one way derail

[Keusink]

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.

Chris

[RAM]

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?

[jward]

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.

[Keusink]

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?

Chris

[jward]

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.

[Keusink]

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.

Chris

[mabloodhound]

Chris,
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.

[Keusink]

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?

Chris

[NarrowMinded]

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

NM

[Keusink]

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.

Chris

[NarrowMinded]

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? 

NM

[OldTimer]

Chris,
I sent you an e-mail.
Jim

[jward]

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.

[Keusink]

JWard

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?

Chris

[Doneldon]

Keusink-

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