1074

THEORY AND PRACTICE OF ENGINEERING.

Book 11.

clay, or gravel. The pile planks were from 9 to 12 inches in breadth, and 4 inches thick,and one frame held 16 pile planks, which were driven at one time: the frames wereplaced along, and embraced three of the main guide piles, and were composed of twoupright timbers of the same thickness as the pile planks, and were sharpened at the end :these uprights were fastened together by two horizontal timbers, one above, the other below,and separated from each other by the thickness of the uprights: when these frames werefixed, they served the purpose of guides to the pile planks: the grooves at their sideswere 2 or 3 inches wide, and as much in depth.

Fig 1641.

Perronet used a similar engine at thebridge of Orleans, and a ram for drivingthe piles, which weighed 1200 pounds, andanother for the pile planks, of only halfthat weight: the windlass for elevatingthe pile was conveniently placed in thecentre, and the pulling ropes were admir-ably arranged.

At the bridge of Neuilly a large drumwheel was made use of, round which arope was wound, worked by a horse, andthe weight of the rams employed variedfrom 1000 to 2000 pounds weight; withthese the piles were driven, until theydid net sink more than \ of an inchduring 16 strokes : this method was notfound convenient, although tackle andcontrivances of various kinds were intro-duced into the machine, to regulate itsaction, and to prevent any accident oc-curring from the breaking of the rope.

The dynamical effect of a horse powerapplied to such an engine employed inpile-driving, and worked by two horses,was found to be equal to a weight of 42,536lbs. raised 1 foot high in 35 seconds, or :

weight of 36,459 lbs raised 1 foot high per

minute per horse.

When the ram is raised by horse instead of human power, the drum or cylinder uponwhich the rope winds ought to be provided with a lever catch to lay hold of the arm bywhich it is fixed or engaged, while the weight is rising, and which can be easily manoeuvredwhen it is required to disengage, so that the rope may be allowed to run back, for re-engaging the weight without the slow process of turning the direction of the horse.

Perronet’s pile-engine placed upon a boat, worked by an armed wheel, has frequentlybeen found admirably adapted for its purpose; the end and side view of this machine at