Of all the coulda, mighta, shoulda beens...
(230) PRR Steam Turbine Class S2 - YouTube
6900 horsepower!
Ah yes, the S2. Good in theory, not so good in practice.
On the other hand, it was pretty darn successful for Lionel! I should know, I've got one!
https://www.tandem-associates.com/lionel/lionel_trains_681_loco.htm
Flintlock76 Ah yes, the S2. Good in theory, not so good in practice. On the other hand, it was pretty darn successful for Lionel! I should know, I've got one! https://www.tandem-associates.com/lionel/lionel_trains_681_loco.htm
The big problem with the S2, it has been reported, was that in starting a train, the turbine drew so much steam that it quickly lowered the boiler pressure, popping staybolts in the process. This made the S2 impractical to operate.
Didn't anyone calculate the stall-speed steam consumption to determine how much the boiler pressure would go down? Didn't the turbine engineers check with any people who knew boilers? Or was the S2 just thrown together with a hope for the best?
The British Turbomotive had a variable number of steam nozzles that could be selected for different amount of starting tractive effort. I never heard that it had a problem with broken staybolts; neither have I heard of such a problem for the Swedish turbine described on another thread. Couldn't the S2 designers build on prior experience?
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
Back in 2012 "Classic Trains" ran a superb in-depth article about the S2, the theory, the design, and the reality. Everything you'd want to know.
It's still available as a back-issue. I wish I kept the one I had.
https://kalmbachhobbystore.com/product/back-issue/ctr120301
PRR had two problems with all of their experimentals in the late steam era.
First, they partnered with Baldwin, probably the least innovative of the three manufacturers.
Second, their own engineers hadn't designed a steam locomotive in 20+ years.
The only "super power" they had were the T1s. It was the blind leading the blind.
Paul Milenkovic The British Turbomotive had a variable number of steam nozzles that could be selected for different amount of starting tractive effort.
The British Turbomotive had a variable number of steam nozzles that could be selected for different amount of starting tractive effort.
This drawing of the S-2 turbine setup shows four steam inlet pipes, thus four nozzles. There is no reason to believe each pipe didn't have it's own valve, so it looks like the S-2 very likely had a "variable number of steam nozzles".
I don't doubt that this locomotive was also a PITA for most engineers and firemen. They were not at all used to this machine, and I'm sure it had new and different traits. I surely would like to read a book that was full of opinions of people who were THERE. Some would be wrong, of course, but they would be honestly held, and thus informative.
Ed
My understanding is that a steam turbine is very effective in say an ocean liner, where the engine was running at full speed for hours and hours continously. When you put it in a steam locomotive speeding up and slowing down, starting and stopping, it's efficiency is lost.
That point's right of course (and also extremely true for reciprocating steam; see Porta's experiments in far South America...) But the S2 turbine was efficient over a wide range of road speed. The low-speed slip issue was essentially solved by Westinghouse with the two-speed planetary transmission but by then any sort of big steam with reciprocating drive was moribund.
Likewise, implementing a 'spoiling' of draft in the front end at low speed while preserving free expansion of turbine exhaust would have fixed most of the trouble except the water rate. Even thd Bowes drive couldn't cure that on a fast engine with high horsepower...
wjstix My understanding is that a steam turbine is very effective in say an ocean liner, where the engine was running at full speed for hours and hours continously. When you put it in a steam locomotive speeding up and slowing down, starting and stopping, it's efficiency is lost.
It's hard to believe the designers weren't told of the typical operating characteristics of a railroad locomotive. And it's also hard to believe they weren't familiar with the power output of steam turbines over a range of speeds.
I would be very interested in what they did about it, or tried to do, or wanted to do. Not to mention some firsthand reports from the various people involved.
Surely there were tests done and results evaluated.
I also wonder about reliability. When you're doing cutting edge work, the machine can work well if all things are perfect. And when they become non-perfect.......
7j43kIt's hard to believe the designers weren't told of the typical operating characteristics of a railroad locomotive. And it's also hard to believe they weren't familiar with the power output of steam turbines over a range of speeds.
Also remember this development isn't occurring in a vacuum; PRR had exhaustively looked at both Steamotive and oil firing before, and was tinkering with that D-C-C-D thing and the Steins Triplex while considering what in 1944 looked attractively cheap and simple compared to 'other alternatives'.
Not to mention some firsthand reports from the various people involved. Surely there were tests done and results evaluated.
It doesn't help that this was a sustained high-speed engine on a railroad with a 50mph freight limit. E7s did its job better even by the time it developed perhaps-convenient foibles.
46% of engine weight was on the drivers of the S-2. That number was 61% for a fairly generic 4-8-4 (SP&S). If it's not on the drivers, it's not pulling.
Not a deal killer, but unfortunate.
As far as the high fuel use at slow speed problem for the S-2, I wonder at using a second, low speed, turbine, with a higher reduction gearing. You would either have to deal with that turbine spinning VERY fast (but not under load) at high locomotive speeds, or have a clutch/disconnect.
Another way to go with the low speed turbine would be to have the incident angles of the blades at a sharper pitch. The two above problems would be gone, but I wonder if it would work.
I was sore tempted to buy a recent model of this locomotive; but I don't have a train for it. S'pose it could have been pulling freight that day. Then just a PRR caboose!
7j43k46% of engine weight was on the drivers of the S-2. That number was 61% for a fairly generic 4-8-4 (SP&S). If it's not on the drivers, it's not pulling.
The right short-term answer, and one applicable to your idea, was that two-speed planetary, here with a couple of preliminary reduction stages from the rotor. I'd at least try to make the smaller turbine like the main, with a Curtis impulse first stage and barrel reaction expansion stages. The issue would be high-speed and high mass flow if speeds much above 80mph were actually needed -- PRR had actual tractive-effort curves defined out to 85mph and the running gear could be easily balanced much faster
Another way to go with the low speed turbine would be to have the incident angles of the blades at a sharper pitch.
I still think the best solution is to use variable excitation for load control in a Bowes drive that optimizes mass flow at a particular perhaps narrow turbine powerband, but without using traction motors and the control modalities that go with them. This was well developed between 1952 and 1956... but had ceased to be relevant for either freight or passenger in the period before TrucTrain service began to develop as a PRR 'advantage'. Even R2s would have been ideal in that service... but Fs and big Alcos even more so...
Were there any conventional locomotives with a 6-8-6 wheel arangment?
Still in training.
Lithonia Operator Were there any conventional locomotives with a 6-8-6 wheel arangment?
No.
I recall reading about Amtrak's gas turbine trains that ran in New York and how they were only efficent when run at high speed. The Chrysler turbine car was the same. The nature of the beast I guess.
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