Martin Gear Anomaly?

Technical Technical Discussion
1

We made two identical gearboxes for our robot using Martin .5" face width, 20*PA 20P gears. (TS Series) One gearbox turns just incredibly smooth. The other one turns REALLY bad, it binds like crazy. They were both made on the same setups in the CNC. We tracked the problem down to one gear, and the problem follws the gear when we put it in the other box.

We are thinking maybe the gear got made with a 14.5* pressure angle by mistake? I know this is highly unlikely but could this have happened in Martin’s manufactuing line? Would a 20PA mating with a 14.5PA still turn but bind bad, like ours does?

See, Martin’s 20P 14.5PA gears are only 3/8" face width, all our (20PA) gears are 1/2" That’s why I’m thinking this is highly unlikely. But, I do think it is possible because while the gear does bind a little more in one spot, it is “crunchy” all the way around while meshing.

The mesh is a 30:45, and we believe the 45 is causing the problem, however we “clocked” the tight spot to the 30.

2

It could be that the gear is oblong.

I suggest that you swap both of the 45 tooth gears to the other one.
Just remember which transmission had the problem.

If the problem still occurs in the same tranny it will be the 30 tooth.
If the problem occurs in the other than it will be the 45 tooth.

It could also be that when you clamped the gear in the cnc that there were metal chips in the vise. I am not sure of how you set it up though?

What exactly did you machine out on the cnc?

3

Or the centre distance.

4

Dave,

From what you wrote, I assume you tried changing just the 30 tooth. If you can make the ‘bad’ gearbox work with the 30:45 set out of the ‘good’ gearbox then it is the gears not the center (centre? :slight_smile: ) distance.

It is possible to get a bad gear. I have run my gearboxes without load, no lube to break them in. Some of the 20 PA boxes have been tight. All the gearboxes I have built with 14-1/2 PA have not had problems.