Gearbox not turning properly

[Walter Deitzler]

Recently, after taking the gearbox apart to diagnose a different issue (which turned out to be crossed PWMs) we began having a problem in out gearbox (Toughhbox) where, whenever we try to run it, it makes a horribly loud sound and turns slower than it should.

We do not know the problem is in the motor or the gearbox, but we have been unsuccessful in diagnosing this issue. We have taken apart the gearbox and all the gears seen to be meshing fine, we just cannot get it to work right once reassembled.

Edit:

Other things to note: The motors turn fine when not geared to the final gear (the 14 tooth to 50 tooth.) and are turned by power from the battery. They will not turn by hand. The final gear also turns fine.

[wilful]

-Any chance we could see some pictures?
-Did you remember to reapply grease when putting it together?
-Also if you think the problem is in the motors, try running them without the gearbox.

[R.C.]

Any chance you can put up front views of the gearbox without the front plate on?

Also did you put the nubs in the correct direction on the gears? They should be facing the bearing.

Is there any powder in the gearbox?

-RC

[Walter Deitzler]

I will get front views by later tonight if we cannot get it working.

The nubs were wrong and we are fixing that now. Why does that make a difference though?

There is no powder in the gearbox.

Could the clear plate that the CIMs mount to be machined wrong, or we are putting the motors into it wrong? The CIMs coming out the back are at a slight angle, unlike, our working gearbox, which has the CIMs coming out straight.

[R.C.]

Originally Posted by LedLover96

I will get front views by later tonight if we cannot get it working.

The nubs were wrong and we are fixing that now. Why does that make a difference though?

If you take a look:

http://puu.sh/4R9P2.jpg
http://puu.sh/4R9Qn.jpg

Basically on the bearing there is an inner race and an outer race. The outer race doesn't move but the inner race does. The nubs on all gears are smaller than the outer race of bearings, that way the gear doesn't "rub" against the bearing and the nub basically acts as a washer/spacer.

Pretty much the gears have built in spacers.

-RC

[Chris is me]

Originally Posted by LedLover96

The nubs were wrong and we are fixing that now. Why does that make a difference though?

As RC said, gears rubbing against non-moving parts = huge friction increase.

Could the clear plate that the CIMs mount to be machined wrong, or we are putting the motors into it wrong? The CIMs coming out the back are at a slight angle, unlike, our working gearbox, which has the CIMs coming out straight.

Slight angle sounds like an assembly problem, honestly. No machining errors should make your CIMs come out anything but perpendicular to that plate. Are the screws tightly fastened? The CIM should be pressed flush against the plastic piece during installation.

[themccannman]

The easiest way to trouble shoot the location of the problem is to assemble the gearbox stage-by-stage and run it by hand before attaching each stage. You should be able to deduce where the problem is at some point when the gearbox stops turning smoothly. If all of the gears run fine but it doesn't with the face plate on then there is a problem with how the face plate is being mounted.

[Walter Deitzler]

So after talking to Akash Rastogi and reading RC's replys, we were able to figure out that there were three problems.
1) The mounting holes for the CIMs were too close together. This caused them to come out at a slight angle. One plate-change later, that was good to go.

2) We over tightened the rest of the gearbox casing, causing a bit more friction to be put on the gears, causing it to turn slightly slower than the other one.

3) Yes, the nubs were the wrong way, that is all fixed.

Thanks for all of the help!

[Redo91]

Originally Posted by LedLover96

1) The mounting holes for the CIMs were too close together. This caused them to come out at a slight angle. One plate-change later, that was good to go.

In what way were they too close together? How did you determine this to be an issue?

[Walter Deitzler]

Originally Posted by Redo91

In what way were they too close together? How did you determine this to be an issue?

When we mounted the CIMs, they came out at an angle, with the ends facing each other. This was because the gear in the center was forcing the the gears on the CIMs outward. Akash Rastogi, from team 11, said that they had this problem a couple of years ago, and fixed it by changing the plate. We did just that, and the problem was fixed.

[Akash Rastogi]

Originally Posted by LedLover96

When we mounted the CIMs, they came out at an angle, with the ends facing each other. This was because the gear in the center was forcing the the gears on the CIMs outward. Akash Rastogi, from team 11, said that they had this problem a couple of years ago, and fixed it by changing the plate. We did just that, and the problem was fixed.

It was an issues in 2012 with 3929. We are pretty sure that was the problem + other small factors. Swap of the plate fixed the issue, so that was our conclusion, but never bothered inspecting the issue further or actually measuring the dimensions on the plate that gave us problems.