Son of RatRacer: Mouse Car

After the ini­tial fail­ure described in yesterday’s blog post about the RatRacer, I thought I would scale down the prob­lem a bit. I fig­ured it would be eas­ier to iter­ate through design tweaks when big parts took 20 min­utes to print ver­sus 120 min­utes per part. If I ended up with a sound design for the mouse­trap car, then I could scale it up to the mul­ti­vari­able prob­lem of both design­ing for the rat trap car and work­ing through print issues.

While at the hard­ware store for some­thing unre­lated, I picked up a 4-pack of lit­tle mouse­traps for $2 on impulse.

Fortunately, the OpenSCAD mod­els I designed for the RatRacer were para­me­ter­ized. After tak­ing some ini­tial mea­sure­ments with my trusty calipers, the axle and wheel were triv­ial to scale down to mouse­trap size. They took about a minute each, includ­ing ren­der time. The end caps took a bit more work. Those needed a much larger redesign, as the axles in the RatRacer are small com­pared to the thick­ness of the rat trap, but the axles on the Mouse Car are thicker than the mouse trap. Although the design is a bit dif­fer­ent, the con­cept is exactly the same.


The fin­ished car itself looks pretty snazzy and only took one revi­sion (to increase the axle length slightly).



Like the RatRacer, you pull back the bar, wind the string around the axle, set it on the ground, and let go. Unfortunately, even the less-powerful mouse­trap spring is still too pow­er­ful. It pulls too hard, yanks the string too hard, the wheels spin out, and when they finally gain trac­tion, there’s only enough power to move a foot or two.

A friend had sug­gested adding an exten­sion to the snappy part. That would increase the lin­ear momen­tum for the same angu­lar momen­tum, which if it were rigid would make things worse, but if the exten­sion was a bit more flex­i­ble, that could bet­ter meter out the pull. That may be a future addi­tion.

For now, the Mouse Car in its cur­rent form is avail­able on Thingiverse. Its big brother, the RatRacer is also avail­able.


Posted in: MakerBot Projects

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Brian Enigma

Brian Enigma is a Portlander, manipulator of atoms & bits, minor-league blogger, and all-around great guy. He typically writes about the interesting “maker” projects he's working on, but sometimes veers off into puzzles, software, games, local news, and current events.

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