MECHANICS-. 
6g6 
properly hooped, to prevent it from fplitting. In rifing 
find falling, it Hides againft the face of the plank, and is 
guided by irons, which are fixed to the ram, and are bent 
round the edges of the plank in the manner of hooks. 
The plank, when placed, upright, is iecured by guy-ropes, 
in the manner of the niaft of a fliip ; the end of the great 
rope which fufpends the ram, has ten or twelve ftmall 
ropes fpliced into it, for as many men to take hold, and 
work it by ; they raife the ram up two or three feet by 
pulling the ropes all together, and, then letting them go, 
the ram falls upon the pile head. When the pile becomes 
firm enough to caufe the ram to rebound, they take care 
to pull the ropes inltantly after the blow, that they may 
■avail themfelves of the leap it makes. 
This is the fimpleft form of the machine. Others, in- 
ffead of a plank, have two upright beams attached toge¬ 
ther, at fucb a diitance afunder, as to leave an opening 
between them, for the reception of a piece of wood which 
•is affixed to the ram, and by this means it is guided. In- 
ftead of guy-ropes, tliefe are ufually fixed upon a bale, 
confifting of a triangular frame, upon one angle of which 
the uprights are eredted ; and, from the other two angles, 
braces arife, which are fo inclined as to reach the uprights 
at half or two-thirds of their height to Heady them. This 
plan is very convenient for driving piles in corners; but, 
for driving rows, it is more advantageous to have the up¬ 
rights fixed at the middle of one fide of the triangular 
bafe, and have flays from all the three angles. A machine 
of this kind, with a ram of beech four feet long and one 
foot fquare, may be worked by ten or twelve men, at the 
rate of twenty-four blows per minute, and fixes the pile 
very quickly. To eftimate the force of the rammer made 
nfe of to drive piles, its weight ought to be multiplied 
into the velocity it acquires in falling. Thus, if a ram¬ 
mer which weighs 500 lb. be let fall from four feet, it will 
fall that height in half a fecond, and have at the time of 
percuflion a velocity capable to carry it uniformly eight 
feet in half a fecond, without any farther help from gra¬ 
vity 5 fo that we mull multiply 500 by 16, or its weight 
by the number of feet it would fall in a fecond, and 
the product 8000 gives the momentum of the firoke. 
If a capftan, pulleys, or windlafs, be made to raife the 
rammer to a confiderable height, and then, by an eafy 
contrivance, loofen it at once from its hook, the momen¬ 
tum of the firoke will always be as the fquare-root of the 
height from which the rammer fell. 
For large works, fuch as bridges, Sec. the piles are 
driven by a different kind of machine: this has a very 
heavy iron rain, with mechanical powers, by which it is 
raifed to a confiderable height, and'then let fall, inftead 
of continually repeating finall blows. Bunce’s pile-en¬ 
gine, of which a fide and front view are given at fig- 62, 63, 
Plate XVI. confilts of'two endlefs ropes or chains A, 
connedted by crofs-pieces of iron B, B, which pafs round 
the wheel C, the crofs-pieces failing into correlponding 
crofs-grooves cut in the periphery of the wheel. When 
the man at S, therefore, drives the wheel m by means 
of the pinion p, he moves alfo the wheel C fixed on the 
axis of 772, and makes the double ropes revolve upon the 
wheels C, D. The wheel D is fixed at the end of a lever 
DHK, whole centre of motion is H, a fixed point in the 
beam FT. L, the iron-rant, is fliown feparately at fig. 64. 
it is connected with the crofs-pieces by the hook M. 
