Method to direct drive HEX Shaft

[Chris Fultz]

use caution if directly driving a load from the CIM output shaft. The "bearing" in the end is a bushing and it cannot handle any offset.

[Kevin Sevcik]

Following on Chris's caveat, if you DO want to drive directly off a CIM 1:1, you can do it though a VEX Versa-Planetary, though it'll be a longer setup. You take out all the planetary stages, and the motor mount block bolts directly to the output block. To mount the CIM, you can either buy a CIM adapter from VEX, or cut down the CIM shaft an alarming amount.

[R.C.]

http://www.wcproducts.net/217-3255

Another item that can allow you to direct drive off a CIM.

[RoboChair]

drill a 5/16 inch hole in the end of the shaft on a lathe and press it in with a little superglue.

[philso]

Originally Posted by Chris Fultz

use caution if directly driving a load from the CIM output shaft. The "bearing" in the end is a bushing and it cannot handle any offset.

^ +1

These motors use sleeve bearings at both ends of the shaft. Excessive side forces on the shaft can and will damage one or the other. One of our team mates broke the bearings at the back end of a CIM that was direct driving a Frisbee shooter wheel when he used too much compression. It only took about 3 shots to damage it.

Kevin's suggestion to use the 1:1 Versa Planetary is the best of the solutions presented because the shaft in the VP has it's own bearings and they absorb the side forces and don't transmit them on to motor shaft.

[Chris is me]

If you have the hex shaft supported in some other way, a quick and dirty solution for protoyping purposes is to drill an 8mm hole in the end of the hex shaft and drop a set screw in it. For competition use, set screws should generally be avoided since they are not great at transmitting torque and tend to come loose exactly when you don't want them to.

The WCP or AndyMark hex adapters combined with Vex's hex coupler is another good way to do it, but again, a well supported hex shaft is essential to any solution.

[philso]

Originally Posted by Chris is me

If you have the hex shaft supported in some other way, a quick and dirty solution for protoyping purposes is to drill an 8mm hole in the end of the hex shaft and drop a set screw in it. For competition use, set screws should generally be avoided since they are not great at transmitting torque and tend to come loose exactly when you don't want them to.

The WCP or AndyMark hex adapters combined with Vex's hex coupler is another good way to do it, but again, a well supported hex shaft is essential to any solution.

Never had a set screw come loose in competition and mess us up. Never!!!
Have never used sets screws again for "high power" applications.

For prototyping, you can use a hand drill with a 1/2" chuck to drive the hex shaft. Much less to build.

[Chris is me]

Originally Posted by philso

Never had a set screw come loose in competition and mess us up. Never!!!
Have never used sets screws again for "high power" applications.

For prototyping, you can use a hand drill with a 1/2" chuck to drive the hex shaft. Much less to build.

Most hand drills can't come close to matching the free speed of a CIM though (roughly 5400 rpm). This is a poor choice for prototyping a shooter.

[Shu]

Originally Posted by Chris is me

Most hand drills can't come close to matching the free speed of a CIM though (roughly 5400 rpm). This is a poor choice for prototyping a shooter.

We are using a hand drill capable of 3000 rpm with an adapter and 1/2" hex socket that is working just fine for initial prototyping of a shooter.

[amesmich]

I am aware of the lateral loads on CIMS. We are not trying to direct drive something with a hex opening we are trying to drive the shaft which is supported by its own bearings. The hex shaft to 8mm adapter really would not do it alone since we would need a coupler. I think we will 3d print a hub into our design and then bolt the 8mm CIM hub to that so its compact strong and clean. Thanks for the feedback.

[Knufire]

If you drill a 8mm hole in the shaft and make a cut lengthwise about half an inch into the shaft, you can put a collar clamp on the end which will cause the shaft to clamp the CIM shaft.

You can see a similar concept here: http://www.andymark.com/product-p/am-3185.htm