Kato Mikado Traction Tire issue

[mike_lawyer]

I have two Kato Mikados that I converted over to PRR L1s using the GHQ conversion kit.  Mikado #1 pulls like crazy and works great.  Mikado #2 exhibits slippage on curves and slightly uneven track.  Anyone have a suggestion on a possible fix?  It seems that the traction tire driver might not be making firm contact with the rails.  This is the first time I have ever had this issue with a Kato Mikado.

[peteski]

So the other identical loco doesn't have the same problem when going over the same uneven track and curves the other loco has problems on?

Did the misbehaving loco always have this problem, or the issue developed recently?  Or the misbehaving loco is now to you?

[Rasputen]

Perhaps the lead truck or trailing truck is bottoming out?  I would repeat the test with them removed.

[mike_lawyer]

So the other identical loco doesn't have the same problem when going over the same uneven track and curves the other loco has problems on?

Did the misbehaving loco always have this problem, or the issue developed recently?  Or the misbehaving loco is now to you?

Yes, the good Mikado runs flawlessly over all track and pulls like a mule.  The second one has always had some slippage at various areas of the layout and does not pull as well.  Kind of a head scratcher as to why.

[mmagliaro]

Rasputen's suggestion is a good one, particularly the trailing truck, so check that first.

As precise as those mechanisms are, there are subtle differences.  And the traction tire protrudes from the wheel only about .003" or so, so it doesn't take much error to cause a problem.
Make sure all the drivers float a little in their slots, and float similarly between the two engines.   Flip the two engines over check this by just wiggling each driver in both engines and comparing how they move (or don't).  Check the gauge of all the drivers on both engines and note any differences.  Check that all the drivers are lined up on each side, not just "in gauge".  You can have the wheelsets all be in gauge, but have one "racked" more toward the left or right than the others.  Slight differences here can make the engine float better or worse. 

Sit the "good" engine on a piece of track.  Check how much the 3rd driver can lift up a little toward the
frame with tweezers.  You will see that it can lift a hair without the rear TT driver being pulled up off the rail.  See if the same is true on the "bad" engine.  I would expect this to be the most likely problem.  If the "bad" engine's 3rd driver can't lift as much (or at all) without disturbing the TT driver, you have two choices.  You can try the old trick of putting a little rectangle of masking tape into the TT driver's slot below the bearing so the wheel is forced downward a hair toward the rails.  Or you can try *judiciously* filing a HAIR out of the bottom of driver #3's slot so it can float upward a bit more.  Remember, we're talking just a few thousandths here.  These are not sloppy mechanisms.

[mike_lawyer]

In terms of the trailing truck potentially bottoming out, what does that mean?  I understand all of the other things to look for, but just did not understand that one point.

I will take a look at everything later tonight and report back!

Mike

[Rasputen]

If the truck can't rise up enough, it will take pressure off of the drivers as it goes over some irregularity.  Similarly, if it can't droop enough, it can derail where every other piece of equipment runs fine.
The truck pivot may be too tight, or the truck could be hitting the ashpan, or the wiring, for example.

[mike_lawyer]

OK, I had a spare traction tire driver, and I swapped it into the locomotive this evening.  Now everything runs really well, no slips.  Could be I just need to replace the traction tires on that driver.

However, one new issue I have is that the new traction tire driver is not in gauge.  It is too narrow.  Is there a preferred tool to use to get drivers in gauge?  I previously have used the "screwdriver between the frame and the driver method", but would prefer a more precise method of getting a driver in gauge.

[peteski]

OK, I had a spare traction tire driver, and I swapped it into the locomotive this evening.  Now everything runs really well, no slips.  Could be I just need to replace the traction tires on that driver.

However, one new issue I have is that the new traction tire driver is not in gauge.  It is too narrow.  Is there a preferred tool to use to get drivers in gauge?  I previously have used the "screwdriver between the frame and the driver method", but would prefer a more precise method of getting a driver in gauge.

Very good. Maybe it did just need a new set of traction tires.  It might also be possible that there was some issue with the way the original driver set was located on the frame and merely reinstalling it would have also fixed the problem.

Screwdriver should  work just fine.  Just pry as close to the axle as possible.  Mikado driver axles have hexagonal cross-section. so it is impossible to get them out of quarter.  Using small jewelers screwdriver as a pry bar you can make very precise adjustments.

[mike_lawyer]

Is there any other method people use to get drivers in gauge other than using a jewelers screwdriver between the frame and the driver?  Is there a tool to use that can do this easily?

[nickelplate759]

Is there any other method people use to get drivers in gauge other than using a jewelers screwdriver between the frame and the driver?  Is there a tool to use that can do this easily?

Sometimes a gear puller can do this in a controlled manner, but it really depends upon the construction of the wheelset.  A gear puller will want to put pressure on the axle end and lift the wheel.  That works well on a solid wheel, but is pretty iffy on a wheel with separate tires and centers (like most steam locomotive wheels).    Also, it requires that wheel not be made from the same piece of material as the axle (some are).

[Lemosteam]

The mikes drivers use a hexagonal driveshaft, and press into the plastic center, so using the screwdriver should not ruin the driver and will not cause the driver to torque slip on the axle or mess up the quartering, if that is what worries you. Once in gauge, add a drop of red thread locker to the hole on the OUTSIDE of the driver axle end.

[mmagliaro]

If you are going to use the "pry" method, I suggest a large Xacto blade (like a #24) rather than a screwdriver.  They are
thin so the can get right down to the axle behind the wheel, which is really where you want to exert the pressure.
Because some engines can tolerate that type of prying and some really can't without ruining the driver hole,
I just plain don't ever do it, by the way, but that's up to you.  The Mikado is probably one of the more robust ones that
you can gauge by prying if you want to.

I use this (the NWSL "The Puller"), with the accessory precision push bolt set they sell for it:


and this, which is sold under a lot of names, but seems to be called the "Walkera" puller these days...


I don't understand the problems people are describing with using a puller on a steam loco wheel.  Whether it has a plastic
center or not, the plate of the pulling device slaps flat against the wheel, and the only thing that can move is the axle being
pushed out of the hole in the center.  You do have to remove the whole driver set from an engine to use these, whereas
the "screwdriver" approach is something you can just do while it's in the engine.