (talk) 04:24, 2 April 2008 (UTC)
The Proposed definition is a sumary of the most common definitions of Simple Machines found on the web. Definitions of the type : "a Simple Machine is one of the following X machines - Lever, Wedge ..." are excluded from participating in this definition discussion as they only lists Classical Simple Machines from a certain standpoint but does not define why they are on the list.
A proposed definition of a Simple Machine must be able to pass the following test :
Can it be applied to the current list of Simple Machines and correctly identify them according to the new definition.
Requires a single force to work
Some definitions include the "Require a single force to work" in one form or another including this article and the following links : [19], [20] [21] [22] [23] [24]
Performs force transformation
You will see the force transformation in one of many variations in most definitions of a Simple Machine :
Including : It is to move an object from one position to another position. [25]
Makes work Easier [26] [27],[28], [29],
A Simple Machine is a device for increasing forces or changing the direction of a force [30] [31] [32] [33]
Is not a Compound Machine
Since the definition of a Compound Machine is that it is made from 2 or more Simple Machines [34], [35], [36], [37] It goes that any Machine that can be broken down into simpler machines is therefore not a Simple Machine but a Compound Machine. Typical wordings for this require includes : "any of various elementary devices considered as the elements of which all machines are composed" [38] "All Machines are build from one or more simple machines" [39]
It is not a variation of an existing simple machine
The list of Simple Machines are not all the simple machines in the world, but the base form of the simple machines that surround us. Example the "baseball bat" is a 3rd class lever, it is therefore a simple machine in itself, but it is not listed among the classical list of Simple Machines as it is listed under its base form: the lever. The knife is a wedge and the bolt is a screw, a Crowbar is a lever etc.
no overzealous application of d) is used
Simple machines fall into families : currently there are two known families : the Inclined plane family (inclined plane, screw and wedge) and the lever family (lever, pulley, wheel & axle). Most Scholars refers to the families but keep the six machines distinct. Some people place gears as a separate simple machine [40], [41] while other claim that gears are just wheels with teeth.[42]
The last requirement is the hardest to quantify, until somebody can describe a method to measure the distance from knife to wedge, from gear to wheel from wedge to inclined plane and from wheel to lever, we will have to make it a judgment call. Current consensus seems to favor :
That the distance from knife to wedge, from seasaw to lever from bolt to screw is "small" and that they therefore are variations of a base Simple Machine.
That the distance from from wedge to inclined plane, and from gear to wheel is "medium" and therefore could fall into either "Variance of base simple machine" or "distinct simple machine"
That the distance from pulley to lever, from wheel to lever, and from screw to the inclined plane is "large" and therefore these are distinct Simple Machines.
That the distance from pulley to lever is shorter than the distance from pulley to inclined plane, and therefore the pulley belongs to the lever family.
That the distance from inclined plane to lever is "Great" and therefore these are separate families.
Other definitions
It is made of 1 or 2 pieces [[43]] [44]
Request for images[edit]
On 25 April 2008, Beland added the {{reqdiagram}} tag at the top of this Talk page. First, I despise those templates. They permanently "tag" a talk page and confuse future editors long after the problem has been addressed. Second, I'm not sure that diagrams are appropriate on this page. This article discusses the aggregate concept of a "simple machine" and prominently links each of the simple machines. Those drill-down pages are very well diagramed. I don't know what picture you could put here that would benefit readers without merely cloning in content that's already better discussed elsewhere. Rossami (talk) 16:15, 27 April 2008 (UTC)
- I agree with Rossami, no need for pictures here Jesper Jurcenoks (talk) 13:11, 11 May 2008 (UTC)
About the Wedge[edit]
In my opinion, the wedge has two distinct purposes, one as an inclined plane and one as a hydraulic. A wedge stuck into a door acts as an inclined plane, turning a horizontal force into a vertical force. An ax, however, is also considered a wedge. When it first strikes a perpendicular surface, it does not rotate any force to other directions. What it does is, like a hydraulic, trade distance for pressure. Consider a piece of wood with a wedge on top of it pointed down, and a cubic weight on top of the wedge. Without the wedge, the weight resting on the wood would apply a pressure equal to its weight divided by the area of one side. With the wedge in place, the weight provides a pressure equal to its weight divided by the very small area of the pointed edge of the wedge. This "concentration of force," if you will, is the entire principle behind blades, which one could consider a form of wedge. But the simple machine most associated with such a concentration is the hydraulic, not the wedge.220.127.116.11 (talk) 14:23, 9 July 2008 (UTC)
- Not to be impolite, but your opinion is wanting of erudition. Although an ax may be shaped like a wedge, in proper use it does not behave like a wedge, which "operates by converting a force applied to the wide end into forces perpendicular to the inclined surfaces". (Wikipedia, Wedge.)
- Furthermore, "concentration of force" is not the "entire principle behind blades". The ability of axes, knives and other blades to "cut" lies in the heat generated by friction at the interface of the blade's edge and the surface being cut. The narrower (sharper) the blade's edge the more that heat is concentrated, resulting in a higher local temperature at the interface. Sufficient heat can be generated by applying a relatively large force to the blade, or by applying a relatively small force while moving the blade longitudinally. An ax blade is used in former manner.
editing talk pages[edit]
what's the etiquette? certain things on here are unlikely to rear their ugly heads again eg the mnemonic. Human fulcrum needs to go. Rolamite disussions should all go. I will start to delete, you can always put it back if you feel it adds anything. I'd also like to edit my 'wheel is not a machine' section back to the basic argument and remove most of the debate with Rossami. PS. Glad to see the article in much better shape than last time I visited. —Preceding unsigned comment added by Jimbowley (talk • contribs) 22:07, 2 January 2009 (UTC)
How many simple machines?[edit]
This article says that there are six simple machines, but there really are only three. A pulley is just a wheel with a rope through it, a wedge is just two inclined planes placed back-to-back, and a screw is just an inclined plane wrapped around a nail. —Preceding unsigned comment added by 18.104.22.168 (talk) 02:30, 4 March 2009 (UTC)
The Blade as a simple machine[edit]
The blade focuses energy on a smaller point, thus manipulating and allowing it to conform to the definition of simple machine. Some would argue that the blade is a variant on the wedge. This is not true as one could remove the point of the wedge and have it remain just as potent as before while removing the edge of a blade would dramatically reduce it's ability to convert energy. The edge is inherent to the blade, not to the wedge. Demagoguery (talk) 23:02, 25 March 2009 (UTC)
- Some would argue... - who? WP:RS please. Vsmith (talk) 02:39, 26 March 2009 (UTC)
- This debate is interesting, but the topic is already being discussed under the heading 'About the Wedge' above. Maybe we should move these entries up to that heading. --ChetvornoTALK 05:09, 26 March 2009 (UTC)
- 22.214.171.124 "argues" it above under "About the Wedge". Rico402 (talk) 09:43, 27 March 2009 (UTC)
- This debate is interesting, but the topic is already being discussed under the heading 'About the Wedge' above. Maybe we should move these entries up to that heading. --ChetvornoTALK 05:09, 26 March 2009 (UTC)
There are some good observations made in this section as well as the referred item "About The Wedge". If the concentration of stress by a sharpened wedge point plays a role in the failure of the "cut" materials one would have to include the Awl (tapered point as opposed to tapered edge) as a similar mechanism.
