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Discussion Boards => General Discussion => Topic started by: Keusink on October 22, 2010, 07:29:03 PM

Title: one way derail
Post by: Keusink on October 22, 2010, 07:29:03 PM
Okay. Anyone following this site knows I'm a newbie. I finally powered up my 9 month track and wiring project and test ran DCC locos on the track.

One exact spot on a trestle derails the F7 every time going in one direction. Coming the opposite direction, the loco does just fine. Its Code 83 flextrack.

I have:

1) felt along and cleared inside of rails.
2) checked rail spacing w/ track gauge
3) bent hose on front coupler so it doesn't drag.
4) watched closely to insure fuel tank clears track
5) put a level along the rail on each rail.
6) Run a 4 8 4 over the same spot with the same result as the F7 experienced.

The level shows a tiny sliver (paper thickness) of air  between level and track surface on one rail near the spot, but it looks too small to make any difference.  It would be the dickens to correct. It is always the front truck of the diesel that derails.

Why would it derail going right to left, but not left to right? I am out of ideas, and I don't want to build the trestle bridge all over again. It is a 2% grade, derailing going up hill.

To forestall the ineveitable question, locos are a Bachmann standard DCC F7, and Bachmann GS-4 Daylight

Anyone have the same experience? What to do?

I begin to understand why they are called "locos". It's Spanish.


Title: Re: one way derail
Post by: RAM on October 22, 2010, 07:56:36 PM
I think it either has to a trestle or a bridge.  Can you put a shim under the low spot?  You say that it is on a 2% grade.  Does the grade continue on pass the bridge?

Title: Re: one way derail
Post by: jward on October 22, 2010, 08:04:09 PM
is this spot at a rail joint? if so, if there a kink in the joint? look carefully and sight along the rail to be sure.

is there a slight twist in the track at or slightly before this point? if so, moving the level along the track will show you where it is.

is this spot on a curve or straight section. if it is a curve, does the loco derail on the outside or inside of the curve?

carefully watch the wheels of the loco as it approaches this spot. sometimes the problem is somewhat further back along the track, if so, you can often see the wheel flange climb up and ride along the top of the rail to the spot where it jumps off. the spot where it climbs on top of the rail will be where your problem is.

one final note: if a relatively flexible loco like an f7 has trouble, chances are that a long stiff wheelbase loco like your 4-8-4 will also derail there. the 4-8-4 is a much pickier engine than the f7 when it cmes to trackwork.

Title: Re: one way derail
Post by: Keusink on October 22, 2010, 08:31:26 PM
F7 steps off track to the outside. Its a curved wooden trestle bridge with a 2% grade. Nothing I can see is lifting the truck off the rail, even when you watch the rest of the loco instead of the truck.

Cant shim the trestle, will just elevate the problem. Cant really shim under the tie, the ties are caulked to the wood and the wood will separate before the caulk does. There is no railjoint on the trestle bridge. The grade continues past the bridge.

When you push the loco by hand from behind, it stays on track. I thought the derail in only one direction should be a clue?


Title: Re: one way derail
Post by: jward on October 22, 2010, 09:04:45 PM
it sounds to me liek a twist in the track. checque the area around that spot and see if the bubble on the level suddenly shifts from side to side as you move the level along the rails.

also, you need to watch the wheels closely, not the truck or entire locomotive. you will be able to see the wheels lift if you watch them carefully. you won't see that if you watch the whole truck.

last resort, easier for me because i lay my own rail on wooden ties, is to install a length of guard rail along the inner rail. if all else fails this will often cure the problem.

the problem you describe with adjustments being difficult because the track is glues down (with caulk) is the main reason i cringe every time i hear the model magazines recommend gluing your track. everybody makes mistakes when laying track, and if you haven't permanently fastened your track down it is possible to correct them. track that has been nailed down is much easier to adjust.

Title: Re: one way derail
Post by: Keusink on October 23, 2010, 01:08:44 AM
Thanks Jward

It occurs to me that I might cut the trestle crossbeam supporting the track away from the uprights, and shim a tiny shim under the crossbeam on the outside. If the loco is stepping off the track to the outside of the curve consistently, what do you think of shimming the outside to creat a slight raise on the outside?

Can you direct me to a site that talks about creating a guardrail? I think you are talking about an inner parallel rail to confine the wheels to where they belong? This is curved flextrack, and I do not know how to bend a rail smoothly to exactly parallel the existing rail curve. You old-timers can probably do that in your sleep.

