Kraton Pinion keeps moving

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In my experience pinions only come loose when either the grub screw or the pinion threads it goes into are not properly cleaned, or blue thread lock is not allowed to cure long enough. Be certain you are cleaning the grub screw and the pinion very well with motor spray, brake cleaner, or similar de-greaser. Run that grub screw in and out a bunch of times way into the pinion (with it not on the motor) and clean clean clean. Let the pinion and grub dry completely. Then put just a drop of blue thread lock on the grub screw and the install it on the motor shaft. Make sure the grub screw is properly seated and tighten it down. Next, let it sit for 24 hours before you run it. If you run it 8 hours after installation, don’t be surprised when the pinion comes loose.

That means wait 24 hours before you spin that motor. If you just “bench test” your rig and spin up the motor to “check” you are going to put force and vibration into that grub screw and you may break the thread lock bond. When I say don’t run it, I mean don’t turn the RC on until it’s fully cured. Check the specs on your thread locker for the full details. If you have thread locker that is old or has been frozen, toss it and get new stuff. It’s not worth the hassle and damage for a few bucks worth of thread lock. The blue gel stuff is your best bet and I go with Permatex or LocTite brand. The small tubes of gel are what you want. Never go cheap on thread lock.
 
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L3phturn said:
In my experience pinions only come loose when either the grub screw or the pinion threads it goes into are not properly cleaned, or blue thread lock is not allowed to cure long enough. Be certain you are cleaning the grub screw and the pinion very well with motor spray, brake cleaner, or similar de-greaser. Run that grub screw in and out a bunch of times way into the pinion (with it not on the motor) and clean clean clean. Let the pinion and grub dry completely. Then put just a drop of blue thread lock on the grub screw and the install it on the motor shaft. Make sure the grub screw is properly seated and tighten it down. Next, let it sit for 24 hours before you run it. If you run it 8 hours after installation, don’t be surprised when the pinion comes loose.
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Thanks - I'll give this a go, admittedly I didn't clean it when I fitted it the first time as it was fresh out the box so didn't think I needed to but definitely noted. I also left it for a week to set..

I kind of wish the flat part of the motor shaft was subtly grated so at least the grub would have something to nestle in between. It still felt pretty tight and worked it's way down the shaft leaving a polished line so it can't have worked its way out very far...
 
M240i_bandit said:
Thanks - I'll give this a go, admittedly I didn't clean it when I fitted it the first time as it was fresh out the box so didn't think I needed to but definitely noted. I also left it for a week to set..

I kind of wish the flat part of the motor shaft was subtly grated so at least the grub would have something to nestle in between. It still felt pretty tight and worked it's way down the shaft leaving a polished line so it can't have worked its way out very far...
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That is when you most have to clean them! Newly machined pinions and screws have a light oil on them to prevent surface rust in storage and transit so you always have to clean them well with degreaser before installation. Always.
 
L3phturn said:
That is when you most have to clean them! Newly machined pinions and screws have a light oil on them to prevent surface rust in storage and transit so you always have to clean them well with degreaser before installation. Always.
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Good to know - thanks!
 
Like you said the crush tube is out of stock every where so ive orederd some stainless sreel tube to cut down to size plus it was alot cheaper and got slot more tube for the money
 
Pablo1980 said:
Like you said the crush tube is out of stock every where so ive orederd some stainless sreel tube to cut down to size plus it was alot cheaper and got slot more tube for the money
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Did you have issues with the steel tube rubbing/drilling into the motor housing?

Edit: Also what size did you go for? 1mm over shaft diameter?
 
I haven't actually fitted it yet but there is no difference between the tube i bought and the crush tube. I bought a tube that's 5mm inner diameter and 8mm external diameter making it 1.5mm thick. I will be fitting it in the next few days when i get the chance
 
Pablo1980 said:
I haven't actually fitted it yet but there is no difference between the tube i bought and the crush tube. I bought a tube that's 5mm inner diameter and 8mm external diameter making it 1.5mm thick. I will be fitting it in the next few days when i get the chance
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I've got some laying around which is 6mm external & 0.4mm thick so 5.2mm inner so I'll give that a go tomorrow and see if it works. I can't imagine much force pushing back against it - I'm assuming it's just the angular momentum vector

On another note - is it expected that the pinion teeth erode away this quickly? I've run it around 30 to 40 mins, and it looks like around 5 to 10% of the teeth (tooth width) have worn down..? There's a noticeable ridge.

I've meshed it correctly I'm sure with a little play, wedging some paper between when setting the mesh - same as I do with my Heli's, but I've not noticed it wearing down on those this quickly - less torque I guess. I'm using a traxxas pinion so wouldn't think its poor quality/soft
 
M240i_bandit said:
I seem to be having the same issue - luckily it didn't work its way down far enough to hide the grub so managed to get it off. This was after the first run so pretty sure everything was clean but I'll try some of the above - I'm sure I tightened it down as far as I could as well...

