If they couldn't be sure of stopping when or where they wanted, it would be better to risk the brake tender, rather than hit something with the locomotive... and occupied cab.

A little off topic, but I did save my employer a teeny bit on fuel costs and recovered a little bit of energy by putting a dead locomotive in reverse and opening the throttle as I was towed dead in train. In no time I had 140 psi in the boiler, and when we got where we were going, I was able to light off and get steam up quickly because all the water in the boiler and tender was pretty warm after the engine had been sitting in the Guatemalan sun all day.

We had been stopping every few kilometers and dumping valve oil into the piston valve inspection ports, of course. While this was expedient that one time, you wouldn't want to fire up that way very often because it filled the boiler with air, rather than leaving the vent valve open and driving off the free oxygen as we usually do. Using the cylinders as air compressors DID increase the train resistance going downhill.

I had the same idea for an auxiliary water tender-looking battery-powered booster/dynamic braking/compressed air vehicle for live steam. Designed to look like a N&W auxiliary tender, but with motorized trucks, an air compressor and storage tank. Radio control, no need for much gingerbread on it outside of a backup headlight. I figure it could provide enough dynamic braking to hold back (but not stop) a train of six cars with adults on a 4% grade, and pull an extra two coaches of adults up same.

Maybe a shade off topic, but drifting valves have been mentioned a few times above.

How essential are drifting valves? I've seen quite a few builders photos of 1920s era coal fired pacifics etc that do not seem to have them.

To get back on topic, wouldn't the N&W Jawn Henry and all those UP steam turbines qualify as steam locomotives with dynamic braking ??

Depends on whether they were built with that capability, Sammy..... I think they also didn't have the stopping problem as much as the keeping them going problem.

Dave, I 'bleeve so --- they had the same troubles as any other kind of motive power would with holding 'em back going down, let's say, Sherman Hill.