The minister of agriculture has recently established a special
laboratory for testing agricultural _materiel_. This establishment,
which is as yet but little known, is destined to render the greatest
services to manufacturers and cultivators.
In fact, agriculture now has recourse to physics and mechanics as well
as to chemistry. Now, although there were agricultural laboratories
whose mission it was to fix the choice of the cultivator upon such or
such a seed or fertilizer, there was no official establishment
designed to inform him as to the value of machines, the models of
which are often very numerous. _Chemical_ advice was to be had, but
_mechanical_ advice was wanting. It is such a want that has just been
supplied. Upon the report presented by Mr. Tisserand, director of
agriculture, a ministerial decree of the 24th of January, 1888,
ordered the establishment of an experimental station. Mr. Ringelmann,
professor of rural engineering at the school of Grignon, was put in
charge of the installation of it, and was appointed its director. He
immediately began to look around for a site, and on the 17th of
December, 1888, the Municipal Council of Paris, taking into
consideration the value of such an establishment to the city's
industries, decided that a plot of ground of an area of 3,309 square
meters, situated on Jenner Street, should be put at the disposal of
the minister of agriculture for fifteen years for the establishment
thereon of a trial station. This land, bordering on a very wide street
and easy of access, opposite the municipal buildings, offers, through
its area, its situation, and its neigborhood, indisputable advantages.
A fence 70 meters in extent surrounds the station. An iron gate opens
upon a paved path that ends at the station.
The year 1889 was devoted to the installation, and the station is now
in full operation. The tests that can be made here are many, and
concern all kinds of apparatus, even those connected with the electric
lighting that the agriculturist may employ to facilitate his
exploitation. However, the tests that are oftenest made are (1) of
rotary apparatus, such as mills, thrashing machines, etc.; (2) of
traction machines, such as wagons, carts, plows, etc.; and (3) of
lifting apparatus. It is possible, also, to make experiments on the
resistance of materials.
The experimental hall contains a 7 horse power gas motor, dynamometers
with automatic registering apparatus, counters, balances, etc. A small
machine shop contains a lathe, a forge, a drilling machine, etc. The
main shaft is 12 meters in length and is 7 centimeters in diameter. It
is supported at a distance of one meter from the floor by four pillow
blocks, and is formed of three sections united by movable coupling
boxes. Out of these 12 meters, 9 are in the hall and 3 extend beyond
the hall to an annex, 14 meters in length and 4 in width, in which
tests are made of machines whose operation creates dust. When the
machines to be tested require more than the power of seven horses that
the motor gives, the persons interested furnish a movable engine,
which, placed under the annex, actuates the driving shaft. Alongside
of the main building there is a ring for experimenting upon machines
actuated by a horse whim. There will soon be erected in the center of
the grounds an 18 meter tower for experiments on pumps. Platforms
spaced 5 meters apart, a crane at the top, and some gauging apparatus
will complete this hydraulic installation.
The equipment of the hall is very complete, and is fitted for all
kinds of experiments.
[Illustration: STATION FOR TESTING AGRICULTURAL MACHINES--DYNAMOMETER
FOR TESTING ROTARY MACHINES.]
The tests of rotary machines are made by means of a dynamometer (see
figure). Two fast pulleys and one loose pulley are interposed between
the machine to be tested and the motor. The pulley connected with the
motor carries along the one connected with the machine, through the
intermedium of spring plates, whose strength varies with the nature of
the apparatus to be tested. The greater or less elongation of these
plates gives the tangential stress exerted by the driving pulley to
carry along the pulley that actuates the machine to be tested. This
elongation is registered by means of a pencil connected with the
spring plates, and which draws a diagram upon a sheet of paper. At the
same time, a special totalizer gives the stress in kilogrammeters.
Besides, the pulley shaft actuates a revolution counter, and a clock
measures the time employed in the experiment. In order to obtain a
simultaneous starting and stopping point for all these apparatus, they
are connected electrically, and, through the maneuver of a commutator,
are all controlled at once. The electric current is furnished by two
series of bichromate batteries.
The tests of traction machines are effected by means of a
three-wheeled vehicle carrying a dynamometer. The front wheel is
capable of turning freely in the horizontal plane, and the dynamometer
is mounted upon a frame provided with a screw that permits of
regulating its position according to the slope of the ground. The
method of suspension of the dynamometer allows it to take
automatically the inclination of the line of traction without any
torsion of the plates. There are two models of this vehicle, one
designed to be drawn by a man, and the other by a horse.
The station is provided, in addition, with registering pressure
gauges, a large double dynamometric indicator, a counter of
electricity, balances of precision, etc.
An apparatus designed for measuring the rendering of presses is now in
course of construction.
Although the station has been in operation only from the 1st of
January, twenty-five machines have already been presented to be
tested.--_Extract from Le Genie Civil_.
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