Spur gear problem with strobe slipper
 

I just finshed installing my 8L/ 9920 in my Emaxx, but now every time I drive it I strip the spur gear. I know the mesh was set right, and Ive seen other cars with much more power than mine with this same set up, so I dont know what to think. The first time I thought it was because the motor mount was flexing because I forgot to put 2 of the screws in, but the second time I used those screws and it stripped even faster (after about 2 minutes of running, first time it took about 5 minutes)

http://memimage.cardomain.net/member...90_80_full.jpg

This is what happened to the spur. Sorry its kinda blurry, but you can see one tooth is almost all gone, and the rest of the teeth are somewhat flat-topped.
http://memimage.cardomain.net/member...90_81_full.jpg

Any help would be appreciated.

You are running a mod 1 pinion right. By the looks of the spur it is not meshing right.

Yea its a mod1 pinion. It was meshing right, until the spur stripped. I had it set to where there was the smallest amount of play I could get it to, without getting rid of all the play.
Im starting to think it was a rock that got caught between the spur and pinion. That explains the one missing tooth, but it still doesnt explain the damage to all the other teeth.

How tight are the screws that hold the motor to the motor mount?

They were plenty tight. The motor didnt move, because the mesh is still tight where the spur teeth are still there.

i think it still might be the motor mount. i have heard that those mounts flex horribly.

Thats kind of what Im afraid of. It doest seem like there could be any other explanation.

How are the tranny mount screws?

If the broken tooth was caught in the pinion gear as it came around it beat the other teeth up on the spur. Did you check and make sure the pinion don't have stuff stuck in it? I set mine as tight as possible as long as there is no drag.

The pinion didnt have anything stuck in it, and the tranny was tight. I think Im going to get some right angle aluminum, something thicker than this motor mount, and cut myself a new one. Something that hopefully wont flex at all. But if the flex is in the chassis, that still wont help. I might make a sheet aluminum brace between the rear bulkhead and the tranny, or maybe a whole aluminum upper deck.

I use the same motor mount as you B15, and have also stripped a few spur gears. I then mounted my motor on the other side and had absolutely no problem (with Mod 0.8/32 pitch gears). I think its the torque the motor produces that causes the mount to twist, but for some reason when mounted on the other side it didn't twist - wierd. Also check that the motor screws are very tight and the motor can't slip.

These things worked for me, so you might or might not want to give them a try (I know how much of a pain it is to change spur gears with that chassis!!!) Good Luck!

why not use the stock motor mount?

The stock motor mount looks rubbish compared to that one, and it also raises the CoG quite a bit too.

but you might not have those problems.... That might be worth it - at least to rule out other probs - if you put the stocker on and have no probs - then have another thicker mount made.....

This really makes perfect sense. The motor only rotates in one direction when youre going forward, so it will only twist the motor mount in one direction. In one of the motor mount positions that twisting will pull the pinion away from the spur, and in the other it will push them together. Thanks alot for pointing that out. So hopefully this next spur will be my last.
And you must be the one who told me about this motor mount in the first place, so this isnt the first time youve helped me out alot. Thanks.