Pilot truck keeps jumping the track


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Modeltrains2021

Modeltrains2021

Active Member
Hi my mantua Hudson's piot truck keeps jumping the track how do I fix that? The wheels dont seem to have a flat spot and it only happens in curves and no where else on the track I was thinking about kit bashing riva rossi trucks to it since my friend did that to his and it made it better Tia jake.
 
I used to be an authorized Mantua repairman and that happened on occasion because of a slightly bent axle. The pilot truck for both 4-6-2 and 4-6-4 are the same. You can find one on ebay.
His Servant and yours,
Lester
 
No flashing or gunk preventing the truck from swinging fully from side to side?

No obstruction under the pilot that hinders the truck's movement?

Truck sits flush and flat on a shiny countertop, along with all the drivers? It's not canted a bit, or light on one wheel? Fall flanges fully contact the countertop surface?

Is the mounting screw for the truck nice and snug? It should be backed out at least half a turn, probably a full turn. The truck needs to wobble.

The truck might be too light, or maybe a spring is missing, or the spring is displaced/deformed, and not performing its function properly. You can glue a small piece of lead weight somewhere, but not so that it confounds the truck's purpose and movement.

Often the culprit isn't any part of the locomotive, but it's the tracks. If the outer rail dips even slightly, but the drivers further back are firmly situated on even rails, the truck might be tempted to lift itself out of the gauge, particularly if that mounting screw is too tight and it can't dip and follow the rail height. Try lifting the outer rail along that trouble spot by a full mm. See what happens.
 
Modeltrains2021 said:
Hi my mantua Hudson's piot truck keeps jumping the track how do I fix that? The wheels dont seem to have a flat spot and it only happens in curves and no where else on the track I was thinking about kit bashing riva rossi trucks to it since my friend did that to his and it made it better Tia jake.
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I didn't see anyone else say check the wheel gauge. If the gauge is a tick too large they would have a hard time cornering.
 
I had a similar challenge with one of my locomotives. Derailing at the same part of layout. After checking varous parts of the locomotive etc. I widened the curve from U.K. radius 2 to radius 3. Success!!! Rather strange as the locomotive manages other radius 2 curves.:confused:

David
 
The closer one gets to engineered limits, the greater the likelihood of 'errors' of any kind. This applies to model trains as well. Tight curves tend to have slightly, but measurable, tighter gauge. It might make the difference. Same with improper gauging of the axles, but that usually manifests near the frog of a turnout.
 
I have one steam engine that was doing the same thing , pilot wheels jumping off , I took a lead sinker for fishing and smashed it flat and with a hefty pair of scissors cut a chunk off and glued it ontop of the pilot , I can’t say whether it runs better because I had did this while I had a couple bridges out and scenery work so haven’t passed that yet. I’m sure it would fix it though , it was climbing the rails on a curve going into a tunnel so after using my nmra guage checking wheels and rail and running the engine with pilot wheels removed , that was the only thing I could think of. Id like to add I may have inadvertently misplaced the brass tang that pushes the pilot wheels down to the track as well, you can probably bend yours down a bit as well.
 
I took a look at it today and one of the wheels has a flat spot so I'm guessing when the flat spot hits its pushing the truck off the rail and causing it to jump.
 
Modeltrains2021 said:
I took a look at it today and one of the wheels has a flat spot so I'm guessing when the flat spot hits its pushing the truck off the rail and causing it to jump.
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The flat spot may contribute but if it comes off at only one location I would suggest modifying the track a little. Although, I had one afternoon where the front trucks would not stay on the track no matter what.

Was frustrated, however put that loco aside for a few days. When I decided to work on it, it worked fine with no derails. Not sure what to make of that however the loco has been working fine ever since, did no tinkering. Could have been a chunk of scenery in there I wasn't seeing.
 
logandsawman said:
The flat spot may contribute but if it comes off at only one location I would suggest modifying the track a little. Although, I had one afternoon where the front trucks would not stay on the track no matter what.

Was frustrated, however put that loco aside for a few days. When I decided to work on it, it worked fine with no derails. Not sure what to make of that however the loco has been working fine ever since, did no tinkering. Could have been a chunk of scenery in there I wasn't seeing.
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That's solid evidence of gremlins.
 
Modeltrains2021 said:
I took a look at it today and one of the wheels has a flat spot so I'm guessing when the flat spot hits its pushing the truck off the rail and causing it to jump.
Click to expand...
Unfortunately, the axles on the 4-wheel lead trucks are staked in the truck frame, so your best bet is to buy one off of ebay. If you go to page 6 of the "Mantua Steam Locomotive listing, there are a couple of them for sale. There is also a bunch of five also for sale, but probably more than you would want to spend. The individual ones are fairly inexpensive...$6.95 and $8.95, respectively, but you'll have to pay a couple of bucks additional for postage.
 
Check the track for a slight dip or rise. Since the drive wheels are solidly mounted, when they hit a slight rise in the track , it will cause the front pilot wheels to lift off the track. This is exaggerated more when going around a curve and the wheels will jump the track
 
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