KoP ToughBox Mini and CIMs Problem/Solution

[SenorZ]

I've tried searching to see if anyone else is having the same issue (and "solution") as us.
Problem:
we assembled our TB's as per directions, but when powered they made a screeching sound.
Attempts to fix:
we disassembled and put in extra lubrication, reassembled step-by-step from in-box instructions (and from online instructions).
Result:
Gears still got stuck. We didn't power it the second time, just assembled the box and attached motor, then tried a manual turn. Gears were difficult to rotate for about 1/2 turn, then jammed up. We noticed the top land of the pinion were making contact with the bottom land of the next gear... a very tight fit.
Solution?:
After an email to AndyMark and a quick reply promising a replacement of both TB's, a parent noticed that the mounting screw holes on the CIM didn't look perfectly inline with the motor shaft's center. We tried flipping the CIM 180 degrees, bolting it in, assembling the gearbox, and it all spun as it should!!! So the problem is technically solved. Since both of out TB's had this issue we flipped the CIM in the other and it seems to work fine, too.

Has ANYONE EVER had a problem like this? It seems the CIMs were the issue, not the TB's. I'm tempted to pull last year's CIMs off the old robot and test them, but really don't want to disrupt the progress we're making.

[Shu]

We did not get the Toughbox Mini's in the KOP because we opted out of the driveline for the voucher. We ordered the TB Mini's separately and we are having the same issue. The output shaft will turn in one direction but will bind when turned the opposite direction. There seems to be some sort of interference between the CIM output gear and the large gear it interfaces with. I pulled some spare gears from other Toughboxes and exchanged them with the new ones it did not make any difference. I am using both the CIMs from the KOP and 2 additional CIMs I ordered from VEX. I don't seem to have a hole alignment issue with the CIMs but will try some older CIMs tomorrow.

[G Fawkes]

Originally Posted by Shu

We did not get the Toughbox Mini's in the KOP because we opted out of the driveline for the voucher. We ordered the TB Mini's separately and we are having the same issue. The output shaft will turn in one direction but will bind when turned the opposite direction. There seems to be some sort of interference between the CIM output gear and the large gear it interfaces with. I pulled some spare gears from other Toughboxes and exchanged them with the new ones it did not make any difference. I am using both the CIMs from the KOP and 2 additional CIMs I ordered from VEX. I don't seem to have a hole alignment issue with the CIMs but will try some older CIMs tomorrow.

We had the same symptoms as this. In our case the students used a R6ZZ in place of the FR6ZZ bearing so the bearing in the metal face plate fell out and caused the gears to lock when turned in the one direction. Could also be caused by not installing the FR6ZZ bearing with flange on the inside. Instructions could be a little clearer on this for the students.

Should be easy to check, just look at the metal output plate and there should be 2 bearings visible.

[Shu]

I was standing next to the students as they were assembling the boxes and watching every step to make sure they were doing it right. I have previous experience with the standard toughbox and never ran into a problem like this. We took them apart several times to make sure everything was exactly as in the instructions. The only modification we made was to use the hex output shaft and hex bearing in place of the standard configuration.

[WileyB-J]

Originally Posted by Shu

I was standing next to the students as they were assembling the boxes and watching every step to make sure they were doing it right. I have previous experience with the standard toughbox and never ran into a problem like this. We took them apart several times to make sure everything was exactly as in the instructions. The only modification we made was to use the hex output shaft and hex bearing in place of the standard configuration.

Can you post pictures?

My guess:

• The cim motor isn't fully seated. (making the pinion mounted on a slight angle)
• Or that a spur gear is mounted backwards. (that the non-lipped side isn't facing a bearing race binding the gear to the transmission case)

[pfreivald]

We're using Toughbox minis with long hex output shafts and have had no problem on six gearboxes thus far.

[Shu]

Originally Posted by pfreivald

We're using Toughbox minis with long hex output shafts and have had no problem on six gearboxes thus far.

What CIMs are you using? Are you using any from VEX? I am not sure if that is the issue but all the ones we are using are from the KOP or ordered from VEX.

[pfreivald]

Originally Posted by Shu

What CIMs are you using? Are you using any from VEX? I am not sure if that is the issue but all the ones we are using are from the KOP or ordered from VEX.

KOP and older KOP.

[Tom Line]

Turning it around in the gearbox suggests that the cim motor fasteners may be drilled / tapped off center. We've used minitoughboxes each of the last several years and not had that problem.

It was noted a couple days ago that one team saw differences between the Vexpro hex bearings and the AndyMark ones.

For those teams effected, are you using Andymark Hex shaft? AndyMark Bearings? Vexpro Cims? Finding a common factor might help.

[Shu]

I seem to recall that the end of the shaft on the CIM was not centered in the hole of the Toughbox mount plate. Could this be another sign that the CIM mounting holes are off either on the CIM or Toughbox?

[thefro526]

One thing to keep in mind when assembling tough-boxes is that the hole for the CIM bore is not designed to be a pilot, as the tough-boxes are designed to use a 14T CIM Pinion. Because of this, it's possible to have a small amount of misalignment between the CIM output shaft and the true 'center' of the CIM mounting hole. I remember encountering an issue similar to this in either 2009 or 2010 and we found that it was best to not fully tighten down the CIM mounting screws until the gearbox had been checked to ensure proper rotation of everything.

[Shu]

Turning the CIMs 180 degrees made a huge difference. You could literally see space between the CIM output gear and large cluster gear where before they were jammed together tight. I could not see the motor mounting holes out of alignment with the shaft but what else could it be? One of the gearboxes is running quiet and smooth. There is still a little noise coming from the other box and you can see the output shaft and bearing wobble a little. I don't know if this is caused by something internal or runout in the VEX hex bearing but will try to find out tomorrow. It seems both AndyMark and VEX are both having problems with the .5" hex bearings. Neither one has them in stock right now.

[SenorZ]

Originally Posted by Shu

Turning the CIMs 180 degrees made a huge difference. You could literally see space between the CIM output gear and large cluster gear where before they were jammed together tight.

Yeah, odd, but thats what worked for us. We also made sure that we screwed the CIM down with it pulled as far to the outside of the gearbox as possible. Its the different between having gears grinding and having ~1mm of clearance.

[sanddrag]

A caliper could solve this mystery.

[dominik.daners]

We had an issue with the 2013 KoP gearbox. One of the gearboxes had a gear contacting the output Hex shaft (inside the gearbox). We fixed it by filing the hex shaft down and had no further problems.

I attached an image (I think)

Could it be that the gearboxes are not always made to spec.?

Dominik Daners

Sydney, Australia