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Steam & Excursion > SP mogul in Houston - is this a compound engine ?Date: 01/22/25 14:54 SP mogul in Houston - is this a compound engine ? Author: WrongWayMurphy Technically a Texas & New Orleans mogul, at the Hardy turntable June of 1915
I am far from a steam expert so I ask as it looks like a low and high pressure cylinder arrangement. For some reason I thought compounding was normally used on heavy drag freights, often in territory with grades. This is a relatively lightweight engine used on the flats close to the Gulf. ![]() Date: 01/22/25 15:08 Re: SP mogul in Houston - is this a compound engine ? Author: LarryDoyle Yes. Specifically, a Baldwin Vauclain compound. High pressure cylinder is on bottom, low pressure cylinder on top - the usual arrangement on locomotives with small drivers. The valve gear and piston valves were between the frames/cylinders.
Photo below shows the arrangement. Vauclain compounds were used on both low drivered freight engines as shown, and on high speed passenger engines with large drivers, in which instance the arrangement was reversed - smalll piston on top. -LD Edited 1 time(s). Last edit at 01/22/25 15:14 by LarryDoyle. ![]() Date: 01/22/25 15:43 Re: SP mogul in Houston - is this a compound engine ? Author: PHall In theory the Baldwin Vauclain Compounds were more efficient and used less fuel and water since the steam was being used twice.
It's a nice theory... Edited 1 time(s). Last edit at 01/22/25 15:43 by PHall. Date: 01/22/25 21:55 Re: SP mogul in Houston - is this a compound engine ? Author: callum_out AKA that second batch of steam is never as good as the first.
Out Date: 01/23/25 07:56 Re: SP mogul in Houston - is this a compound engine ? Author: LarryDoyle Compound locomotives were were still built in 1949 for use in the US. {Corrected below - 1952 by N&W. Last commercial builders compounds were 1949)
-LD Edited 1 time(s). Last edit at 01/27/25 11:57 by LarryDoyle. Date: 01/23/25 07:59 Re: SP mogul in Houston - is this a compound engine ? Author: jkh2cpu And when was the last Y6b errected?
Date: 01/23/25 11:07 Re: SP mogul in Houston - is this a compound engine ? Author: timz At least 1949, wasn't it?
Date: 01/23/25 11:20 Re: SP mogul in Houston - is this a compound engine ? Author: wcamp1472 "Compounding" is used today in today's steam turbines.
Turbines have successive rows of turbine fins, on larger and larger in diameter turbine 'stages' Between each rotating disk with the turbine fins, are the 'stator' fins --- they are fixed, and serve to re-direct the steam flow for most effective flow direction to the next stages of successive rotor fins. Each rotor disk of fins is larger in diameter than the predecessor turbine disk and it's blades. The progression in increasing fin-diameters, allows each stage's torque-force to have equal rotative leverage applied to the length of the turbine center shaft. The expanding disk diameters is "compounding" the flow of steam through many stages. Now, consider that aircraft jet engines descended from successful steam turbines. Turbo-jet engines have a first stage of fuel burning, compressor-fins to provide the hot gasses to exert force on the aft turbine stages. And, each stage of the turbine, is staged, and larger in diameter than the previous turbine-stage diameter. The output torque of the engine shaft is sent forward, through the turbo-jet center shaft to power the large-diameter, propeller-disk at the front, inlet stage. Such an arrangement was a successor to the earlier "turbo-prop" aircraft engines. The trubo-props had 4 propeller blades, today's turbo-fans use hundreds of smaller blades. It is the turbo-fins that move the air, and pull the plane through the atmosphere. They are called TurboFan engines. Upon landing, the propeller-fins can be individually pivoted, so that the air is forced forwards, acting as a turbo-brake. The engine shaft remains turning in the same direction --- but, the thrust of the turbo-fan is reveresed, slowing the plane as it approaches the terminal. It's common to say that the pilot has 'reversed the engines', but that's not accurate. Whenever I see con-trails in the sky, I'm reminded of 'compounding' and how it's evolved. A further successor from the Y6b. A British inventor, Charles Parsons, developed the first steam turbine in 1884. W. not proofed yet... Edited 3 time(s). Last edit at 01/23/25 11:36 by wcamp1472. Date: 01/23/25 11:26 Re: SP mogul in Houston - is this a compound engine ? Author: timz > Upon landing, the propeller-fins can be
> individually pivoted, > so that the air is forced forwards, acting as a > turbo-brake. > The engine shaft remains turning in the same > direction --- > but the thrust of the turbo-fan is reveresed, > slowing the plane ... Waitaminnit! Turboprops could reverse-pitch, turbofans don't. Each blade is fixed. The reversing is further back. Date: 01/23/25 14:22 Re: SP mogul in Houston - is this a compound engine ? Author: Earlk Another SP Mogul in Vauclain Compound form. In this case 1744, which is under overhaul by the Nile Canyon folks in CA.