I'll check for a twist, but I can see nothing untoward in the rail appearance.

This 6 X  10 set lifts to the garage ceiling with an electric hoist when not in use, gets a lot of movement. Has to be sturdier than most, hence caulking and also soldering all rail joints.

Please let me know thoughts on shimming, guardrail construction.


Title: Re: one way derail
Post by: mabloodhound on October 23, 2010, 10:52:52 AM
The good thing with caulk is that you can separate it and the track ties.   Sometimes just inserting a putty knife between the ties and bed will lift it enough to see if that corrects the problem.
This way you would know how to attack the permanent fix.

Title: Re: one way derail
Post by: Keusink on October 23, 2010, 11:32:37 AM
Thanks mabloodhound. I have done that with cork roadbed for several false starts, but it doesn't work with a softwood trestle bridge. On roadbed, you can trash the track and smooth the roadbed, re-lay new track. On softwood trestle bridge, the wood rips out instead of the track.

I think I like the suggestions of adding a guardrail, because it would look good as well.

However, my internet research does not disclose whether you can use the same gauge for the guardrail (nearest LHS is 3.5 hours away to get a smaller gauge)

Also, I do not know how to bend the rail without buying an expensive rail bender from Flexx, and having to wait three weeks to get it.

Anyone have suggestions?


Title: Re: one way derail
Post by: NarrowMinded on October 23, 2010, 12:21:23 PM
Take a pane of glass out of a picture frame large enough to cover the tressel and lay it on top of your track you can see every bump dip and twist all at once, Then push  tooth picks with a little glue on them in to shim where needed, when the glue drys trim the tooth pick away.

If the faulk won't flex enough to allow the shims to work use a chisle end exacto blade to seperate the ties from the tressel


Title: Re: one way derail
Post by: Keusink on October 23, 2010, 01:51:27 PM
Thanks, narrowminded

I shimmed one tie with the smallest piece of flat styrene I had, and it fixed the dip sufficiently for the F7, but not the GS 4.

The GS-4 484 is having problems all over w/ 22" radius. What I see happening is that the second driver raises the first driver off the track. It is happening on the trestle bridges, all on the uphill. All the trestles are curved; if there are declevities, they are not big enough to see w/ naked eye.

Son (honestly) has asked Santa for a Spectrum J Class, and Santa ordered it from his elves to the great grief of Santa's pocketbook. Since it is the same sized loco (again, that's Spanish) I dread Christmas morning unless I can fix the track.

Will guardrails alleviate the problem?

Is guardrail configuration different than track?

Where do you get it?

How can you bend it to parallel the trestle bridge without using a machine?

I appreciate everyone's input. This is a tough one for me because it is more art than science.


Title: Re: one way derail
Post by: NarrowMinded on October 23, 2010, 03:10:00 PM
You can use square styrene for you guard rails works well. have you checked the wheels on your loco's to make sure they are gauged correctly? 


Title: Re: one way derail
Post by: OldTimer on October 23, 2010, 03:42:38 PM
I sent you an e-mail.

Title: Re: one way derail
Post by: jward on October 23, 2010, 07:31:12 PM
there really aren't any shortcuts. you've gotten the f7 to run, use the same techniques to fix the problems with the steamer one by one eventually you'll have them all fixed. i have used long wheelbase locos like the dd40 or alco pa for just this process. if your biggest, longest locos will make it around with no problems the others should too......
narrow has a good idea with using the glass to find the twists. i hadn't thought of  that, i always ran a level along the rails and watched the bubble.

as for building a guardrail, i don't use flex or other prefab track. so building a guardrail for me is a simple matter of spiking the rail alongide the existing rail. i can also solder it to the other one without worrying about melting ties. you, on the other hand, don't have those luxuries. your saving grace is going to be the fact that your trouble spot is on a wooden trestle, which will hold spikes......

that said, here is how i'd approach this problem.  first, i'dglue the rail to the plastic ties, on the outside of the rail. (just to be clear, we are talking about the rail on the inside of the curve.)  then, after the glue had set, i'd carefully trim off the plastic nubs that hold the rail, where your guard rail will fit alongside. then i would take a piece of rail (salvaged from a leftover piece of track, bend about 1/4" of the rail on each end, outward. look at the guardrails on a switch and you'll see how you need to do this. it's easy with a pair of needle nose pliers.

next, i'd lay this rail alongside the other, where you removed the nubs. the rail is flexible enough that you shouldn't need a machine to bend it. secure it at each end, and it should naturally form the curve you want. i'd secure the ends with track spikes, with holes drilled through the plastic ties with a pin vise if necessary. checque the flangeways using the nmra guage for proper spacing, then glue the guard rail in place the same way you glued the other rail.

one final note, and this is vital!

before you install that guard rail, find the place where that wheel climbs the rail, you want to have the guard rail at that spot rather than where the wheel goes off the track.having the guard rail in the wrong location will not solve the problem......

good luck.

