More Steam History

Downing, R.D. 1, Box 181, Ellwood City, Pa. 16117.

Thought I would take a minute to drop a line and say how much I
liked the article in Sept.-Oct. 1973 I.M.A. on ‘Pre-History of
Steam’ which might also be called just the early history of
actual use of steam to do useful work. Anyhow I was in England a
year ago and wrote of my experiences in an earlier letter. If
anyone missed it I will repeat my advise to plan on at least one
full day in the Museum of Science in South Kensington, London. They
have many originals of steam power and I don’t mean mock-ups or
reproductions either. I had never realized that Watt limited
pressures to 15 pounds maximum and depended on the separate
condenser to raise the effective or differential working pressure
to near 30 pounds until my visit there. It is easy to see why the
condenser which is rare, except in industrial work here, was so
useful in view of the fact that it doubled the working pressure.
Many of our antiques could really earn their way again if the
boilers could stand double the pressure to feed the cylinders.

In addition to this, Watt was reportedly very fearful of steam
at higher pressures probably through sad experiences or his own or
his co-workers and verily preached against raising pressures. This
set the stage for a hero we don’t hear so much about, named
Richard Trevithick. He was a Cornishman of courage or to Watt
foolishness, and did away with the huge condensers by raising
boiler pressure to a horrifying 55 pounds in both stationary and a
rail hauling engine he built. They are both very similar looking in
general and rather typical of design in that day. The boilers are
short cylinders with bolted on heads of lids so that they look a
lot like a stew pot laying on its side with the lid bolted on. To
stand the fearful pressure the wrought iron is over half an inch
thick making the weight more fearful than the pressure on the rail
engine. The cylinder vertical as it was feared horizontal ones
would wear excessively from the weight of the piston and is mounted
down into the boiler to keep it hot. That sounds like a good idea
if it could easily be done and English traction engines used steam
jacketed cylinders right to the end, but I wonder how they got
condensed water out of the bottom of that cylinder? The fire flue
was also interesting to me. It was ‘U’ shaped and mounted
in the bolted-on boiler head so that the fire door and bottom of
the stack (or chimney) were side by side. The door opening was
about sixteen inches in diameter and the chimney about eleven if I
recall correctly, making the flue tapered. Quite a job of
engineering for the early 1800’s. Anyway it was quite enough to
make Richard Trevithick the steam hero of Cornwall and a nice
statue of him adorns the corner in front of the library at
Cambourne and that Scotsman is not so much spoken of there.

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