Kato GS-4 drive gear slippage help needed

[up1950s]

Ok I had a change of mind and added a head light to my UP 819 powered by a modified Kato GS-4 chassis . I added Loon where no Loon had gone before to counter the lost Loon in adding a lite to the light front end . Well in doing so I put a rub on the gear tower U-Cup face . It was well hidden and I thought the problem was in the motor or the rods . In the process of trying to convince the wheels to turn I spun , or the motor spun the the gear on the only driven split axle with the TT's . I have tried to Krazy glue the metal half axles in that Engineering Plastic gear four times , only for it to slip out of quarter after less that a hour of up in the air testing . So I have some of these thoughts .....

1  Plead for help to save time .
2  Goo baby Goo .
3  Try that very expensive slipery plastic glue .
4  Epoxy
5  Rough up the steel and drill holes through the gear hubs so the Krazy glue has grippy places to hold on to.

What is your go to fix , and thanks in advance ?

[Zox]

I'd say make a flat spot on the shaft, a notch in the inside of the gear hub, line 'em up, and fill the newly-created space with epoxy. That should give you a "keyed" joint that won't slip.

My only concern with this would be making sure the epoxy goes in the space, and nowhere else...

[superturbine]

Key way will likely not work due to quarting that needs to be perfect.  That is why your driver has come loose.  My advice would be to ruff up the axel and ruff up the driver bearing point so that super glue can grab onto both.  Check quartering again..... Unfortunately, the drivers are no longer available from Kato.

[peteski]

Richie,
are you sure that the plastic axle tube is not split?  I've heard of those splitting (on the Atlas forum).  That would explain why the half-axles are slipping.

If not, then my way to taking care of this kind of slippage is to take a Dremel with a cutoff wheel (which I'll use as a precision grinding wheel) and either grind a shallow flat spot on the half-axles (as has been mentioned) or grind a very shallow spiral groove (simply roughen the surface) along the half-axles.  Then find a way to roughen the inside of the plastic axle tube (you could just take a sharp #11 blade and make a series of scores along the length of the inside of the tube.  Then make sure to thoroughly degrease all the parts (this is vital for a good bond!!) and glue the half-axles into the tube using super glue. Make sure you have them quartered properly. Good think that the quartering does not have to be aligned with the gear's teeth on this loco as that would make things very difficult.

[victor miranda]

yeah, cracked is the most likely.

the best fix is get a new axle.
I happen to know that Kato has no axles at the moment.

second best is to put a brass collar around the split plastic axle holder.
 red loc-tite it together.

happy quartering.

[up1950s]

I have no crack . I have seen lots of them on HO and N , but this is not cracked .  Thanks for the responses so far

[mmagliaro]

On such a critical joint that takes a lot of mechanical pressure, I would never trust super glue.

I second Victor's idea of using LocTite.  That stuff can really hold. 

But I think you need shear pins.

After you glue it, quarter it, and test it, let it get hard.  THEN...

Drill and insert shear pins.
I would drill a small hole, perhaps .020" right through the plastic axle tube, right througn the metal
axle, and out the other side.  You'll have to do it by hand with a pin vise and much patience, but it can be done.  Drilling
through that axle will be no fun.  Start with a nice sharp, new bit.

Having the thing all
glued together before you do this is important, so the tube doesn't slip while you are drilling.

Then, dip some .020" wire in super glue, epoxy, or anything like that, even more Loctite,
and shove it through the hole.
You'll need to drill and wire both axle tubes, of course.

Ain't no way that thing will slip after that.   Better make sure the quartering and the gauge are right
before you glue/drill/pin.

I have joined two gears together to make compound gears for my K4 rebuilds this way.  I was joining
delrin to delrin, or delrin to brass.  And it was the main drive worm, so it takes all the mechanical
pressure.   Not one has failed yet.   But without shear pins, forget it. 

[peteski]

Max, the GS-4 axles are *REALLY* thin. Something like 0.020"!  Have you ever tried to drill a hole through a 0.020" steel rod?!

I also don't understand the thread lock thing.  Why do you think that it has better shear strength than CA glue? After all, the thread lockers are designed to shear when the bolt is removed. They are designed to prevent the bold from loosening under vibration. Vibrations of threaded assemblies do not generate lots of shear forces on the thread locking compound.

Not to burst your bubble but thread locker compound  is related to CA glue.  It is Methacrylate ester.  Here is the data sheet:
http://www.loctiteproducts.com/tds/T_LKR_GREEN_tds.pdf

Besides, even with all the shear strength I don't think that thread locker will have a strong bond with the slippery plastic used in the axle tubes. So a bond between the hardened compound and the plastic will shear very easily.

