mousecar-side

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.

endcapaxlewheel

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

mousecar-side

mousecar-topmousecar-angle

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.

ratracer-mousecar

Posted in: MakerBot Projects

2 thoughts on “Son of RatRacer: Mouse Car

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>