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Discussion Starter #1
My son has rebuilt an Athearn Fp45 blue box locomotive. Has an MED sound decoders in it and a small speaker in it. The issue is that when it turns right going forward only if details the front truck. This occurs on 22r turns so it is not the radious. This is the only locomotive with this issue. Verified the axles are not cracked, wheels in speck, all gears move smoothly. The trucks turn freely wire to side. In reverse there is no issue. Also no issue you going left. My next thought is to convert its twin and see if that one has the same issue.

Any ideas? The sd45 with a very close wheelbase and similar truck design has no issues. This is derailing at random spots in the first 1/2 of a right turn regardless of speed. He is proud he's figured out all of the wiring and the lighting with LESs but disappointed it only turns left. He said it is ready for Nasscar though.
 

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The best way to investigate mystery derailments is to very slowly slide the loco through the problem section by hand, while watching the wheels carefully. Look for anything out of the ordinary and assume that nothing is correct before you start.
Model railroading is a game of the minutest fraction of an inch in many cases. Differences in rail height side-to-side, slight kinks in joints, grade elevation changes.
I once worked all night trying to figure out a F45 derail problem. Turned out to be the rear ladder on one side that was restricting the truck swivel - it only occurred when going one direction around a curve. Not saying this is your problem, just that I assumed that was not a problem before I started and never looked for it.
You may also want to check that the wheels on the axles of the truck are all similarly biased. Meaning that if the lead axle wheels are biased toward the right, and wheels on the other axles are biased toward the left, this could lead to a derailment.
Again...push it slooowly through the problem area and observe.
Good luck.
 

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One assumes that this derailment occurs on all right hand sections of track? If so, then you are correct to discount the track being the issue. My experience with Athearn BB 3 axle trucks is that they can be reassembled in such a manner as to create a very slight warp that results in what you have described. Gently twisting the truck back into a level plane has worked for me.

Additionally, the most peculiar derailments, even one time when a certain coach insisted on hopping off the rails on a straight section of track. No other vehicle of any weight, length, etc. did this, so it was natural to think the problem lay in the bogie. I changed wheels, bogies, turned it around, added weight, changed its location in the consist, and no matter what: flop-buddabuddabudda.

At wits end, I pulled up the nine inch section of track, and otherwise invisible to my line of sight, the section had a
small downward warp caused by a missed hammer blow when adding a track nail. Utterly invisible until I had removed the section, and it only affected this one coach and none of its identical members.

Temperature changes, humidity can all serve to create micrometers of difference which are just enough to change the relationship of wheel to rail, and off she goes.
 

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Discussion Starter #4
Any curve is a problem area so I really doubt it is the track. It did this prior to and after completely disassembling the front truck. Only thing we did not do was change outlets in it. What really bothers me is that these blue box engines where built to handle 18r and this thing is having issues with 22r. Only thing I have not checked is the rear ladder like you said of if there is enough 'slide' to allow the drive shaft to shorten for the curve. If anyone has Any other idea I will make a list and try them with the next running.
 

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Given all that, I run six axle trucks all the time on Armodilloville 18 inch curves. I would look at the bogie and see if a gentle twist will fix your problem. Is it both bogies or one?
 

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The best way to investigate mystery derailments is to very slowly slide the loco through the problem section by hand, while watching the wheels carefully. Look for anything out of the ordinary and assume that nothing is correct before you start.
Model railroading is a game of the minutest fraction of an inch in many cases. Differences in rail height side-to-side, slight kinks in joints, grade elevation changes.
I once worked all night trying to figure out a F45 derail problem. Turned out to be the rear ladder on one side that was restricting the truck swivel - it only occurred when going one direction around a curve. Not saying this is your problem, just that I assumed that was not a problem before I started and never looked for it.
You may also want to check that the wheels on the axles of the truck are all similarly biased. Meaning that if the lead axle wheels are biased toward the right, and wheels on the other axles are biased toward the left, this could lead to a derailment.
Again...push it slooowly through the problem area and observe.
Good luck.
I am not sure what you mean by biased. I have never heard of this problem. How do tell which way or how which axle or wheels are biased? Thank you.
 

