Tri-Mode Spring Motor Car - Larger Spring, no more O-Rings and more

thingiverse

Thank you, gzumwalt, for this incredible design! While gzumwalt's idea to hide the spring within its gear is a brilliant concept, it proved too subtle for my somewhat limited motor skills: Trying to get the maximum distance out of the car I damaged three springs. Therefore, I combined the pull-back system with the larger and more open spring from gzumwalt's previous work. As I needed to counteract the spring's force somehow, I built a frame around the front axle. And as I started working on it, I made a few other changes that came to my mind: * I designed new wheels that work well with tires printed using TPU. I found this method easier and more cost-effective (a 50g sample will cost you approximately 3 euros and give you an unlimited supply of tires). * All the disassembling and reassembling for testing purposes wore down the axles and wheels, resulting in reduced friction that sometimes failed to make them stick together. So I built axles with screws at the end and matching screw nuts. I also designed an o-ring version. * My tire design is the result of extensive testing aimed at resolving the problem of the wheels tending to spin, causing the car to spin itself. My conclusion was that the issue lies less in the friction between tires and ground, but rather in the lightweight nature of the car. So I added an additional thread to include some steel nuts (M10). These steel nuts are not mandatory but highly recommended. * edit 19/01/13: I added two alternative tire designs: a tire with some kind of profile - I tested it and found no advantage over the flat design, but maybe it will work for you. And just now, I created a new tire that I cannot print as I ran out of TPU (50gr sample, see above...). The idea is to print it at 0% infill (I know bridging TPU can be challenging, which is why I didn't add fillets at the top), resulting in a very soft tire. Maybe the weight of the car will be enough for the tires to cave in slightly, augmenting their surface and grip. I also uploaded the F360 file, so feel free to play with it. And please let me know if it works.