July 31, 2011

Arch Bar Trucks

Arch bar truck on a house car at Chattanooga, TN. I used this
car a guide in developing my arch bar trucks
Though most photos from the USMRR show freight cars equipped with wood beam trucks, there were also a good number of arch bar trucks in use too. I used some SMR trains brass arch bar trucks on one of my flat cars. But when I checked his web site recently to order some more, I learned that they were discontinued.

So I tried to make some of my own. I used the arch bars visible on the car in the prototype photo at the top left as a guide.  After a few nights of experimenting I was able to develop a design that looks good, are reasonably sturdy and have working brakes. The trucks are somewhat less work to assemble compared to my wood ones, as there are fewer NBWs to install. However, the laser cut acrylic side frames are very fragile. They need to have a piece of brass bar epoxied along the bottom to provide stiffness.

Example of how brake beams are suspended from the car frame.




Adding working brakes were tricky as most early arch bar trucks had the brake beams suspended from the frame of the car. That would not work on my layout with its sharp curves.  Later designs had the brakes in between the wheels. That was also not going to work if I wanted them to operate. So I modified the design slightly so the brake beams hang from a safety beam inside the truck similar to the design shown on page 179 of John White's book, "The American Railroad Freight Car."

I installed a set of home made arch bars on house car 1445 as shown in the photo.  The truck with the brakes is the latest design. The truck on the right was the first iteration.



House car with home made arch bar trucks with working brakes.

Another flat car enters service with wood beam trucks and working brakes.  I added a brake wheel support stand that I had seen in some prototype photos.
The cannon is the latest design. The laser cut details look good. Now I just need to mass produce the barrels. I'm working on it.

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