All About Engines
Forfatter: Edward Cressy
År: 1918
Forlag: Cassell and Company, LTD
Sted: London, New York, Toronto and Melbourne
Sider: 352
UDK: 621 1
With a coloured Frontispiece, and 182 halftone Illustrations and Diagrams.
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18 All About Engines
Having made a piece of apparatus like this, it is
no use playing with it. Make several copies of the
card d with varying amounts of lap, study the effect
of lead varying from nothing up to a quarter of the
width of the port, and measure roughly the magni-
tude of the angle of advance. Note also the cut-off
for varying lengths of lap, and find out why it is that
with a valve like this steam is never cut off earlier
than half stroke. There is more real knowledge to
be got out of this model in a couple of hours than in
weeks of reading, and if this advice is followed it
will not be necessary to eat humble pie by asking
somebody to set the valve of your engine for you.
It is as well to remember that the man you asked had
to learn it, or he would not be able to do it for you ,
and it is not wise to confess too early in life that other
fellows have more perseverance than you have.
Time enough for that later.
We propose now to leave this simple engine and
get on to something bigger. But before we proceed
to examine boilers that evaporate fifteen tons of
water every hour, and engines that yield a thousand
or ten thousand horse-power, it will be a good plan
to look backwards and see how the eaily pioneers
succeeded in the face of difficulty and disappoint-
ment in clearing the way for those who came after.
What is that you say ? You want to know what
horse-power is, and how to find the horse-power of
an engine? Well, here you are.
If a weight of i lb. is lifted a- height o i foot,
i ft.-lb. of work has been done, and that is a unit