MoW: Pony truck derails at St Williams team track switch

Today felt like a good day to tackle the maintenance and repair list I drafted after last weekend’s visit by Hunter Hughson.

I started with the intermittent derailment by the moguls as they pulled out of the team track in St. Williams:
 photo Repairs-StW-Team-Derailment-01_zpsf86213f5.jpg

Sometimes – but only sometimes – the two-wheel pilot truck would go onto the ties as a mogul left the switch. This was a puzzler in part because the derailment was not consistent. I slowly pushed a mogul through the whole turnout and determined that when the derailment occurred, it occurred right as the pony truck left the points, as shown here:
 photo Repairs-StW-Team-Derailment-02_zpse8f6ab9b.jpg

Further investigation revealed that the locomotive could waddle slightly as it traversed the turnout, and the derailment only happened when the locomotive was rotated as in “C” in the diagram below. Hitting the problem spot while straight – as in “A” – or waddling the other direction – as in “B” – caused no problems:
 photo Repairs-StW-Team-Derailment-04_zpsbf6829eb.jpg

That led me to look closely at the diverging stock rail. I determined that the rail need to have a smoother transition between the normal track to the right of the turnout, and the notched portion that accommodates the points when the switch is set for the normal (straight) route. If the pony truck of a mogul hit this area while the mogul was oriented as in diagram “C” (above), the flange on the wheel would catch on the stock rail, ride up and over it, and voila – a derailment.

The solution called for two tools – a graver made for me by my friend Chris Abbott, and a small file:
 photo GraverAndFile_zps6916120f.jpg

I used the graver to carve away a bit of the inside of the head of the stock rail to make a smoother transition – one that wouldn’t catch the flange on the pony truck. I then cleaned up the transition with a file. The photo below shows the area that needed work:
 photo Repairs-StW-Team-Derailment-03_zpsc4ed9dd9.jpg

It’s amazing how tiny a spot can cause such trouble – and it took longer to diagnose than it did to fix. But I’ve run a mogul through this switch several times since making this small adjustment and I seem to have fixed the problem. Fingers crossed!

Since I want to keep better track of issues like this, I’ve created a new category for the blog called “maintenance and repair”. It’s located in the drop-down Categories menu to the right on the main page. I’ll use it to collect future notes about fixes. It should prove useful.

13 thoughts on “MoW: Pony truck derails at St Williams team track switch

  1. Trevor,
    As an engineer, I love it when one tracks the faults and failures by documenting the analysis and corrections. Great.

  2. Trevor,

    Great post. Thanks for the information. I am having trouble with an Atlas switch on Keeney Creek with you guessed it a pony truck on a consolidation. I did not think to kick the engine one way or another. Ah (hit forehead) never even occurred to me!

    p.s. Guess we won’t see the engine crew with rerailers and other trackside items trying to rerail the pony truck on the Port Rowan sub. Did the CN ever need to send “the big hook” onto the branch for a mishap?

    • Many train crews were very handy with blocks of wood and other devices to rerail cars. Just about every CN loco carried rerailers, usually the cast “Buda” design.

      I watched ten or more cars get rerailed one morning using these rerailers and a lot of oil to lube the flanges as they were pushed off the ground, up the rerailers, and back onto the rails.

  3. A few factors at play here, Trevor.

    I note that you found it necessary to cut away some of the head of the stock rail to accommodate the closed switch point. The prototype bent the stock rail away where you cut that bit of rail head off. Examples–CN bent the stock rail sharply 9 7/16″ ahead of the straight point of a No. 8 turnout having 11′ switch points.

    I can’t find an online CN diagram, but here is a Victorian Railways (Australia) diagram for a 5′-3″ gauge turnout showing the bend in the stock rail before the point that is very similar in design to that of CN —

    CN practice results in a slight gauge widening of 3/8″ at the switch point tip as the switch point is deflected towards the stock rail. Track gauge is gradually narrowed to standard at the heel of the switch as the points join the closure rails.

    Another factor is the suspension of the pony truck on the loco. The Central London Area Group Scalefour modellers have examined this to some length, and have a number of ideas to improve pony truck tracking on model steam loco’s–if you are interested.

    This is a small part of an online tome on loco suspension, aka “Everything that you ever wanted to know about model loco suspension”..

    On the other hand, I think it useful that you have a loco that finds faults in trackwork on the layout. Might help you find those faults before–visitors come over?? šŸ˜‰

  4. Great post. I would probably never look for that slight waggle. The idea of keeping a record will help all of us when we can’t seem to find the problem.
    Thanks again, Gord

  5. Often a prototype would add a short guard rail immediately past the end of the point(s) to keep things going straight.

  6. Great deduction and solution Trevor! But the main reason I’m writing is your continuing-to-astound track and scenery work (minor derailment notwithstanding). The photos of your work in this post are stunning, and all the more impressive since they’re “just there” to illustrate what you’re talking about rather than there for their own sake. Really great work, oh, and congrats on fixing the derailment šŸ™‚

  7. Good to see that you found and fixed the problem. Honestly, I thought it was going to be the kind of flukey thing that couldn’t be replicated with enough consistency to facilitate trouble-shooting. Nice work.

    On another note, now that I have some benchwork up, I’m recruiting you to show me a few tricks for making such nice track.


  8. Not sure where Howie’s Hardware is on your layout but the following look like a must have for the room decor!

    Port Rowan Decoy pr – scroll down quite a way

    Cool pair of lowhead Bluebills by Ted Palister, Port Rowan, Lake Erie, Ontario. Circa 2008. Painted signature on keel of hen. Excellent all original paint & in unused condition. Solid wide carved body measures approx 12 1/4 inches long, with stylish low head with original keels. Glass eyes with nice head carving style. This pair of decoys were purchased on a duck hunt in the fall of 2008 out of Howie’s Hardware Store which is in Port Rowan which is on the banks of Lake Erie & right at the base of Long Point, Ontario. Very famous duck hunting area. Palister made high & snuggle head models as above. They were sold thru “Howie’s Hardware Store” to use for gunning in area up until the closing of Howie’s last year. Cool pair of birds to collect or add to the hunting rig. More pics available.
    $325 pair

    • Thanks Bill – but I think I’ll pass.
      The rail yard at Port Rowan was at the north end of town – well away from the lake.

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