The deLavaud Automatic Transmission

D. SENSAUD DELAVAUD

doi:10.4271/280038

1928-01-01

The deLavaud Automatic Transmission 280038

MENTIONING the various attempts that have been made to secure continuous progressive changes of gear in the automobile, the author states that nothing of this sort is of value unless it is automatic.

He has designed a transmission consisting of a wabble-plate which actuates six connecting-rods that operate as many roller clutches on the rear axle. Changes in speed result from varying the inclination of the wabble-plate, and this is controlled automatically through the combined effects of inertia and the reaction of resistance.

This transmission has been applied to a number of cars of different weights, some of which have seen much service. The action of the various elements of the transmission is analyzed with the aid of drawings, diagrams and formulas, and the proportions that have been found most successful are stated. This transmission is combined with a gearless differential and a planetary reverse-gear.

Some who took part in the discussion were handicapped by not understanding clearly the action of the transmission. This probably was due, in part at least, to an error in the translation as it appeared in the preprint of the paper, which made it appear that the effect of inertia was to straighten the disc in the transmission, rather than to make it assume a greater inclination. The error was corrected, and answers to remarks in the discussion have been given by M. deLavaud in a written communication, as he was not present at the meeting.

Criticism of the transmission was made on the grounds of increased complication and expense, increased unsprung weight, predicted short life for the one-way clutches, and rendering the engine unable to act as a brake. All these criticisms are answered by M. deLavaud, who believes that the cost would not be greater in quantity manufacture than that of the conventional construction, that the additional unsprung weight is unobjectionable, that the one-way clutches are so made that they have proved to be as durable as any other part of the car, and that using the engine as a brake is undesirable.

Approval of several features in the transmission is expressed by the discussers, who believe that simplification of the control system is desirable and that automatic control cannot come as a result of gradual evolution. Saving in fuel consumption, in wear and tear of the car mechanism, and in maintenance expense are seen to be probable results of the adoption of an automatic transmission that would reduce the average number of engine revolutions per mile of car travel.

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The deLavaud Automatic Transmission 280038

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