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The laboratory

A SMALL MECHANICS LABORATORY IN THE MID 1800'S

Due to their activities in mechanics through teaching, planning and constructions, the Piarist priests of the Ximenian Observatory used small laboratories and workshops run by local craftsmen. Only in some cases did they go to bigger workshops, as when they constructed the Barsanti and Matteucci engine. The craftsmen to whom f. Antonelli and f. Cecchi often referred to were Corrado Wolf, Galgano Gori and Giustino Paggi, who had local workshops (Giustino Paggi had his workshop on Via Martelli, next to the Scuole Pie).
For other things, inside the Scuole Pie and the Ximenian Observatory one could imagine the machinery and instruments used for the measurements of simple experiments: some of the machines were a lathe, a small press, a jack, and some gears and some of the measuring instruments were a Prony brake, a spring dynamometer, a Bourdon manometer, and a tribometer. These were the most common devices used.

Barsanti and Matteucci tested their engines in the Ximenian Observatory, advised and directed in part by f. Antonelli and Cecchi. One of the principle objectives of the test was to estimate the intensity of the impulse produced by the detonation of the gaseous mixture and the measurements of the upward thrust of the piston after the explosion. Even at this point, f. Cecchi's help was fundamental.
One must not forget that f. Cecchi, besides being an expert in mechanics, had much knowledge of chemistry, and had written a widely used text book on the subject.

The small amount of hydrogen necessary for the mixture and air were prepared in lead recipients in which sulfuric acid reacted with pieces of zinc in an acqueous solution. The most interesting test were the ones in mechanics. The Ximenian Manuscript hints at a test for parasite resistances and a measurement of the engine's power, both surely done with flywheels of different dimensions and mass, the Prony brake, and the dymanometer. For the experimental valuation of the piston's thrust in the cylinder and the measurement of the vertical movement distance, Barsanti and Matteucci used a Morin recording cylinder, constructed on purpose for them by F. Antonelli and Cecchi. The "same" Morin cylinder is still kept in the Ximenian Observatory among the antique instruments on display there.

Arthur Morin (Paris 1775-1880), director of the Conservatoire des Arts et Metièrs presented his machine or "continual indication apparatus" realized in 1836, on January 7, 1850 at the Acadèmie des Sciences in France, improving a previous idea of Poncelet. A meticulous description of it can be found in his book Lecons de mecanique pratique. Notions fondamentals de mecanique (pages 86-93, II edition, Hachette, Paris 1855). The Morin recording cylinder or barrel marks an important point in the history of science, because it represents the first recording instrument that was quite exact in its measurements. In some cases it could distinguish up to one thousandth of a second, therefore measuring speeds very accurately.

The device is formed by a wooden cylinder that can be held by two points placed on the vertical axis of the cylinder's two extremities. The friction which would oppose the rotation around the vertical axis are this way reduced to minimal terms. Rotation is produced by a cord which unwinds in the sheave of two small pulleys fixed to the rotation axis. The cord passes through the two pulley's sheaves and onto each extremity two bodies of different mass were attached, therefore these masses were able to move vertically. The falling mechanism of the larger mass was similar to the Atwood device, except for the fact that now the falling energy was partially transformed into the rotation energy of the cylinder. By using different masses, one could obtain different values from the rotation velocity. The different masses of the two bodies could have produced an accelerated motion. Instead, the passive resistances, even those artificially introduced using a small finned flywheel, equilibrated the driving force so the rotations occurred at a constant angular velocity.
A writing head, rigidly connected to a body in transitory vertical movement, writes on a piece of paper wrapped around the cylinder and therefore leaves a mark of the curve produced by the union of motions: the cylinder rotation and the translatory motion of the body. The Prony brake (with the weight forces known), permitted the measurement of the resisting forces or friction, which would have been able to zero the work done by the active forces of a machine. The Piarist priests of the Ximenian Observatory had a long tradition of research, especially for the measurement of friction, which had begun with Leonardo Ximenes, a contemporary of Augustin de Coulomb. Device used in the mid 1800's for the production of hydrogen.

SOME OBJECTS OF THE LABORATORY

Volta pistol used by f. Barsanti during his experiments at St. Micheal's College of Volterra. Father Barsanti built the device by using a copper sheet to make the cylinder and the top cover which had a copper tube closed by a piece of cork, which was used as a safety valve; the other base was made of an elastic membrane. The cylinder would be filled with a mixture of air and hydrogen that was ignited by an electric spark, which was produced by small brass rods isolated from the cylinder and terminating in two brass spheres. During the explosion, Barsanti showed his students how the membrane would move.

The device Barsanti built is still kept at the City Hall of Volterra. Induction bobbin built in Paris in 1852 by the famous constructor, (Physics Laboratory at Macchiavelli High School of Lucca) The Scuole Pie of Florence still keep some Ruhmkorff bobbins of the same period in their Physics Laboratory. Maybe they were also used by Barsanti and Matteucci during their experiments at the Ximenian Observatory.

Device for making hydrogen. Barsanti and Matteucci's first experiments with hydrogen and atmospheric air and subsequently with hydrogen and oxygen. The instrument, which is actually kept in the Physics Laboratory at Macchiavelli High School of Lucca, was once part of the private Physics Laboratory of Carlo Ludovico of Bourbon, duke of Lucca. Another device for making hydrogen. (Physics Laboratory at Macchiavelli High School of Lucca) The instrument was used in Laboratory to produce the hydrogen that was needed to charge eudiometers. Even this device once belonged to the private Physics Laboratory of Carlo Ludovico of Bourbon, duke of Lucca. Morin recording cylinder used by Barsanti and Matteucci during their first experiments at the Ximenian Observatory in Florence.

In order to determine the upward thrust of the free piston in the cylinder and to measure the duration of its vertical movement, Barsanti and Matteucci used a Morin recording cylinder, built for them by f. Antonelli and Cecchi. The same Morin cylinder is still kept in the Ximenian Observatory among the antique instruments on display there. Prony Brake. The Prony brake (with the weight forces known), permitted the measurement of the resisting forces or friction, which would have been able to zero the work done by the active forces of a machine.

Ximenian Manuscript. An important document, still kept in the archives of the Ximenian Observatory, and probabily written near the end of 1863 or the beginning of 1864, starts with a well known phrase: " Father Barsanti of the Scuole Pie, while repeating to his physics students at the college of Volterra the experiment of the famous Volta pistol, realized in 1843 the idea of using as a work force, the expansion of a gaseous mixture of atmospheric air and hydrogen detonated by and electric spark". The Ximenian Manuscript goes through all the salient phases of the experiments done by Barsanti and Matteucci n the Observatory on the internal combustion engine.

Fondazione Barsanti & Matteucci
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