when you put the reverse lever all the way forward are you letting in steam for 100% of the intake stroke?
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Originally Posted by ironlake2:
when you put the reverse lever all the way forward are you letting in steam for 100% of the intake stroke?
No. Few if any locomotives were built for 100% admission. The steam lap of the valve determined the percentage of admission. Most locomotives without what was called "limited cutoff" admitted steam for about 80-85% of the stroke.
Many locomotives were fitted with extended steam lap which might limit steam admission to 75% or less of the stroke; this was referred to as limited cutoff. The most extreme limited cutoff of which I'm aware was 50%, applied to PRR I1s 2-10-0s as originally built, and PRR's one-of-a-kind HC1s simple 2-8-8-0. The I1s's had auxiliary starting ports in the cylinders, because they could get into a rod position where one side was on dead center and the other side was at the point of cutoff.
In the book "Set Up Running", the biography of a PRR engineer who ran many different locomotives including the I1s, it was noted that the I1s were very sluggish, poor performers when first built.
It has been noted that at some point PRR became aware that the 50% on these locomotives was not satisfactory, and the lap of the valves was adjusted to provide a cutoff of 78%. After this change was made, the PRR engineer cited above testified that the I1s were much better performers, more satisfactory in every way. AFAIK, the 2-8-8-0 was never changed.
Lima's first 2-8-4 of 1925 had a limited cutoff of 60% for maximum economy, but it also had a trailing truck booster so that starting a train wouldn't be a problem.
EdKing
thankyou for the great info.
Originally Posted by Edward King:
In the book "Set Up Running", the biography of a PRR engineer who ran many different locomotives including the I1s, it was noted that the I1s were very sluggish, poor performers when first built.
And as a slightly irrelevant note, I'd like to add that Set Up Running is an excellent book, highly recommended. And not just for PRR fans. It's a virtual one-volume encyclopedia of steam railroading as it was lived.
Originally Posted by Balshis:
Originally Posted by Edward King:
In the book "Set Up Running", the biography of a PRR engineer who ran many different locomotives including the I1s, it was noted that the I1s were very sluggish, poor performers when first built.
And as a slightly irrelevant note, I'd like to add that Set Up Running is an excellent book, highly recommended. And not just for PRR fans. It's a virtual one-volume encyclopedia of steam railroading as it was lived.
I'd add an emphatic AMEN to that. It is very readable and has a great appeal not only to steam aficionados, but for students of general railroad history.
EdKing
