A simple, low friction, 3-wheel car powered by mousetrap (or other stuff) for teaching physics concepts.
Created using FreeCAD. STL files are exported from FreeCAD.
| File | Description | Print instructions |
|---|---|---|
| clamp | Clamps pull rod onto mousetrap | Print, cut apart in the middle for two halves |
| crossmember | middle crossmember for front and rear frame dowels | Print 1x |
| crossmember_front | narrow crossmember for front part of frame | Print 1x |
| crossmember_rear | (optional) narrow crossmember for rear part of frame | Print 1x |
| drive_flange | attaches each side of drive wheel | Print 2x |
| drive_wheel | a wider wheel for stability and traction | Print 1x |
| hub | holds axles/wheels in place | Print 4x |
| pull_end | add to end of pull rod, has loop to tie fishing wire | Print 1x |
| rod_end | slips on to frame ends, with hole for axle | Print 4x with full support |
| trap mount | Mounts the mousetrap offset in the frame to center pull rod | see below |
| trap_mount_A | Mounts the mousetrap on the front of the frame | Print 1x |
| trap_mount_B | Mounts the mousetrap on the rear of the frame | Print 1x |
| wheel | Low friction, low mass rear wheels | Print 2x |
In addition to the following 3d printed parts, you'll need:
- (4) 4.8mm x 30cm (3/16" x 11-7/8") wood dowels
- (1) 1.95mm x 915mm (0.078" x 36") piano wire
- (8) #6 x 1/2" wood screws
- (2) #6 x 1" machine screws
- (2) #6 machine nuts (nylock or use Loctite blue)
- (1) length of fishing wire, >= 6lb test
- (1) standard mousetrap e.g., Victor
- Safety goggles
- Ear plugs if using power tools
- Something to cut steel piano wire - Dremel with cutoff wheel, file to nick and pliers to bend back and forth and break
- Screwdriver(s) for #6 hardware
- Wrench for #6 nuts
- Knife or scissors to cut clamp apart
- Push two rods into front crossmember about halfway.
- Push other end of these two rods into the inner holes of the middle crossmember just enough so their ends are flush with the other side of the crossmember.
- Push two new rods into the outer holes of the middle crossmember just enough so their ends are flush with the other side of the crossmember.
- Push front trap mount onto rear rods
- Insert trap into front trap mount so, when sprung, arm is to the rear.
- Push rear trap mount onto rear rods and push onto rear of trap
- Push rear crossmember onto rods a few inches
- Push the rod ends onto ends of each rod
- Insert wire, which will become rear axle, into rear rod end holes
- Push rear wheels, hub inboard, onto each axle end
- Push hub onto each end of the axle. Adjust for stable, low friction spin
- Trim axle length
- Use #6 wood screws to attach drive flanges to drive wheel
- Hold drive wheel/flanges in between front rod ends
- Push another wire through one rod end, through drive wheel, and through other rod end.
- Push hub onto each end of the axle. Adjust for stable, low friction spin
- Trim axle length
- Cut clamp tab off, separating each half of the clamp
- Use the #6 machine screws and nuts to loosely attach clamp onto the mouse trap arm
- Insert pull rod into clamp
- Insert pull rod end onto end of pull rod
- Tie fishing wire onto pull rod end with a strong knot that won't pull loose
- Attach fishing line to drive flange.
- Rotate drive wheel to spool up fishing line and hold it to keep from rotating
- Place on ground, release drive wheel, and zoom! :)