I've FINALLY started building my robot that I planned years ago! Except right now the only thing the same as the one I planned is the shape.
Anyway, I'm building a 4 wheeled omniwheeled robot, and I just finished assembling the first motor/gears combination. I think it looks AWESOME, and I just wanted to share. I pretty much just built it as I went. I didn't plan anything and it got me into trouble a couple of times. So if you look REALLY closely you'll see most of my holes for the screws are ovals, to give them some play so the part would end up in the right place.
Anyway, I'm just going to disassemble it and make 4 more sets just like it. Oh it works too, and that little tiny motor is sweet. At 12V it's spinning REALLY fast. I forget what the final gear ratio is, but it's manageable. At 5-6 volts I think it'll be pretty slow, but that's where I'm going to start. Then I might power the motors by 12V and have to use a lot lower duty cycle for the PWM. I think at 12V the wheels will have a max RPM of 2720.
(Off the top of my head the motor spins at 13,600RPM with no load, and the gears are 12, 20, 30, and 40 teeth, so
13600x12/30 = 5400 RPM.
Then the next two gears spin on the same axis and are joined, so 5400x20/40 = 2720RPM final, at 6V it's a little less than half of that)
So assuming 2 inch wheels,
Pi*d = 3.14 * 2 = 6.28 * 1350ish RPM = 8482 in/min / 60 seconds = 141 inches/second / 12 inches = 11ish feet per second at 6V.
I think I did that right. I guess that's not that slow, but the motor will most likely be spinning slower with load. And since it's omniwheeled, it'll probably never travel on the same axis as the wheels are pointed, (unless I program it that way), so I'll need more speed to get a decent net velocity.
Anyway, here's what I came to post about. I know it's not perfect, but it works, and I'm happy with it. The next 3 should be a ton better.
Oh and I wish I could weld, cause it took 12 threaded holes to put this together. Do you know how annoying/hard it is to thread holes in steel? The bulk of the body is built from aluminum, but I built the brackets from steel, as I was afraid aluminum wouldn't be tough enough. (Yes I know different metals don't play nice together, but I doubt this thing will be together long enough to start corroding.) I threaded the steel cause for some reason I remember reading somewhere that aluminum strips easily? And it looks much cooler to have the bolt heads on the outside of the robot than to have a bunch of bolts sticking out from the inside. AND it makes it REALLY easy to take apart.