Pinewood derby racing is a popular pastime for scouting groups and many others besides. [Mr Coster] whipped up his own track with the assistance of some 3D printed parts, and used it to run a competition with a fun twist on the usual theme.
The track starts with a pair of MDF panels, on to which some strips are placed to act as guides for the racers. There’s also a release mechanism built with hinges and a pair of dowels that ensures both racers start the competition at exactly the same time. To give the track a nice transition from the downward slope to the horizontal, a series of curved transition pieces were designed in Fusion 360, 3D printed, and added to the course.
As for the competition, [Mr Coster] decided to eschew the usual focus on outright speed. Instead, students were charged with building the slowest possible car that could still complete the course. Just for the fun of it, though, the kids were then given one day to modify their slowest cars to compete in a more typical fastest-wins event. It gives the students a great lesson in optimizing for different performance parameters.
You might be old-school, though, and want to ruin the fun by taking it all way too seriously. Those competitors may wish to consider some of the advanced equipment we’ve featured before. Alternatively, you could run a no-holds-barred cheater’s version of the contest. Video after the break.
Last day of building/testing before race day tomorrow. Students were tasked with designing the SLOWEST car able to complete the race. Love seeing the excitement & hearing the laughter while the kids worked through the engineering design process! 💛🖤🏎💛🖤#WeareCedarGrove pic.twitter.com/gmNoJ18C7E
— MrCosterTeachesMath (@CosterMath) May 5, 2022
Awesome way to end the week in Engineering 1. Students were given one day to modify their cars from the slowest racers to the fastest. The kids were absolutely tremendous and with their help we ran 70+ races each class period! 💛🖤🏎💛🖤 #WeAreCedarGrove pic.twitter.com/Bw6mc52tl1
— MrCosterTeachesMath (@CosterMath) May 15, 2022
With foreknowledge of the criteria (perform slowest without halting, then fastest with modification but not replacement): you need a system with extreme damping but as minimal friction as possible. A highly geared copper rotor plus a fixed magnet may work well, in combination with some de-greased bearings: near zero static friction (so should never stop on its own with any appreciable slope) but very high gearing gives a lot of braking force from eddy current braking. A fan in place of the copper ring could also work, but gearing would be limited due to the need to start moving the full air volume from 0 RPM (so gearing is limited by target slope). Removing the magnet and replacing with an inert mass removes all braking force leaving a low friction racer.
Just wrap a piece of greased paper around the axle. The viscosity of the grease makes it move like molasses – and when you take the paper off it zips along like normal.
Of course the paper needs to be attached to something on one end – otherwise it’ll just spin along.
Nope. No dampening.
Just a flywheel with the appropriate rear ratio and low friction.
The slanting part is used to crank up the speed of the flywheel, and thus slows it down, while at the horizontal part you want to release the energy stored in the flywheel to drive the car.
I’d be inclined to design a fast car, then add a large sailor and/or trailing streamers for drag. Adjust size of sail/streamers to allow race completion. Remove them and run fast.
*sail
(D’oh!)
A large sailor would certainly aid in slowing the vehicle….
If it’s done on a heat basis, obviously you need to build an MHD “caterpillar” drive each side of the car, which is highly ineffective on air of course at low power, but set in reverse, should fling opposing car forward of you if it’s got any metal in it… then you just flip the direction for fast day :-D
I was thinking of putting molasses on the wheel hubs…
They clocked a molasses tsunami at 35Mph in Boston, which will forever make me doubt the “slow as molasses” saying.
That was heated molasses.
They had boiled the molasses to be able to pump it out of the ship, but they overfilled the container. Carbon dioxide from fermenting molasses and thermal expansion broke the tank. Once the warm molasses hit the 4 C ambient air, it turned into sticky goo and people and horses got stuck like “on fly paper”.
Just enter a block of pitch. By the time the race is over, everyone will be dead, and you won’t need to bother with the second race.
I admire your thought process.
My first thoughts too, but it won’t work for the horizontal part.
But it is debatable whether it would be fair to have to wait for the car stopping at the horizontal part before the race is stopped.
I wonder if they allow some electronics to be used.
If anything you could probably connect the two axels together with a flipped transmission is such a way that the rear and front wheels spin in opposite directions slowin the car down as it moves. One can just flip the transmission for fastest car race. The transmission can be a rubber band.
…in such a way…
…slowing…
Edit button when?
I’m thinking along a clockspring idea.
In the slanted part it winds up a sping to store some energy, and in the horizontal part the mode flips and the energy is released slowly. It could be hours or days to complete the horizontal part.
Putting in a battery and electromotor and just have it run slowly is probably not allowed.
Given that you want a lot of braking action on the slope but almost none on the flat part, I’d have considered some kind of drag-inducing arm whose position was dependent on the pitch of the car.