Title: Re: one way derail
Post by: Keusink on October 23, 2010, 07:49:20 PM

Thank you so much for the description. Think I'd like the guardrail along the entire bridge (about 2 feet long) so it will surely cover the trouble spots.

Answer me this please. Can I use a standard code 83 rail from a section of flextrack, or do I need to find a "flange-less" rail? Or does it matter?


Title: Re: one way derail
Post by: Doneldon on October 23, 2010, 08:04:13 PM

It's not unheard of to have trains derail going one way but not the other.  This can be a devil of a situation to resolve.  You've received some excellent advice here.  I'll add a little piece.

Checking your track with instruments when it's not under load may not reveal the problem.  You may need to try to do your measurements when you have a train on the trestle.  Also, Micro Mark makes a clear lucite "flat car" which you can finger- or loco-push while watching what the wheels do.  It isn't expensive and it can reveal tracking problems we might not otherwise see.

Good luck with your problem.
                                                                                                  -- D

Title: Re: one way derail
Post by: mabloodhound on October 23, 2010, 08:36:25 PM
I found this definition on another modeling site:
 "Guard Rail:   A longitudinal rail running alongside a railway track and raised in height above the running rails. Guard rails are sometimes found on bridges and are intended to restrain the lateral movement of vehicles which might become derailed."

And I found this: " I looked this up in the ATSF system standards vol 1. ATSF standard was 45' from point to bridge. I also found some other interesting stuff that you may also find interesting. Please enjoy this daily dose of useless information.

The General manager had the option of extending guard rails up to 300'

The points were # 10 frog points.

Guard rails are spaced 10" on center away from main rail. (I'm not sure how this compares to NMRA)

The guard rail begins to taper inward 1'-8" away from the bridge.

Using the same weight of rail for the track and the guard was acceptable. (good because I don't want to order more rail)

The front of the point is beveled at 45 degrees (relative to the horizon)

No tie plates are used beneath the guard rail.

 On double track mains that had dedicated directions of traffic (like a highway), points were only required on the leading end of the guard (before the bridge). The unpointed end of the guard rails (after the bridge) ended 10' after the bridge without any bends.... never heard of this before. I wonder if this ever existed outside the standards, "

from the MR forum (

I do like your though of using a guard rail as it is most prototypical.

Title: Re: one way derail
Post by: jward on October 23, 2010, 09:41:54 PM
code 83 rail makes excellent guard rail. it's what i use, but then all my track is code 83. doing the entire bridge with guard rail would look good. usually bridges had guard rails on both rails. but some lines with extra sharp curves had guard rail on the inner rail of the curve whether it was on a bridge or not. the western maryland railway's lines out of elkins, wv to weebster springs, and to cumberland, md were good examples of this. the affected curves were usually restricted to 10 or 15 mph.

the atsf standards quoted mentioned that the guard rail was taller than the running rail. i've never seen that except in rare instances, such as a guard rail to keep wheel flanges away from swithpoints. most of the real ones i've seen, including the western maryland ones, were slightly lower than the running rails. for simplicity, i use the same size rail for everything.

Title: Re: one way derail
Post by: Keusink on October 24, 2010, 11:35:33 AM

Thank you all so much for your feedback. I think I know how to do it now.

Because this is a 4 year project (I have a professional life and twin 8 year old boys) I took on the most interesting set I could find. I only want to do this once. Combine long, curved, 2% grade to make a trestle bridges  together with DCC wiring and you have more than a challenge for a newbie.

I'm in Southern Oregon, 4.5 hours away from the nearest competent LHS. Nearest club is 3.5 hours away. Without you guys, this trainset would never be finished.

What a helpful group of real gentlemen.

(Be sure I'll bother you again).


