The Pelterie Air-cooled Motor, known as the R.E.P.

Progress, Volume III, Issue 9, 1 July 1908, Page 309

The Pelterie Air-cooled Motor, known as the R.E.P.

This motor is regarded in Paris as the first in lightness, power, and ingenuity of construction. Its inventor, M. Esnault-Pelterie is one of the Paris aeronauts who has had considerable success of late. For his new aeroplane, he designed a motor which has some striking features, and finding it to be well adapted for this kind of work, he has now gone into the manufacture of such motors at his establishment near the city. What he desired was to secure solidity, a good distribution of the forces, and constant torque. For this latter purpose the explosions must come very near together, and the impulses be transmitted to a single crankshaft. Such an idea can bo realised by disposing the cylinders in stai fashion around a central crank case. It is of the greatest interest to suppress the flywheel, but to do this, the explosions must be exactly distributed. Moreover, in two revolutions, all the cylinders should be fired, but in the second revolution the same set ot cylinders must not be used as in the first. Thus it is necessary to have an uneven number of cylinders, which is the only means of satisfying the above conditions In practice, all the cylinders should be above the horizontal plane passing through the axis of the motor, so that the oil will not run into the lower cylinders. To do this the second set of cylinders must be in a second vertical plane parallel to that of the first set, which secures the fcrm of motor illustrated herewith. According to the description which M. Esnault-Pelterie kindly furnished to the public, the crankshatt has two cranks placed at the 180 degrees apart. The arrangement of the cylinders in fan shape allows of shortening up the length of the crank case, and thus the crank is much shorter and much stronger. The crank has been designed according to the best formula?, and weighs but 5i pounds for 30 horse-power. Nowhere does it bear a strain of more than 15 kilos per square millimeter (21,334 lbs. per square inch) when running. The bearings are of very liberal dimensions, especially the propeller bearing. An interesting feature of the 7cylinder motor is the arrangement of three connecting rods on one crank, and four on the other. As can be seen from the crosssectional drawing, one connecting rod is integral with the crank-pin box, which has suitable sockets for the pivot pins of the other connecting rods.