Designed using Fusion 360, sliced using Cura 2.3.1, and printed in PLA on an Ultimaker 3 Extended at .1mm resolution. Print "Key.stl", "Spring.stl", "Axle Spring.stl", "Axle Gear Idler Large.stl" at 100% infill, the remaining parts at 20% infill. Prior to assembly, test fit and trim, file, sand, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on the colors you chose and your printer settings, more or less trimming, filing and/or sanding may be required. Study "Assembly.stl", carefully noting the locations and positions of the various components as assembly proceeds. It is imperative that "Cross Member.stl" and "Axle Gear Idler Large.stl" fit very tight between "Body Left.stl" and "Body Right.stl" in order to maintain torsional stability. I assembled Dual Mode Windup Car in the following order. 1) Position "Axle Spring.stl" into "Chassis Right.stl", then press "Spring.stl" and "Pawl.stl" onto "Axle Spring.stl". 2) Press one each of "Cross Member.stl" into "Chassis Right.stl" at the front and rear. 3) Press "Gear Floating Pinion Guide Right.stl" into "Chassis Right.stl". 4) Press "Gear Floating Pinion Guide Left.stl" into "Chassis Left.stl". 5) Press "Axle Gear Idler Large.stl" into "Chassis Right.stl". When fully installed, there should be 15.5mm between the inside surface of "Chassis Right.stl" and the shoulder on "Axle Gear Idler Large.stl". 6) Press "Axle Gear Idler Floating.stl" into "Gear Pinion Floating.stl". There should be 4mm of "Axle Gear Idler Floating.stl" extending from both ends of "Gear Pinion Floating.stl". 7) Press "Gear Axle Rear.stl" onto "Axle Rear.stl", aligning "Gear Axle Rear.stl" with the spline on "Axle Rear.stl". 8) Position the rear axle assembly in "Body Right.stl". 9) Position the floating idler assembly in "Body Right.stl. 10) Position "Gear Pawl.stl" onto the axle spring assembly. 11) Position "Gear Idler Large.stl" onto "Axle Gear Idler Large.stl". 12) Position "Spacer Axle Gear Idler Large.stl" onto "Axle Gear Idler Large.stl". 13) Position "Spacer Axle Spring.stl" onto "Axle Spring.stl". 14) Press "Body Left.stl" onto the body right assembly. When complete, the front and rear cross members must be flush with the outside surfaces of the body sides, and there should be 37mm distance between the inside surfaces of "Body Right.stl" and "Body Left.stl". 15) Install the o-rings on all wheels, then install one each of "Wheel Right.stl" and "Wheel Left.stl" onto the rear axle assembly. 16) Press "Axle Front.stl" into the remaining "Wheel Right.stl", then slide the assembly into position and press the remaining "Wheel Left.stl" onto the axle assembly. 17) Attach "Body Top.stl" onto the front and rear "Cross Member.stl". Hope you like it!