Stripped motor pinion on my crawler

[jdss13]

Today I stripped the motor pinion on my crawler and I wanted to ask you guys if you have any clue why. I was hill climbing a sandy muddy hill and then I started hearing some loud noises and I decided to head home. I found out my metal motor pinion is stripped, the spur seems fine (also metal) though. I had greased the pinion/spur and this is inside a closed compartment but there was still sand and dirt in there. Why do you think the pinion stripped? Too much sand/friction, bad assembly/spacing between the pinion and spur or loose motor screws (they didn't have threadlock)? I've also heard that having an all metal pinion/spur combo is bad because there's nothing that "gives" but I don't think this was the case because the pinion actually gave away.
All of these are possible options IMO, would they cause the pinion to strip?

[RCBrutus]

You are right, all of those are possibilities for sure.

Another thought that comes to mind is, was the spur hardened steel and the pinion not? If so, it could just be a case of one metal was stronger than the other, so something had to give.

[jdss13]

I have no idea but I'm kinda happy it was the pinion (the least expensive piece in there) and not the spur or even worse some gear in the gearbox. I'm also wondering if the grease might accumulate more sand and dirt vs dry spur/pinion resulting in more friction

[23drumerboy]

Originally Posted by jdss13

I have no idea but I'm kinda happy it was the pinion (the least expensive piece in there) and not the spur or even worse some gear in the gearbox. I'm also wondering if the grease might accumulate more sand and dirt vs dry spur/pinion resulting in more friction

Grease will ALWAYS ATTRACT/allow dirt to stick and hang around near bearings,/bushings, etc. Its a compromise IMO, to be messy and dirt-attractant,while keeping water/salt/sand/(insert abrasives here) out. Just need 2 exercise caution when cleaning/maintenance etc

R.C. means both;Radio control, and Rock Crawler, oh..and Race Car! annd, Rice Cake, as well as
..Real cash, Remote Contr, etc

[QuesoDelDiablo]

Originally Posted by RCBrutus

You are right, all of those are possibilities for sure.

Another thought that comes to mind is, was the spur hardened steel and the pinion not? If so, it could just be a case of one metal was stronger than the other, so something had to give.

My guess would be that the pinion was aluminum and the spur was steel, that's a fairly common configuration. It's almost as effective a fuse as steel pinion/plastic spur.

[jdss13]

Originally Posted by 23drumerboy

Grease will ALWAYS ATTRACT/allow dirt to stick and hang around near bearings,/bushings, etc. Its a compromise IMO, to be messy and dirt-attractant,while keeping water/salt/sand/(insert abrasives here) out. Just need 2 exercise caution when cleaning/maintenance etc

R.C. means both;Radio control, and Rock Crawler, oh..and Race Car! annd, Rice Cake, as well as
..Real cash, Remote Contr, etc

Yeah, I think I'll leave the spur and pinion dry and just grease the gearbox and axles as I've been doing since they seem better enclosed.

Originally Posted by QuesoDelDiablo

My guess would be that the pinion was aluminum and the spur was steel, that's a fairly common configuration. It's almost as effective a fuse as steel pinion/plastic spur.

I think the spur is black painted steel and the pinion has a gold raw color so it's probably.. brass??

[QuesoDelDiablo]

Originally Posted by jdss13

Yeah, I think I'll leave the spur and pinion dry and just grease the gearbox and axles as I've been doing since they seem better enclosed.





I think the spur is black painted steel and the pinion has a gold raw color so it's probably.. brass??

In my experience the black painted ones are usually aluminum and without having looked at it, I'd guess the spur is plated steel. My assumption is somewhat reinforced buy the fact the pinion stripped and not the spur; a brass spur would strip before a steel pinion. Not that it really matters..

As for grease, I always grease gears if they're metal on metal. I can definitely understand the argument for not doing that if they're exposed but if they're encased, I'd put a little grease on them. That pinion'll spin at up to 30k rpm (or more) and doing that without grease could increase the heat (not much obviously but possibly enough to soften fine edges of aluminum gear teeth, there's a lot of friction in gear meshes) which might lead to increased wear of the soft aluminum pinion gear.

That's just my thoughts though and I don't claim to be an industry leading expert or anything..

[jokersinsanity]

I've also seen bad bearings cause the spur and pinion to separate at high torque or speed also causing the pinion to strip

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[Gula]

I've never lubed a spur and pinion with grease. If i ever needed to, i would use bar soap as a lubricant on those as it doesn't attract dirt.