In fact the "blade" concept is a little ambigious since the mechanics of the failure of the target material are varied. For example does a fibrous material break by concentrated shear stress or is there a wedging action (inclined plane) forcing the fibres to break in tension or is the fibre actually crushed (by a blunter "blade") or a combination of all three?
High speed blades, cutting grass or other natural fibres, actually may involve crude collisions with the fibre, in effect smashing the target, although the taper of the blade increases the efficiency.
Further the blade metaphor is also clouded by the fact that the motion is not always solely vertical but there is tranverse or horozontal motion as well. "Sharp" blades are not always defined by a smooth fine point but rather by many fine serrations where the cutting motion is important.
Perhaps somewhere in primitive cultures, hunters and craftsmen quickly realized that sharpening the edges and points of their tools and projectiles greatly improved the performance. They probably appreciated this concept long before rolling a wheel around(?). In that context, perhaps this topic warrants a little more consideration.
Pete318 (talk) 19:05, 27 March 2009 (UTC)
A postscript to the last comment: The sharpened edge of a wedge or a blade or the sharpened point of an awl multiplies pressure not force. If a machine is defined a device that multiplies force then the blade is a different mechanism. The same way a spring can multiply power - it is a mechanism but is it a simple machine?
The analogy with an hydraulic mechanism is misleading. An hydraulic device uses the same pressure to multiply force, but the blade uses the same force to multiply pressure. Thus the question is if an hydraulic system is a "simple" machine, that is, is it basic enough?
Pete318 (talk) 18:41, 30 March 2009 (UTC)
Basic enough? I think that is not an 'enough' rigorous point. The real question In My Humble Opinion should be, "can it be represented by other simple machines"? That is, if it (hydraulics) transforms one mechanical energy mode into another and no (other) simple machine can replace it, add it to the list. Perhaps it wasn't known at the time of the original list. Though if one includes machines made in the digital age, like the transistor, the list may grow unwieldy. But then you've nearly reduced it to two machines!188.8.131.52 (talk) 21:46, 29 June 2011 (UTC)LeucineZipper
Machines are not studied as combinations of simple machines[edit]
Elementary school teachers like the concept of simple machines because it appears to move their students toward knowledge of technology and even engineering. There are many web-pages that illustrate simple machines and analyze their operation as applications of physics and mathematics. Unfortunately, the engineering is wrong and sometimes the physics as well. In the 1800's the classification of machines along the lines of Aristotle became increasingly complex as more machines were designed. The individual who most diligently pursued this effort was Franz Reuleaux. His collection of 800 machine elements can be found at Cornell's KMODDL site. It is, perhaps, no surprise that it was Franz Reuleaux, who identified a more fundamental approach to describing machines that informs designers to this day. This approach, which is over one hundred years old, has nothing to do with the statement: "A simple machine is a device that transforms the direction or magnitude of a force." Prof McCarthy (talk) 05:04, 29 November 2011 (UTC)
Pillars that support a highway overpass transform the magnitude and direction of bridge and highway loads. Similarly, a dam that holds back water transforms the magnitude and direction of hydraulic forces. I do not believe anyone would classify these devices as simple machines. The concept of set of simple machines from which other machines are constructed is a Renaissance interpretation of Greek texts on technology. This viewpoint lasted until the late 1800's, at which time the number of simple machines was found to be many hundreds, including the various devices in the figure that is part of this article. This article on simple machines should be written as a historical piece that provides insight to an elementary mechanical movement. But it should be recognized that this approach has been abandoned for a long time as a useful tool for machine analysis and design. Prof McCarthy (talk) 05:37, 29 November 2011 (UTC)
- I respect your expertise in this field. As a professor of mechanical engineering at a major university, If you say the concept of "simple machine" is outdated, I am inclined to believe you. However, your changes to the article require the citation of reliable sources. Secondly, as you mention above, the concept of "simple machines" is still widely taught. And not just in elementary school; the references in this article show it appears in secondary school and college texts, and is knowlege required on standardized tests. Thirdly, even if this approach has been abandoned in machine design, in everyday usage the term "simple machine" has a specific meaning, which is the traditional concept of a force scaler or amplifier linkage. I think this is the primary definition and must appear in the article's lead paragraph.
