The Front or Engine Truck
While getting the pivot ready to bolt into the frame, I couldn’t quite figure out at what height to mount it and couldn’t figure out how the frame was supported on it. So I decided to start from the ground up and the side frames
The pattern out of MDF
It will take two patterns to cast one frame. I decided to not cut out for the axle journals because it may have made them weak
Then I started working on the mount to the frame and the center pin for the engine truck and here is the finished product.
I still need to cut out the bushing for the truck to first axle equalizer. It fits into the center pin through the bushing, and on an equalizer seat. The center pin does not turn in the bushing, only up and down. The rotating motion will be between the bolster and center pin and the side to side swing will be between the bolster and what is called the roller seat. On a steamer the engine truck (when going into a turn) will be forced down on the rails to prevent derailment. The bottom of the bolster and the roller plate will have two v groves running fore and aft (1 in 3 on the sides). A rack gear at the same angles and a gear between the bolster and roller plate will provide the added weight shift hill.
This is the start of the patterns they will be mounted to a match plate and cast in iron
And this is how they turned out
With a bit more machining done
An axle box pattern
The inner workings are a bit of a trick. As the engine enters a curve two things happen, First this assembly turns and secondly it must shift to the side. As it shifts to the side it needs to transfer weight to the assembly to keep it from derailing this is what does the trick