Chewed Up Pinion - Help!

[ridgehead44]

Hey all,


I took out my Asuga for its maiden run with the MAX6 G2 motor/esc combo. It was awesome...for about 3 seconds. I could hear a high-pitched whine just before I lost all power. I took it back to the bench and saw my 19t pinion had been chewed to bits.

Obviously, I've got some bad gear mesh. Is it too loose? Too tight? Is there anything else that could cause this? I'd used what I thought was a hardened steel pinion, but maybe not, given the results. Any advice on how to troubleshoot this is mightily appreciated. Thank you!

 

[Sandracer_NL]

If it lasted 3 seconds, it was not hardened even with a bad mesh.
Difficult to see in the pic, but it looks like it may have been on the loose side.
There are pinions on Amazon/Aliexpress that are made out of monkey metal and can’t handle 6s power.
But I’ve tried cheap are expensive (brand) pinions and currently I buy all my pinions from Aliexpress and so do others in our RC group.
Some use the paper ‘trick’ to,set the mesh, I push the pinion tight against the spur gear and then pull it backwards a tiny bit (maybe about 1 mm) , wiggle the spur gear to listen for ‘the click/clack’ sound I’m looking for. Tighten all motor mount screws and wiggle the spur gear again to see if it still feels and sounds the same. Sometimes the mesh may change after fully tightening the screws so don’t forget this check.

 

[danl]

The tekno pinions with 5mm set screw are awesome. The factory corally ones are good, but the set screws can round, even with new MIP driver bits.

I set my mesh by hand, as described above. It’s important to check it at multiple positions as that can uncover underlying issues.

Like this…

Sized bearing, under rotating, smoked the plastic consumable part, mesh was all over the place.

 

[Atomic Skull]

I switched from a Robinson pinion to a Tekno one because the M4 setscrew kept coming loose. Hasn't happened since with the M5 setscrew.

It's tempting to go gorilla mode on a setscrew and bear down on it but DON'T DO IT! If the setscrew rounds out you are really, really, really screwed. Getting the pinion off will now be a massive pain in the arse and likely means a new motor shaft and possibly a new rotor assuming they even sell them seperatly for your motor.

Also if a setscrew won't come loose STOP and get the heat gun, do NOT gorilla fist it. Even if you have to remove the whole motor and mount. The alternative is you might round it out and again, if that happens you are really screwed.

Wera "hex plus" drivers are great for preserving the sockets on button heads and setscrews.

The hex plus head has a modified shape that puts more of the driver bit in contact with the sides of the socket.

Alternatively you could just switch to torx setscrews.

 

[Nelson.81]

 

[Atomic Skull]

I push the pinion tight against the spur gear and then pull it backwards a tiny bit (maybe about 1 mm)

1mm is too much what I do is back it off so that is has about 0.1mm backlash and check the gear all the way around, if I find a tight spot with no backlash I try again at that spot. 90% of the time the second attempt will have backlash all the way around the gear, if I still find a tight spot repeat again only this time with the absolute minimum backlash possible (maybe 0.05mm)

Also, make sure that your diff is shimmed with about 0.1mm fore/aft play at most (don't make it zero you might overload the bearings) and make sure you have the gear centered on the pinion. I find that a magnifying visor and a flashlight helps with this.

Seriously get a magnifying visor you will wonder how you ever did without it.

 

[Atomic Skull]

woops double post

 

[ridgehead44]

Thanks for the help, everybody! I'm going to install the new pinion tonight. Hopefully, I can get it done right this time.

 

[danl]

1mm is too much what I do is back it off so that is has about 0.1mm backlash and check the gear all the way around, if I find a tight spot with no backlash I try again at that spot. 90% of the time the second attempt will have backlash all the way around the gear, if I still find a tight spot repeat again only this time with the absolute minimum backlash possible (maybe 0.05mm)

Also, make sure that your diff is shimmed with about 0.1mm fore/aft play at most (don't make it zero you might overload the bearings) and make sure you have the gear centered on the pinion. I find that a magnifying visor and a flashlight helps with this.

Seriously get a magnifying visor you will wonder how you ever did without it.

Have you found shims that can be used without having to remove diff cups to install them?

 

[Atomic Skull]

Have you found shims that can be used without having to remove diff cups to install them?

You shim the bearing not the diff cup, the shims are installed in the bearing seat under the bearing in order to reduce the distance between the two bearings that support the diff.

 

[Manolis]

That "paper method" never worked for me.

 

[danl]

You shim the bearing not the diff cup, the shims are installed in the bearing seat under the bearing in order to reduce the distance between the two bearings that support the diff.

What I am not following is how do I shim the bearing when my shims do not go over the output cup.

 

[Atomic Skull]

What I am not following is how do I shim the bearing when my shims do not go over the output cup.

The center diff cups are 12.85mm OD so a 13x16 shim will fit over them. Not the front and rear diff cups though because they are flared. In that case you can snip a small section out of the shim with diagonal cutters then squeeze it in a bench vice to flatten the cut edges and it can then be pushed over the flare in the cup.

 

[danl]

My shims are 12x16mm. I’ll see if I can source some different ones. Thanks.

 

[Atomic Skull]

My shims are 12x16mm. I’ll see if I can source some different ones. Thanks.

https://www.amainhobbies.com/tekno-rc-13x16x.1mm-differential-shim-10-tkr1222/p231848
https://www.amainhobbies.com/protek-rc-13x16mm-drive-cup-washer-10-0.1mm-ptk-h-5903/p1501662
https://www.amainhobbies.com/kyosho-13x16x0.15mm-differential-shim-set-kyo96772/p37363

The 0.15 are useful for when a single 0.1 isn't enough but two 0.1 are too much.

EDIT: you could also just use the trick I mentioned with your 12x16 shims i.e. cut a small section out of them so they can be pushed over the cups.

 

[Horatio]

That "paper method" never worked for me.

The paper trick helps ensure the tooth mesh is square/parallel - which is more helpful with nitro models where it is much easier to introduce unwanted angle with the clutchbell/pinion.

With electric models, 1/10th and 1/8th, the motors alignment is governed by the sliding mount, so it's merely the backlash that needs to be determined by the user. Nobody really needs paper for that.

A 'tick' of play is sufficient. The tick of play needs to be checked @ 0°, 90°, 180° for any tight spots - spurs aren't always perfectly round, especially plastic ones.