GS-4 General Problem Observations

[peteski]

Maybe I should have responded a bit differently. You mentioned The #1 driver runs light so slop free bearings lessens the chance of the driver wobbling under the drive of the side rods.   To me that implied that if #1 driver wasn't slop free, it would wobble because it was rod-driven.  But yet #2 and #4 have plenty of slop (vertically and laterally), are driven by the side rods just as #1 driver is, yet I don't recall them wobbling when the model is running.

For me the reason #1 axle is slop free is because it is the part of a 4-point suspension of this model.  The fact that it is rod driven has no bearing on that.   But in either case, it is what it is, no matter what we speculate the reason is.

[victor miranda]

Hi Skipgear,
it is good to read you.  I have not seen you much.

you know what Conversations with Peteski can be like.

on to Max's bearings
I went into the catacombs and found a gs4 I got at parts for a prr t1 project.

first driver...
yes the bearing is snug. 
I have a bearing block I pulled out of a failed axle repair.
it will wiggle like the ears are held on the sides  so the block is not held tight

#2 is free to slide up and down
my #3 is not as snug as #1 and not as loose as #2.

and now #4 axle...
the bearing block can slide up and down easily.
mine will NOT move back into the chassis.
If you angle it a little  it can be moved into the chassis and I doubt the angle required
could be done with an axle in place unless the bearing is well past worn-out.

I am thinking the chassis may be bent or some one flattened the ears.
undersized the ears perhaps?
trade #1 axle for #4 ?

I am trying to figure out how the blocks stay in!  If they can go into the chassis
they should be able to come out as well.

are all three of your locos this way?

victor

[mmagliaro]

Victor,
I tried swapping 1 and 4- no difference.
Of the 3, this one is the worst.  The other two seem to just barely manage to stay in the slots.
When I would push the driver up and down, after reassembly with the cover plate on, one or both
of the bearings would start to angle and *almost* come out but would hang on. 

This one is the only one that really pops out completely and fouls the axle.

Still likin' my plastic inverted U.  The spring action of the driver is preserved, the lateral motion of the axle is preserved,
and the bearings stay in.  Yay.

[peteski]

Could the problem be (like Victor said) with the chassis itself? Maybe not fully molded bearing slots?  Or the ear (flange) of the bearing is not large enough?  If not all the models exhibit that problem to the same degree, something in that model has to be causing this loose fit.

[mmagliaro]

The chassis is the most likely culprit.  I put a micrometer on the bearings and they are all the same
(within .001 or .002").   So yes, it certainly seems like the metal around the slots must not be as high,
or the whole axle channel is just a little big... something like that.
What bugs me is that I can see a whif of this problem in the others, just not enough for the bearings
to quite pop out.  I don't like things like that.  The bearings could have easily been made with bigger ears
and deeper recesses to hold them

In any event, it's back together, ran for a good 5-6 hours with no hiccups, so it's now back in its box for
the trip home.

[Lemosteam]

Sounds like Kato needs to take a look at their tool wear.  Injecting metals into die cast molds can have an effect on thin or shallow features over time and/or pressure may not be pushing metal into finer areas anymore.  Has anyone compared a newer unit with a very early unit?

Max it may be a good idea to let Kato know, because we do not have the drawings of the castings to measure against.

[victor miranda]

Hi Max,
I like the U as well.  It seems a good solution.

I would have set it in the other way so the axle can be removed without
having to pull it or cut it

Has anyone else swapped out the new Kato Drivers?
noticed the same issue?

Hi Lemosteam,
If there is a company that does not chance wearing out a mold
I suspect Kato is in the lead pack.

on to the next adventure!

[mmagliaro]

Yes, Victor, there are definitely better ways I could have fashioned the "U".  But then, it is a version 1.0 of
the idea.  I like the U being upside down like I have it, because then I don't have to worry about
the bottom of the U getting in the way of the sprung fingers that are lurking down there below the bearings.

If I were to do it again, I think I would try to glue a strip across the top of the U that would stick out as little "tabs"
on the left and right of the axle channel.
Then, I could cut some small recesses into the frame to accept them.  It wouldn't be too hard; Just slice two little grooves in
there with a spinning Dremel wheel.   Then, the "U" could be dropped in, the tabs would drop into the recesses,
and that would hold it in position, especially after the cover plate goes back on.

Now, it would be easily removable, and always go back in in the exact same spot.   I did put a drop of glue on each
"wall" of my "U", which means that to get it out, yes, I would probably have to cut it. 

John makes a good point about the frame tooling.   The black "war time" scheme, which is the one
that has this problem, came out much later than the others.   So it is possible that by then,
 the frame slots were a little too wide.   It's also possible that Kato routinely retires molds after
producing so many models from them, but didn't quite retire this one soon enough.

But (beat-dead-horse) this problem could be avoided by better design.  Make slightly larger bearings with wider ears,
and they could be far more tolerant of slight frame variations and would assemble more easily.

[peteski]

But (beat-dead-horse) this problem could be avoided by better design.  Make slightly larger bearings with wider ears,
and they could be far more tolerant of slight frame variations and would assemble more easily.

Um, they already did that - see FEF-3.  Much larger diameter axles and bearings.   

[mmagliaro]

Um, they already did that - see FEF-3.  Much larger diameter axles and bearings.   