- If the engineering or physics in this article is wrong, it should certainly be corrected, with sources. If machines are no longer analyzed as combinations of simple machines, I would support a properly sourced section saying so. However, I feel the major changes you made to the article misrepresent the term, so I am reverting them. --ChetvornoTALK 21:21, 29 November 2011 (UTC)
I did my best to preserve the basic ideas of simple machines and present the fundamentals correctly. If you disagree then fine, I will leave it alone. Prof McCarthy (talk) 21:29, 29 November 2011 (UTC)
800 Simple Machines[edit]
Well, our colleague Chetvorno in a desire to keep the unusual definition that "simple machine is a device that transforms the direction or magnitude of a force," has reverted all of my edits with little attention to their individual value. I have to say that his statement that a " 'simple machine' has a specific meaning, which is the traditional concept of a force scaler or amplifier linkage" captures the essence of mechanical advantage, but does not represent a transformation of the direction and magnitude of a force. All things change the direction and magnitude of a force in some way. I am willing to let him have his way with this topic, I have had this experience before. However, I do have one regret, that the listing of simple machines stops with those identified in the Renaissance and does not include those recited in the later years of the Industrial Revolution, for example the listing of 60 or more simple machines shown in the figure attached to this article or the more than 800 simple machines identified by Franz Reuleaux. Prof McCarthy (talk) 22:34, 29 November 2011 (UTC)
Did identification of simple machines end in the Renaissance?[edit]
The list of simple machines discussed in this article is known to have been identified by the time of the Renaissance. During the Industrial Revolution that followed many additional simple machines were identified. I assume gears may be considered examples of the wheel and axle, however their engagement to provide power transmission is not among the simple machines of the Renaissance. More importantly, the discovery of the involute tooth which makes standardization and commercialization practical is of fundamental importance. I would propose that cam mechanisms, the geneva wheel, escapements, the universal joint, and the flyball governor are all examples of simple machines that were discovered after the Renaissance and deserve consideration as fundamental components used to make more complex machines. Some would consider Watt's linkage to be of such importance that it qualifies it as having the significance of a wheel and axle, because it is considered to have made the steam engine practical. Why is it off-limits in this article to simply mention that after the Renaissance other simple machines were identified? Prof McCarthy (talk) 06:22, 1 December 2011 (UTC)
No word from Chetvorno as yet.[edit]
I am trying to get Chevorno to address whether it is enough to leave the sentence "a simple machine transforms the magnitude and direction of a force" in the lead. This would allow my to reinstate the other 24 or so edits. His mass elimination of these edits seemed an ill-considered action to maintain this one sentence, which I had simply moved to a later section. I have asked on his talk page if I may interpret his silence as approval. Prof McCarthy (talk) 01:37, 2 December 2011 (UTC)
I will try again[edit]
I have not heard from anyone, so I assume that if I leave the sentence "a simple machine transforms the magnitude or direction of a force" alone, though most everything does this, and work on the remaining parts of this article, I will not have my edits completely reverted. At least I hope this is the case. Prof McCarthy (talk) 18:20, 3 December 2011 (UTC)
Compound machines[edit]
This article describes a compound machine as a series of simple machines and computes the mechanical advantage of a compound machine as the product of the mechanical advantage of simple machines. This was obtained from the reference: [1]
- ^ "Compound Machines". University of Virginia Physics Department. Retrieved 11 June 2010.
It is important to recognize that this is a special case that is useful for introducing elementary school students to the idea of mechanical advantage, and not a description of machines in general. Prof McCarthy (talk) 19:22, 3 December 2011 (UTC)
Alternate definitions[edit]
The section Simple machine#Alternate definitions exposes the error in a focus on "the transformation of the magnitude or direction of a force." This is a useful simplification if the only concern is the six classical simple machines. But there are many other machine components that transform the magnitude and direction of forces. In fact a close look at most devices shows that they transform forces in some way---please see my examples of pillars and a dam above. The critical concept in understanding classical simple machines that has an important modern form is mechanical advantage. From this point of view, hydraulic systems are clearly simple machines, though not one of the classical cases. The expansion of the list of simple machines in the late 1800's is what lead to a revision of the basic view of the analysis of machines that has now been in place for over one hundred years. Prof McCarthy (talk) 19:36, 3 December 2011 (UTC)
I have looked into the references in this section and found that they are not very substantial. I would like to replace them with a very old physics text that addresses these issues nicely. It is Robert Hunt, (1851), Elementary Physics: and introduction to the study of natural philosophy, Reeve and Benham, London. Prof McCarthy (talk) 07:16, 6 December 2011 (UTC)
I am trying to figure out how to fix the section on alternate definitions. I have checked the references and found them to be elementary school notes or summaries that are equivalent to these notes. So the alternate definitions seems to be what various writers have proposed to help their students understand simple machines. It is correct that a wedge, screw and inclined plane have the same basic physics. A lever, wheel and axle, and pulley also have the same basic physics. This does not change the fact that the Renaissance scientists identified these devices as simple machines. I do not think this section is very helpful to the reader. There is no controversy about what was considered to be a simple machine in the 1500's. Prof McCarthy (talk) 07:30, 6 December 2011 (UTC)
Frictionless analysis[edit]
I renamed the section "Frictionless analysis" to be "Mechanical advantage," because this is what is discussed in this section. The derivation of mechanical advantage based on work is the standard approach used in the various notes for elementary schools. However, this is better done using power, because mechanical advantage depends on the configuration of the machine, and is actually an instantaneous property like velocity. In contrast, work is path dependent and is best used for simple cases, such as falling weights, unless the displacement is held to be very small, in which case it becomes a velocity analysis. Prof McCarthy (talk) 16:24, 6 December 2011 (UTC)
Friction and self-locking[edit]
The section on "Self-locking machines" is based on the reference Gujral, I.S. (2005). Engineering Mechanics. Firewall Media. pp. 382. ISBN 8170086361. It seems to say that if the efficiency is poor enough, the machine will be self-locking. I guess this is a way of saying there is good in a poorly performing machine. Prof McCarthy (talk) 05:07, 7 December 2011 (UTC)
- The analysis of self-locking due to friction does not seem to be appropriate for this article on simple machines for a number of reasons. Perhaps the most important is that it is overly simplified to the point of being incorrect in the cases where it matters the most, the inclined plane. Self-locking due to friction is a characteristic of the analysis of an inclined plane and includes the wedge and power screw. The mechanical advantage of a frictionless inclined plane is 1/tanφ where φ is the angle of the inclined plane. In the presence of friction, let the angle of the plane where friction forces balance be α, then the mechanical advantage is 1/tan(α+φ), when raising a load. The system is self-locking if α≥φ. Clearly the inclined plane with friction has the efficiency η=tanφ/tan(α+φ). If the friction angle is exactly α≡φ, and φ<10degrees, then η≈φ/2φ = 1/2. This analysis changes in the case of lowering the load. This is a much more subtle analysis than simply adding work due to the load and work due to friction, and probably should be reserved for the articles on inclined planes. Prof McCarthy (talk) 18:00, 7 December 2011 (UTC)
I propose deleting the section on self-locking from this article and introducing the appropriate derivations in the articles on the inclined plane, wedge (mechanical device), and screw (simple machine). Prof McCarthy (talk) 17:54, 7 December 2011 (UTC)
The application of friction is essential in mechanical devices such as fastners - helical bolts and screws - by preventing the helix turning and releasing the axial preload on the machine part. It is a stretch (no pun) but if a rod was clamped with a wedge to prevent the rod from moving it would be useless without friction. However this application of friction is not an ACTIVE machine element. It does not multiply force, but rather increases the PASSIVE resistance to force on a bona fide simple machine.
That is the best defense that I can think of just now.
