QCGB assembly: is this correct? I have some gears binding

[ARC-170]

PROBLEM
I'm assembling a QCGB for my 12" and it all has gone together quite well, except there appears to be something binding when I turn the gears. I can turn them all the way, but at one point it gets very hard to turn them by hand, then they release and get smooth, then release, etc... There don't appear to be and burrs or edges catching on anything.

MY THOUGHTS
1. I have not tightened any of the set screws. Could that be the problem?
2. Are the gears meshing properly? They all seem to, but maybe I've got some in the wrong place?
3. I have light lube on the shafts. Do I need any on the gears for testing purposes? I will of course lube these before running them under power.
4. There are newer gears (the ones on the far right of both shafts). Could these not be "broken in"?
5. Burrs/dents/imperfections on the gear teeth? I don't see any, and filed a few seemingly minor ones down.

Here is a photo of the assembly. I used the parts diagram in the MOLO as a guide:


Here are some other reference photos:




If anyone sees any glaring errors, please let me know. I'd like to make sure this will run smoothly before I use power to turn it.

 

[Lo-Fi]

Is the set screw on the collar closest to the small gear getting hung up on the wide gear?

 

[markba633csi]

Something doesn't look right to me- are you sure it's assembled correctly?
-M

 

[ARC-170]

Is the set screw on the collar closest to the small gear getting hung up on the wide gear?

No, I checked that. It would get hung up if it rotated, but it's currently not rotating, but the shaft is. I'll check it again, though. Maybe the shaft is getting caught on the set screw.

Something doesn't look right to me- are you sure it's assembled correctly?
-M

What doesn't look right to you? I think I assembled it correctly. It matches the parts diagram I have. I thought I took "before" pictures, but I think I deleted them. I'm still trying to find them. However, the machine was so dirty, it might be hard to see some of the parts.

 

[Lo-Fi]

Hmmm. Is the shaft with the gear stack on straight along the entire length?

 

[ARC-170]

Hmmm. Is the shaft with the gear stack on straight along the entire length?

I thought the same thing, but I checked it and, as far as I can tell it's straight and not binding.

 

[ARC-170]

I found the "before" photo. There is a collar I didn't put on shown by the arrow. I don't think this is the source of my problem, though.

 

[Lo-Fi]

Tricky one! I think you may be down to stripping it and reassembling in stages to find where the source of the problem is.
The gears on the right hand side must be pinned or keyed in pairs and running on bushings as a compound reduction set? Are you sure they went back together in the same pairs on the same bushings? That strikes me as a place to check for trouble. Along the lines of one gear is maybe running out and meshing tightly at one spot.

 

[ErichKeane]

So I will say it looks like the top bar,. 2nd from the right gear looks like it is too close to the 2nd from the right (lower) in the original picture. I would think that a little bit of bend or misalignment to either of the shafts could cause some of those teeth to catch and stick.

 

[ARC-170]

I found the problem: a bent tooth on one of the gears. I took apart the assembly and meshed various gears to see which ones went together smoothly. I put them on the shaft and engaged them because just doing it freehand didn't simulate them being engaged. I traced it to one gear. I managed to ascertain the location of the "sticky-ness" on that gear and noticed that the gear teeth were a very small amount farther apart than the adjacent ones. It would be easy to miss if you weren't looking for it.

Here is a picture. The arrow indicates the bent tooth.