The Application of Electric-Motors to Machine-Driving (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1905 Excerpt: ...reverse is obtained by belts; but these may almost be eliminated, as in fig. 41A, and the motor reversed by a switch operated by the table. In addition to reversing the motor the switch may be arranged to insert a resistance in the field winding, and so raise the speed for the return stroke. By this arrangement, which involves special switching arrangements, the motor may be geared directly to the machine shaft. An arrangement of this kind is in use, among other places, at Messrs Harland and Wolffs Shipbuilding Yard, Belfast, and Messrs Vickers, Sons and Maxim. In all cases where there are heavy masses to be accelerated, as in the case with planers, belts should be avoided, as their maintenance is excessive, and not only is the power lost due to slip, but the machine does not reach its maximum cutting speed for some seconds after reversal, thus losing time which totals up to several hours over a week's work. At the Ingersoll Sergeant Drill Co.'s Works, New Jersey, U.S.A., the motors are as in Fig. 41A; that is, they are mounted on the top of the columns, and drive direct down to the main shaft of the machine. The motors are all fitted with flywheels to supply the energy necessary to accelerate the table at the moment of reversal, and thus prevent any fluctuations of the current. Particulars of the power required to drive planing machines of various sizes are given in Table VIII. The last two machines used high-speed tool steel. Table VIII. TOWER REQUIRED TO DRIVE PLANING MACHINES--MATERIAL, WROUGHT-IRON Fig. 41A PLANING MACHINE WITH LAHMEYER MOTOR ON TOP OF FRAME An edge-planing machine is in some respects similar to a planing machine, but as the tool cuts, no matter in what direction it is moving, speed changes of the kind already mentioned are unnecessary...