Pete318 (talk) 18:57, 24 January 2012 (UTC)
- Pete318, you are correct fasteners use internal forces and even mechanical advantage to maintain a structure. Other examples are toggle clamps and door stops. I believe you are right because the Renaissance notion of a simple machine is a device that moves loads, not one that makes a structure rigid. Thank you. Prof McCarthy (talk) 00:48, 25 January 2012 (UTC)
Egyptians and the Great Wall[edit]
Apparently, there is not enough about the Pyramids and the Great Wall in other articles in Wikipedia, they must be discussed in this article as well. It is true that Usher attributes a misreading of a Greek text on moving heavy loads as the source of the concept of Simple machines. However, is it necessary to list all ancient monuments that have benefited from this construction technology? I suppose we could include Stonehenge, the Mayan Temples, as well as the temples of the Acropolis. Then there are mythical structures like the Tower of Babel, the Colossus of Rhodes and maybe the lost city of Atlantis. Prof McCarthy (talk) 07:37, 17 February 2012 (UTC)
- I really also wasn't done with the section. I just decided to add the section because it really is important to the history of the simple machine. Algamicagrat (talk) 15:02, 17 February 2012 (UTC)
It would help me to know what part of the following description of the history of the Great Wall is important to the history of the simple machine:
- The Great Wall of China is the longest man made structure ever built in the history of mankind, with its present length of 8,851.8 km or 5,500.3 miles stretching into several provinces of China such as Liaoning, Hebei, Tianjin, Beijing, Shanxi, Inner Mongolia, Shaanxi, Gansu, and Qinghai. However, the Great Wall of China is a noncontinuous series of walls in different places, especially during the period of its initial construction. It was primarily built by several states during the Warring State Period in China to prevent attacks from other neighboring states. Later on, when the states vanished, leaving the Qin State in a unified China, Emperor Qin Shi Huang ordered the connection of the series of walls and termed it as "10,000 li Long Wall." It was connected to prevent further attacks, that time from the northern nomadic tribes. Later on, the last reconstruction of the Great Wall undertook during the Ming Dynasty after change of several dynasties. The Ming Dynasty purposely reconstructed the wall to strengthen its defense further from the Mongol in the northern part of the country.
Prof McCarthy (talk) 15:39, 17 February 2012 (UTC)
- Good Point...Algamicagrat (talk) 23:55, 17 February 2012 (UTC)
Machine elements v. Simple machines[edit]
Recent edits by our colleague 3/4-10 appear to assert an equivalence between machine elements and simple machines. At least this is the way I interpret the following taken from the lede to this article:
- Various authors have compiled lists of simple machines and machine elements, sometimes lumping them together under a single term such as "simple machines",[1] "basic machines",[2] "compound machines",[3] or "machine elements"; the use of the term "simple machines" in this broader sense is a departure from the neoclassical sense of the six essential simple machines, which is why many authors prefer to avoid its use, preferring the other terms (such as "machine element")
I believe is it appropriate to consider the phrase simple machine as referring either to a machine that is simple or to one of the set of six simple machines identified by Renaissance scientists. However, machine element is a modern concept that should be separated from what is actually an odd concept that machines are constructed from combinations of six devices identified by Renaissance scientists. As Usher notes this was a misunderstanding of a text on devices used to move heavy loads. It was not the result of a scientific study of the decomposition of mechanical movement. In contrast, Reuleaux did perform such a study of mechanical movement and constructed models of 800 different devices that can be considered machines that are simple. As a result, Reuleaux identified the rotary, linear and direct contact joints, which he described a lower pairs and higher pairs, as the elemental components of mechanical movement. These are the predecessors to what are now known as machine elements, and the list has expanded to other important mechanical components. However, blending the terms simple machines and machine elements is to blur the important distinction between a failed tradition and its modern successful approach. Prof McCarthy (talk) 06:58, 13 March 2012 (UTC)
- The concept I was trying to cover is that one word sense of the term "simple machines" is only the 6 fundamental classical/neoclassical ones, whereas another word sense of the term treats it more like "machine elements" (for example, at least 2 of the cited refs use it in that sense). I personally would rather see people confine the term to the first sense mentioned, because it better allows for precise-while-brief (that is, succinct) communication. What I saw in the earlier version was the remnants of various editors coming here and disputing the definition of the term—the answer to that is to have the article explain that both word senses exist, even if one is not preferred. If anyone wants to work on refining the coverage so it's clearer, that's fine. — ¾-10 00:58, 15 March 2012 (UTC)
- I appreciate your thoughts on this. I have had many run-ins with editors who insist this article must limit the notion of simple machines to the Renaissance view because of the many elementary school web-sites that use this as an introduction to technology. I believe it makes sense to broaden the term to at least include the many simple machines that are represented by Reuleaux's models as well as other listings such as the figure in the lede. While I do think there is a technical concern with blending this definition with machine elements, I could be persuaded that if elementary school teachers viewed axles, bearings, screws, gears and other machine elements as simple machines this could actually be a good thing for elementary school engineering, in particular, and machine theory in general.Prof McCarthy (talk) 01:18, 15 March 2012 (UTC)
- I agree with the Prof that this article should discuss the Renaissance list as a historical item (which has been the previous consensus) and also that adding eg Reuleaux's work is appropriate. I also agree that we don't want to mix machine elements with simple machines Jimbowley (talk) 16:37, 10 July 2012 (UTC)
I think to improve this page we should include a comparision between simple machines and compound machines. I do not know how to explain it right so if you know how could you please edit it because I would just like to help this wikipedia page better. Thanks for your time.
~Lily Clarissa Smithers~ — Preceding unsigned comment added by 184.108.40.206 (talk) 17:54, 25 March 2012 (UTC)
- The article contains a section on compound machines that explains that a compound machine is made up of several simple machines connected in series. What would you like to see added? --ChetvornoTALK 01:31, 26 March 2012 (UTC)
I think the question that arises in the consideration of simple machines is how do we get from simple machines to more complex machines. While it would seem that a start might be attaching simple machines in series, this turns out not to be correct. The correct strategy was identified by Franz Reuleaux, and by many elementary school teachers, who realize that a lever, pulley and wheel and axle are basically the same device, a body rotating about a hinge, and that an inclined plane, wedge and screw are similarly a block sliding on a flat surface.
With this realization it becomes clear that there are fundamental joints, or connections between moving bodies, and that machines are constructed from these joints in standardized ways. Starting with four types of joints, the rotary joint, sliding joint, cam joint and gear joint, and related connections such as cables and belts, it is possible to understand a machine as an assembly of solid parts that connect these joints.
