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 Posted - April 06 2015 : 7:18:00 PM
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I have a Tyco GP20 that derails on a curve going forward. It is the front drive wheels that derail. Going backwards over that curve, it does not derail. It is the only engine I have that I have a problem with derailing over that curve. I checked the wheels with a gauge and everything is ok. I checked the curve track with a gauge and all is ok. What could be the problem? Thanks in advance.
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Posted - April 06 2015 : 8:05:57 PM
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| Maybe check the traction tires and make sure they aren't twisted. Also make sure the truck swivels freely and is fully/properly installed in the shell. Also check the track to see if there is any ballast stuck to the inside of the rail. That's what I'd check, hope it helps!
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Posted - April 06 2015 : 8:10:11 PM
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That's a tough one tramp but I'll take a stab at it.
Have you turned the loco around and run it through the curve the opposite direction?
Sometimes even when everything is in gauge the two axles are offset in relation to each other, meaning one axle is skewed to one side and the other to the opposite side. This can cause the lead axle to "climb" up the outside rail.
http://tycodepot.com/
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Posted - April 06 2015 : 8:18:44 PM
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| Thanks guys, I will check out these suggestions and get back to you.
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Posted - April 06 2015 : 9:26:53 PM
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Ok, I checked the tires and they look ok. I put a dab of grease on the swivel part of the front trucks and it swivels pretty good. It is a MU motor. It is solid in the shell and no ballast on the inside of the track.
The front wheels have very little side to side play and they are pretty tight. I turned the engine around and running left hand curves it does not derail. Than I ran the engine backwards so it was turning on right hand curves, no derailing.
Than I turned it back around and running the engine frontward and into the right hand curve, it derailed in the same spot on the same curve. It only derails on that curve.
Maybe it is the mu motor. I have another GP20 with the power torque motor and it does not derail at any speed forward or backwards. And my luck, I have no spare power torque motor to try. I will look for one on ebay.
Any other ideas?
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Posted - April 06 2015 : 10:13:46 PM
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I'll add one more thing tramp.
If possible, run the loco through the curve very slowly while watching the wheels. This may give you clues as to where/why/how the derailing is occurring.
Even using your hand and pushing the loco through with the power off sometimes yields information.
Are there any joints in the curve where this is happening?
http://tycodepot.com/
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Posted - April 06 2015 : 10:32:18 PM
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Jerry's suggestion is a good one. I ran into a similar problem on my trolley layout. The trolley would always get stuck in the exact same place. I would push it through slowly with my hand as Jerry suggested watching for any irregularities. It turned out the roadway on the outer edge of the rail was catching the wheels, but it took me a long time to pick up on it as the height difference between the road and rail was so small. Perhaps one of your rails is slightly higher on one side?
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Posted - April 06 2015 : 11:58:12 PM
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Check the flanges on the left side of the front truck. Any damage or flash might cause a rough spot that would want to climb. Combine that with a rough joint or a little dip in the track and that could cause a derailment.
Carpe Manana!
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Posted - April 07 2015 : 08:50:33 AM
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| I am stumped. I ran my other Tyco GP20 with the power torque motor this morning and no derailing. Then I ran the GP20 with the MU motor and guess what - yes it derailed. The swivel motion is not the greatest and also, it does not swivel as easily as the power torque one. It takes a little more effort to turn the trucks. I am beginning to think the MU motor does not have enough swivel for the 18" curves.
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Posted - April 08 2015 : 10:16:58 AM
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quote:| front wheels have very little side to side play and they are pretty tight |
The truck needs to be free to rock and roll. Compare rockability with your other locos. Good health!
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Posted - April 08 2015 : 10:22:57 AM
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Methinks offtrackthoroughbred has the answer. Just one
little catch, not noticeable when you pick it up, shaking
your head, and off the rails she goes. Sounds like
offtrackthroughbread has correctly diagnosed stickytruckitis. One remedy is to throw it over the
garden wall, my favorite. The other is to tinker
with it, sometimes it is the coupler that is catching
on something in the opening and a little bending,
cursing, shouting, and twisting will relieve the
bind.
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Posted - April 08 2015 : 11:56:20 AM
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These mystery derailing problems can be very hard to track down, because we (or at least I) tend to attack them with certain assumptions in my head. i.e. "it couldn't be that" and so we bang our heads against the wall when the answer may be staring us in the face.
I have a Athearn BB FP45 that was always derailing on one curve without fail. It wouldn't do it going the opposite way, or backing through it. Other 6-axle BB locos went through just fine. I made the assumption it was in the wheel gauge and fiddled with that half the night. After I had switched and traded all the wheelsets in the loco to every possible configuration, I gave up on that and thought maybe it wasn't swiveling right. I lubed it, polished the bolsters, even traded trucks...no change.
Then I thought the electrical pickup tab was pushing down too hard on the truck, so I fiddled with that for an hour. Even hard wired the trucks. No change.
After that, the last straw was that it needed more weight to hold it down and make it track better. Another hour burned into the night.
About to sit down and cry (or wing the loco over the hill) I did what I should have done in the first place - I manually pushed it through the curve and simply observed.
It turned out that the ladders on the FP45 are offset in the rear, and on that particular curve the radius was just small enough that the outside ladder would bind the truck, keeping it from swiveling just enough.
A simple fix, once I saw it...and it was really an obvious issue if I had only taken a minute at the outset and watched.
http://tycodepot.com/
Edited by - JNXT 7707 on April 08 2015 11:58:16 AM
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Posted - April 08 2015 : 1:31:16 PM
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| I gave up. Now it derails on the rerailer. I think this engine is haunted. I will look for a power torque motor to replace the MU. Perhaps that is the problem.
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Posted - April 08 2015 : 5:15:23 PM
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I have an MU here from some hairball unit I scrapped. Before you get your knickers in a twist, someone had filled the top of the shell with something....mass amounts of AC, or plastic cement...melted the shell, bowed it all in....junk.
Anyway...the plate on the one (fixes) is aluminium, if I recall. Due to dropping, shipping, rough handling, it was warped and would not allow the truck to operate properly in a curve. I drilled off the rivet flares, took is all apart, cleaned, straightened, lubed, tapped 4-4-0, screwed it back together and it pivots fine. Look for bent plates, look for binding at the cast pieces fore and aft.
Daave
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