ies in this line. Its distinctive
features include a connecting rod much shorter than usual, and a crank
shaft located the length of the crank from the central axis of the
cylinder. This has the effect of increasing the piston stroke, and also
of increasing the proportion of the crank circle during which effective
pressure is applied to the crank.

Making the connecting rod shorter and leaving the crank mechanism the
same would introduce excessive cylinder friction. This Ramsey overcomes
by the location of his crank shaft. The effect of the long piston stroke
thus secured, is to increase the expansion of the gases, which in turn
increases the power of the engine without increasing the amount of fuel
used.

Propeller Thrust Important.

There is one great principle in flying machine propulsion which must
not be overlooked. No matter how powerful the engine may be unless the
propeller thrust more than overcomes the wind pressure there can be no
progress forward. Should the force of this propeller thrust and that of
the wind pressure be equal the result is obvious. The machine is at a
stand-still so far as forward progress is concerned and is deprived of
the essential advancing movement.

Speed not only furnishes sustentation for the airship, but adds to the
stability of the machine. An aeroplane which may be jerky and uncertain
in its movements, so far as equilibrium is concerned, when moving at
a slow gait, will readily maintain an even keel when the speed is
increased.

Designs for Propeller Blades.

It is the object of all men who design propellers to obtain the maximum
of thrust with the minimum expenditure of engine energy. With this
purpose in view many peculiar forms of propeller blades have been
evolved. In theory it would seem that the best effects could be secured
with blades so shaped as to present a thin (or cutting) edge when they
come out of the wind, and then at the climax of displacement afford a
maximum of surface so as to displace as much air as possible. While
this is the form most generally favored there are others in successful
operation.

There is also wide difference in opinion as to the equipment of the
propeller shaft with two or more blades. Some aviators use two and some
four. All have more or less success. As a mathematical proposition it
would seem that four blades should give more propulsive force than two,
but here again comes in one of the puzzles of aviation, as this result
is not