Scientific American Supplement, No. 484, April 11, 1885 | Page 6

1838.
Other difficulties were found in using these engines; the pistons
became exceedingly hot. In the case of the Lenoir larger engines, it
sometimes became red hot, and caused complete ruin of the cylinder by
scoring and cutting up. Hugon to prevent this injected some water.
In the all important question of economy, these engines were found
grievously wanting, Lenoir consuming 95 cubic feet per I.H.P. per hour;
Hugon consuming 85 cubic feet per I.H.P. per hour.
The surviving engines of this type are only used for very small powers,
from one to four man power, or 1/8 to 1/2 horse, the most widely
known of this kind being the "Bischoff," which is very largely used; its
consumption of gas is even greater than the Lenoir, being 110 cubic
feet per horse power per hour, as tested with a half-horse engine at a
late exhibition of gas apparatus at Stockport.
So large a consumption of gas prevented these engines coming into
extended use for engines of moderate power, and led inventors to work
to obtain better results. The force generated by the explosion of a
mixture of gas and air is very short lived, and if it is to be fully utilized
must be used quickly; a high pressure is produced, but it very quickly

disappears.
The quicker the piston moves after the maximum pressure is reached,
the less will be the loss of heat to the sides of the cylinder. The flame
which fills the cylinder and causes the increase of pressure rapidly loses
heat, and the pressure falls.
The idea of using a free piston was proposed as a remedy; it was
thought that a piston connected to a crank in the ordinary manner could
not move fast enough to utilize the pressure before it was lost. Many
inventors proposed to perform work upon a piston free from any direct
connection with the crank or shaft of the engine; the explosion after
attaining its maximum pressure expends its force in giving velocity to a
piston; the velocity so acquired carries it on against atmospheric
pressure until the energy is all absorbed, and a vacuum or deficit of
pressure exists in the cylinder instead of an excess of pressure. The
return stroke is accomplished by the atmospheric pressure, and the
work is now done upon the engine shaft on the return only. The method
of connecting on the return stroke while leaving the piston free on the
out stroke varies, but in many engines the principle was the same.
Barsante and Matteucci, year 1857, British patent No. 1,625, describe
the first engine of this kind, but Messrs. Otto and Langen were the first
to successfully overcome all difficulties and make a marketable engine
of it. Their patent was dated 1866, No. 434. To distinguish it from
Otto's later patents, it may be called the rack and clutch engine.
The economy obtained by this engine was a great advance upon the
Lenoir. According to a test by Prof. Tresca, at the Paris Exhibition of
1867, the gas consumed was 44 cubic feet per indicated horse power
per hour. According to tests I have made myself in Manchester with a
two horse power engine, Otto and Langen's free piston engine
consumes 40 cubic feet per I.H.P. per hour. This is less than one-half of
the gas used by the Hugon engine for one horse power.
The igniting arrangement is a very good modification of Barnett's
lighting cock, which I have explained already, but a slide valve is used
instead of a cock.
Other engines carried out the same principle in a different manner,
including Gilles' engine, but they were not commercially so successful
as the Otto and Langen. Mr. F.H. Wenham's engine was of this type,
and was working in England, Mr. Wenham informed me, in 1866, his

patent being taken out in 1864.
The great objection to this kind of engine is the irregularity and great
noise in working; this was so great as to prevent engines from being
made larger than three horse power. The engine, however, did good
work, and was largely used from 1866 until the end of 1876, when Mr.
Otto produced his famous engine, now known as "The Otto Silent Gas
Engine." In this engine great economy is attained without the
objectionable free piston by a method proposed first by Burnett, 1838,
and also by a Frenchman, Millein, in 1861; this method is compression
before ignition. Other inventors also described very clearly the
advantages to be expected from compression, but none were able to
make it commercially successful till Mr. Otto. To him belongs the great
credit of inventing a cycle of operations capable of realizing
compression in a simple manner.
Starting from the same point as inventors did to produce the free piston
engine--namely, that the