An engineer wants a sufficient amount of "sand," but he don't want it in
the road. However, you will find it there and it is the meanest road
you will have to travel. A bad sand road requires considerable sleight
of hand on the part of the engineer if he wishes to pull much of a load
through it. You will find it to your advantage to keep your engine as
straight as possible, as you are not so liable to start one wheel to
slipping any sooner than the other. Never attempt to "wiggle" through a
sand bar, and don't try to hurry through; be satisfied with going slow,
just so you are going. An engine will stand a certain speed through
sand, and the moment you attempt to increase that speed, you break its
footing, and then you are gone. In a case of this kind, a few bundles
of hay is about the best thing you can use under your drivers in order
to get started again. But don't loose your temper; it won't help the
sand any.
Now no doubt the reader wonders why I have said nothing about compound
engines. Well in the first place, it is not necessary to assist you in
your work, and if you can handle the single cylinder engine, you can
handle the compound.
The question as to the advantage of a compound engine is, or would be an
interesting one if we cared to discuss it.
The compound traction engine has come into use within the past few
years, and I am inclined to think more for sort of a novelty or talking
point rather than to produce a better engine. There is no question but
that there is a great advantage in the compound engine, for stationary
and marine engines.
In a compound engine the steam first enters the small or high pressure
cylinder and is then exhausted into the large or low pressure cylinder,
where the expansive force is all obtained.
Two cylinders are used because we can get better results from high
pressure in the use of two cylinders of different areas than by using
but one cylinder, or simple engine.
That there is a gain in a high pressure, can be shown very easily:
For instance, 100 pounds of coal will raise a certain amount of water
from 60 degrees, to 5 pounds steam pressure, and 102.9 pounds would
raise the same water to 80 pounds, and 104.4 would raise it to 160
pounds, and this 160 pounds would produce a large increase of power over
the 80 pounds at a very slight increase of fuel. The compound engine
will furnish the same number of horse power, with less fuel than the
simple engine, but only when they are run at the full load all the time.
If, however, the load fluctuates and should the load be light for any
considerable part of the day, they will waste the fuel instead of saving
it over the simple engine.
No engine can be subjected to more variation of loads than the traction
engine, and as the above are facts the reader can draw his own
conclusions.