The friction clutch is now used almost exclusively for engaging the
engine with the propelling gearing of the traction drivers, and it will
most likely give you more trouble than any one thing on your engine,
from the fact that to be satisfactory they require a nicety of
adjustment, that is very difficult to attain, a half turn of the
expansion bolt one way or the other may make your clutch work very
nicely, or very unsatisfactory, and you can only learn this by carefully
adjusting of friction shoes, until you learn just how much clearance
they will stand when lever is out, in order to hold sufficient when
lever is thrown in. If your clutch fails to hold, or sticks, it is not
the fault of the clutch, it is not adjusted properly. And you may have
it correct today and tomorrow it will need readjustment, caused by the
wear in the shoes; you will have to learn the clutch by patience and
experience.
But I want to say to you that the friction clutch is a source of abuse
to many a good engineer, because the engineer uses no judgment in its
use.
A certain writer on engineering makes use of the following, and gives me
credit: "Sometimes you may come to an obstacle in the road, over which
your engine refuses to go, you may perhaps get over it in this way,
throw the clutch-lever so as to disconnect the road wheels, let the
engine get up to full speed and then throw the clutch level back so as to
connect the road wheels." Now I don't thank any one for giving me credit
for saying any such thing. That kind of thing is the hight of abuse of
an engine.
I am aware that when the friction clutch first came into use, their
representatives made a great talk on that sort of thing to the green
buyer. But the good engineer knows better than to treat his engine that
way.
Never attempt to pull your loads over a steep hill without being certain
that your clutch is in good shape, and if you have any doubts about it
put in the tight gear pin. Most all engines have both the friction and
the tight gear pin. The pin is much the safer in a hilly country, and
if you have learned the secret of the throttle you can handle just as
big load with the pin as with the clutch, and will never tear your
gearing off or lose the stud bolts in boiler.
The following may assist you in determining or arriving at some idea of
the amount of power you are supplying with your engine:
For instance, a I inch belt of the standard grade with the proper
tention, neither too tight or too loose, running at a. maximum spead of
800 ft. a minute will transmit one horse power, running 1600 ft. 2 horse
power and 2400 ft. 3 horse power. A 2 inch belt, at the same speed,
twice the power.
Now if you know the circumference of your fly wheel, the number of
revolutions your engine is making and the width of belt, you can figure
very nearly the amount of power you can supply without slipping your
belt. For instance, we will say your fly wheel is 40 inches in diameter
or 10.5 feet nearly in circumference and your engine was running 225
revolutions a minute, your belt would be traveling 225 x 10.5 feet =
2362.5 feet or very nearly 2400 ft. and if I inch of belt would transmit
3 H. P. running this speed, a 6 inch belt would transmit 18 H.P., a 7
inch belt, 21 H.P., an 8 inch belt 24 H.P., and so on. With the above
as a basis for figuring you can satisfy yourself as to the power you are
furnishing. To get the best results a belt wants to sag slightly as it
hugs the pulley closer, and will last much longer.