From this point of view we build machines as follows, a power source drives a rotational or linear movement, which is then transformed into another movement by a mechanism. Mechanisms start out as a frame, a hinge and one bar or crank to form a lever, door, wheel, door knob, and on and on. They become increasingly complicated by combining a frame and two cranks connected by one floating bar to form a four-bar linkage which is the input-output mechanism in door-openers, trashcan lids, door and hood lift mechanisms and many more. A variation of this uses a lever or crank connected by a floating bar to a slider which is the heart of an internal combustion engine, and devices such as clamps, slicers and more. And the process continues with the addition of gear trains, and cam and follower mechanisms.
The key insight is that there are, in fact, primitive mechanisms that form all machines. Its just that these primitive mechanisms, unfortunately, are not the six simple machines identified by Renaissance scientists. Prof McCarthy (talk) 04:04, 26 March 2012 (UTC)
- Very good food for thought. I for one would like to see this article contain a section called "alternative classification schemes" (or something along those lines) that basically says what Prof McCarthy said above. — ¾-10 00:38, 27 March 2012 (UTC)
- The section as written is not incorrect. If you define a compound machine as a series of simple machines, then the equations etc are correct. The section does not state that all complex machines are compound machines. I have not come to an opinion on whether the section is useful for the article yet. Jimbowley (talk) 17:03, 10 July 2012 (UTC)
- I'd like to see a clearer separation between the classical Renaissance theory of simple machines and the different modern concept based on kinematic chains added by Prof McCarthy. In the classical theory, still taught in physics classes, there are only 6 simple machines and "compound machines" consist of series of simple machines. In the modern theory by Franz Reuleaux and others, there are hundreds of "simple machines". Both theories are important, but in its present condition the article doesn't cleanly distinguish between them. This will confuse nontechnical readers. I think the two theories should have separate sections. Perhaps the main body of the article can be devoted to the classical theory, which is what most readers want when they look up "simple machine", and a separate section at the end can explain "kinematic chains". --ChetvornoTALK 19:54, 10 July 2012 (UTC)
- Chetvorno, this is the spirit in which the section on kinematic chains was added. Prof McCarthy (talk) 02:21, 11 July 2012 (UTC)
- It looks good as far as it goes, but the last paragraph of the introduction doesn't emphasize enough that it refers to a modern departure from the classical concepts. Also, it needs to be clearer that the last two sections, "Kinematic chains" and "Classification of machines" are separate from the preceding sections which refer to classical machines. Couldn't they be grouped under a section titled "Modern machine theory" or something like that? --ChetvornoTALK 21:00, 11 July 2012 (UTC)
- My initial reaction is that this gives the modern theory more prominence than perhaps is necessary in this article on simple machines, but it may be a good idea. Prof McCarthy (talk) 22:15, 11 July 2012 (UTC)
- Chetvorno, this is the spirit in which the section on kinematic chains was added. Prof McCarthy (talk) 02:21, 11 July 2012 (UTC)
2 Classes ????[edit]
I've only just noticed that the '2 classes' paragraph is wrong.
A pulley is not characterized by the equilibrium of torques and movement around a pivot. Pulleys are about vector resolution of forces, there are no torques involved. And the movement is linear not around a pivot.
The screw is not characterized by the vector resolution of forces and movement along a line. The input is a torque.
This all goes back to 2008 when there was a lot of discussion about what this page was about. I seem to remember that the agreement was that the 'list of 6' was at least a recognised historic list. Somehow the unreferenced '2 classes' seems to have slipped through and gone unchallenged since (unless I missed the challenge, if so, sorry).
Jimbowley (talk) 12:08, 4 May 2012 (UTC)
There really should only be Two Simple Machines[edit]
I beleive that there should only be two Simple Machines: an Inclined Plane and a Lever, in actual fact an inclined plane could be contrued to be a Lever. — Preceding unsigned comment added by 188.8.131.52 (talk) 20:56, 4 March 2014 (UTC)
- Modern machine theory would describe these simple machines in terms of the joints that allow movement of their component parts. The wedge and inclined plane are defined by linear sliding joints and the wheel, pulley and lever are defined by rotary joints. The screw is a combination of the two. Generally, an inclined plane is not construed as a lever. However, theoreticians do consider the linear sliding joint to be equivalent to the rotation of a long lever about a fulcrum at infinity. Prof McCarthy (talk) 13:02, 5 March 2014 (UTC)
- Maybe consider mentioning that the mechanical advantage of (force) vector addition has often been ignored. In the context of this section it would provide, not new material, but rather an observation on current encylopedic knowledge of the subject. The most common example might be the compression of a gas or pumping of a liquid by a Crank and Connecting Rod/Piston assembly. Less common would be parbuckling of mooring lines.
- Would some text in that context be eligible for an entery on the Article Page?
- Pete318 (talk) 22:21, 20 May 2014 (UTC)
- I'm not exactly sure what you mean. The two examples you give are not simple machines. However the hydraulic press, which amplifies force with two different sized pistons, has mechanical advantage, and has often been suggested as an addition to the 6 classical simple machines. Is that what you were referring to? Again, the article mentioned that before someone eviscerated it. --ChetvornoTALK 23:18, 20 May 2014 (UTC)
- Pete318 (talk) 22:21, 20 May 2014 (UTC)
- hmmmm... I suppose the crank/connecting rod/piston is a complex machine - I see your point(?). However a single piece of rope or string can generate a significant mechanical advantage. The simplest example is probably how a bow string bends the bow (as in bow and arrow). The Bow itself may be a complex device, but the bowstring is about as simple as it gets.
- ...the problem is, if the bow string is classified as new material, then under generic encylopedic rules - wiki included - it cannot (ought not) be entered into the main article, thus the discussion is moot(?)! "....Primary research. If you have discovered something or found something out, put your ideas in a book for a learning school, not on Wikipedia. Wikipedia will talk about your ideas once it is known to a lot of people...."[45]
- Even as an observation of the current understanding of the subject by the entry author/editor, there ought to be at least one more source - established in the particular field - making a similar observation. Non?
I don't know what it is about this page that so consistently attracts vandalism from anonymous users. Looking at several years of history, the vandalism is not correlated with the school year (which had been my hypothesis in early lock-downs). I fear that there is no choice but to restrict the editing of this article to confirmed users only. Rossami (talk) 18:27, 28 May 2015 (UTC)
Semi-protected edit request on 7 February 2017[edit]
THIS WEBSITE IS TRASH DONT TRUST IT — Preceding unsigned comment added by 22.214.171.124 (talk) 14:45, 7 February 2017 (UTC)
- ^ Cite error: The named reference
Mechanickswas invoked but never defined (see the help page).
