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This problem only exists with this locomotive--all diesels work fine on this loop.  I wasted a whole day and so I've come here for help.  This is the problem:  As the locomotive passes a 022 switch preceding a curve, the pilot truck runs off causing a derailment.  I banked the curve because this is a heavy locomotive, thinking it might have caused the track to twist or move.  That didn't work even though it did make a few passes before derailing again.  I even bought a complete new pilot truck.  That made no difference.  I placed the locomotive on another loop without any switches, and it ran fine.  I examined the switch.  It looked O.K. I thought that maybe it was glitch in the electrical system of the switch and I pulled the constant voltage plug out.  No difference.   So I manually pushed the locomotive over the switch very slowly.  Just as the pilot wheels were exiting the switch and before the curve, the outside wheel ran off the rail.  When I pushed the locomotive backwards over the switch, the pilot wheels got back on the track.  What's the problem?  My diesels have no problem negotiating this switch.  Thanks...

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Steam locomotive pilot truck wheels of are very light with no weight on them, so they derail easily. Diesels have all their weight on the wheels, so they are more difficult to derail. Try swapping the switch with another one if you can, to isolate the switch. Make sure the track is level and not twisted. Make sure the truck swivels freely underneath the locomotive. If the curve comes right after the switch, try swapping out that curved track with another one. Add a straight track before the curve to see if that helps. Check the gauging of the wheels also; if they are slightly out of gauge, that may cause a problem. Since this happens only after exiting a switch, check the transition between the switch and track to be smooth, and not have a bump, due to distorted rail ends.

 

Larry

Some of the things that I did to try to fix the problem:  Changed the curve track after the switch--this did not solve the problem.  Then I put a tiny piece of foam on the inside corner of the switch where the frog meets the inside rail in a straight position-still derailed.  I cleaned the switch of any and all grease or oil--it worked!  Took off the foam and it derailed again.  So I guess the tiny foam keeping the frog a small space out from the inner rail of the switch was necessary. I ran the engine around the loop and now it derailed on the next switch.  Cleaned that switch as well.  Then derailed on the very next switch.  There are a total of six switches on this platform, but the engine seems hung up on the three consecutive ones at the end of the platform.  As I mentioned, the one that gave me the trouble initially has been corrected; now, it's the next two.  I tried two different pilot trucks with the same result.

The pilot trucks you tried, are they new production or reproduction? the reason is the new trucks have a shorter rivet that hold the spring for downward pressure. The original one has a longer rivet. The shorter rivet version won't have enough downward pressure from the cylinder casting it rides on. Be sure to lube the rivet head so the pilot truck slides smoothly back and forth. Oil the axle in the casting also.

Using the diagram of the switch here, it sounds like you are talking about the swivel rail and not the frog. Note the frog is called the auxiliary rail in the diagram. If in fact your problem is with the swivel rail, is the rail loose and can it be moved by hand a little, or does it rock from side to side? You should not have to keep the swivel rail away from the long curved rail to get your locomotive not to derail.

 

Larry

 

 

OK, here's what's happening with this engine.  I purchased a repo pilot truck when this problem developed with the original one.  It made no difference regardless of which truck I installed.  Today, I tried running the engine again.  I thought I'd beat the problem with the original problem switch.  Alas, it derailed again despite my prior efforts.  I decided to place the engine on an entirely different loop, transferring it from "0" to "027."  This loop also had a switch but it was manual without any power to it other than from the track.  As the engine went around, it derailed at the switch just like on the other loop.  When I investigated the original problem switch 022, I carefully pushed the engine across the switch.  Where the swivel section meets the inner rail when in a straight position, at that point where the transition occurs the right truck comes off the rail.  When I push it backwards, surprisingly, it returns right on the rail again.  That is why I placed just a tiny piece of foam at the spot, to keep the slider rail slightly apart from the junction with the inner rail of the switch.  Once the engine clears the three problematical switches on one side of the layout, it seems to have no problem going on the other three switches on the other side.  I suspected an electrical abnormality but my experience with the manual switch on the other loop seems to negate that.  Anyway the old engine chugs along until it hits one of the three problem switches.  The flashing spark tells me that it has derailed again on one of those three.  Keep in mind that this has never happened before.

It seems that the wheels on the front truck may be slightly out of gauge. Carefully measure the dimensions between the backs of the front truck wheels and do the same thing for the wheels on the rear truck. Compare the dimensions. Try running the locomotive backwards without the tender and see if the rear truck derails. A clear, close up picture taken at track level of the front truck just as it derails would help. Also, since the problem seemingly occurs only on one side of your layout, is the layout completely level? Try turning the layout 180 degrees and see what happens.

 

Larry

Last edited by TrainLarry

I had extensive derailing problems with my front pilot on the 726 and the 2026.  For me it was the longitudinal gauge of the pilot wheels.  I had to very carefully tweet the inside dimension from flange to flange to get the right distance.  Both now run without derailing on any switch.  You will spend considerable time tweeking this because it is a very small adjustment needed.  To wide no good too narrow no good.... 

 

Don't give up, it will work. 

I was just wondering whether anything electrical might be a contributing factor.  Today I was showing my layout to some visitors.  Of course, the 726 was off the table and in its place was a diesel switcher.  The diesel negotiated the problem switches just fine except when I switched one of them to go around a curve rather than straight.  Somehow, the diesel kept on going straight and derailed

As far as the specs for the pilot wheels, unfortunately, in the process of doing that I bent the axle which I have to replace.  This engine seems to have the problem in just the same area of my layout regardless of what pilot truck I install--it doesn't happen elsewhere.  I suspect maybe weight distribution has something to do with it, but this oldtimer had the same weight distribution for years and didn't derail before.

All my switches run on constant voltage.  I did try to run the problem switch on track power by removing the plug from the switch.  I was thinking that maybe the entire train has to pass the preceding switch before I can change the one I want to switch or at least be off the preceding one at the time I switch because of the automatic non-derailing feature of constant voltage application.  My thought was that some electrical glitch was causing this.  When I stopped the engine, then did the switching, and started it up again, there seemed to be no problem.  In the past, I've noticed under certain unknown circumstances, a switch will automatically flip in an incomplete fashion as the engine rides over it, causing a derailment.

First, put a level on the layout and see if it is completely level, especially in the problem area. Next, turn the layout 180 degrees around if you can and see if the problem follows the switches, or stays in the same physical location. If a switch throws while a train is passing over it, it sounds like the non-derail feature is being activated. Make sure the insulating pins are in the proper rails, and disconnect the controller to the problem switch to see if this clears up the problem. Also check that the swivel rails are tight and cannot be moved at all by hand. Swap out a problem switch with another one to see if the problem follows the switch or not. These suggestions need to be done to narrow down the problem, or it may never be diagnosed.

 

Larry

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