Wind Up Dragster

I set out to improve a previous design I had "Wind Up Toy Car" and ended up with a completely different design. I wanted the toy to be something that kids will actually play with and be durable enough to hold up to some abuse. I also didn't want to use any glue, so I ended up using a self tapping machine screw (10-24 x 5/8 FH) so parts could be replaced. I made 4 of them for some gifts for a family friend and they have 4 boys who would put this design to the test! Considering all of the windup toys on Thingiverse, I don't think there is anything with this kind of performance (see the video)

I kept changing the design trying to get more performance... more winds and torque from the main spring. It was getting ridiculous. I was up to 3 turns with marginal torque on a PLA spring that weighed 200 grams! I ended up going with a metal spring from Amazon ($1.50 each sold in a 5 pack for 6.99) and that made all the difference. This light spring offers substantial torque and 4 full tur