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A. J. Amsler

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Dr. Alfred J. Amsler (c1858-1940) of Alfred J. Amsler and Co

1940 Obituary [1]

THE death occurred on April 2nd of Dr. Alfred J. Amsler, whose name was well known throughout the whole world in connection with the invention and development of numerous scientific and mathematical instruments, and of various machines for the testing of materials. Dr. Amsler died in his eighty-third year at his home in Schaffhausen, Switzerland.

His father, Professor Jakob Amsler, was the inventor of the well-known polar planimeter familiar to all engineers. Alfred entered his father's business in 1885, and at first devoted himself to the development of mechanical integrators and produced a number of elegant variations including instruments for measuring moments of areas up to those of the fourth order.

At the same time he manifested his high mechanical genius in other directions. One invention which he produced in his early career was an automatic machine for sorting cartridge cases as they came from the drawing presses, the sorting consisting of arranging them with the bottom ends upmost, ready for the fixing of the percussion caps or with the open ends upmost ready for filling with the charge. The construction of machines for this purpose involved many difficult problems, but they were solved by young Amsler so satisfactorily that some of the machines which he supplied fifty years ago are still in use to-day at the Swiss Federal Arsenals. Another machine which he produced at the opening of his career was a semi-automatic multiple dividing machine for the logarithmic division of slide rules.

Soon, however, Alfred Amsler began to manifest an interest in the field which was to become t he principal one of his work, the design and construction of machines for testing materials. His father had already entered that field, first with the development of certain power measuring instruments and dynamometers, and then, as a direct outcome, of a few material testing machines. In these machines Jakob Amsler departed from the established means of measuring the applied load, namely, by means of a beam scale, and adopted the hydrttulic principle. The friction between the measuring piston and its cylinder was a source of trouble and error, but following the method employed by the celebrated French physicist, Amagat, his contemporary and close friend, Jakob Amsler made use of a piston without packing, ground into its cylinder with very high precision.

One of Alfred Amsler's first tasks in this new field was to devise an instrument for indicating with accuracy the high pressures set up in the measuring cylinder. In conjunction with his father he developed the mercury load indicator whereby with the aid of frictionless differential rams the high oil pressure was transformed into a moderate mercury pressure, the magnitude of which could be measured by means of a mercury column or recorded on a diagram by means of a float mechanism.

For a number of years the hydraulic principle was employed in the Amsler testing machine merely for measuring the load while the load itself was applied in the customary way by means of a screw and gear wheel mechanism. Then Alfred Amsler developed the idea of using the hydraulic principle for both purposes. This development enabled the control of the load and its measurement to be centralised at a position remote from the machine itself. To give it effect a number of new problems had to be solved, one of the most important being the construction of an oil pump which would deliver oil at several hundred atmospheres pressure without serious pulsations. The final solution of this problem consisted of a pump with a low pressure plunger driven by a crankshaft and a high pressure plunger driven by a cam.

Simultaneously Alfred Amsler developed an oil-delivery regulator and the so-called 'pendulum dynamometer' which served as an alternative to the mercury load indicators. In the pendulum dynamometer he applied for the first time the principle of rotating the measuring piston for the purpose of overcoming its friction to linear movement.

In connection with the development of testing machines, Alfred Amsler produced his "standardising box" for checking the accuracy of the load indicators. This "box" consisted of a hollow steel cylinder filled with mercury and fitted with a plunger attached to a micrometer screw by means of which the quantity of mercury displaced from the interior of the cylinder when stress was applied could be measured. In some recent Amsler testing machines the elastic deformation of the columns of the machine itself is used as a means of measuring the applied load.

Impact, abrasion, and fatigue testing machines next claimed Alfred Amsler's attention, and in each be made notable advances. In particular there should be mentioned his "pulsator" fatigue tester in which the cyclical load variation is produced by a pulsating oil pressure. As a logical development of his work on testing machines he turned towards the improvement of dynamometers. His first essay in this direction was the rotation dynamometer for measuring the power transmitted in machine tools. Subsequently he developed his torsion dynamometer for measuring the power of turbines running at high speeds.

His greatest fame in this direction, however, is to be sought in the work which he did in developing the railway dynamometer car. Jakob Amsler had made a beginning in this direction in 1900 by constructing certain recording devices for use on railways. Alfred Amsler developed the subject and applied the hydraulic measuring principle to it. In its modern form the Amsler railway dynamometer car equipment includes devices for measuring the tractive and braking forces, the speed and the work done by the locomotive in its cylinders and at the coupling.

In addition to his work in the fields we have mentioned above, Alfred Amsler developed a number of other devices including hydraulic current meters, recording and integrating liquid gauges and equipment for automatically recording the condition of railway tracks.

He was undoubtedly the worthy son of an able father. Undoubtedly, too, the world has lost by his death an inventive brain of a rare and refined character.

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