Title: Re: one way derail
Post by: Jim Banner on October 25, 2010, 01:58:17 AM
Tuning in late, but here is another thought for you.  Earlier, jward suggested there might be a twist in the track.    If you  have a curve on a grade, there is automatically a twist in the track if you insist on using a helical curve, that is, if you make both rails radially level with one another.  If the amount of twist results in more than about 1/2 of a flange being lifted off a rail head, there is a very good possibility of a derailment occurring.  Long wheel bases and unsprung drivers make it pretty easy for steam locomotive to derail on twists.  Diesels usually do not derail on a twisted track as long as both trucks rotate freely about the  roll and pitch axes.

If your GS-4 is having problems on flat 22" radius curves, then it will almost certainly have problems with the twist in 22" radius rising curves.  I assume you have checked both the track and the wheels with an NMRA track and wheel gauge adjusted things accordingly.  When checking, be sure the gauge is parallel to the axle or to the ties, which ever applies.  Otherwise the gauge will be narrower than you think it is.  If your track was hand laid, I would suggest spacing the curves a little wider apart than straight track to avoid pinching problems.  This is rather more difficult to do with flex track.  The alternative is to set the locomotive drivers slightly under gauge, which may get you around the bends but may give you problems with the turnouts.  In that case, a more radical solution is called for - removing the flanges from the drivers on the second and third axles, leaving flanges only on the end drivers.  Check your locomotive - this may already be the case.  Before doing anything so radical, I would suggest you check the side play of the driver axles after gauging the wheels.  Flanged drivers need more side play than unflanged ones.  Sometimes there is something restricting side play, such as flash on the wheel hubs, bent valve gear, or stuck power pickups.  Sometimes there is lint/hair wrapped around an axle preventing it from moving sideways.  Sometimes the side play is restricted for only part of a revolution of an axle.  This can be hard to see but shows up quickly if you power up the locomotive while it is upside down and gently move each axle back and forth repeatedly as the wheels are turning slowly.  Don't be surprised if some axles have no side play, but be suspicious if two axles next to each other both lack side play.

If all of this gets you GS-4 running on flat curves but not on the trestles, then have another close look at the trestles to see if you can make the curves non-helical.  If the curves are relatively short, they can be made non-helical, that is, they can be canted so that the tops of the rails lie in the same plane throughout the curve.  This moves the twist to the straight track next to the curve where is generally causes fewer problems.  However, if the straights are short, the twist may be more than enough to derail the locomotives even on straight track.

If none of this works, or if it is impossible to do on your layout, the last resort would be to spring the drivers, assuming they are not already sprung.  In its simplest form, the slots that the driver axle runs in are lengthened vertically, a hole is drilled in the frame above each end of the axle, and a small spring is dropped into the hole.  Now instead of the frame riding on the axle, it is riding on two springs which are riding on the axle.  Generally this type of work is best farmed out and most likely things will never come to this.

Bottom line:
(1) check the gauge of wheels and track
(2) check for side to side free play in the axles.
(3) check to see if the second axle is really lifting the first or whether the track itself is pushing the axle up (pinch.)
(4) check the frame for warp or bend.  Set the locomotive on a mirror (preferably a front silvered one) and check that all wheels touch the mirror.

If any of these test show a problem, correct the problem before continuing.  Lots of luck.


Title: Re: one way derail
Post by: Keusink on October 25, 2010, 06:21:18 PM
Thanks Jim Banner.

I think you have touched on the problem. The trestle bridge components are made from a well known kit provider When put together, I noticed the bridge crossties are not level. Instead of laying the track directly on the crossties, therefore, I caulked flextrack onto the bridge ties. I had hoped the caulking and flexties would even out any declivities.

I put on guardrails, inside curve. They have helped a good deal. Toothpicks under the inside tie edges also seem to help. Raising the inside of the curve with a finger seems to help. I think what is happening is a declevity is miniscule, but combined with the twist it raises the first driver off the rail. Because of the turn, it does not come back down in the right place, and the loco derails.

There is VERY little side to side play in the drivers. They are not following the diverging route on two of the Walthers DCC friendly turnouts, either. I do not know if the lack of driver play is unique to my loco, or whether it is typical of the Bachmann GS4.

Being a newbie, I do not know what you are referring to re: spring drivers?

