Kato GS4 Driver Replacement Tutorial

[mmagliaro]

On the heels of the other few threads that have recently been opened regarding the Kato GS4, the driver
replacement, bearings, and the cracked axles, I put together a little step-by-step on replacing the
drivers.   Perhaps these photos, and a bit of video at the end, will be helpful.

The video shows how I put crankpins back in.  I think that may be one of the most vexing tasks that face
modelers who take steam locos apart, so I thought a video demo might help more.

The pictures are BIG so you can see what's going on.















































Here's the demonstration video on inserting crankpins:

https://www.youtube.com/watch?v=7j3J1j6xjMM

[peteski]

Excellent tutorial!

[carlso]

Max,

I can only second peteski's comment but add that you are truly a talented, willing to share your knowledge guy. My hat is off to you.

I appreciate your work on, my problem, and with this fine tutorial and short video perhaps it will help others as well.

This thread should be put in the archives for reference by all.

Carl

[mmagliaro]

Thank you, guys.  I corrected one photo, the one showing how the shim is inserted between the frames at the lower rear.
I had the lines pointing out the frame screws going to the wrong places.

All of this is pretty common stuff in the world of fixing up steam locos, but it doesn't seem to be written down or
photographed anywhere so I thought it would be worthwhile to document.  There is a short piece by me in one of the recent
NTrak newsletters showing the crankpin removal and replacement techniques, done on a Kato Mikado.  The procedure
is really the same on almost any engine.

[Rasputen]

Instead of making that U-shaped spacer, could you put a temporary shim between each driver and the frame, until the bottom plate is installed?  It looks to me like if the drivers were kept centered, then the bearing wouldn't be able to slide off of the driver. I don't own one of these so I can't tell for sure.  Kato must have some sort of assembly jig in order to accomplish this.

[victor miranda]

this may seem a little strange.

the problem is the axle...
it is much smaller in diameter than the original axle,
 that allows the axle to move far enough down
to allow the bearing 'ears' to escape the slot

it is easier to add the plastic to the frame when compared
to adding a fattened axle to the driver axle.

victor

[mmagliaro]

Instead of making that U-shaped spacer, could you put a temporary shim between each driver and the frame, until the bottom plate is installed?  It looks to me like if the drivers were kept centered, then the bearing wouldn't be able to slide off of the driver. I don't own one of these so I can't tell for sure.  Kato must have some sort of assembly jig in order to accomplish this.

No, that wouldn't help.  The issue is that even if you have the bearings seated in the frame slots, all nice and straight with the
bearing "ears" in place and the bearings vertical, and you put the cover plate back on, the bearings cannot stay in
those frame slots.  The "ears" can easily pop out, particularly on driver #4 (most likely because that's the one
that can move up and down a lot in the vertical direction owing to the sprung fingers it has).

It's not an issue of the bearing popping out during reassembly.  Even if you get it in there just fine, it will still come out while the engine is running.  It happened to me twice before I figured out what was going on.  The "ears" of the bearing simply
aren't big enough, and the frame lots that accomodate them aren't deep enough, to keep them reliably
in place.

On the old drivers, there was an axle tube in between the bearings, which did what my U channel does: it acted as a
brace against the insides of the bearings, keeping them from tipping in enough to escape from the frame slots.
That, and the old bearing design had bearings with a very small hole in them; the thin steel axle ran in that hole.
A smaller hole means less slop and less ability for the bearing to wiggle and wobble on the axle.
The new ones have bearings that go over the big "nub" on the back of the wheel and as the axle slides back and forth
laterally, when it slides all the way over in one direction, the nub is just barely in the bearing (another sore point
about this new design I do not like).   When it is in that position, it can wiggle a lot on that nub, opening the door
to more opportunity to jump out of the frame slots.

[GaryHinshaw]

... it doesn't seem to be written down or photographed anywhere so I thought it would be worthwhile to document.

Indeed.  Thank you!

[mmagliaro]

this may seem a little strange.

the problem is the axle...
it is much smaller in diameter than the original axle,
 that allows the axle to move far enough down
to allow the bearing 'ears' to escape the slot

it is easier to add the plastic to the frame when compared
to adding a fattened axle to the driver axle.

victor

Ooooh, wait.
You mean,  picture driver #4.  The engine is right-side up.  The back end lifts up a little as it goes over some uneven track.
Driver #4 drops (because of it's spring loading feature).   But now, because the axle is just a thin steel rod,
that driver can drop *further* than it could before, and so it drops enough for the bearing ears to come out of the slots?

