KATO PA1 truck performance mystery

[OldEastRR]

I recently acquired my first KATO PA. I have lots of E8s but this is my first PA (I don't count the ConCor/Kato version I have). While running it with a consist around my layout I noticed the front truck frequently had one set of wheels off the rails after travelling through a moderate (16-18"R) curve on a nearly 2% grade. My friend commented that this happened to his PAs often while running on a club layout's much wider curves. I'm wondering if anybody else has this problem.The E8s never did this, and as both locos have similar weight and wheel arrangements, I'm wondering why the PA does this. 

[RBrodzinsky]

Make sure it is seated squarely in the frame and pivots nicely. Also, check the wheel gauge; for whatever reason, I have adjusted more PA wheelsets (mine and others) than any other Kato model. 

Also, check to see if the truck is coming derailed in the same spot. Possible that a single wheel's flange is slightly large, and catching on a solder joint or piece of ballast.

[Tom Todd]

I had a similar problem with a KATO F7.  I spoke with KATO reps in Springfield about this.  They said that sometimes it was a problem with an improperly seated contact strip between the front truck and the motor.  This problem stopped the truck from turning properly.  A disassembly and re-seating fixed it.  I haven't any idea if it is the same problem you are having, but its worth checking.

Tom

[nkalanaga]

I had that problem with a Kato EF-58 electric (2-C+C-2), with the lead axle of the rear power truck derailing, always at the same spot.  My MILW branch is entirely curves, including a 180 degree 16 inch radius, code 40 curve.  It took YEARS to find the problem, which turned out to be a rail joint in the outside rail.  There was a very small piece of solder on top of the rail joiner, on the inside of curve, that didn't reach the NMRA gauge, and couldn't be seen from the aisle side.  When I finally found and removed that tiny piece, the derailments stopped.  Nothing else derailed there, and the bump couldn't be felt pushing the loco, or even just the truck, through by hand.  Weird.

[OldEastRR]

i'll check out the wheel guage and the contact strip, but at the derail point there's no joints or joiners. I have other equipment that sounds like it makes a clickety-clack when going over other curves where there's no joints or joiners. Maybe I have a haunted layout.

[nkalanaga]

It could be haunted...

Other possibilities are:

Assuming it's commercial track, a piece of flash on top of a spike head, or in the rail web.  I've seen quite a bit of that on newer ME code 40, as the molds wore out.

A slight kink in the track.  It may not be easily visible, but if there's a spot where the curve is a little sharper, that can cause derailments.

A low spot in the outside rail, or a high spot followed by a normal or low spot, or a high spot on the inside rail.  In any case, if the rails aren't level, the leading flange can be lifted over the outside rail, causing a derailment.  Note that grades are fine, the track doesn't have to be horizontal, but anything that lifts the inside wheels, or the rear of the truck, relative to the front outside wheel, can cause trouble.

A spot with slightly narrow track gauge.  The PA-1 has a fairly long truck wheelbase, which makes it more prone to binding on curves anyway, and narrow track can squeeze a wheel, causing it to ride up and over the rail.

My layout had all of these, plus warped frogs in the early ME turnouts, and I spent about a year shimming, filing, and regauging everything!

[SecretWeapon]

The Kato PA-1's are the best tool to test your track work. If you have a bad spot, it will find it. I'm in the middle of a new layout, & as I get to a point, I grab my trusty EL PA'1 & let it rip. If it finds a bad spot, I address it immediately. Yesterday, I ran a couple of engines in the area I redid. No Problems. The PA found a bad spot. It took about a 1/2 hour to correct the problem. I'll never have worry about that spot again. Use it to your advantage.

[nkalanaga]

Not having a PA, my test train was a passenger train, four Kato first-run Fs and 12 very mixed passenger cars.  An F, or even two or three, would run fine.  Four with the train found every bad spot - and the lead truck of the third unit found most of them.  Those things have absolutely no "rocking" motion in their trucks, and I had Trainworx turn the flanges down, when Pat Sanders was specializing in that.  Between small flanges and no play, they would find any spot where one rail was higher, or lower, than the other.  As for kinks and gauge problems, the passenger cars found most of them!

[randgust]

I have a layout that's 30+ years old on the main line alignment, and runs all manner of six-axle EMD power, mostly Kato.  Main line curves run 13 & 15", with superelevation.

I have a Hallmark 4-8-4 with eight-wheel tender trucks, it runs fine.  That's usually my ultimate track tester.  All this runs just fine.

I hosted a BLI PA1 with fine flanges and all it did was derail.  Any axial (cross-level) twist and the trucks climbed off the curves.   Those big feet on a PA1 are a long wheelbase, add finer flanges and a stiff frame that doesn't have any tolerance for truck twist is a tough combination.   

You could experiment with dropping one of the trucks and rolling it through the track spot problem with your fingers and see what you feel.  It's one of those odd things that you may have to deliberately narrow the gauge on the center axle to buy some lateral movement and take the end axles to full gauge.    If it passes all that, then focus on the frame and if anything can be done to develop some torsional tolerance.  I'm guessing you're ever so slightly off on cross-level twist there and it's climbing the outer rail.  You can experiment with shimming under the ties with paper shims to increase or decrease the tolerances; it won't be much.

[OldEastRR]

The Kato PA-1's are the best tool to test your track work. If you have a bad spot, it will find it. I'm in the middle of a new layout, & as I get to a point, I grab my trusty EL PA'1 & let it rip. If it finds a bad spot, I address it immediately. Yesterday, I ran a couple of engines in the area I redid. No Problems. The PA found a bad spot. It took about a 1/2 hour to correct the problem. I'll never have worry about that spot again. Use it to your advantage.

Another positive aspect of a KATO loco! No really, you're right. I made an inch by inch inspection of the curve -- which I thought was one continuous piece -- and found it wasn't. Then I found a pretty considerable gap in both rails at the joint. I'd laid that part of the line during the warmest parts of the summer. The PA, I got last month. I'm inclined to believe that with the colder weather the joints --- which might not have been tight to begin with -- got wider and the new loco found it. Since I haven't yet finished working out all these kinks I have the track only nailed down, and I closed the gap by relaying the whole curve a tiny bit tighter (it's over 18"R).
But yeah, only the new KATO PA found this problem -- all my other locos and rolling stock sailed right through. A handy feature!

[nkalanaga]

So it was the track after all.  Now, if you have the room, I'd suggest cutting new expansion joints at both ends of the curve.  Otherwise, when everything re-expands this summer, you'll have kinks, which will likely cause even more derailments.

The new joints don't have to be opposite each other, the joints in one rail can be offset from those in the other by a few ties.   This will help keep the track in line, because the tie strip will still connect the two ends.

[JanesCustomTrain]

The Kato PA-1's are the best tool to test your track work. If you have a bad spot, it will find it.

What he said. 100% agree.

Jane