I know that many steam engine types and models had boosters. I have also come to understand the criticism of the Triplex in that it’s “third” exhaust was ported to a separate stack, and did not therefore contribute to the overall firebox draughting. We’ll forget the criticism about traction as its tender load lightened; it’s not relevant so much to the question that follows. I think.
So, that raises the question…if so many of the larger, later, steamers had boosters, how were they plumbed? Did their exhaust contribute to the draught?
Crandell, it depends on which particular engine you are looking at. Some did, some didn’t. The Erie triplex wasn’t anywhere near comparable to modern locos in terms of generating steam, so it’s not a like-for-like comparison. At low speed a modern boiler could produce more steam than the cylinders could use, so the loss of some draught from the booster exhaust was not critical. Also, the volume of the booster cylinders was far less than the volume of the triplexes rear engine, so the amount of steam used is considerably less.
So…the answer to the question is…that they exhausted down to the tracks, or were ported back to the stack with a conduit of some kind? Clearly there was a hot pipe to feed the cylinder, but once the cylinder had done its work stroke, the used steam must have been evacuated to some place. I gather from your answer that it was comparatively minor in quantity in view of all that the boiler was capable of, and that it was just lost to the atmosphere directly?
I seem to recall having been told that the booster steam was fed to the Worthington feedwater heater on the NYC Niagara - but that was many years ago, and my informant (old round house super) is probably dead.
The Wikipedia plumbing drawing (Booster Engine) shows the exhaust feeding into the bottom of the main blast pipe. This was probably the most common arrangement.
Mark, I believe the boosters were meant to be shut by 15 mph, give or take…30 mph sounds a bit high, particularly for a drag engine that spend much of its mainline time at 30 mph or less anyway. Maybe Mark Newton or someone else reading can help us with that one.
G’day Crandell. Engines I have seen where the booster exhaust went straight to atmosphere vent the steam upwards, not down to the track. On some US locos with a separate booster exhaust it was behind the stack, on other engines, such as the SAR 4-8-4s, the exhaust was straight up the side of the firebox. Locos where the booster exhaust was via the stack had an exhaust pipe running from the booster to the exhaust passaes in the cylinder saddle, below the blastpipe. If I can find some photos and/or drawings to illustrate the differing arrangements, I’ll post them.
If it didn’t get exhausted via the blastpipe, then yes, it went directly to atmosphere. The quantities used were, as you say, minor.
No, that figure is about right - the Franklin booster engines have a governor, and will disengage automatically at 30mph if they haven’t been already by the crew. But I reckon most railways would have operating procedures requiring dis-engagement at a lower speed than that. A booster can be engaged at up to 15mph, though.
I don’t see boosters as being a drag-freight engine accessory, as you’ve suggested. They were most useful fitted to passenger engines such as the NYC 4-8-4s, or dual-service power that was designed to run at speed. A steam loco at speed can haul a heavier train than it can start by itself, which is what made the booster viable.
I have a fairly large steam loco library, and up to date I didn’t find any note that a NYC Niagara had a booster. Instead I did find many notes stating that this has been regarded as unnecessary. Did you or the old roundhouse super mean the 4-6-4 Hudson? These had boosters.
Derr! I must have been asleep when I was posting last night!
You’re right, of course, the Niagaras didn’t have boosters. The old super must have meant the Js, or the various L-class engines that were booster fitted.
Actually, the roundhouse was in North White Plains, a location which never saw either 4-8-4s or 4-6-4s. It’s entirely possible that the old feller was pulling an impressionable young teen’s leg.
Chuck (modeling Central Japan in September, 1964 - sans boosters)
Here’s a model of mine showing typical non-superpower booster engine plumbing:
This is a Nickel Plate H-6b, a USRA clone delivered with a booster. The booster is fed from a pipe running from the cylinders (using waste steam), behind the air tanks and feedwater heater, across the firebox and down to the motor carried by the Delta trailing truck (the pipe extending lowest under the cab). There were three sets of flexible pipe connections hooking the feed line to the motor.
The exhaust pipe ran along the engineer’s side of the engine, ran along the lower edge of the boiler, and up to a point behind the stack, where the steam exhausted.
This is a pretty typical piping arrangement for most Mikes equipped with boosters, and is an arrangement that the Nickel Plate adopted from the NYC.
Less volume, for sure. In fact, the Erie Triplex exhausted fully half the total steam from that third-engine stack (it was a compound, with one set of HP cylinders and two LP, one of which LP sets was the third engine). Even at that, the Matt H. Shay could produce enough steam at very low speeds, 8 mph or so.
Ray, a minor quibble, but wouldn’t the booster be running on live steam, as opposed to exhaust? From your photo, the delivery pipe to the booster is coming from the live steam part of the valve chest. Unless the NKP 2-8-2s were outside admission?
Nice modelling, by the way! [:D]
Cheers,
Mark.
EDIT: I just had a look at the photo of NKP 587’s front end in the thread in General Discussion, as far as I can see it’s your normal inside admission engine… So the booster you’ve modelled would definitely be running on live steam.
