Hi all. A few years back, I bought a pair of BaneBots RS-775 12V motors in the hope of making a really fast robot. I messed around with them when I first got them, but did not get good results because I could not find a way to securely attach decent wheels. I now finally have time to work on it again, and I believe I have a better plan this time. I would like to use the BaneBots T40 wheels (the 2 7/8" ones) and the matching hubs. The hubs only come in 3, 4, and 6mm bores, and my motors have 5mm shafts... What I am thinking about doing is buying the 4mm ones and drilling them out to 5mm. They mention on their website that the bores are "easily modifiable" but they don't elaborate on how. I would also probably file a flat on the otherwise round motor shafts so that the set screw would have something to grab onto, we'll see if that ends up being necesary. Does this sound like a reasonable plan? The other issue is that the shafts are only 0.3 inches long, so they would just barely be long enough to get the set screw, judging by the dimensional drawings on the website. Do you think they would be likely to pull/be vibrated off of the shafts at higher speeds? Free-run on the motors is 8700 RPM. I don't plan to come anywhere close to this, but it will still be moving fast. Please let me know if this sounds reasonable, or if you have a better idea. I'm not stuck on the BaneBots wheels if someone has a better solution.
Thanks,
Andy
Links for motors, wheels, and hubs:
Motors: http://www.banebots.com/product/M7-RS775-12.html
Wheels: http://www.banebots.com/product/T40P-293BG-HS4.html
Hubs: http://www.banebots.com/product/T40H-SM41.html
RS775 Motors
I suspect this indeed would be a “very” fast robot if you could get it started and then control the speed. Rough speed calculation with stated wheel would be approx 75,000 inch per minute or 70mph or 115khp. Notice that Banebot sells the motor for approx $10US and thegearbox for $45US (big clue).
Your motors are rated at 8700RPM under ideal no-load conditions. What you really need to do is estimate the torque and speed required and then get a drive train that can deliver to your specifications.
You might want to look into getting some 12V motors with attached gear boxes. Some also come equiped with quadrature encoders for feedback. LMR sponsor RobotShop, carries the 12V DFR motor (RB-Dfr-444) for approx $29US.
RS775 Motors
Thanks for the input. I had a similar robot functioning about a year ago. It used these motors and some Pololu 70mm wheels, so the speed was comparable. It was pretty fast, but it was handleable because I was running the motors at a fraction of full speed, and they don’t have enough torque to make it accelerate all that quickly if I remember correctly. For this, I wanted to do the same thing, but find better wheels with more traction. After looking arround, I settled on the Banebots ones because they I could probably make them work without too much trouble. No one seems to make much of anything with a 5mm bore. I have built lots of robots with motors with attached gearboxes (I have used a pair that are similar to the ones you referenced), and I know that these motors were intended to be used with a gearbox: this is just an experiment. I am not trying to build a precision machine here, and it will probably not ever get past being remote controlled. I do not have a set goal in mind, I just want to build the thing and see what happens. My question is really just about the attachment of motor to hub to wheel. Do you personally think that will work the way that I layed it out above with drilling out the hub? I think it sould, I just though I’d get someone else’s opinion before I spent the money.
Wheel Hubs
I did a google search for “12mm hex wheel hub adaptor for 5mm shaft” and found some parts.
Suspect the drilliing results would be a function of the tools and skill. Lathe mould be preferable, hand drill the worst.
Another option might be 3D printing a hub.
My reply was based on my first robot experience that was prior to hearing the terms PWM, PID and H-Bridge. Thought all motors were perfect, batteries supplied infinite power, and speed feedback didn’t apply to me. Good luck and post a video of your robot getting a speeding ticket.
Hubs
Thanks! I’ll probably just try to drill them. Since I’m doing it with a drill press and I’m only widening an existing hole, I think it will work well enough, as long as the wheels don’t fly off when it hits 50 MPH 
I’ve 3D printed hubs in the past (for these motors actually) and it didn’t go all that well. The plastic broke down too quickly. My dog aparently agreed with my assesment because he got one off of the work bench/coffee table and bit it in half… I’ll definitely post a video if/when I get it working.
Thanks for your input, I appreciate it very much.
It worked!
Got the hubs and wheels in the mail today. Drilling them out worked perfectly! I like the wheels, they are sturdy and have a lot of grip. I have them attached to the motors now, so all I have to do now is build the chassis. I’ll probably make something with 1/8th inch plywood and zip-ties, that usually works well…
Wheel hubs
Good to hear of a success. They seem to be eluding me this week. Don’t forget the duct tape and hot glue. Wouldn’t want that speedster to break apart at at 8700RPM.
I’ve 3D printed hubs in the past (for these motors actually) and it didn’t go all that well. The plastic broke down too quickly. My dog aparently agreed with my assesment because he got one off of the work bench/coffee table and bit it in half… I’ll definitely post a video if/when I get it working.