I have a brass,USRA,4-6-2 that jumps the track on 24" radius curves.Before I take the pilot truck apart,I would like to try to get a idea of what to look for-and possible cures.I have already tried to loosen the screw that holds the truck to the boiler, tightened it,stretched the spring,checked the wheel guage,checked the track.I’m now at a loss as to where to look next,Any ideas?
Sounds like the piolet wheels can’t swivel far enough to make the curve, they may seem free when it’s off the track but may be hitting something when the weight of the boiler is applied. Jerry
Welcome to the club. I have found that all my problems were with the track, not the wheels. I still have some problems, and may yet modify the engines. I learned to look for TINY track issues: rail joints, bumps, swaying etc. I also learned that the problems were not always where the wheels actually jumped, but ealier where things were bumped out of line. I have leaned that I cannot lay track perfect enough for my too big brass and repair is a way of life, but I love my brass and am committed to making it work.
I also have the problem of shorts in certain places that defey solution, though they have to be related to small radiouses. I will certaily follow this tread to see what I can learn.
perhaps the pilot truck is backwards? I’ve had a few steam locos that have had that problem (ok, it was my fault… but i digress) - it looks like it is on right, but as soon as you hit a curve, the flanges on the wheel of the pilot and the lead driver would bind up (on the inside of the curve). the fix was as simple as removing the pilot, rotating it 180º, and reattaching it ot the frame.
Take a very small piece of lead, first just attach with a little piece of two sided tape.Put it just above the wheels, remember just a small piece. Then if it works you can attach it with some super glue gel,and paint it black. Its worked it the pass for me, you may have to slide it up or down to find the right balance.
When it is tightly screwed to the boiler, can it still flop a bit, up and down, and can it rock sideways, as in yaw? If not, you need some of both.
However, I believe the problem is with your track, and it is the rearward drivers that are careening , albeit in a tiny way, over dips that may only be apparent when the weight of the locomotive causes them. If the loco dips or lifts its drivers, the firmly screwed front truck will experience yaw at the axles, so one of the flanges will be lifted clear of the rail tops. If that happens near or in a curve, you know the rest.
Lay a straightedge over the troublesome places and use a good backlight behind the straightedge to see, with your eyes right down level with the rails and straightedge, if there are any gaps with light showing through. Even then, as I said earlier, they may not show until the heavy loco depresses the tracks, even if it manages to do that to only one rail due to poor support below it.
Your roadbed must be level and planar to the extent possible, except at vertical transitions and in places where you gently superelevate. Once you get a locomotive rocking for any reason, one or more axles elsewhere gets raised with the rocking.
I do concur that the sweep of the truck may be a problem, but only when it is bearing. Once you lift the loco to inspect it, it may rotate quite nicely, thanks, but something makes it bind when all wheels are contacting the rails.
Frustrating, I know, especially for such a nice loco.
I think you have already received pretty good advice. Adding weight addresses the symptom rather than the problem, BUT it may work, and do you care why (I do, but I am strange). As already stated, somewhere, somehow, it’s the track.
Now I’m not sure what worked,but the engine now tracks great.I removed the truck,turned it 180 degrees,found the main boiler screw was a little loose(the pilot screw attaches to the main boiler screw),tightened that and added a little weight to the truck.At this point,I don’t want to remove anything in reverse order in order to find the original problem.
Thank all of you…As a “lone wolf”,this forum has been invaluable to me in solving these nagging little problems.At least I get away from my tunnel vision and get ideas on where else to look in order to solve them.
I had the same problem with a BLI Santa Fe 4-8-4. It wasn’t until I ran it at a very slow speed that I noticed that one of the axles wobbled. A quick call to BLI and a new set was on the way.