Robot Army

Evidently the attempt to make an easy-to-build robot was pointless; robots are hard and people are stupid. This is the new plan, tentatively named 'devilkitten'. It will feature many components copied from tb2. Surface mount components and custom machined mechanics are now back in play, however.

I'm having this cut today.

It is sort of hard for canal to give me something out of spec since they don't really have specs to begin with. In any case, when they say 0.25" acrylic, they mean "somewhere in the 0.20-0.25 range". I usually just measure the last thing I had made with the micrometers, assume it's the same, and cross my fingers. Maybe if I stuck to one color it would help. In any case it fit after a wee bit of dremeling. This robot is my second "super traditional" robot, i.e. round with differential drive and two casters, the first being devilcat. Therefore, this one being somewhat smaller, it is is going to be called either DevilCatII, DevilCatMini, or DevilKitten, or something equally dorky. Undecided on that. Like TB2 it's mostly cnc lasercut acrylic (about 3x more than TB2) and so far it seems pretty sturdy. The drive shafts -- which have to fit the wheel bolt pattern, the bearing I.D. and the motor shaft shape -- will have to be very carefully machined, though, which officially makes this "hard". It has two 6cm omniwheel casters, which are theoretically better than swivel casters because they are stateless, but I'm a little skeptical. Of course, mounted on such short radius swingarms as they are, swivel casters were basically a non-starter. It's powered by a pair of rc-car battery packs, that is, 2x3 flat C packs, particularly 4.2AH NiMH ones, for ~60Wh total.

Some more notes on the latest:

• 0.22" instead of 0.23". (Or maybe even 0.24?)
• Confused bearing flange and body diameters.
• The motors have M3 screws. I even got to buy M2, M2.5, and M4 screws to figure that out.

I've also decided to resurrect the Logo computer system. I hadn't been planning on having a whole x86+hdd system onboard so this is starting to push the weight limits imposed by the relatively small drive motors. Fortunately the design would be pretty easily modified to accept larger side-by-side motors instead of smallish end-to-end motors, if it comes to that.

These are the main drive shafts. They're turned from 1" round 6061. One end is 1" diameter with a 0.348" radius 5 hole 4-40 bolt circle; this matches the wheels. The middle is turned to exactly 0.375" to fit a ball bearing that is set in the outer rib. The other end is drilled out to 6mm to fit the motors and has a 6-32 cross drill -- clearance hole on one side and tapped on the other -- which matches the hole in the motor shaft. These are definitely the most labor intensive part of the robot so far.

This is what it looks like so far.