SMARS Modified Slave Wheel - 3d Printed Screws and Nuts for 28BYJ-48 Stepper Motor SMARS Variant

thingiverse

Goal is to reduce costs of the SMARS robot. The 28BYJ-48 SMARS stepper variant (https://www.thingiverse.com/thing:2778904) is very affordable to build, but requires screws which are expensive. The modified slave screwed SMARS wheel here https://www.thingiverse.com/thing:2732013) uses an M4 screw but the stepper variant chassis has an M3 hole. ****Please note these screws are not for the original SMARS screw slave wheel but the modified one linked above.**** The modified version offers more hub surface area and is thus more stable (less runout). These screws have a perfectly sized hub that minimizes friction (saves battery power also) with a skinnier threaded part. The wider unthreaded section allows reasonably tight screwing of the shaft without compressing the wheel against the body at all. Nuts are longer than usual (10mm) so that they stick out of the nut hole in the chassis. They fit as loose as possible for easy removal. With a an accurate printer, these fit perfectly. The 28BYJ-48 stepper motors are slow, but very cheap and come with their own controllers, which eliminates the need to purchase a motor controller for the SMARS bot entirely. 3d printing the screws will make this robot more accessible for STEM programs on a budget. The wheel spins freely like a pinewood derby car wheel and thus is unlikely to unscrew itself in reverse. https://www.youtube.com/watch?v=YaUtcA_j-W4 I used https://www.thingiverse.com/thing:193647 parametric nut and bolt set to create this bolts. If your print does not fit, try starting with my settings and adjusting them yourself in openscad to get a better fit (my openscad remix is in files section).