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X31F Part 1: Early Progress

In part 0, I discuss the inspiration and background for this model. Sunshine Models had produced a resin kit of the Pennsylvania X31F, but the owner has retired, and the kits are no longer in production. Fortunately, Bowser produces a model in styrene – a medium more modelers are comfortable working with.

Breaking news: David Sieber writes to tell me “One happy bit of info:  Sunshine Models is still active and Martin Lofton has not retired from the resin kit business (though last year, his wife Tricia shared that he had been considering it due to health problems).  However, all PRR X31-series kits were retired from his line due to sales plummeting after Bowser came out with their X31s.  This has happened with several of his resin offerings after various manufacturers have brought out a plastic version.  You can still get other unique cars like Pennsy X37 and X41 boxcars, B&O M-55C and H boxcars, and many others from Sunshine; see Jim Hayes’ unofficial Sunshine website at – Sunshine themselves are not online.  If you order, be prepared to wait at least 6 months for your order to be filled, since except for newly issued cars produced for the few shows that Sunshine attends, everything is cast to order and they are just that backlogged with orders.”

Perhaps the biggest problem with this model is the underframe. The model has four stringers instead of two, and the center sill is greatly simplified.

The X31Fs were rebuilt with four stringers instead of two starting in 1954. The problem is these stringers went the entire length of the car, eliminating the diagonal braces outside of the bolster. So, either the diagonal brace has to go, and the four stringers extended to the ends of the car, or the four stringers have to go, and replaced by two. Since I wanted the model to represent a car in 1953, this eliminated the option of building the car with four stringers.

So I carefully milled the underframe to eliminate the four stringers, and the mounting holes for the brake gear that Bowser had included. I also milled away the coupler pockets to make way for the scale sized draft gear from Accurail. I carefully chiseled and sanded away the parts I couldn’t mill, and then rescribed the wood plank flooring. I also puttied the brake mounting holes.

Construction began moving from the floor up (down, but inverted). The first thing I did was add the stringers. The prototype stringer is a Z-angle with the open face toward the center sill. This goes under all the frame crossbearers, which was impractical on the one-piece floor, so I had to do it in sections between the crossbearers. The Z-angle was simulated by two pieces of Evergreen styrene – a 0.030″ square piece, with a 0.010″ x 0.030″ strip for the flange portion that mounts to the floor. A pair of calipers came in handy to measure the distance between each crossbearer, and cut the styrene to length.

When this was done, attention was turned to the Brake Pipe. So far, this has been only added between the bolsters, but will eventually extend to the end of the car to mate up to the air hoses. This will be T-ed off to the triple valve and other brake parts at a later date. Although I’ve done this in the past with brass wire, I was encouraged to try 0.020″ Plastruct Styrene Rod, and I really like how this works.

Attention was then turned to the center sill. The model has just a vertical rib with rivets on the end, while the prototype has two I-beams, spaced 12″ between the top flange. I filed off the rivets, and cut 0.020″ x 0.060″ styrene strips to fit between the bolsters and each of the larger crossbearers. Those crossbearers, as near as I can tell, have straps that fit over the center sill, so rather than sand them flush with the top of what becomes the I-beam web of the center sill, I just put the top flange between them.

I have also been working on the body. There was a large casting blob on the roof. Although it would be mostly hidden by the roofwalk, I decided that since the model will encourage close scrutiny, I would do my best to remove it. The bodywork was completed with a coat of Gunze-Sangyo Mr. Surfacer 1000 (don’t you just love Japanese product names?) thinned with MEK.

In part 2, I’ll continue to work on the brake rigging of the underframe, and describe some of the work I’m doing to the body.

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