Tabletop Tri-Mode Spring Motor Rolling Chassis adds yet another mode to my previous spring motor designs, "pull back windup".

While this small vehicle will not outperform my previous designs for distance, it does add a third mode "pull back windup" to the power and true coast modes of my previous floating pinion designs (here: https://www.myminifactory.com/object/dual-mode-windup-car-27061 and here: https://www.myminifactory.com/object/dual-mode-spring-motor-rolling-chassis-26862). The previous designs utilized a single floating pinion ("Drive Pinion") that allowed the vehicle to truly coast by disengaging the rear axle from the spring motor, but depended on a knob or key to wind the spring.  This design adds a second floating pinion ("Wind Pinion") that provides the mechanism for winding the spring by rapidly rolling the vehicle in reverse, thus no knob or key are required.

Video of prototype is here:

You will need to purchase 12 "AS 568" size 221 (1 7/16 O.D., 1 11/16 I.D., 1/8" diameter) o-rings for the tires.

I probably forgot a file or two or something, so if you have any questions, please feel free to ask.

Designed using Fusion 360, sliced using Cura 2.3.1, and printed in PLA on an Ultimaker 3 Extended.

Printing and Assembly.

Sliced using Cura 2.3.1 and printed on both an Ultimaker 2+ Extended and an Ultimaker 3 Extended at .1mm resolution. The "Spring.stl", "Gear Spring.stl" and all axles were printed with 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.

I assembled Table Top Tri-Mode Spring Motor Rolling Chassis as follows:

1) Press both "Gear Axle Rear.stl" onto "Axle Rear.stl".

2) Assemble "Spring.stl", "Gear Spring.stl" and "Cap Gear Spring.stl" onto "Axle Spring.stl".

3) Press "Axle Gear Idler Small.stl" into "Gear Idler Small.stl" for both gear idler small assemblies.

4) Press "Axle Gear Idler Large.stl" into "Chassis Right.stl".

5) Press the axle spring assembly into "Chassis Right.stl".

6) Position one of the gear idler small assemblies into "Chassis Right.stl", then press "Chassis Center.stl" into "Chassis Right.stl". Note the gear idler small assembly must freely spin and slide in the guide slot.  This is the "Drive Pinion".

7) Position one "Gear Idler Large.stl" onto "Axle Gear Idler Large.stl".

8) Position "Spacer Axle Gear Idler Large.stl" onto "Axle Gear Idler Large.stl".

9) Position the remaining "Gear Idler Large.stl" onto "Axle Gear Idler Large.stl".

10) Position the remaining gear idler small assembly into "Chassis Center.stl".  This is the "Wind Pinion".

11) Position the rear axle assembly into the chassis right assembly.

12) Press "Chassis Left.stl" onto "Chassis Right.stl". Note that all gears must move freely.

13) Press "Axle Front.stl" into one "Wheel Front.stl". Slide the assembly into the chassis assembly, then press the remaining "Wheel Front.stl" onto the remaining end of "Axle Front.stl".

14) Press both "Wheel Rear.stl" onto each end of the rear axle assembly.

15) At this point, the chassis should easily roll forward when pushed forward. When the chassis is rapidly moved in reverse, the winding floating pinion (the pinion adjacent to "Chassis Right.stl") should engage and cause a winding of the spring.

I do not recommend exceeding a 30" total rollback distance in order to avoid spring separation.

Hope you like it!