Yes, yes.  I know.  But to me, this wasn't a linear, upward-going evolution.  The Mikado bearings
did not have this problem, so they took a step backwards on the GS4 and then seem to have
gone back to bigger bearings with the FEF.

[peteski]

Yes, yes.  I know.  But to me, this wasn't a linear, upward-going evolution.  The Mikado bearings
did not have this problem, so they took a step backwards on the GS4 and then seem to have
gone back to bigger bearings with the FEF.

In my view those thin axles used in GS-4 was an attempt to minimize friction of the drive train.  Judging by the issues with broken axle tubes, this experiment have proven unsuccessful. They came out with a decent workaround and also decided to beef up the axles on the next steamer they released.  Good to see Kato learning from their mistakes and offer retrofits for those models.  Something they also did for Mikado (which had couple of issues in the initial run). Remember the original drivers with poor electrical contact?   Or no traction tire?  They took care of both problems too.

[mmagliaro]

Now that you mention it...
I wish they had stuck with the thinner axles and the original bearings, and just made the axle solid all the way across
like they did on the new drivers.  And also put a "faux" plastic axle tube, just like a sleeve, over the thinner axle, but
not holding anything together.   The plastic tubes would keep the bearings upright - just a safety measure,
and all the original design benefits would still be there (lower friction).    The thin metal axle wasn't the thing that failed.
It was those plastic tubes.

[peteski]

Now that you mention it...
I wish they had stuck with the thinner axles and the original bearings, and just made the axle solid all the way across
like they did on the new drivers.  And also put a "faux" plastic axle tube, just like a sleeve, over the thinner axle, but
not holding anything together.   The plastic tubes would keep the bearings upright - just a safety measure,
and all the original design benefits would still be there (lower friction).    The thin metal axle wasn't the thing that failed.
It was those plastic tubes.

Not sure what that would buy you since the that would not change the shape or the outside diameter  of the bearings.  IIRC the axle diameter of the steel axle is the same on the old and new drivers.

The original drivers had couple of possible problems

1. No positive locking of the axle halves - could lead to the drivers getting out of quarter.
2. The plastic axle tubes (which held and electrically isolated  the axle halves were prone to breaking.

The new design now uses a solid axle between the drivers. But in order to electrically isolate the drivers they changed the wheel insert design to provide a plastic sleeves at the wheel center. That electrically isolates the wheels from the axle. In order to do that they had to increase the diameter of the inside opening in the bearings.
They also knurled the axle ends to provide a locking mechanism which prevents the drivers getting out of quarter.

I suppose that they could have included a plastic sleeve over the entire axle, but that would be extra part to produce and assemble (at extra cost) which Kato didn't think would be of any use.  I have a feeling that Kato engineers didn't expect the bearings to pop out of their nests.  I also suspect that even with a plastic sleeve over the axle, if the bearing pope out it will still get skewed enough to cause a bind.

I also suspect that the 3 problematic engines you have are more of an exception than norm. But the only way to know that for sure would be to ask Kato USA employees who repair the GS-4.

Speaking with Kelley at the Springfield show (the guy who does Kato repairs) he mentioned that they were seeing lots of broken plastic axle sleeves (so the new version of the drivers was introduced). He didn't mention anything about the bearing problem (but I didn't ask him specifically for that).

[mmagliaro]

Actually, now that I've had some of these apart, there are small metal "fins" on the half-axles that are pushed into the plastic tubes, so Kato thought of that.  Unless the tube cracks, the wheels would not go out of quarter.

As for the plastic tubes solving the bearing problem... yes, they would, for the same reason my "inverted U" does.
It's not that the bearings rise up and out of the top of their slots.  They tilt in or out right out of the grooves because
the ears on the bearings aren't quite big enough, nor the grooves deep enough, to assure that this never happens.
I grant you that it must not be chronic, but, by the way, I just did the 4th GS4, and had to put the U in there.
So that's 2 out of 4.    Honest, I could set those bearings in there with the greatest care, put the cover plate on,
confirm they are still in there, even test bob the driver up and down on the spring fingers, check again, yep, still
in the slots.  Run it for a minute, and pop.. one comes out.   

The plastic tube running just behind the bearings prevents them from tilting then the wheel nub is
only about half in the bearing (as the axle slides back and forth).

I'm surprised they didn't just make a new plastic tube out of a different material that wouldn't crack.
I suppose they decided it was tough to know exactly what would hold up in that application.

I have another "while we're at it"... the new drivers have plastic centers popped into an outer metal tire.
But they push in and are only held by a plastic locking pin and friction.  Amongst all 4 sets of these I just replaced,
I found a number of them where the plastic center could push in and out of that rim without much effort.
The problem here is that if that rim moves in or out on the center, that throws the wheel gauge off.
It isn't a lot. About .010", but that's quite a bit on the NMRA plate notches.

If you're getting the impression that I want to bash Kato here, please don't.   They make great stuff.
But this is just one of those cases where the more I get into this particular engine, the more trouble spots I am seeing.
The Mikado had its problems, but I think the remedies were better when they came along.

[victor miranda]

that means we should put a sleeve on the axle to keep the bearing block straight.

an un expected interaction.

and I think the u shaped insert is the better solution.

victor