CIM Motor Direct Drive or Supporting Axle

[asid61]

Originally Posted by Monochron

This is kind of unrelated to the other conversations here, but I thought I would offer my own suggestion against using this type of set screw hub. I have had to deal with getting these to fit just right and keeping the setscrew from backing out and it is a pain. Especially with your CIM at 5000+ RPM I think this is going to be a headache for you.

I would recommend using this coupler on your CIM shaft to make it so you can use any wheel with a Hex bore. Then you could use tons of different wheels as long as they have that Hex hole in the middle. You would also be able to use this hub to connect to wheels without the hex hole in the midle.

It's totally up to you (and I know you already sunk money into that hub), but I just hate trying to use set screw hubs on a keyed shaft.

We did set screws on our 2012 shooter robot, and the way the set screws go onto the keyed area makes it so that the wheels rotate with the shaft. We also have a 2-sprocket reduction before the output wheels, which are attache with set screws. I think it really depends on how hard you go on it, and what tip the set screw has.

[jwfoss]

You might want to consider going with something like the SpinBox from AndyMark and doing a single spinning axle/wheel with a hood.

[Monochron]

Originally Posted by asid61

We did set screws on our 2012 shooter robot, and the way the set screws go onto the keyed area makes it so that the wheels rotate with the shaft. We also have a 2-sprocket reduction before the output wheels, which are attache with set screws. I think it really depends on how hard you go on it, and what tip the set screw has.

Yeah, assuming the set screw is the right size to fit snugly in the keyway, it isn't quite as bad. In my experience the set screw was slightly too small and the walls of the keyway beat it up a bit.
Either way, even red locktite couldn't keep that thing from slowly backing out after an hour or two, and I think his application would require something long lasting. I'm thinking that an ungeared CIM like he is planning would make this problem much worse, but that's purely anecdotal.

[asid61]

Originally Posted by Monochron

Yeah, assuming the set screw is the right size to fit snugly in the keyway, it isn't quite as bad. In my experience the set screw was slightly too small and the walls of the keyway beat it up a bit.
Either way, even red locktite couldn't keep that thing from slowly backing out after an hour or two, and I think his application would require something long lasting. I'm thinking that an ungeared CIM like he is planning would make this problem much worse, but that's purely anecdotal.

Ours is slightly too large and ends up sitting on top of the keyway, actually. That combined with a soft steel shaft might account for the good seating, not to mention the accumulated grime holding it in.

[Joe Derrick]

Tennis Ball shooter Project from our AP physics Class

[philso]

Originally Posted by akoscielski3

As a rule: never ever side load a motor. So you should not directly drive the wheel from the CIM Motor. You should add a set of gears/belts and pulleys/sprocket and chain to each wheel

Why to not side load the motor? You will likely destroy it. The bearings will not last as long, break and then your motor will burn out. You could also bend the shaft of it or something else can happen

In 2013, some of our team members made prototype frisbee shooter with the wheel driven directly off the motor shaft. After several shots where the compression (= side load) was set too high, the motor bearing at the back end failed.