Re: engine braking on steam locomotives

Mike, I am sure that everyone is holding their breath, anxious to hear more about truck anbd bus auxiliary braking systems, but the transmission retarder you describe is less common on Class 8 trucks than
the "Jake" Brake. Manufactured by Jacobs, it changes the engine exhaust valve timing to make the diesel engine function in a manner similar to an air compressor creating braking resistance, rather than energy output.

Additionally, don't forget the exhaust retarder brake. Within the past hour, I chauffeured a Freightliner Chassis fire truck on a "business call". It is equipped with an exhaust retarder that basically blocks exhaust release into the muffler, creating back pressure in the engine that slows the truck.

That said, how bout some discussion about engine braking characteristics of steam locomotives? Does the type of valve system have any affect on braking? What braking function, if any, is acquired by
changing the Johnson Bar position?

I have minimal "right seat" time in a locomotive. I've noticed that the Shay's have a "drift valve" for downhill operation, but I was of the impression that it was more for cylinder lubrication than actual
braking effort.