I hope I interpreted you right.

But I don't think that's what happens.  Remember, the axle drop is limited by the bearings themselves hitting the gear cover plate.
That hasn't changed, and I don't think the axle can drop any more than it could before.

The thing is, the bearing ears can pop inward out of those slots even if the bearing is all the way down
deep into the axle channel.  It doesn't have to come up to get out (or in the case of the engine being
right-side-up on the track, it doesn't have to come *down* to get out).  Those ears JUST BARELY hold
the bearing in ... there just ain't enough metal to make sure it doesn't wiggle out of there.

[victor miranda]

hi Max,

I think you have read it as I intended...
I am going with maybe as the answer here.

when I was tinkering with the bearing block...
I found I could get it in and out from the top sneaking it past the spring
.... it would often fall out the bottom... with the bottom plate in place.

I do not recall the issue with the #2 driver... I do not recall testing it either...

I decided it could get loose if the axle got low enough.  I think the block in the old style
is restrained by the steel axle itself so it can't angle outward and from dropping further
by the plastic of the axle. 

the plastic stops the new block from angling out at the bottom...
 and dropping out past the bottom plate.

frankly, I doubt putting a fattened axle on the new style will stop the problem as effectively.

victor

ETA
the inward movement of the bearing was not a problem for me.
and the u-channel also effectively addresses that issue

[up1950s]

Thanks Max , you are well worth cloning en masse and assigned to QC drives and chassis from all manufacturers .

[mmagliaro]

Thanks Richie...  But I'm just tinkering and observing.

So sad... I wish Kato had stuck with the original axle tube design and just made new
drivers with stronger axle tubes.
The bearings were better, the friction was lower., the lateral play was controlled,
and there was no issue of the wheel nubs sliding in and out of the bearings.

[Rasputen]

No, that wouldn't help.  The issue is that even if you have the bearings seated in the frame slots, all nice and straight with the
bearing "ears" in place and the bearings vertical, and you put the cover plate back on, the bearings cannot stay in
those frame slots.  The "ears" can easily pop out, particularly on driver #4 (most likely because that's the one
that can move up and down a lot in the vertical direction owing to the sprung fingers it has).

It's not an issue of the bearing popping out during reassembly.  Even if you get it in there just fine, it will still come out while the engine is running.  It happened to me twice before I figured out what was going on.  The "ears" of the bearing simply
aren't big enough, and the frame lots that accomodate them aren't deep enough, to keep them reliably
in place.

On the old drivers, there was an axle tube in between the bearings, which did what my U channel does: it acted as a
brace against the insides of the bearings, keeping them from tipping in enough to escape from the frame slots.
That, and the old bearing design had bearings with a very small hole in them; the thin steel axle ran in that hole.
A smaller hole means less slop and less ability for the bearing to wiggle and wobble on the axle.
The new ones have bearings that go over the big "nub" on the back of the wheel and as the axle slides back and forth
laterally, when it slides all the way over in one direction, the nub is just barely in the bearing (another sore point
about this new design I do not like).   When it is in that position, it can wiggle a lot on that nub, opening the door
to more opportunity to jump out of the frame slots.

Thanks for clarifying that.  I thought maybe it was just an assembly issue, but if they can fall out while running, that looks like a good fix!

[peteski]

Thanks Richie...  But I'm just tinkering and observing.

So sad... I wish Kato had stuck with the original axle tube design and just made new
drivers with stronger axle tubes.
The bearings were better, the friction was lower., the lateral play was controlled,
and there was no issue of the wheel nubs sliding in and out of the bearings.

To be honest, I'm not sure if that would have been the optimal solution either. Remember, this is a retrofit fix for an existing model.  They couldn't have beefed up the plastic tubes by much before the would start rubbing against the frame.  Plus, I still prefer to have a solid axle between the drivers. There is too much stress there to just rely on a plastic tube axle. 

Kato seems to have learned from this weak design and the FEF-3 design is much better.  Similar  to the Kato 2-8-2 which is widely praised as one of the top steam loco designs.

[glakedylan]

Max
very helpful and very detailed write up and photos
I appreciate you sharing your genius and craftsmanship with us all here
keep up the super work
sincerely--