Runaway Escapement Mechanism With Optional Windup Car

Designed as a science fair project for the grandkids, this model can be used as just a 3D printed runaway escapement spring motor demonstrator, or with the additional drive components, a 3D printed runaway escapement spring motor car. The grandkids have a 3D printer and as such will 3D print their own parts, although I may have to assist just a little with assembly, but hey, it's fun to have some grandkid time!

As usual I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to ask as I do make plenty of mistakes.

Designed using Autodesk Fusion 360, sliced using Ultimaker Cura 4.12.1, and 3D printed in PLA on Ultimaker S5s.

Thick cyanoacrylate glue.

I acquired the following parts:

1. Four "R-20 O-Rings (26.5mm ID, 3.5mm section)".

I 3D printed the following parts at .15mm layer height, 20% infill and no supports:

1. One "Axle Pallet.stl."
2. Four "Bolt (M8 by 8mm).stl."
3. One "Escapement Compound (1m 8t).stl."
4. One "Frame Front.stl."
5. One "Frame Rear.stl."
6. Two "Gear Compound (1m 40t, 1m 8t).stl."
7. One "Gear Pawl (1m 40t).stl."
8. One "Knob And Axle.stl."
9. One "Pallet.stl."
10. One "Pawl.stl."
11. One "PTO Axle.stl."
12. One "PTO Front.stl."
13. One "PTO Gear (1m 8t).stl."
14. One "PTO Rear.stl."
15. One "Spring.stl."
16. One "Wheel Mount Front Axle.stl."
17. One "Wheel Mount Front Left.stl."
18. One "Wheel Mount Front Right.stl."
19. Four "Wheel.stl."

This mechanism is a high precision print and assembly using at times very small precision 3D printed parts in confined spaces with highly precise alignment. Prior to assembly, I test fitted and trimmed, filed, drilled, sanded, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on your slicer, printer, printer settings and the colors you chose, more or less trimming, filing, drilling and/or sanding may be required to successfully recreate this model. I carefully filed all edges that contacted the build plate to make absolutely certain that all build plate "ooze" is removed and that all edges are smooth using small jewelers files and plenty of patience.

This mechanism also uses threaded assembly, so I used a tap and die set (M8 by 1.25) as required for thread cleaning.

To assemble the rear frame, I performed the following steps:

1. Attached "Pallet.stl" to "Frame Rear.stl" using "Axle Pallet.stl" making certain the palette rotated with ease.
2. Slid "Escapement Compound (1m 8t).stl" over the escapement axle.
3. Positioned one "Gear Compound (1m 40t, 1m 8t).stl" over the knob axle guide hole.
4. Slid one "Gear Compound (1m 40t, 1m 8t).stl" over the escapement axle.

To assemble the front frame, I performed the following steps:

1. Slid "Knob And Axle.stl" into "Frame Front.stl".
2. Pressed "Spring.stl" onto the knob and axle.
3. Pressed "Pawl.stl" onto the knob and axle.
4. Slid "Gear Pawl (1m 40t).stl" onto the knob and axle.

To join the frames, I carefully aligned the two assemblies such that the knob axle extended through the previously positioned compound gear and into the rear frame knob axle guide hole, and that the rear frame escapement axle slid through the spring mount hole and into the front frame escapement axle hole. Once completely joined, I secured the two frames together using two "Bolt (M8 by 8mm).stl".

At this point, the runaway escapement mechanism is complete. I tested the mechanism by winding the knob then letting the mechanism run.

To convert the runaway escapement mechanism into a car, I performed the following steps:

1. Removed the front frame bolt and attached "PTO Front.stl" to the front frame, then reinstalled the bolt.
2. Placed "PTO Rear.stl" over the rear frame hole then secured in place with one "Bolt (M8 by 8mm).stl".
3. Pressed one "Wheel.stl" onto "PTO Axle.stl".
4. Partially slid the wheel and axle assembly into the rear PTO axle hole, slid "PTO Gear (1m 8t).stl" onto the axle, then slid the free end of the axle into the remaining PTO axle hole.
5. Aligned the PTO gear with the rear compound gear then secured in place with a small drop of glue.
6. Pressed one "Wheel.stl" onto the free end of the axle such that the wheels rotated with ease.
7. Removed the remaining front frame bolt and attached "Wheel Mount Front.stl" to the front frame, then reinstalled the bolt.
8. Place "Wheel Mount Rear.stl" over the rear frame hole then secured in place with one "Bolt (M8 by 8mm).stl".
9. Pressed one "Wheel.stl" onto "Wheel Mount Front Axle.stl" then slid the axle into the wheel mount holes.
10. Pressed one "Wheel.stl" onto the free end of the axle such that the axle rotated with ease.
11. Slipped one o-ring onto each of the wheels.

And that is how I 3D printed and assembled my prototype of "Runaway Escape Mechanism With Optional Windup Car".

I hope you and the science fair judges enjoy it!