![]() Date: 01/23/25 16:52 Re: SP mogul in Houston - is this a compound engine ? Author: PHall timz Wrote:
------------------------------------------------------- > > Upon landing, the propeller-fins can be > > individually pivoted, > > so that the air is forced forwards, acting as a > > turbo-brake. > > The engine shaft remains turning in the same > > direction --- > > but the thrust of the turbo-fan is reveresed, > > slowing the plane ... > > Waitaminnit! Turboprops could reverse-pitch, > turbofans don't. Each blade is fixed. The > reversing > is further back. But you don't do anything to the blades when a turbofan engine goes into reverse thrust. Depending on the engine you either put the air blocker doors to the reverse position which redirects the fan thrust or the clam shell target reverser closes behind the engine to redirect the thrust coming out of the tail pipe. The Boeing 737-100 and 200 used the target reversers, they used low bypass turbofan engines. The Boeing 737-300 thru the 900 use the air blockers and cascade vanes to reverse the fan thrust of the CFM-56 engines which are high bypass engines. Date: 01/23/25 17:57 Re: SP mogul in Houston - is this a compound engine ? Author: wcamp1472 Thank you for the clarification and the work-arounds that
use the power of the jet engines to provide powerful dynamic braking... They still use-up many sets of new tires ---- worn most heavily during braking ..... its where the rubber meets the road. W. Date: 01/23/25 18:24 Re: SP mogul in Houston - is this a compound engine ? Author: ts1457 jkh2cpu Wrote:
------------------------------------------------------- > And when was the last Y6b errected? No. 2200 left the shop on the afternoon of April 22, 1952 per Louis M. Newton, Rails Remembered Volume 3, page 648. Date: 01/24/25 13:27 Re: SP mogul in Houston - is this a compound engine ? Author: PHall wcamp1472 Wrote:
------------------------------------------------------- > Thank you for the clarification and the > work-arounds that > use the power of the jet engines to provide > powerful dynamic braking... > > They still use-up many sets of new tires ---- worn > most heavily > during braking ..... its where the rubber meets > the road. > > W. > > > Reverse thrust works best above 100 knots and must be stowed before 60 knots so the engine won't suck in it's own exhaust. That results in compressor stalls, aka backfires. Not good for the engine. Date: 01/24/25 17:03 Re: SP mogul in Houston - is this a compound engine ? Author: NCA1022 PHall Wrote:
------------------------------------------------------- > In theory the Baldwin Vauclain Compounds were more > efficient and used less fuel and water since the > steam was being used twice. > It's a nice theory... From what I learned when I looked into Vauclain compound steam locos: Yes, they were more efficient in the use of steam and hence fuel and water consumption. And possessed good power. However, those efficiencies were more than offset by greatly increased maintenance costs incurred when compounds were used in regular service. The high pressure and low pressure piston rods were connected at a common crosshead which in turn powered the main rod to the drivers Unfortunately, the high and low pressure pistons exerted significantly uneven forces on the shared crosshead, causing rapid wear. The inside-the-frame valve gear was surely a pain to access so maintenance was more difficult and prehaps paid less attention to compared to external valve gear. That is why the Vauclain compounds were rebuilt with conventional cylinders. i checked into this after the ATSF 1010 2-6-2 was put on display at the California State RR museum last summer. (I'm a volunteer docent there.) While the loco is listed as being built in 1901, the cylinders clearly show a much later date on the front of the cylinder casting (July, 1923 as I remember). I wanted to figure out why it got new cylinders. From the looks of the 1010, at the same time it was fittted with conventional Walschaerts valve gear and it also got a superheater and new set of drivers. It was built with 79" drivers for fast passenger service. but the drivers it has now are much smaller. Wikipedia says 69" drivers, but somehow they seemed smaller than that to me. Maybe the resulting wide axle spacing was throwing me off. During a subsequent rebuilding in 1936 the 1010 was converted to oil and got a different tender from another ATSF loco.. The smaller drivers plus the wide axle spacing unfortunately give the 1010 a rather "squatty" appearance, but beauty is as beauty does and it served the ATSF reasonably well as a commuter train and branch line loco after losing its compound cylinders. - Norm Edited 1 time(s). Last edit at 01/24/25 17:10 by NCA1022. |