The crush tube seems to be OOS everywhere - is putting blue threadlock on the shaft as well to slightly fuse the shaft to the pinion an option?
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NO. Don't blob the the TL onto the shaft, thinking it will glue the pinion in place on the shaft. If you just use TL on the pinion setscrew ( cleaned well enough), it Will hold. Using "L" hex wrenches are your enemy if you were using them. Hand Drivers only. Best are MIP's if you don't have H drivers aready.
The crush tube is just cheap insurance. Not a necessity at all. The most important consideration after all is said and done, is to allow the TL to cure for 24 hours. If you run it before TL cures, It will loosen again 99% of the time. Just the way that all TL works. And TL is only used on metal to metal threads. TL is bad on plastic.

CRUSH TUBE 5x7x5mm (2pcs) (ARA311026) | ARRMA - Designed Fast, Designed Tough (arrma-rc.com)
 
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By all means, you can always buy a brass tube in a hobby store and cut it yourself.
Cleaning the grub and the pinion from old threadlocker is typically all it takes plus the 24h cure.
If you use a new pinion, clean threads with alcohol as well, any oil will prevent a proper seating.
 
SrC said:
NO. Don't blob the the TL onto the shaft, thinking it will glue the pinion in place on the shaft. If you just use TL on the pinion setscrew ( cleaned well enough), it Will hold. Using "L" hex wrenches are your enemy if you were using them. Hand Drivers only. Best are MIP's if you don't have H drivers aready.
The crush tube is just cheap insurance. Not a necessity at all. The most important consideration after all is said and done, is to allow the TL to cure for 24 hours. If you run it before TL cures, It will loosen again 99% of the time. Just the way that all TL works. And TL is only used on metal to metal threads. TL is bad on plastic.

CRUSH TUBE 5x7x5mm (2pcs) (ARA311026) | ARRMA - Designed Fast, Designed Tough (arrma-rc.com)
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Oh I really can't stand the L Allen keys - I have a couple of sets of hand drivers for my Heli's so I've just been using those, they seem to be holding up fine

Sorry if this is a stupid question but what's the downside to dabbing a bit of blue LT on the shaft (or between the pinion and the shaft)? Obviously it won't be a replacement to fitting the grub properly but just to add an extra bit of tension in the system

Some of the smaller Heli's I have (250) are designed to use green LT as a permanent solution to mounting the pinion on the shaft so I assumed doing the same with blue would have a similar but less permanent effect
 
Green TL is different. I don't recommend it though. It does have some locking properties. But you don't want TL of any type on Motor shafts. Simply Blue TL on threads only. Pinions can get stuck onto motor shafts simply from using too much TL.
Out the Box Arrma tends to over TL pinions using Red TL and they are stuck/ frozen on with the setscrew removed.. (n) A torch or flame and a puller is needed. Been there.
Setscrews installed properly will always be fine.
 
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So I took the exb out for a blast today - 3 packs down and the pinion is still solid! Appreciate the advice - looks like cleaning everything before LT was the trick, I did pop a small drop on the shaft as well but not enough where it should be an issue to remove later on - I'm in two minds now whether I should just leave it alone or go through the whole process again just to install some tubing behind it

Either way I have some time to figure it out, managed to snap the front lower a arm around the hinge pin on a bad landing towards the end of the session - which is OOS until April in the UK (n)
 
M240i_bandit said:
So I took the exb out for a blast today - 3 packs down and the pinion is still solid! Appreciate the advice - looks like cleaning everything before LT was the trick, I did pop a small drop on the shaft as well but not enough where it should be an issue to remove later on - I'm in two minds now whether I should just leave it alone or go through the whole process again just to install some tubing behind it

Either way I have some time to figure it out, managed to snap the front lower a arm around the hinge pin on a bad landing towards the end of the session - which is OOS until April in the UK (n)
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There has to be something that will work. RPM arms (just get the shock pins that fit them.
 
L3phturn said:
There has to be something that will work. RPM arms (just get the shock pins that fit them.
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That's a good shout, and they're like half the price! - I assume I just need the v4 shock pins?

Still need to pull it apart to see what else is busted, hinge pin looks bent at least and the drive (cvd) shaft popped out of the diff
 
M240i_bandit said:
That's a good shout, and they're like half the price! - I assume I just need the v4 shock pins?

Still need to pull it apart to see what else is busted, hinge pin looks bent at least and the drive (cvd) shaft popped out of the diff
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Hinge pins will bend, good to have spares. I got a bag of bits from JennysRC so I have spare stock hinge pins. I hope you mean the drive shaft popped out of the out-drive - not that the out drive ripped out of the diff!
 
Pablo1980 said:
Ive got a kraton exb with the max6 combo but my pinion gear keeps moving which ends up grinding against the motor mount. Im using the blue normal locktite thread lock but it seems to not hold very well.
I was just curious in what any of you guys use.

View attachment 126019
Click to expand...
Use Locktite 222, that should do it.
 
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