1076

THEORY ANI) PRACTICE OF ENGINEERING.

Book II,

Fig. 1645.

I>E cessart’s pile-engine.

De Cessart found that when dri-ving piles into the bed of the Loire he could not make them enter morethan 28 or 29 feet below the heightof low water, after having received8000 blows from a ram of from1200 to 1400 pounds weight. Heexperienced some difficulty in pre-venting the heads from splitting, asthe foundations were laid at 12 feetbelow the surface, and the piles cutoff at 14 feet 1 inch; he imaginedthat the longitudinal fracture wasnot prolonged to this depth, beingcompressed by the natural ground.

The plan of this machine is shownas placed to drive the pile A. Thecylinder is turned by the 10 feetwheel, which has roundles 18 inchesapart on the circumference; therope which coils round the cylin-der passes over a wheel at the topof the machine, 4 feet in diameter,and is then attached to the ram,which weighed from 1200 to 1400pounds; to release the ram when ithad arrived at its proper height, arope was attached to a hook, which,when pulled, released the ram.

Workmen, with the ordinary pile-engine, generally give 25 blows of the ram in a minute,each time raising three feet, consequently 75 feet per minute, after which they rest 2minutes, giving the same velocity to the wheel, with the same number of men ; thatunder consideration being 30 feet in circumference, it would make two turns and a half

trt .1

Fig. 1646.

PLAN OF DE CESSART’S PILE.