- ^ Cite error: The named reference
Prater1994was invoked but never defined (see the help page).
- ^ Cite error: The named reference
U_Virginia_elementary_curriculumwas invoked but never defined (see the help page).
- Wikipedia level-3 vital articles in Technology
- Wikipedia C-Class vital articles in Technology
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- High-importance Engineering articles
- WikiProject Engineering articles


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A selection of current stock items of companies listed in the Graniteland stone companies directory. For questions regarding a stock item, please contact the company directly.
- M.I.G. SRL has Rosa Sardo Beta on stockRosa Beta Slabs Rosa Beta Tiles Rosa Beta Blocks
- STONE HUB INDIA has Star Galaxy on stockBlack Galaxy granite is undoubtedly one of the world s most popular and successful granites and has been exported to every continent. It is a fine to medium-grained, black gabbros with golden-yellow s
- Regatta Universal Exports has A - Red on stockProducts Available: Tiles, gangsaw slabs 260x160cm up in 2 & 3cm, cutter slabs 180x60cm up in 2 & 3cm, countertops, vanity tops Finishes Available: Polished, honed, sandblasted, antique (sandblaste

subset: commoncrawl


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Chimiotherapy for fibrosarcoma in children (1 course) в Andreasklinik Cham Zug
Chimiotherapy for fibrosarcoma in children (1 course)
Center of Oncology and Hematology in Andreas Clinic Cham Zug is making every effort to provide you best advices and treatments. The center sees itself as a provider of comprehensive diagnostic and treatment services for blood diseases and tumors.
Duration 5 days
Type of Treatment: Inpatient
location_onCountry: Germany
location_searchingCity: Cham
Price 0.00


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Farm Dinner
Saturday, August 5th, 2017 from 5 - 9pm
(rain date Sun. August 6th)
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We're building our Intern team for 2017!
Click here to apply for a fun, exciting, hands-on
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text:
The soil on Mars is similar to Hawaii
Early experiments by Curiosity Rover in Martian soil has begun to show results, some amazing, among whom it was learned that the mineralogy of mars has compositions similar to that of basaltic volcanic soils found in Hawaii.
The analysis resulted in a composition consisting of feldspar, pyroxene and olivine, which according to David Bish of Indiana University and CheMin team "was something that pn us, even though we had an incomplete understanding of Martian mineralogy ".
The soil composition is the same as that in the volcanic basaltic material of Hawaii, of meteoric origin.
The Curiosity instrument used his chemistry and mineralogy, CheMin name, to analyze the composition of the soil and the fine powder spread on their way Martian.
As said David Blake, scientific CheMin team leader, there were many previous discussions on the mineralogy of Mars: "Our results provide a refined quantitative and in some cases new identifications of minerals in the first analyzes of X-ray diffraction on Mars."
This type of analysis of X-ray diffraction is the same used by geologists on Earth in their laboratory instruments, which provides more accurate identification of the minerals, and that "reads" the internal structure of each, unlike analysis of the age and evolution of a mineral, which only provides inaccurate information.
To illustrate this process, Blake recalls that two such different minerals both in structure and properties as diamond and graphite, through the study of their chemical composition is obtained as a result they are equal.
The X-ray diffracting mini installed on Curiosity processes samples in a sieve to exclude particles larger than 0.006 inches (150 micrometers) and identifies two components, the overall powder distributed by fine sand storms and local origin.
Unlike the analyzed rocks weeks ago, they have billions of years old, and they are the main source of research to conclude whether the Martian soil once had flowing water on its surface, these analyzes of dust and sand allow processes to meet current soil evolution.
Link: Curiosity Mars Rover Finds similar to Hawaii's soil (BBC Science)Tags: Curiosity Rover, mars, minerals, Space Exploration, volcanic rock


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Dog Training Treats and Biscuits
We have a great range of dog training treats and dog training biscuits for your dog and are perfect for use in reward based training aswell as a delicious treat for your dog.
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ProReward Chicken is simply 100% air dried chicken meat, a great way of giving your pet a lower fat treat. These are cut into small squares and ready and easy to use.
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Delicious and completely natural ingredients. Used throughout the world by professional dog owners.
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Specifically designed for puppies (eight weeks and over), these tasty chicken based treats are perfect to use in reward-based training. The semi-moist heart shaped treats are highly palatable and don't break up in your pocket or treat bag.
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Coachies Natural Training Treats are the healthy training treat. They are super tasty, so your dog will love them.
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A must for the fashion-conscious dog trainer, CLIX Treat Bags have many useful features. A wide opening allows easy access to treats, while the drawstring closure ensures that it is rain and dog proof!.
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These hypoallergenic treats are made from fresh cuts of chicken breast in a convenient tube made without animal derivatives, chemicals or other mystery ingredients.
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The Coachies Treat Bag is ideal for all reward-based training methods and can be attached easily to any trouser belt or pocket.
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The treat bag gives you a no fuss way to communicate good dog to your best pal. Fill your treat bag with treats hang it onto your belt and let training begin.
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- Security Fences in Glendale, CA
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Fences in Glendale, CA
You will quickly discover that there are many different types of fences Glendale, CA has to offer, making it extremely important that you review the choices you have carefully before deciding on one of them in particular. It is crucial to get the best fence in Glendale, CA for a number of reasons, including the fact that doing so can increase security around your home. If you do not want just anyone to get onto your property, you will definitely need to start looking for a type of fencing that is highly secure.
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A good fence company in Glendale, CA will be able to do all of the necessary installation work so you don't have to worry about doing any of it yourself. A Glendale wrought iron fence is a particularly good option because this type of fencing is both stylish as well as secure. If you want to improve the aesthetic in front of your home while keeping it safe from intruders, wrought iron is a great option to look into. The kind of fencing that you choose to have installed should look just how you want it to, because otherwise you are going to regret the decision you make.