I thought if there was an incline to the inside, the loco would be inclined to fall into the set. Outside is a loooooong drop to the concrete in what would probably be the longest (scale) locomotive fall in history. So originally there was a slight elevation to the outside rail. The problem seems to lessen when I try to level the rails. I suspect each rail has very hard to see bumps, but I do not know how to eliminate them. When you raise one place, it causes the rail to change shape further along the rail.

Gee. Now I can say I've talked with Jim Banner.
Thank you. I appreciate any more thoughts.


Title: Re: one way derail
Post by: Jim Banner on October 26, 2010, 01:26:45 AM
When a locomotive has sprung drivers, it means the weight of the locomotive is transfered to the drivers via springs.  This helps insure that all the drivers are on the rails all the time, even if the rails have humps, bumps, twists and other problems that make the trains rock and roll.

And hey, now I can say that I have talked to Chris -  TWICE.


Title: Re: one way derail
Post by: glennk28 on October 26, 2010, 12:34:47 PM
Keep in mind--before asjusring the coupler pins--be certain that the coupler is mounted at the correct height.  gj

Title: Re: one way derail
Post by: jward on October 26, 2010, 07:56:06 PM

I put on guardrails, inside curve. They have helped a good deal. Toothpicks under the inside tie edges also seem to help. Raising the inside of the curve with a finger seems to help. I think what is happening is a declevity is miniscule, but combined with the twist it raises the first driver off the rail. Because of the turn, it does not come back down in the right place, and the loco derails.

therein lies the problem. the driver SHOULDN'T lift off the rail. it really doesn't metter whether it comes back down on the rail or off the rail, if it lifts, you have a potential problem. i think you are on the right track trying to level your track. the toothpicks as wedges are accomplishing what i would have done with pieces of index card. my experience has been that it isn't where your track tilts toward the inside of the curve that's the problem, but where it tilts toward the outside, or where there is a twist. you are methodically trying to eliminate both on a temporary basis before deciding on a permanent fix. experimant, use logic and some common sense, and you'll find and fix the problem.

btw, jim is one of the best resources we have here. i think he's been in the hobby longer than i've been alive... ;D

Title: Re: one way derail
Post by: Doneldon on October 27, 2010, 09:05:37 PM

Look at it this way: When you curve your track you are changing the direction of the track in one dimension.  If you add an elevation change as well you are introducing a direction change in a second dimension.  If your track is not level side to side, even if intentionally such as with a superelevated curve, you are changing direction in all three dimensions.  It's no wonder there are tracking problems.  The solution is to manage these changes and, insofar as is possible, change only one dimension at a time.  For example, start the grade a little before you start the curve.  Get into the curve before you start the twist (superelevation).  You can visualize these three dimensions as lines through a locomotive on your track.  The curve represents rotation around the vertical line running up and down through the center of the loco.  The grade change represents rotation around the line running horizontally from side to side.  The superelevation represents rotation around the horizontal line running from front to back of your loco.
                                                                                                                            -- D

Title: Re: one way derail
Post by: Keusink on November 01, 2010, 03:52:11 PM
Thank you all. There are so many permutations of twists that I would at least level the trestle bridges and leave the curves and grade for the l girders were I ever to do it again. I'll keep working at it; doesn't look like I have a choice.

You've all been most helpful.


Title: Re: one way derail
Post by: BradKT on November 14, 2010, 02:49:40 AM
Have you considered the possibility that you simply have a defective piece of track?  Maybe it wasn't originally defective, but you may have slightly twisted it so the rails are not the exact same height.  Try replacing it and see if you have this same problem before you do all of this other stuff that has been suggested.  If you have the same problem a second time, at least you have eliminated this issue, but it really sounds to me that this might be a real possibility as soon as I read that you were using flex-track at this location.

The problem could be in one of two locations...either where the wheels on the front truck derail or the location where the REAR wheels are located when the derailment happens.  These engines weigh enough to keep both trucks on the track and if the front truck is slipping off, the problem could easily be where the rear wheels are located when the derailment happens because it raises that front truck slightly...just enough to derail when you are going one way, but not the other way.  We are talking about an incline here.  It could be just a rise or a dip...that's all it takes.

This really sounds like a track issue to me.  When it comes to derailments, HO scale trains are really unforgiving (the engines and cars all have a straight, inflexible chassis and do not have independent front and rear suspensions) and the track has to be installed just right the first time or you are going to have to do it over...eventually.  Get it right the first time or you will have to do it over after endless frustration.  Trust me on that!  I know.