At the large hotel where I work in the engineering department the big Halloween event is the annual Pumpkin Derby...and we've lost every year to the culinary department. It's embarrasing!

This year, though, we caught them in the act. Since they're in charge of distributing the pumpkins, they kept a half dozen or so for themselves, tricked them out, and we caught them testing the racers to select the best one. We, on the other hand, are limited to a single pumpkin. So I'm soliciting advice for building a hot-rod pumpkin!

The rules are that you may use any kind of wheels, from ball bearing casters up to wheelchair wheels. The catch is that they must be attached only to the pumpkin. You can use axles which go through the body of the pumpkin, but you can't have any kind of a chassis or even a tie wire to align them. That's what killed us in the past; our pumpkin wouldn't travel in a straight line and dissipated its kinetic energy in a turn. The pumpkin is let go from the top of a ramp to roll across the lobby floor, and the prize goes to the pumpkin which travels the longest distance from the base of the ramp. The floor is low-pile carpet.

My preliminary idea this time is to use casters such as you might find in an office chair, three of them. They have 5/16" threaded stems, and we have some threaded anchors intended for concrete. My idea is to use three of them, drilling mounting holes vertically into the base of the pumpkin, and to use a pane of glass to level them into the same plane and then use RTV or similar to glue them in place.

One challenge I'm looking at is how to keep the pumpkin from spinning as it rolls down the ramp. I had thought that by using a triangle of casters and starting it down the ramp heaviest end first we might have the most luck. But I'm open to suggestions.

Help the engineers beat out the cooks!

Edit To Add: Thinking about it, possibly the biggest challenge is keeping the pumpkin from spinning when it leaves the ramp. While accelerating the net force is directed forward, while when it's on the carpet net force is to the rear. We plan on using swiveling casters; perhaps a touch of hot glue on the one in the lead to hold it straight?

Here are the casters we plan to use:

[![(Casters we plan to use)](https://i.stack.imgur.com/RqC6f.jpg)](https://i.stack.imgur.com/RqC6f.jpg)

We also have these wheels available (only two, but we could use a caster before or behind):

[![4.10/3.50 wheels](https://i.stack.imgur.com/07ps0.jpg)](https://i.stack.imgur.com/07ps0.jpg)

Here's the ramp. Pumpkin needs to fit between first two lines. Long wheelbase is a problem:

[![Pumpkin Derby ramp](https://i.stack.imgur.com/SmZnG.jpg)](https://i.stack.imgur.com/SmZnG.jpg)

Preliminary components:

[![Derby racer components](https://i.stack.imgur.com/JITUs.jpg)](https://i.stack.imgur.com/JITUs.jpg)