When they are placed flat on the bed at intended prtint orientation, there are no vertical features on the parts, allowing them to be printed at any layer height you wish. Multiples of 0.04 for best results, 0.2mm would be ideal though i printed some of the parts with .28 layer height while prototyping and they work great too.
Only the small geared part requires (minimal) supports. There are files that have all parts in single file, already laid out and ready to be printed(if it fits your build plate) BUT I recommend printing the small gears and the left side plate seperately from other parts, i found the long shafts turn up stronger this way. (I guess layers adhere better this way. If you print them together with all the other parts they have a lot of time to cooldown and cool layers do not stick to each other as much.) Also you can have different infill/layer height values if you slice and print seperately.
See here for the print orientations: https://www.tinkercad.com/things/jDV8QM1M71p-wind-up-running-buggy-print-layout
There is also a photo above where all parts are laid out in their printing orientations. When printed in orientations shown in the photo, only the small gears require minimal supports.
- You need print files with x2 in their name twice. Note that legs for left and right side are mirrored and different files, so do not print 4 copies of one leg, print 2 copies of each.
- There are 2 different spring files, one is stiffer but has less windings than the other. If you find you do not have enough torque you may want to try the spring-hard file. If one skips and the other does not have enough torque(so you need something in the middle), copy the design in tinkercad and modify the thicknes and winding count of the spring. It's a custom generators so you can adjust these just by using the sliders. The current values on the TinkerCad design is for the normal spring. Also take note of the remarks about tolerances and gear distances below if you have locking/skipping issues.
- Print the left side plate,small gears and the winup arm at 100% infill. Rest is up to you but i do not recommend going below 40%. Also cubic infill does not really make sense for such flat parts, so either use Grid,Lines or ZigZag infill pattern.
Note about tolerances: I printed this on an Ender-3 Pro with Klipper firmware, i don't have the best setup when it comes to tolerances and size accuracy so the spacing on the tinkercad project may be too much or too little if you have a better printer. Either print parts with 101% - 99% scale or modify the spaces on TinkerCad. If your gears skip a lot try moving small gears closer to larger gears about .1-.2 mm(do not forget the holes on side plates!)
Assembly: Video here. Take note of the orientation of the legs. You should assamble it as shown in the TinkerCad project. Each leg is perpendicular to the one behind it and the other leg on the same side. So the front-left&rear-right and front-right&rear-left are parallel, but perpendicular to others. (I hope this makes sense, when in doubt check the video). Sorry for not-the-best video, recording while assambling is harder than it looks.
Note: You SHOULD NOT print exploded view file and assembled file, these are for reference only.
Note: Do note that the spring's orientation on the TinkerCad project is wrong(for easier design purposes), the spring arm should come from below not from above the shaft. Does not affect how you print it though, since it's flat you can just flip it.
Scaling the model up should not be a problem, just scale all parts and print. But i do not recommend going any smaller than it already is.