pic: Two Motor, 4WD

[Arefin Bari]

Originally Posted by nikkibajbaj

What are the diametral pitch of the gears and their thicknesses? I'm worried about that 20-tooth as well...

The thickness for the gears are .25". I suggested him to make them .375". As far the pitch of the gears go... Matt will answer that. There are no 20 tooth gear in that transmission. He is using 3 15 tooth gear and 3 60 tooth gear. Each sprockets has 16 tooth.

[Tristan Lall]

Originally Posted by Arefin Bari

The thickness for the gears are .25". I suggested him to make them .375". As far the pitch of the gears go... Matt will answer that. There are no 20 tooth gear in that transmission. He is using 3 15 tooth gear and 3 60 tooth gear. Each sprockets has 16 tooth.

Are you sure about the 0.25" thickness for the gears? Compared to the front plate of the CIM (which is definately 0.25"), they seem smaller. Maybe Matt changed them without posting an updated picture? Depending on the material, I think that these narrow gears could be made to work for the first (higher speed) stage; it's the second stage that will fail first.

And as for 15 vs. 20 teeth, 15 just makes things worse! (Higher stresses on the pinion, and depending on the pressure angle of the gear, the potential for some significantly undercut teeth.)

[Nikhil Bajaj]

Originally Posted by Tristan Lall

Are you sure about the 0.25" thickness for the gears?

And as for 15 vs. 20 teeth, 15 just makes things worse! (Higher stresses on the pinion, and depending on the pressure angle of the gear, the potential for some significantly undercut teeth.)

I'm going to second the .375 suggestion--that'll definitely be safe...even our 12 tooth, 20 pitch, .375 gears on our gearbox that used 2 chips and a fish was fine...then again the small gears were early to middle stages in the gearbox so the torque was not so high. But I think .375 should be fine. And if you do go with the wider gears then it may make it easier for you to work out the spacing for the gearbox.

By the way, how are the plates with the bearings and such mounted to the other section? For gearboxes, precise and accurate alignment is absolutely critical. A few thousandths of an inch of misalignment can have a horrendous effect on efficiency. You may want to figure out a way to keep it spaced well...we picked a silly design last year and we ended up having to remake the spacing blocks like three times, and even after that had to use a shim or two.