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engine. The engine was kept cool by the breeze from an electric fan which was directed on the exhaust side. The engine was started by connecting an electric motor to the fan shaft by a belt. The electric motor was started, causing the engine to rotate. As soon as the engine started the belt was thrown off and the motor stopped.
The engine was connected to the fan. by several different sets of gears and the maximum horsepower found for the various speeds. It will be seen from the following data and the curve in Fig. 2 that the maximum horsepower was attained at a speed of about 2800 r.p.m. The horsepower increases with the speed up to that point and then gradually falls off.
WITH GASOLINE-CAM No. 1.
R.p.m., fan 2050
R.p.m., fan 2300
WITH GASOLINE-CAM No. 2.
R.p.m., fan 2420
WITH GASOLINE AND KEROSENE
CAM No. 1.
Motorcycle Engine Horsepower
11.9 10.9 8.1
WITH GASOLINE AND KEROSENE
CAM No. 2.
For curves showing the variation of the horsepower with the speed and the character of the fuel used, see Fig. 2. For the efficiencies under different conditions, see Fig. 3.
Tests of a Racing Engine.
An engine which was used for racing purposes was tested and gave remarkable results. It differed from a stock engine in having the pistons and connecting rods drilled to remove excess weight. It also had auxiliary exhaust ports drilled in the cylinder walls at the bottom of the piston travel and was equipped with a large cam. The fan was driven by this engine at a speed of 2820 r.p.m. with the valve at opening No. 10, which shows that it was developing 20.3 horsepower.
The engine was run for a short time at 2700 r.p.m., developing 16.5 horsepower. The weight of the gasoline was accurately determined and found to be .42 pounds per horsepower hour. This gives an efficiency of 30.8 percent. (In this and other tests quoted, no record is given of the lubricating oil used. Ed.)
The type of manifold used to convey the gas from the carbureter to the cylinders affects greatly the efficiency of the engine. Two types were tested; one in which the pipe from the carbureter connected to a tee, each side of which was joined to a cylinder, the other in which the pipe curved gradually from the carbureter to each cylinder. In the former (No. 1), the gas, in going to the cylinder, passed through two right angle bends. In the latter (No. 2), one right-angle bend was eliminated and the path of travel was thereby shortened 11⁄2 inches.
an instant before the piston reached the end of the expansion stroke, and remained open until the piston had completed the exhaust stroke and had passed center. The exhaust valve then closed just before the inlet valve opened. Two cams were tested, both of which operated the valves at the same relative time but one opened the valves wider than the other. The small cam No. 1, opened the inlet valves 3-32 inch and the exhaust valves 9-32 inch; the large cam No. 2, opened the inlet valves 3-16 inch and the exhaust valves 11-32 inch.
It will be seen by the following tables that with cam No. 2 much more power
R.p.m., cycle Horse- Horsepower
The engine was operated with several
different fuels for the purpose of finding
what horsepower it would develop and
how efficiently it would operate with each.
To find the efficiency of the engine it was
necessary to know the heat content of
each of the fuels in B.t.u. per pound,
fuels were made by mixing to the percents
shown, by weight. The tests were run in
the same manner as other efficiency tests
described herein, and the efficiency found
The first two were commercial products
These fuels, with the exception of the
mixture of gasoline and kerosene, gave
the same brake horsepower. The relation
between speed and horsepower for these
fuels is the same as that shown for gasoline
on curve 2, Fig. 2. With the mixture of
gasoline and kerosene the engine developed
much more power than with any other
fuel. This will be seen by referring to;the
The efficiency of the engine with these
different fuels is shown by the following
R.p.m., cycle Horse- Horsepower
under his arm. Vibration is almost entirely eliminated, due to the fact that the pistons are not reciprocating; there is a constant application of power in one direction, and as almost all parts of the engine revolve, the fly wheel is dispensed with, or in other words, the engine acts as its own fly wheel. The photograph of the engine making 2500 r.p.m. is convincing proof of its absence of vibration, for the motor is not bolted to the trestles on which it rests.
MR. WALTER MACOMBER, THE INVENTOR, HOLDING A 12-HP. MOTOR UNDER HIS ARM.
The engine is air cooled, of unusually simple construction and the wiring is reduced to a few inches instead of many feet as in a standard gas engine. These points make for simplicity of operation, low cost of upkeep and cheapness of construction.
The inventor built his first model about six years ago from odds and ends, but produced an an actual operating engine. At that time he was foreman on a pumping plant in the desert near Mohave, Cal., and had few facilities and little material to work with. A wagon tire and a brass cartridge were among the objects that he used in making parts of his miniature. engine, but it worked. Since then a plant has been operated in Los Angeles and the perfected engine has been developed.
One of the most important features of the Macomber engine is the entire absence of reciprocating parts. The ordinary engine has a stationary cylinder containing a piston which is forced rapidly from one end of the cylinder to the other by pressure of steam or exploding gas. This piston is attached to a crank by a connecting rod which converts the reciprocating motion into a rotary motion. It is a well known fact that a large amount of energy is consumed in the ordinary engine by the act of stopping and starting each piston, as it requires energy to start a weight and an equal amount of energy to stop it, and when done rapidly it results in vibration. To reciprocate a piston rapidly, say from one to four thousand times a minute, results in vibration very destructive to the bearings.
The pistons of the Macomber rotary do not reciprocate, but the marvelously simple method of connecting these parts of this engine, the cylinders, pistons and shaft all travel at the same speed, but in slightly different planes of rotation, so there is neither inertia nor momentum to
The results are far greater power for the amount of fuel consumed and much less wear and tear on the engine. This is not merely theory, but the results of exhaustive tests, for one of the fifty h.p. seven-cylinder Macomber engines has been run for more than 10,000 miles under very trying conditions, giving perfect satisfaction.
Gasoline contains fourteen times as much energy as dynamite