Ugly CIM sound in WCP 3-cim gearbox
 

So, our WCP 3-cim SS gearboxes finally came in recently, and yesterday we were doing our first drive code test on our finally assembled AM14U with 3-cim gearboxes.

Unfortunately, some issues emerged and in the course of ruling out various problems we decided to check each CIM individually, running straight from a battery. A couple of them, as it happens, are making a really ugly pulsating sound when they run. It's unnerving, and we're not sure what the cause could be. Additionally, we notice a not-too-pleasant smell upon running any of the motors (before anyone asks, our gearboxes are, indeed, greased) - though this is my first experience with open gearboxes, so a hot-metal smell might be normal, I'm not sure. Also, when running only a single motor, the peak speed reached is far under (about half, by my count) the ostensible free speed of the motor, though this might just be from the required torque to turn the other two CIMs on the gearbox.

The only thing that I know could be wrong with the gearboxes is that they did not come with wave washers, which were mentioned in the assembly instructions, but I have a hard time seeing that as the problem as I've never needed a wave washer in a gearbox before and there's not much play without it. For reference, the gearboxes are standard, non-WCD.

The CIMs are new, and the only damage I could imagine having been done to them is if our gearbox mounting screws went too far into the holes in the motor (we had to cut our own to size, since the ones that shipped with the gearbox were not long enough to pass through the extra 1/4'' of material we needed to mount the gearboxes to the AM14U, but I find this doubtful as I'm pretty sure they're going less than 1/2'' deep.

Any ideas as to what could be causing the problem?

As a side-note, I really don't like the fundamentally hard-to-service design of the kitbot this year - swapping out a motor or a belt is a major endeavor.

Re: Ugly CIM sound in WCP 3-cim gearbox
 

Dumb question - are you running the top CIM in reverse relative to the lower 2? The gear in between the top-CIM pinion and the first stage output gear requires this.

Re: Ugly CIM sound in WCP 3-cim gearbox
 

Eli,
Is it the retaining Rings or the Wave Washers? My suspicion, is that you might have pushed the pinions onto the shaft too far and they are rubbing the end of the CIM motor. This is set by the placement of the retaining washers. Also be sure to follow the instructions on mounting the CIM motors, the note on Page 2 is important. Misalignment here could also cause the effect you describe.

Re: Ugly CIM sound in WCP 3-cim gearbox
 

The next step is to remove a CIM from the gearbox and run it like that. If you get the nasty noise, then it's a bad motor. The smell is likely what ever is in the motor heating up. Heating up grease makes quite a smell.


A few more questions
Can you turn the gearbox by hand by spinning the CIM pinion gears?
Are your CIM motors mounted in the right set of mounting holes for the pinions that you're using?

What it sounds like to me is that your center to center some gears are off. This causes a pulsing noise, excess heat, stinky gearboxes, and slow motors.

Re: Ugly CIM sound in WCP 3-cim gearbox
 

Eli,

A picture (front view) or a video would def help here. Questions for you/re-confirm:

-3 CIM Single Speed Standard?
-Pinion Count?
-No Wave Washers were used? The large 1.125" ID ones?
-New CIMs?

Thanks,

Re: Ugly CIM sound in WCP 3-cim gearbox
 

We are currently only running one motor on each side at a time to prevent any accidents from running motors against each other. However, this is the single-speed, not the dual-speed, so all three CIMS are meshing to the same gear.

It's the wave washers that were missing. The retaining rings/pinions are not in contact with the CIM bodies (or at least, they weren't when we put the gearbox together, so unless someone whacked them I imagine they still aren't). Both CIMs are in the inboard position with 12-tooth pinions.

Yes, that was our planned next step, though we're not looking forward to it because removing anything from this setup is a royal pain (you have to take off the entire side plate of the AM14U to gain satisfactory access to anything).

As mentioned, the CIMs are mounted in the inboard position with 12-tooth pinions. I doubt I'm strong enough to turn the pinions by hand with the whole drive hooked up to it, but if I unscrewed the motor and rotated the motor it certainly would turn (the gearbox seemed fine when we assembled it).

I'll send a video/picture as soon as I'm able, which will be tomorrow. To review, yes, it is a 3-CIM single speed standard, pinions are 12t and CIMs in the inboard position, no wave washers were used, and the CIMs are new. FWIW, our setup doesn't feel like there's any more friction when turning the wheels than the other setup I'm working with (using the WC-style gearboxes) over at 449, and certainly no more than other drives I've done in the past.

Thanks.

Re: Ugly CIM sound in WCP 3-cim gearbox
 

Odd,

Seems like everything is g2g. Checking through the model, you don't *need* the wave washer/it won't mess up the CIM.

Please send video/pic when you can.

Re: Ugly CIM sound in WCP 3-cim gearbox
 

Well, upon further troubleshooting, it appears the problem is with the electronics, which is bizarre. I have no idea what exactly could be causing this, so any advice would be appreciated.

In the course of running each motor independently off of the battery, we found that the problem (ugly pulsating sound, bad smell) only occurred when a motor on the same gearbox as the motor being driven was plugged in to a certain victor. During this test, there was no battery plugged into the main electronics system. The other victors caused no such problem.

I hope that testing a motor separately while other motors on the same gearbox are plugged into motor controllers is not a serious hazard for damaging motor controllers - I know that the other motors essentially function as generators when you do it, but I never figured this could cause electronics problems as seeing various lights come on while wheeling robots around is something that I see all the time.

So, any insight into what type of problem could cause this and/or confirmation that our testing procedure isn't horribly wrong would be welcome.

Re: Ugly CIM sound in WCP 3-cim gearbox
 

It sounds like the suspect motor controller is in brake mode. Check the jumper and if it is in the brake position swap it to coast and test again the problem should go away.

Re: Ugly CIM sound in WCP 3-cim gearbox
 

I thought only jaguars have the brake/coast jumpers. I'll check this, thanks.

Re: Ugly CIM sound in WCP 3-cim gearbox
 

Eli,
When testing multi motor drives while checking one motor at a time, it is advised that you disconnect the unused motors and insulate the wire. Driven motors become generators when not driven by a controller. This generated current can back feed the controllers and be affected by the electronics if driven in the locked rotor mode or in brake. Removing the wiring eliminates all of these issues.