zzle was
not reduced at all. However, you must reduce it sufficiently to give
draught, but don't impair the power by making the engine clean its own
flues. I think ninety per cent of the fires started by. traction
engines can be traced to the engineer having his engine choked at the
exhaust nozzle. This is dangerous for the reason that the excessive
draught created throws fire out at the stack. It cuts the power of the
engine by creating back pressure. We will illustrate this: Suppose you
close the exhaust entirely, and the engine would not turn itself. If
this is true, you can readily understand that partly closing it will
weaken it to a certain extent. So, remember that the nozzle has
something to do with the power of the engine, and you can see why the
fellow that makes his engine clean its own flues is not the brightest
engineer in the world.

While it is not my intention to encourage the foolish habit of pulling
engines, to see which is the best puller, should you get into this kind
of a test, you will show the other fellow a trick by dropping the
exhaust nozzle off entirely, and no one need know it. Your engine will
not appear to be making any effort, either, in making the pull. Many a
test has been won more through the shrewdness of the operator than the
superiority of the engine.

The knowing of this little trick may also help you out of a bad hole
some time when you want a little extra power. And this brings us to the
point to which I want you to pay special attention. The majority of
engineers, when they want a little extra power, give the safety valve a
twist.

Now, I have already told you to carry a good head of steam, anywhere
from 100 to 120 pounds of steam is good pressure and is plenty, and if
you have your valve set to blow off at 115, let it be there; and don't
screw it down every time you want more power, for if you do you will
soon have it up to I25, and should you want more steam at some other
time you will find yourself screwing it down again, and what was really
intended for a safety valve loses all its virtue as a safety, as far as
you and those around you are concerned. If you know you have a good
boiler you are safe in setting it at I25 pounds, provided you are
determined to not set it up to any higher pressure. But my advice to
you is that if your engine won't do the work required of it at 115
pounds, you had best do what you can with it until you can get a larger
one.

A safet