What would it take to mimic dynamic braking on a steam locomotive? I've heard of 'water brakes' on some western US locomotives, but would it be worth the effort?

Brian

Quite a few examples of shoving the poor engine in reverse in Disney's "The Great Locomotive Chase" which I suppose is a form of steam dynamic braking. Would've done wonders to the bearings...

Hmmmm. Remove everything above the frame except the main generator, electrical cabinet etc., on a recent but disliked 6-axle unit (e.g. almost anything from the 1990s), install a steam driven industrial motor to turn the generator, run a steam line back from the engine, install a line of brake grids on a lowered hood on the order of a slug, install a dynamic brake control lever in the engine. Worth it? Well, hopefully you would extend the life of a lot of engine brake shoes.

Known also as the counterpressure brake, it uses the cylinders as compressors - the water injection was for heat dissapation, lubrication as well as cushioning. Some form of steam oil injection as well as pressure controls and a means for not sucking grunge in from the smokebox during part of the stroke are recommended.

OK. How 'bout a Jake Brake instead ??

That might not be quite as bad as it seems. It's my understanding you wouldn't need the full power of the main generator, just excitation current. That's quite small compared with traction power, or the power you'd be getting from the traction motors in braking mode. You just might be able to get what you'd need from a small genset, or an enlarged turbine driven dynamo (like for headlights but a bit larger, maybe like what CNJ and C&NW had on steam engines for early head end lighting on commuter trains), or even batteries.

And for aesthetics, cover the grids and the ballast (you'll need some of that, though not necessarily full locomotive weight) with a body that looks like a baggage car or something.

And paint it Pullman green.

With the control technology available now, you could initiate dynamic braking with just a battery to energize the motor fields and provide initial control, then tap the output to charge the battery and provide continuing motor field power and control.

PC

Oh hell, just stick a set of traction motors with permanent magnets on the tender trucks and don't forget to plate them with Imitation Gold...

No, no, no, you've got it all wrong, you could put a belt driven generator on the trailing truck, and use THAT to excite the field windings in the tender truck traction motors. Maybe you could set up the braking grids so they could heat the boiler feedwater. Now THERE's a practical idea.

It was a serious question and deserves real information. Counterpressure brakes were used but weren't popular due to the increased wear in the mechanical parts - brake shoes were more easily replaced. Don't forget the alternative was learning to ping pong between the jam and automatic brakes to keep the train charged while going down long grades without loosening the tires on the locomotive. Of course, retainers did a lot of good, but you can't stop a train on a grade with retainers. Certainly not exactly dynamic brakes in the modern sense, but akin to them in general purpose.

.

Actually Dave, I was being at least semi-serious concerning the traction motors (generators) with permanent magnets thing unless you draw the excitation current from the locomotive's generator and as Sammy alluded to, you could use the extra juice to preheat the feedwater and even while it's still in the tender if you put the resistor grids in or around the tank. You can't get the feedwater too hot, either, so you'd need an option to vent the extra generated heat to atmosphere as well.

Dammitt, you guys make me start thinking too much sometimes but then again, they were probably thinking about this sort of stuff a century ago, also. LOL

I used to use a jake brake about 100 miles a night five nights a week, but I only know the basics of how it works, it cuts off the fuel and then opens the exhaust valve at the very top/end of the compression stroke, so the engine must expend energy both compressing and pulling the piston down again. Would something like this be possible on a steam piston?

Believe it or not, Clessie Cummins invented the Jake Brake. Or more correctly a Compression Release Brake. He licensed it to Jacobs Engine Systems; hence the nickname. But it it's been around only since 1961, so no steam application.

RGS 20's water brake (Kelly) and Dave's counterpressure brake sound like a steam era solution. Didn't Santa Fe use such a system coming down Cajon and Raton Passes?

If you put traction motors on the tender, had a means of excitation and control, and a way of dissipating the current generated, you've got dynamic brakes.

Phil Mulligan

Clessie Cummins was the founder (and chief developer) of Cummins Diesel.

Further thoughts on what I would call a "dynamic brake tender" for excursion locomotives.

I mentioned fabricating a cover for it that could look like a baggage car, just to make it look better.

Given that you likely would need some ballast (but not as much as a slug delivering tractive effort would need), you just might have enough room in the body to actually use it for something, locker room, tools, whatever. That would depend on how you might distribute the ballast, say by concentrating it at the ends, over the trucks, where it would be needed.

Air brakes provide a couple of different options. One could be to have an engine of some sort drive a compressor for additional air capacity, but I don't think you'd really need that. It's not like we'd be running 200 car coal or ore trains with steam, and most locomotives would have more than adequate air capacity for anything we'd do.

No, I'd keep things simple. I'd set up the air on the "brake tender" as I would on a passenger car, tuned for the heavier than normal weight of the brake tender.

Which reminds me-- I seem to recall the British using something called a "brake tender," or something similar. Turns out they were older cars ballasted for braking service with diesel locomotives--a use very much like what we're proposing here. The reason was the diesels didn't have the stopping power of the steam engines they were replacing, which would make this a serious consideration at a time when a great deal of British Railway freight equipment lacked anything but a handbrake--just like this country in pre-air, link and pin days!

https://www.gcrailway.co.uk/2017/11/the ... ke-tender/

An interesting point is that these brake tenders were normally operated ahead of the locomotive. I wonder why that was done?







All these images are from this page, and were taken by a poster there who goes by Dave F.

https://www.rmweb.co.uk/community/index ... ent-845232