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I can only relate my own experience, now totaling 15 years in the hobby. I have a history of acquiring a new locomotive about every year. Each time I get a new locomotive, or almost every time, I find it has trouble with a small section of my tracks.

In one instance, a very nice BLI 'hybrid brass' UP TTT-6's tender would not stay railed on a 46" sweeping and descending curve. It was all groomed with ballast, and had worked flawlessly for three years by then with at least 10 different steamers and early diesels from different importers. Not for this tender. In the end, I softened the ballast, tore up about 3' of rails, and started over. I learned that the outer rail simply wasn't high enough in a couple of spots, and when the tender came to them, the flange on one axle cleared the top of the rail just enough to let the truck slip off the rails.

Long way of answering your question, but I then got two Athearn Genesis SD-75M models. Both of them would not make another sweeping curve. I decided it was the same problem, softened the ballast in two spots, and shoved thin clear plastic strips from packaging under the ties to lift the outer rails. I repaired the ballast, and the locomotives were happy after that.

Uneven rail heights, especially on tighter curves (<24" radius), and on long frames such as modern diesels, will often cause grief. Super-elevation is desirable for many of us who want a realistic look, but it takes care and demands pains to get it right. I have learned that at least twice now.

This is not to discount the other persons replying. Trucks that can't pivot properly in one direction, or to the fullest designed range, will often cause derailments, again, on tighter curves.
 

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If you take the shell off, and run it that way, does it still derail?

If not, could the problem truck's "gear tower" be hitting something "above the frame level"?

Could the front and rear trucks be "swapped around"?
 

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My son has rebuilt an Athearn Fp45 blue box locomotive. Has an MED sound decoders in it and a small speaker in it. The issue is that when it turns right going forward only if details the front truck. This occurs on 22r turns so it is not the radious. This is the only locomotive with this issue. Verified the axles are not cracked, wheels in speck, all gears move smoothly. The trucks turn freely wire to side. In reverse there is no issue. Also no issue you going left. My next thought is to convert its twin and see if that one has the same issue.

Any ideas? The sd45 with a very close wheelbase and similar truck design has no issues. This is derailing at random spots in the first 1/2 of a right turn regardless of speed. He is proud he's figured out all of the wiring and the lighting with LESs but disappointed it only turns left. He said it is ready for Nasscar though.
The trucks turn freely, but do they turn far enough? More importantly, do they "turn freely" when held in your hand or when upside down in a workbench repair cradle? Do they turn freely rightside up on the track.

Get your eyes and some magnification and light right down at track level and watch closely. It sounds like something is binding (worm gear, maybe) and preventing the truck from turning when it's under power.
 

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I am not sure what you mean by biased. I have never heard of this problem. How do tell which way or how which axle or wheels are biased? Thank you.
It means that the wheels are not centered between the truck frames, but ride toward one side or the other. Both (or all 3) sets of wheels being biased to the same side usually isn't an issue. If they are biased in opposite directions it might be.
 

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I’ve had issues with the Athearn FP45 on my layout as well. I’d put a thin metal straight edge (I use my scale ruler) to check that the rail has no dips in it. Keep us updated. The issue I have with my FP is the back end has a wobble in it at higher speed. Doesn’t affect its operation, but I don’t care for the “shimmy”...cheers
 

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Discussion Starter #13
Thanks for all the help. Found the issue. On the top of the truck there is a tab that the truck rides on between it and the frame. The was slightly bent and causing the front of the truck to lift slightly after it turned so far. Bent it a little and this issue was solved.
 

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Excellent! May you go on to enjoy many hours with your fixed locomotive.

What CTValley means by 'bias' is this; The flanges don't line up back-to-front when the truck is running on the rails.

<=)(=======)(=>

<==)(=======)(>

Both axles have wheels that are in gauge, but working in the same truck they'll want to climb a guard or a frog point, or pick a point rail.
 
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