Glue shaft on back case of CIM motor

Is it legal to glue a shaft on the backend case of a CIM motor, so that we can mount an encoder or pot (like the VEX 276-2156 or 276-2216)?

The case of a CIM motor rotates when we set the angle of our wheel shooter. We need to know the shooter angle, so we planned on using an encoder or potentiometer. Space constrains makes it difficult to use a pg71 type gearmoter with encoder. We are looking at using an old worm drive, Taigene (door motor), but it has no encoder.

What other ways are there to measure our shooter angle?

I don’t know if you are allowed to glue something to the outside of a motor, what do the rules say? I know we are allowed to attach things using other methods, such as Zip ties or hose clamps, and I think we’re allowed to attach identifying labels.

As for other suggestions of how to do it…we have no idea what your shooter thingy looks like, so it’s rather difficult to make suggestions. How about some pictures?

I am not at shop, for a photo. The attached sketch might help.
As you can tell, my CAD skills are lacking.

by “set the angle”, it sounds like you have something with a limited number of degrees of rotation. If this is the case, wiring a potentiometer to an analog I/O port might do the trick. Mount it to one end of the shaft and couple the shaft to the pot’s stem.

Edit: picture came up during drafting the above; this looks like what you have in mind.

I can’t think of any legal issues with gluing it, but I would use something removable. If you do find a legal issue with glue or just want to avoid it, you could use a rubber stopper with a small hole as a “knob” on your potentiometer and mount it so that it pushes against the mini-CIM. If it 's not glued, you may need to recalibrate from time to time.

You might be able to make a simple bracket that goes across the back of the CIM, and has two or more fingers that fit under a hose clamp, around the outer housing of the motor.

My cad skilz are even worse…don’t sweat it, I was able to understand what you mean from your drawing.

If you are looking for an encoder directly attached to the CIM motor I would recommend AndyMark CIMcoder but it is out of stock for another 2 days, I would talk to your team to see if this would work for you, it sounds more like what you should do if you want to be safe on inspection rules instead of using glue to attach an encoder which could move

I don’t see anything in R30 that prohibits gluing a shaft or bracket to the back of a CIM. You are not actually modifying the motor.

We are planning on using am-3314 for wheel speed. What we need is the angle of the CIM motor housing.

Someone on the team asked if we could use the single axis gyro?

My immediate response was NO.

But we can always tilt our shooter back to a home position, then use the gyro to tilt to a shoot position (to minimize drift concerns). We might try that when we have a lot of time to waste.

I love simple, and a simple bracket and a hose clamps seems better than glue. Easier to repair when it breaks.

Hopefully it’ll work!

If you think that is simple, wait till you see our robot…I only hope it works…

We are using a string pot to keep track of the angle of the shooter. We should be able to know the angle of the shooter that way.

Gluing onto the motor just doesn’t feel like a good idea overall. It will work, but during competition it might come loose on a violent fall from a tower for instance.

Keep in mind, that part of the motor gets extremely hot.

On a drive motor, yeah, it’ll get hot. On a shooter motor that has very little load, it should not get hot.

Am I missing something? The back of the CIM motor does not have a shaft so to attach an encoder you would have to modify the case. R30 is very specific about what allowed mods can be made to motors and drilling into the case is not allowed.

They are not trying to determine the rotation of the shaft, but of the enclosure/housing.

string-pot wrap string around case of cim, and mount String-pot nearby?

How are you going to mount the body of the encoder? If the axis of rotation of the encoder is not exactly lined up with the axis of rotation of the object you are measuring, the forces will break the glue joint as the assembly rotates. If exact alignment cannot be guaranteed, it would be best to use some compliant coupling between the encoder shaft and the component being measured.

It might be easier for you to measure the rotation of some other point in your system. If you are using a motor with a gear or sprocket to rotate the assembly, attach your encoder to the shaft of that motor or to the shaft the assembly rotates on.

It sounds like a better idea to mount the encoder to the worm drive shaft itself.