[DKS]

Loctite 609, Stud and bearing mount, is what I use for set-ups like that, as I have it in my machine shop. You may have to get it at a bearing supply company like Applied Industrial.  MSC Supply, or McMaster/Carr also carry it. If it will hold a spinning bearing on a Bridgeport milling machine, it will hold that axle even though the surface area is small. Don't use it as a thread locker, you'll twist the head off before you break the thread bond. As aready stated, rough up the axle and tube. 609 is good for up to a .005 inch gap. Charley.

I was having no luck finding Loctite 601. Then I see the post was edited...

[DKS]

Sorry I'm "OLD" with a poor memory, I went in the shop and checked. It's 609, and is listed on the "Industrial" Henkel/Loctite site. Charley

Thanks, no problem. Just placed an order with Amazon.

[victor miranda]

check for a cracked axle.
no loc-tite, threadlocker, superglue will hold without a collar.

victor

[SkipGear]

Max, the GS-4 axles are *REALLY* thin. Something like 0.020"!  Have you ever tried to drill a hole through a 0.020" steel rod?!

I also don't understand the thread lock thing.  Why do you think that it has better shear strength than CA glue? After all, the thread lockers are designed to shear when the bolt is removed. They are designed to prevent the bold from loosening under vibration. Vibrations of threaded assemblies do not generate lots of shear forces on the thread locking compound.

Not to burst your bubble but thread locker compound  is related to CA glue.  It is Methacrylate ester.  Here is the data sheet:
http://www.loctiteproducts.com/tds/T_LKR_GREEN_tds.pdf

Besides, even with all the shear strength I don't think that thread locker will have a strong bond with the slippery plastic used in the axle tubes. So a bond between the hardened compound and the plastic will shear very easily.

The advantage to thread lock is the flexibility. CA is just too brittle. The only analogy I can give is from flying foam RC airplanes. A lot of guys want to use "foam safe" CA to build and repair these planes. The problem is, the glue joint is more brittle than what it is gluing. The foam will fail, along the joint. The glue holds but the as the foam flexes, it cracks next to the joint because the joint can't flex. I prefer a less brittle glue, Epoxy, etc. for a more durable joint.

Also, CA just doesn't glue to steel very well, especially polished, hardened steel of the axles. Even after some knurling with a file, you can still scrape the glue off with your fingernail without too much effort.

[up1950s]

I am trying 5 minute epoxy , applied at 11 am this morning  . If that fails on tomorrows test I will buy some locktite . The metal axle is .040  . You know the eccentric pin though much larger in diameter is square on the end . Kato should have taken that design that they used on a non-critical function and applied it to the drive gear . But that's just me . It would have been fool proof . They treated the driven and traction tire axle with the same standards as the other 3 . It deserved more attention being that it was expected to do so much more work than the others .

[victor miranda]

hi up1950s

I hope the epoxy holds.

a couple of comments.
the axle design on this loco is a weakpoint
in that once it breaks, it is tough to get a good repair.

the concern for making sure it does not break in the first place
is a lot harder to justify.

another way to say that; how tough is the part or the drivetrain?
If the loco is dropped Kato is not responsible.
you are not the first to both stall the geared driver
and have the motor snap the gear loose from the axle.

my opinion is that the drivetrain should be stout enough
to stall the motor under those circumstances.

I will give Kato some credit in that I did test the
motor and gears by stalling the axle
so I believe the motor can't break BOTH drivers loose at the same time.
I am pretty sure the motor and gears can pop one side loose.
Kato's design is very close to will not fail.
Since the drive-train can 'pop an axle,'
 I know not to run the loco with only one traction tire
and take some care when running and testing to use only half the throttle.


the one case I have met, the plastic axle was cracked.

 

[mmagliaro]

The epoxy might hold.  But with a .040" axle, it should be possible to drill a hole in there.  It would
be a little tedious, but possible. 

The thing about epoxy on those smooth plastic surfaces is that even when it seems to be strong,
it has a tendency to "peel" right off sometimes.   If you roughened it up a little, that will help.

I have tried ACC on worm/axle and other situations where I use LocTite or JB Weld.  The ACC has never
held well for me.  In general, ACC hasn't ever worked on anything for me for the reason Tony cited: it is
just too brittle.  Any sharp rap on the joint and it breaks.   I did use it on my brass TrainCat bridge model,
and it seemed to do okay.  But I reenforced a lot of the larger more critical joints with some JB.