Allen Mogul Pony Pivot Repair

by Daris A. Nevil

I heard stories about how much maintenance goes into a live steam locomotive. Now that I'm an owner I am finding that I have to do some kind of repair or maintenance following almost every run. Most of what I have done has been to improve operation or change operation to my preference. But #486 experienced some real damage on a run at the Annetta Valley & Western Railroad during a recent run.

The Incident
A cool front blew through north Texas August 17, 2013. It was the first break in the heat all summer, so I took advantage of the opportunity. I made the first run on the track that morning. Unfortunately, the track had not been "walked", and as #486 began its climb out of Stamey Loop I noticed a 1/2 inch stick across the rails. I didn't have time to stop, and hoped the cow-catcher would throw the stick clear of the tracks. Well, it didn't, and old #486 went right over it. The pony truck went right over it, followed by all six drivers. They didn't event derail! But the tender did, so I stopped to clear the track and re-rail. All seemed fine, but I found that the pony truck kept derailing in curves. Another engineer passing by pointed out that #486's pony truck was not tracking straight. I got down on my hands and knees and noticed the pony truck pivot pin was missing.

By this time I was far from the engine stands. The same helpful engineer suggested I run backwards back to Terry Town Station. That worked like a charm, and I didn't derail anymore.

Upon closer inspection I realized that not only was the pivot pin missing, but the pivot bearing had broken off.

The OEM part that had broken was Allen Models #201, "Center Plate". It is a cast aluminum cover for the bottom of the saddle. The casting includes a pivot point for the pony truck. This cylindrical pivot is what broke completely off during the impact with the branch.

The Repair
I decided to manufacture my own "Center Plate" from steel components, mainly because I did not want to wait for a replacement part. I also wanted a stronger material than cast aluminum and decided to reduce the diameter of the pivot so the pony truck would have more vertical freedom.

The photos below show how I made the replacement parts.

Test Results
I am happy to report that the next run of #486 was a successful one. The repair is working well, and is keeping the pony truck in its place.