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sachin tendulkar's 100th ton News
Salman Khan takes another swipe at Shahrukh Khan
Cineswami gets you all the dope from the much-talked about Ambani party for Sachin Tendulkar
The event organised by Mukesh and Nita Ambani at their ostentatious hotel, sorry, home, Antilla, was ostensibly to celebrate Sachin Tendulkar's century of centuries. However, the perennially attention seeking Bollywood stars who are used to being the cynosure of all eyes tried to hijack the event and make it all about themselves. Priyanka Chopra, the hostess of the evening, gushed, as is her wont and babbled, as is her curse and nobody paid her the slightest attention, as is correct. Aamir Khan spoke at length about how he had spotted Sachin when the cricketer was a 14-year-old boy and predicted great things for him. He claimed that he had a bet with Ambani in 2009 that Sachin would reach his landmark soon. Aamir continued speaking for a while, so long-winded that Shatrughan Sinha was openly bored, Hrithik Roshan was reduced to staring glassily into space and Shankar Mahadevan began checking messages on his phone. Click here to read more
B-towners congratulate Sachin Tendulkar on his 100th 100!
The master blaster's BIG number was long overdue and when it did happen, everyone in Bollywood was euphoric
It was the Big Day for cricket fans everywhere. Master Blaster Sachin Tendulkar finally managed to grab the title that had eluded him over the last few matches that he played. A few moments ago, he made his 100th 100, putting him into a new and exalted level in the sporting stratusphere. Click here to read more


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Be Friends with Someone when They Might Have a Girlfriend
Edited by Robbi, Eng, Lynn, Marian Raquel F. Roncesvalles and 3 others
Asking a guy to be friends and then finding out he has a girlfriend who is jealous can put you in an uncomfortable situation. Reality is there are a lot of women who remain to be close-minded and indifferent about friendships between their boyfriends and other women. It really depends on the girlfriend's mindset and attitude. While a bit of jealousy could ignite some degree of excitement in a relations, the green-eyed monster can be very hard to contain in some women and can be overpowering and self-destructive at some point. Girlfriends could at times be too focused on their man that they seem to forget that other people exist. This world is in fact a matter of coexistence and people are wired to be social and are bound to evolve and interact with each other on a day-to-day grind.
While it should not make any difference if a guy has a girlfriend if you are just friends, it all too often does end up being a problem that you don't need to deal with. But, if you are really just buddies then the problem could be mainly on the guy's girlfriend. She needs to open up and accept that a healthy relationship should involve other people too. It's not just about a couple in love but a support system or network of family, friends, and colleagues are crucial to the success and longevity of any relationship.
If the guy knows his girlfriend is jealous but accepts your friendship anyway, he could be using you to make her jealous and that is not really friendship. But, he could just be genuinely interested in pursuing friendship with you just as he does with his other close friends. So it could be in your best interests to ask him if he has a girlfriend. If he does, there are quick questions that need real answers - Does she have a problem with him having friends who happen to be women? Will it matter that you are a woman or she is cool with it? Is it absolutely clear that you are both in the friend zone and not attempting to cross lines?
Steps to Having an Honest Friendship with a Guy who may have a Girlfriend
- 1Ask his friends if he has a girlfriend if you don't want to put him on the spot.Advertisement
- 2Make it clear that you are only interested in friendship with him, his friends and any of his family members that you may know.Advertisement
- 3Ask him either directly or indirectly in a way that leaves him feeling at ease about answering.
- 4Decide if your interest in being friends with him is really for friendship or to get your foot into the door of a relationship with him.
- 5If his answer is that he has a girlfriend and he accepts your friendship, set some ground rules regarding the friendship right away so future problems can be avoided.
- 6Make an extra effort to befriend his girlfriend.Advertisement
The Right Attitude
- Accept the fact that he has a girlfriend, she must come first for him.
- Keep a little bit of emotional distance so you don't make the mistake of thinking it could be more than friendship.
- Be realistic on your expectations of the relationship so you know when to back off and maybe end the friendship if necessary.
- Keep it friendly but not too friendly so he knows you are only asking for friendship.
- Let him know up front that his girlfriend won't need to feel threatened by your friendship.
- Ask to meet her and try to develop a friendship with her as well.
- If he says he does have a girlfriend, show interest in meeting and getting to know her.
- If he has a girlfriend and accepts your friendship, set clear limits, not just for him but for you as well.
- Have other friends, both male and female, so you are not depending on his friendship entirely. Socialize, mingle, and continue to meet diverse individuals and keep genuine connections.
- Go slow in developing a friendship with someone who has a girlfriend and be ready to back off at any time.
- Be prepared if he says he does not have a girlfriend to let him know you do not intend more than friendship.
- If he has a girlfriend but does not want you to meet her, it could prove problematic for the friendship. This can also mean that he is not being entirely honest about his relationship and could be pulling your strings.
- An emotional distance is best so you do not get entangled in something you are not prepared to deal with.
- Letting yourself become too involved in a friendship with a guy before knowing whether he has a girlfriend can lead to problems.
Questions and Answers
How can you tell if a guy has a girlfriend without asking him?
Well we are friends and I met him at my apprenticeship program. Based off his Facebook it looks as if he may have a girlfriend, but it doesn't say they are in a relationship...I just want to know so I know where the boundaries are
VisiHow QnA. This section is not written yet. Want to join in? Click EDIT to write this answer.
- If you have problems with any of these steps, ask a question for more help, or post in the comments section below.
Article Info
Categories : Friends
Recent edits by: Doug Collins, Alma, Marian Raquel F. Roncesvalles


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I volunteered here from 2009-2010, I had to move away for awhile am now back and WOW! Every donation to these animals went to such great use. We always try to keep the animals happy. Gary and Carol really are just trying to give these gorgeous animals a better life, and believe me, they are.
(pictures below are of other places I volunteered, or personal pets. I do love animals, and Gary and Carol treat their beloved animals in the best way possible)
A great location with knowledgeable and caring staff.
It takes a very special kind of person to devote their lives to caring for those others are willing to throw away. Carol and her crew go above and beyond to provide for the magnificent creatures. They are not just a mission to them they are a life choice. Carol treats all of them like they are her children and insists the same from her helpers. I have a respect for the people there that words can not express. Bless Carol and everyone involved with this wonderful organization.
Gary and Carol Holliman have the biggest hearts to take in these beautiful creatures. The lions, tigers, cougars, bears, wolves and even the many dogs they have adopted that make up this refuge are loved and well taken care of.
Previous Stories
Carol, Gary and all the other workers and volunteers have made this facility and the animals they care for a wonderful place. There is so much love and dedication to their animals.
