June 3, 2010

Working Brakes



The photos show the brake parts that are part of the new etching. The brakes work just about like the real ones, though you don't have to make the brakes operate if you don't want to. There are also other freight car detail parts on the etch. I intend to offer this etch with each freight car model I produce. I will also make the etch available separately.

These trucks are designed for Intermountain O Scale wheel sets. I will also produce a set for P48 wheel sets.

The linkage parts are etched. The links use etched clevises soldered to 0.032 inch rod. The main link is a single etching. The parts in effect create a four bar linkage, a favorite of mechanical engineers.

The hanger straps act as a spring to retract the brake beams away from the wheels. The kit will include both stainless steel or laser cut resin board for different forces of retraction. In a prototype truck, the hangers are just for safety and the weight of the beam is sufficient to retract it. This is a key departure of the model design from the prototype, but essentially transparent to the user.

When installed in a car they work as follows. The brake wheel turns and winds a small section of chain around the brake wheel shaft. The chain is secured to the upper link. (There is a clevis for that link included in the etch but is not shown in the photo.) The chain pulls the upper link toward the rear of the car. The displacement of the upper link acts on the main vertical link. It rotates about the center link while also displacing to the center of the truck, thus pulling the brake beam towards the wheels. As the vertical link pivots it pulls the lower link to the center of the car, pulling the rear brake beam into the wheels. Thus the two brake beams pull together. The strap rails retract the brakes when the chain is slackened.

The links are articulated so that as the car negotiates curves the brake linkage doesn't snag. All in all it's pretty cool. See this post for a video of the brakes in action.

The switch stands are also done and will be available for sale soon.


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