The graphs for the Y6b on locofonic look OK for the last iteration of the Y6's. Without enlarging them and checking each value, the peak value and general shape seem to be OK compared with other sources. Starting drawbar pull seems to reflect the highest values achieved on test, STE of about 166,000 lbs simple and about 133,000 lbs compound. The curve for the A also seems to be based on test data, with a DB pull of about 122,000 lbs. If I were a little sharper I could probably figure out where the pages came from. They look very familiar.
Keep in mind that a lot of the discussion here has been on tractive effort. That's going to be higher than DB pull. Jeffries book (first edition, p83) has curves that were derived directly from the original sketches IIRC. They would be somewhat better than the ones on locofonic because they are larger scale and easier to read, but they appear to be identical.
Timz, you are right, and I was unclear. Obviously you wouldn't put 300 psi to those big front cylinders. But I am not aware of N&W having anything that would change the system to keep the pressure in the LP cylinder constant during the stroke. So if the reworked valves do a better job of maintaining pressure over the stroke (up to the cutoff), they might have increased the mean pressure.
Also, your comment about the valves being open or closed at start really only sort-of applies to the absolute very start. Remeber, even a full revolution of a 58-inch driver only moves you about 15 ft, and the locomotive has barely picked up the slack before the valves begin to have some effect on the TE. Now how much effect at such low speeds, I don't know.
Also, I was aware of the lead in the front engine, but strictly speaking, that affects the factor of adhesion, but not, at least in the traditional understanding, the TE. Factor of adhesion does of course affect how well the locomotive can use its TE. (To analogize, a car's torque and horsepower are factors of its engine--and, in some ratings systems, the accessories the engine drives and the driveline to the wheels--unrelated to its tires, but of course the tires affect how well the car can use the engine's torque and horsepower.)
No?
dredmann wrote:if the reworked valves do a better job of maintaining pressure over the stroke (up to the cutoff), they might have increased the mean pressure.
N&W reduced the maximum cutoff to increase the engine's TE at 25 mph, or whatever-- but how would reduced cutoff increase the TE at 0-5 mph? I assume it wouldn't, and I assume N&W didn't imagine it would.
Another aspect-- you've heard that the engine's ability to start a train depends to some extent on the crank position. Probably you've heard that the best position is to have the right crank at 4:30 and the left crank at 1:30, viewed from the right side of the engine with its front pointed to our right.
If maximum cutoff is 80% or less, when the left crank is at 1:30 the valve on that side has already closed. One wonders how the enginemen liked that change.
Probably you've heard that the best position is to have the right crank at 4:30 and the left crank at 1:30, viewed from the right side of the engine with its front pointed to our right.
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No one assumed he could see the crank position (from the cab)-- I just said that's supposed to be the best position. If it's not visible, cest la vie.
I guess it would be easy enough to see the rear engine crank position-- the rod for the rear driver is almost beneath the cab-- but maybe not the front engine.
Another thread is dead :-( ?
Thank you everybody,
for voting ;-) and particitating to this thread. It contained valuable infos about performances of various steam engines, some questions could be answered, some not...
Somebody interesting to go further on?
Regards
Lars
Lars,
Check your pms.
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