PrideRock is an amazing place where lions, tigers, mountain lions, bears and a hyena now call their forever home. I was fortunate to get to see this wonderful place up close when I attended an animal related workshop being held there. Many of these animals were used by humans to make a profit or kept as an exotic pet by people who didn't know how to care for them properly. Many of them have very sad, tragic stories. These animals should never have been taken out of the wild to begin with. Since they can not be released, having no knowledge of how to hunt for food, sanctuaries like this are a must. The love that I felt the day I was there from both the animals and the caregivers was amazing. These animals are well cared for and lead enriching lives. There wasn't the pacing etc you often see in zoos. The atmosphere was different. I heard noises coming from the cats and saw behaviors one never sees when they are held in captivity on display for humans. It is a beautiful place and deserves as much support as they can get, so they can build better bigger enclosures and feed all these wonderful critters who have been fortunate enough to come and live here.
I had only been to zoos to see any wild animal. Then, I met Carol. I went to PrideRock in 2009 for the first time. I was blown away and in awe of these magnificent creatures, especially the tigers. I met Damien (RIP) and all the others in an afternoon that I didn't want to end. The sheer power of their private "calls" to one another and their large presence just astounded me. I learned what happens when you neuter a Lion, he looses his mane plus many more things I didn't know. Although they can never return to the wild they seem to be quite at home and understand this. You can hear the roars when you get closer and it it awesome! I have been back 2 more times and hope to visit many more. Brenda Blake, Dallas, TX
I know these people & Carol has loved, worked with & saved animals her whole life. This is her passion,love & purpose! I have made donations here & will continue to. The work they do is not easy & not everyone is cut out for it. It takes a large amount of time, patients & money for this to work.These magnificent animals come to them needing love,attention,medical attention & understanding. Through donations it can continue to flourish & these wonderful beast can live without fear of being abused, or neglected. Honor someone, or in memory of someone by donating or do so because you love animals!!!
I have seen this group again and again volunteer to take in large cats and other wild animals to give them a safe environment to live in. Last year, they took in a li-liger cub that developed a serious illness probably due to the cross breeding. Their dedication night and day to trying to save the cub's life was truly inspirirational. The cub did not survive but it was not due to a lack of care on the part of this great staff.
The knowledge and love of wild animals of these people had inspired in me a desire to do more to save our beautiful amazing wildlife. Pride Rock is a refuge that also works to educate the public. Something that is truly needed
Carol and crew are absolutely amazing! The love and concern that they provide each one of their fur babies, is stupendous! Love this place and these folks!
The only way for me to describe PrideRock is complete serenity and peace...It is breath taking from the moment I pull onto the property. Truly, good for my soul and hands down one of the most rewarding experiences of my life. One of my longest best friends (with permission from Carol) gave me the opportunity to volunteer and clean enclosures (aka scoop poop) and join her for enrichment. I have been back to volunteer every week since. I was told there will be my "favorites" and "they will choose you"; all true and Diego (Baby D-Lion) and Toro (the "shy" black bear) have stolen my heart. I love them all in their mighty greatness and will continue too, as often as possible and allowed. Grateful, honored and humble.


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Watch Hour of the Wolf movie online for free, Download Hour of the Wolf full length movie:
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2. http://veehd.com/video/2821890_The-Hour-of-the-Wolf-Movieplex-org
3. http://vidzi.tv/i5dj3gg62x0v.html
4. http://www.youtube.com/watch?v=ITG2SXj_-Rg
Title: Hour of the Wolf
Release year: 1968
Movie genres: Drama; Horror
Directors: Ingmar Bergman
Actors: Max von Sydow, Liv Ullmann, Gertrud Fridh, Georg Rydeberg, Erland Josephson, Naima Wifstrand, Ulf Johansson, Gudrun Brost, Bertil Anderberg, Ingrid Thulin, Ingmar Bergman
Duration: 90 min.
Hour of the Wolf online anschauen und downloaden kinofilm. Stream Film online anschauen und downloaden.
Hour of the Wolf Gratuit en streaming. Regarder en Streaming gratuitement sans limit.
Watch Hour of the Wolf movie online for free. Download Hour of the Wolf full free movie, hd, mp4, avi, mpeg.
Ver Pelicula Hour of the Wolf Online Gratis. Ver Online HD Espanol Latino.
Hour of the Wolf film is a pretty cool movie, that filled with lots of good action. If you fed up with all the same tapes in Horror genre and wish to watch something cool and not ordinary then get congratulations because Hour of the Wolf is before you in this moment! Both the director and good actors like Naima Wifstrand, Liv Ullmann, Ingmar Bergman are real pro and it seems they are not play but living their roles, becoming parts of their heroes. We think this is one of the best of all tapes of 1968. Hour of the Wolf duration is 90 minutes where you will see so many unforgettable and great scenes! You should sit more comfortable and start getting tons of pleasure! We hope that you will take pleasure in this movie. Bookmark Hour of the Wolf film and share with friends.


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Consistency and relevance are your best allies when grabbing the attention of global customers and keep feeding them. You should also bear in mind some dependencies and factors that are tied to digital globalization as a whole. Here are some points that are even more crucial to consider when deploying and valuing bite-sized content internationally, wherever it must be understood, consumed, remembered and shared.
Dec 02, 2005
Elsevier has announced that access to EMBASE.com is now available to faculty, students, researchers, and physicians affiliated with 11 of China's universities as the result of a new consortium licensing agreement. The agreement will enable tens of thousands of individuals throughout China at institutions of varying sizes and resources to benefit from access to this biomedical and pharmacological information resource.
EMBASE.com provides coverage of articles published both inside and outside of China of particular relevance to the Chinese biomedical community--from the latest information about the menace of avian flu to proprietary Chinese drugs and traditional Chinese herbal medicines such as Hochuekkito, Cordyceps sinensis, Bupleurum root and Isatidis extract, and acupuncture and related physical therapies. Recall is facilitated by a thesaurus of indexing terms, many of which are specific to Chinese medicine, concept terms like evidence-based medicine and clinical trials and trade and manufacturer drug and device name fields.
(www.elsevier.com; www.embase.com)


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Not jealous per se, more envious? Like I'm happy for them, just wish it was me too! LOL
Not jealous per se, more envious? Like I'm happy for them, just wish it was me too! LOL
It use to be one if my most debilitating and consuming emotions, it went beautifully with depression and low self esteem!!
But slowly and surely I am opening my eyes to how freakin' awesome my life is! I am pretty materialistic so it's usually what people "have" that I don't that makes me jealous. But I know I'll have it one day!
I think after DS I felt such low self esteem with the weight I put on and I constantly compared myself to others and wished I looked like them. I think I'm slowly coming out of that slump now but it's taken a few months.
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