Kraton Pinion keeps moving

[M240i_bandit]

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!

Yep sorry that's what I meant, the dogbone? bit popped out of the out drive - need to check if the shaft is bent. I think I hit a hidden tree stump at full pelt...

 

[Sloclone100]

^^^ THIS Clean TL parts always. Brake cleaner. A hard rule for sure.
I use Locktite 243 instead of 242.
It assembles well with dirty oily pre TL'ed screws no issue. Sometimes its hard to remove/ clean off old TL completely, especially RED TL FWIW.
Clean the pinion and setscrew and armature shaft.

View attachment 126026

This formula is designed for 1/4" - 3/4" bolts. It will not hold (even if your has been around since "Happy Days"}. He wants something more like 222.

 

[jkflow]

Only secret to make the pinion stick is cleaning the screw and the pinion threads. All the old threadlock needs to go and clean with alcohol or brake cleaner. Let the loctite cure for 24h. Don't put anything on the shaft, that is just bad advice imho and asking for problems during removal.

 

[M240i_bandit]

Only secret to make the pinion stick is cleaning the screw and the pinion threads. All the old threadlock needs to go and clean with alcohol or brake cleaner. Let the loctite cure for 24h. Don't put anything on the shaft, that is just bad advice imho and asking for problems during removal.

Blue LT can't be that bad can it? If you can break the bond on a screw with hand torque and a hex driver then the same level of torque (give or take) will be needed to break the bond between the shaft and the pinion - should be achievable with pliers I'd have thought? No experience with this btw, just thinking logically (obviously just talking about a small amount, not dipping it in the stuff)

Or just remove the grub and blip the throttle, I'm sure that'll do it

I guess I'll find out when I need to remove my pinion

 

[jkflow]

Only one way to find out
No it's not exactly the same, you have more surface area on the shaft/pinion and will be significantly harder to remove. Heating it up is not a good solution as the heat transfers into the motor and damages the rotor epoxy.
All around a bad idea but yes the pinion will stick.

 

[L3phturn]

Pretty sure it will turn on the shaft once the grub screw is removed. Just roll the truck, that should be enough to spin it on the shaft.

 

[M240i_bandit]

Only one way to find out
No it's not exactly the same, you have more surface area on the shaft/pinion and will be significantly harder to remove. Heating it up is not a good solution as the heat transfers into the motor and damages the rotor epoxy.
All around a bad idea but yes the pinion will stick.

Okay so I was curious about this and did some calculations:

LT on the shaft:
Shaft diameter = 5mm, radius = 2.5mm
Assume a 0.5mm thickness of LT which spreads to cover 3mm across the shaft

So surface area = 2*pi*r*w = 2*pi*2.5*3 = 47.12mm^2

LT on grub:
Grub screw is an M3 x 3 screw which gives a pitch (peak to peak distance of threads) of 0.5mm according to Google & wiki, 3mm in length and 3mm in diameter

If the grub wasn't threaded the contact surface area = 2*pi*r*w = 2*pi*1.5*3 = 28.27mm^2

However approximately accounting for the threading by assuming each side of each thread isn't a helical plane (so therefore underestimating the surface area slightly) is equivalent to the partial surface area of a cone

Length = 3mm and pitch of 0.5mm => 6 threads on the grub

Surface area of a cone = pi*r(r + sqrt(h^2 + r^2))

Each thread represents an equilateral triangle according to wiki - so taking the top half of a thread

1 - base radius = 1.5mm, perpendicular height of cone = 1.5 * tan(30) = 0.866

2 - top radius = 1.067mm (perpendicular height of thread = 0.5mm * cos(30) = 0.433) & perpendicular height of cone = 1.067 * tan(30) = 0.616

So surface area of cone 2 - cone 1 = 15.23 - 7.71 = 7.52mm^2

This is the surface area of half of a thread so * 2 * 6 = 90.24mm^2 is the total surface area of the grub

https://en.m.wikipedia.org/wiki/ISO_metric_screw_thread

Also for blue LT the breakaway torque is between 8nm & 17nm for a steel screw of 3/8 x 16 after curing for 24 hrs
(bearing in mind the average torque required to open a jar is between 3nm & 5.5nm)

Also interestingly blue LT full cure time is 24 hours as mentioned by a few guys here but after 1 hour the strength is around 65% of peak strength so a material difference (and around 85% after 3 hours)

Anyway long story short the contact surface area on the grub is higher than if you were to put it directly on the shaft so will require less torque to break - but with blue LT the breakaway torque is pretty low so can't see any issues really of putting some on the shaft - once the grub is in the LT on the shaft isn't countering rotational torque anyway, just lateral along the shaft axis to stop sliding so doesn't need to provide much fusing strength, so not much is needed

 

[SrC]

This formula is designed for 1/4" - 3/4" bolts. It will not hold (even if your has been around since "Happy Days"}. He wants something more like 222.

What is special about 222 Purple? 222 is the lightest weakest, holding TL
I Don't understand your comment at all..

 

[M240i_bandit]

Pretty sure it will turn on the shaft once the grub screw is removed. Just roll the truck, that should be enough to spin it on the shaft.

