Solving brass steamer derailments

[Loren Perry]

For a few years, I've been living with two minor problems that caused derailments of my largest brass and plastic steam locomotives (4-8-2's, 4-8-4's and 2-10-4's mostly.) These engines have unsprung drivers, very rigid and lengthy frames/wheelbases, and small, scale-like flanges. None of my other locomotives or rolling stock suffered any derailments in these areas. Today I finally decided to take the time to get rid of the problems and the corrections were successful.

Problem 1: A 22" radius curve inside a tunnel caused the engines to jump the track. During construction, I had made sure the curve was very smooth and uniform, but had neglected to carefully check the vertical level of the railheads. In short, there was a minor "hump" in the track that I didn't catch and allowed to creep in. When the locomotive entered this section of the curve and started up this hump, the leading drivers were lifted high enough that the tiny flanges just cleared the tops of the rails and ended up actually riding on top of the rail where they eventually slid outside the curving outer rail and dropped back down; the engine was now on the ground.

Solution: Because of the location of the track inside a tunnel, my options were limited unless I was prepared to rip up mountain scenery and possibly make things worse. I ended up using a large flat file and slipped it inside the tunnel so it could rest on the tracks. I had enough access that I could slide the file back and forth on top of the rails which allowed me to reduce the severity of that offending hump. I eventually got it down to the point that the flanges were able to keep their grip reliably through the curve and the train stayed on the track. A thorough vacuuming of the tunnel interior got rid of the metal filings. Problem solved. (The track is Peco Code 55.)

Problem 2: A Peco Code 55 double crossover caused the engines to derail when set for the tracks to cross (as opposed to two parallel tangents.) When the crossover function was selected, the steamer would pick the point and short out. This was caused by a point rail that sagged slightly when against the stock rail, allowing the locomotive's small driver flanges to ride over the railhead of the curved point rail while attempting to stay on the straight stock rail. A derailment and short circuit was the result.

Solution: I made a .015" thick shim of black Evergreen styrene that was about the width of a Peco tie and about 3/16" long. Using tweezers to lift the sagging point rail, I slipped the shim under it and up against the stock rail. A small brush was used to apply liquid plastic cement to bond the shim permanently in place. This shim now holds the movable point rail at the same height as the stock rail while allowing it to move freely back and forth without binding. The locomotive's flanges now engage the curved point rail reliably and follow it onto the diverging track as intended. Problem solved.

These difficulties were the result of very fine low-profile flanges on long, rigid wheelbase steam locomotives attempting to negotiate track work with flaws that were almost invisible to the naked eye. It took me a little time to finally discover the exact nature of what was happening, but once I found out, the solutions were fairly quick and easy. I hope this helps someone else out there who might be having similar frustrations with running their large steamers on their layout.

The reason I procrastinated was due to the inconvenient locations of the track that needed attention. One was inside a tunnel, and the other was far enough back on the benchwork that I need a small stepladder to access it. As it turned out, the fixes were so simple and easy that I'm ashamed to admit that I delayed this long. I just took the easy way out and used smaller and more flexible locomotives, leaving my bigger ones in the roundhouse. But now the tracks on my so-called "steam-friendly layout" are finally steam friendly indeed.

[up1950s]

Good finds . Perhaps one can make a hump/ditch detection car . Just 2 trucks on both ends of a 1/4 " plexi floor . The shorter the car the more sensitive the read out .  In the center mount that digital angle indicator from Micro Mark . As you roll this thing you can see the readout . If there is a vertical change in the level or mean grade you will see it and know where it is as you lay the tracks . Much easier to fix at that time that latter on . One can turn the thing sideways to read for unwanted super elevation or consistent degree of super elevation .

http://www.micromark.com/miniature-digital-level,9409.html

[UP4-8-8-4]

I had the exact problems with my brass 2-10-4, 2-10-2 and AC-12.
Ended up being a slight uneven rail on a curve, did the same as you and filed it down until level.

Speaking of the hump/ditch detection car, a guy Gary on another forum years back made them. Piece of plexiglass for the floor and two mounted MT trucks.
Have used it many time to locate hard to detect problems with track and switchs, so far 100% success.

[randgust]

I've got just enough big steam to find problems that otherwise wouldn't exist - an ultra-fussy brass 4-8-4 (3751 with 8-wheel tender trucks), a Life-Like Berk, and a Kato / GHQ L1 2-8-2.    The 2-8-2 is stellar, the other two....

The biggest thing I've noticed - and I've got 13" and 15" mainline curves - is that the position of the drawbar on the locomotive literally pries the lead driver off the rails under load.   If that drawbar post is under the cab, it's twisting against the tender post laterally as it negotiates curves.  The tendency for the lead driver to climb up and over the outer rail is significantly more.   Also, if it is pulling 'high' above the axle centerline, the harder it pulls, the more it wants to lift the lead driver.   If you can get enough weight over the nose, this will help, but if the locomotive is a bit tail-heavy anyway, you're in trouble.   And it's not just brass.  It 'used to be' that only brass had the finer flanges, now it's pretty much anything made.  I'm not complaining, I'm just saying that there's no comparison of the likelihood of derailment between an old classic like a Trix 4-6-2 and anything out of the box today.   Tolerances are a lot tighter now.

The Kato 2-8-2 pulls through its trailing truck, and the trailing truck is mounted low and pulls from under and just behind the #4 driver.  No problems with that design, but that's pretty unusual.   You'll see an awful lot of drawbar posts behind the trailing truck and right up under the tender deck.

I changed the drawbar on the LL 2-8-4 to go all the way up to the screw hole on the trailing truck, and what a difference that made.   No more climbing on curves.    On the brass 4-8-4, there was still room in the boiler to change the balance point to be more nose-heavy, so I went that route instead. Works for now, but it still has the nomination as the track geometry tester for anything I've got.  If that makes it reliably, I'm good for anything else I own.   

One sure way to check this is to let a locomotive slip as it goes through a curve and watch it and see if it climbs the outer rail.   It's pretty drastic to make new drawbars, but if you study the mechanics involved you'll see what I mean.  Now, throw a switch or anything in that mix when the drawbar is torqueing over the drivers through the tender and it's even more likely to derail.

On the other side, one of the most derailment-prone locomotives I own has been the Atlas 4-4-0.   I've added more weight to the cab, weight to the tender, and put a little sleeve of lead around the lead truck front axle to tame the idiosyncrasies in that one.  The lead truck is too light, the gauge is narrow on the first driver (meaning the front end goes way far over on a curve, taking the lead truck with it) and the locomotive is generally balanced all wrong.