I wanted to design (actually took reference on a couple of existing design) my quadcopter frame. My main purpose is to have a quadcopter carry a gopro for aerial video/photo for our surfing trips and maybe used it for scenery / other video usage. I am still a noob at autopilot system so I am having a hard time figuring out which flight control to use... By the way, I will be using an all aluminum frame with dampening cushions to absorb the shock and vibrations. Aluminum is environmental friendly unlike carbon fiber and fiber glass... Just my own thought..
MY first design was derived from xproheli but i had made it with 600mm motor to motor distance.
I like the idea of sheet metal frame-- just like the real aircraft construction.
I have access to shops that can cut my design through a sheet of aluminum. Bending it would not be a problem. I have designed some jigs for my arm and center housing.
The height of the landing gear is designed for gopro or min dslr.
My second design is based on a square aluminum tube (3/4 x 3/4). But when I measured it from a caliper, It is only 17mm x 17mm. Anyways, I had made my centerplate a bit large to accommodate my electronics cleanly. The landing gear is also the same as the previous design.. Landing gear and centerplate is connected t by vibration resisting shock absorbing balls (I dont know the real name of it).
Solidedge calculated the weight of Frame+motor+props - 1.1kgs. aprox. the same as the previous quad's weight.
Now I am a bit confused in which design to go. the first design is kind of work extensive than the 2nd one. The second one is plain simple design, sheet metal bending to do and jigs to make.. But honestly The first quad looks kinda cool and professional.
I will be posting new developments soon..
Good work, keep us posted.
Thanks Morli. I think I am going with the first design (the xp2-like quad).
BTW did you mean "First blog or Fist blog " ?
I mean first blog Morli.
Forgot to mention - don't forget to add mount holes for the electronics deck. Should make raising the APM easier to do.
Thanks Euan for the reminder.I was so busy drawing the frame that I forgot to plot the mounting plates for the APM. I am gonna read blogs regularly so I will learn on how to install and set-up my electronics.
Just like 3dr's quad. A stacked-up electronics bay for my apm 2.6 or other electronics.
The weight of the motors and battery are the usual things that really add the weight. Especially the motors and arms, because they're the weight times X. The motors you're buying seem to weigh in at 120g. That's a bit on the high side for 700kV as there are others (T-motor?) which have (according to spec) 80-90g. That doesn't seem like much, but it's 30g * 4 == 120g less. 120g for a quad is a lot and makes the difference between mounting a gopro or not. In terms of endurance on your quad it's probably around 20% flying time. You can also decide to go with CF props that you can mount directly on the motor without using the hub. That also has the advantage that the CCW props won't rotate off the spindle and CF props are better at fighting off vibration, because the props don't bend during flight.
The battery is another thing to look at for shaving off weight. A high C-rating is desirable when you want to use the quad aggressively or for large weights or when you increase prop count. So as always it's a trade-off. The best you can do is define the type of flying you expect to do and the max weight you'll carry. Then you can choose the correct C-rating battery. There's a lot of quality differences in terms of how batteries deliver current considering the capacity left in the battery and when voltage reduces, the current increases slightly which you need to take into consideration. In general you can't choose cheap batteries that are very close to the C-rating you need for general flight because they're not actually delivering that much consistently.
There's an online utility called e-calc, which you can use to get an idea how the multi-rotor will perform for specific setups and the differences some components make for flight time, power reserves, current, motor temperature and so on.
Don't feel bad about using floppy materials either (1mm thin epoxy) for body plates. Slightly larger plates reduces the force on the plate a bit and they allow you to build a stronger center section. You need to make sure however they're never in the prop wash. I'm using two round 1mm r=8.5cm epoxy plates as the body, giving a sizable platform to mount electronics on (and more top plates to increase distance between metal and compass). These plates by themselves are flimsy and bendy, but every arm is fixed with 4 metal 2-2.5mm nuts and bolts, two through the arm near the center and two at the edge around the arm. The space between the arms has additional plastic spacers which are eventually used to mount the top plates and a battery holder at the bottom. In the end the two body plates act like a single rigid body and work out any bending stress that would otherwise occur.
My landing gear is made of strong black plastic in a T-beam shape with feet made of RC antenna tubes. It weighs 53g. What you could do as an alternative is attach the legs on the arms directly, but then using plastic made of two beams with some hexagonal shape inbetween (should be around 25g each). Also here: if you use two strips of 0.5mm alu with some spacers inbetween it's going to be stronger than a single 2mm alu strip, yet lighter. That way you can also ditch the bottom alu tube and just bend the final part over.
I had a quad from bent alu before and the legs were bent from 2mm alu. Since it's a single piece, the bending stresses aren't resolved properly, so a slightly rough landing will bend the gear. After a couple of landings that way the material tires out a bit and the quad will not be completely level when started, which could lead to drifting when the electronics are initialized.
You might want to consider making the arms more narrow towards their outer ends where they obstruct downward airflow from the props. I have no data regarding that but it seems pretty obvious that any reduction (and streamlining for that matter) there would be beneficial to some extent.