So just as an update to this - decided to remove the pinion as I'm going to take the thing to bits anyway fixing the busted up a arm

Taking the grub out and just giving the throttle a blip loosened it up straight away - as mentioned before the breakaway torque for blue LT is pretty low

To be honest contrary to what others have said I'd actually recommend fixing the pinion in this way because you don't have to torque the F out of the grub screw to get the pinion to stay still, it just has to be up against the flat part of the shaft and LT in place so it doesn't back out to counteract the rotational force

I think it's far worse having to tighten up the grub a lot to stop the pinion both rotating and sliding down because you risk over tightening the grub and rounding out the hexing - which will give you far more issues later trying to dremel or drill out the grub/pinion

So leave the grub to stop rotational slipping and use a bit of blue LT on the shaft to stop it sliding down

 

[L3phturn]

So just as an update to this - decided to remove the pinion as I'm going to take the thing to bits anyway fixing the busted up a arm

Taking the grub out and just giving the throttle a blip loosened it up straight away - as mentioned before the breakaway torque for blue LT is pretty low

To be honest contrary to what others have said I'd actually recommend fixing the pinion in this way because you don't have to torque the F out of the grub screw to get the pinion to stay still, it just has to be up against the flat part of the shaft and LT in place so it doesn't back out to counteract the rotational force

I think it's far worse having to tighten up the grub a lot to stop the pinion both rotating and sliding down because you risk over tightening the grub and rounding out the hexing - which will give you far more issues later trying to dremel or drill out the grub/pinion

So leave the grub to stop rotational slipping and use a bit of blue LT on the shaft to stop it sliding down

Thanks for the follow up! As long as it comes off ok I cants see any problem with it. Just don’t use too much.

 

[jkflow]

If it doesn't hold why bother? Clean the grub and the threads and you are done but if it works it works. People were using red loctite and busted their shafts or had major issues removing.

 

[Prowler666]

So many people have issues with pinions, get some bearing fit. Used to secure bearings onto shafts, it stops any vibrations between the gear and the shaft, but still allows it to be removed. Just smear a little on the shaft before fitting the gear. Allow to dry and job done.

 

[M240i_bandit]

Yeah I think that's the key - you don't want to be using anything that's designed to be permanently binding like LT red

Haven't come across the bearing fit before - will check it out

 

[Prowler666]

Its good stuff, we use it at work for bearings. Anything like said gearing that has constantly changing forces and vibration needs a little help with bearing lock it basically fills all the gaps between the shaft and the pinion hole.

 

[Prowler666]

I think this is the one we use at work, but need to check bottle, it's one of those things.. use it every day but don't look at the details on the bottle lol.

 

[SrC]

If it doesn't hold why bother? Clean the grub and the threads and you are done but if it works it works. People were using red loctite and busted their shafts or had major issues removing.

^^^ This.
If your grub ain't holding, replace it. Maybe the pinion is galled out also. They are consumables, IMO. Clean all. This is not hard stuff. No TL on the shaft or compound should be needed. The TL'ed (cured 24 hours) grub screw either holds the pinion at 50k+ RPMS or it doesn't. If there is a problem, don't need to start trying to glue or use compound or something to keep the pinion on the shaft. Better not be using L hex wrenches on the grub screws either.

 

[M240i_bandit]

^^^ This.
If your grub ain't holding, replace it. Maybe the pinion is galled out also. They are consumables, IMO. Clean all. This is not hard stuff. No TL on the shaft or compound should be needed. The TL'ed (cured 24 hours) grub screw either holds the pinion at 50k+ RPMS or it doesn't. If there is a problem, don't need to start trying to glue or use compound or something to keep the pinion on the shaft. Better not be using L hex wrenches on the grub screws either.

Yeah but that can't be 100% reliable - if it was then arrma wouldn't have bothered mass producing and selling those crush tubes (+all associated r&d/testing etc), especially when the pinion grubs come with LT already applied so shouldn't need cleaning on first use, FYI mine were brand new grubs when it happened

I don't know why you'd want to risk over tightening and rounding out the grub just to have comfort that it'll stick (seen a few posts on this before, usually resulting in a lot of blood, sweat and tears involving dremels, drills and destroyed pinions), and if it fails on top of the above you potentially have a destroyed motor mount and a sheered shaft (worse if the grub gets hidden under the mount) - when you can have peace of mind with a bit of LT - especially when we now know 100% it is easy enough to remove when required, and everyone has blue LT knocking around already. At worst think of it as insurance...

I think this is the one we use at work, but need to check bottle, it's one of those things.. use it every day but don't look at the details on the bottle lol.View attachment 130593

This stuff looks like gold btw - thanks for posting

 

[Prowler666]

Just remember this isn't "standard TL" i know he calls it TL in vid lol

 

[M240i_bandit]

Just remember this isn't "standard TL" i know he calls it TL in vid lol

Yeah - I did notice actually that they have an absolute shed load of products under the LT brand I'll probably still use blue anyway as it seems to work fine & I have boat loads of the stuff already lol

 

[L3phturn]

New machined parts are coated lightly in oil to avoid rust during storage and transit. You should clean the pinion and the grub thoroughly before you install it, every time. I know from Arrma the grubs will come with LT on them... but I don’t trust it on new parts. Always clean with a strong degreaser and something volatile like electric contact cleaner or alcohol. Keep an older but clean grub around to run all the way in and out of the hole in the pinion and get it super clean. I keep a stock pinion to clean grub screw with too.