N is a cylindrical piece of wood fufpenried at the hook 
at O, which, by Aiding freely up the bar that connedls 
the hook to the ram, always brings the hook upright 
upon the chain when at the bottom of the machine, in 
the polition of G L, fig. 62. Now, when the ram is fixed 
to one of the crofs-pieces B by the hook M, the weight 
of the ram, acting by the rope, moves the lever D K 
round H, and brings the wheel D to G, fo that, by turn¬ 
ing the winch, the ram is raifed in the vertical line LRG; 
but, when it reaches R, the projefling piece R difengages 
the ram from the crofs-piece B, by linking the bar Q ; 
and, as the weight is removed from the extremity D of 
•the lever, the cotmterpoife I brings it back from G to its 
old pofition at F, and the ram falls without interfering 
with the chain. When the hook is defeending, it is pre¬ 
vented from catching the rope by means of the piece of 
wood N fufpended from the hook M at O; for, being 
fpecifically lighter than the iron weight L, and moving 
with lefs velocity, it does not come in contadl with L till 
the ram is flopped at the end of its path. When N, there¬ 
fore, falls upon L, it depreffes the extremity M of the 
hook, and thus brings the hook over one of the crofs- 
pieces B, by which the ram is again raifed. In this ma¬ 
chine the motion of the firft wheel is uninterrupted, fo 
that very little time is loft in the operation ; and with a 
flight alteration it may be made to work with horfes. 
The piles of the works at Weftminfter-bridge, whilft it 
was building, was driven by a horfe-machine invented by 
Mr. Valoue. A pair of uprights, R, R, fig. 65. thirty feet 
high, were eredted at one end of a frame, which fupported 
a vertical (haft A, turned round by horfes yoked at SS; 
and the framing was of courfe large enough to admit a 
circular walk of fufneient (ize for them to work in, when 
they drew the ends of arms or levers S, S, projedting 
from the vertical lhaft A. The whole was eredted upon 
a platform, which was built over a barge in the manner 
of a deck. The vertical (haft had a wheel or drum upon 
it, to wind up the rope of the follower, and it was in 
the conftruction of this part that the invention lay. A 
fedlion, therefore, of the upper part of the vertical lhaft 
and drum is given in fig. 66. and a plan in fig. 67. while 
the whole machine is reprefented complete at fig. 65. and 
the fame letters apply to the fame parts in each figure. 
A is the great upright lhaft, or axle, turned by the horfes 
attached to the levers SS. The cog-wheel, B, turns the 
pinion X, having a fly, O, at the top, to regulate the mo¬ 
tion, and to adl againft the horfes, and keep them from 
falling, when the heavy ram is difengaged to drive the 
pile down into the earth in the bottom of the river. The 
drum, C, is loofe upon the axle of the lhaft A, but is 
locked to the wheel B by the bolt Y. On this drum 
the great rope, H, H, H, is wound, one end of it being 
fixed to the drum, and the other to the follower, G, paffing 
over the pulleys I and K. When the follower G reaches 
the top of the frame, the upper legs of the tongs at H 
are clofed by prefting againft the adjacent beams; and 
their lower legs are opened, fo that they drop the ram Q, 
which falls and ltrikes the pile P. When G is at the top 
of the frame, its crooked handle preffes againft the cords 
a, a, which raife the end of the lever L round m as a 
centre, and, by depreffing the extremity N, and con- 
fequently the bar S S, unlock the drum C and the wheel 
B, fo that the follower G falls by its weight, and feizes 
the ram Q by the handle r. As loon as the follower 
drops, the weight L pulhes up the bolt Y into the drum 
C, and locks the wheel and the drum ; and the lame’ope¬ 
ration is afterwards repeated. But we mull give a more 
particular defeription of the parts which are lliown fepa¬ 
rately at figs. 66 and 67. 
D, fig. 66, is a fpiral, or fufee, fixed to the drum C, on 
which winds the imall rope T : it goes over a pulley, and 
has a fmall counterpoife hung to the end of it, which 
hinders the follower from accelerating as it goes down to 
take hold of the ram; for, as the follower tends to ac¬ 
quire velocity in its defeent, the iineT winds downwards 
upon the fulee on a larger and larger radius, by which 
means the counterpoife adts ftronger and Itronger againft 
it, and fo allows it to come down with only a moderate 
and uniform velocity. The bolt Y locks the drum to the 
great wheel, being pufhed upwards by the (mall lever 3, 
which paffes through a mortife on the (haft A, and turns 
upon a pin; the lower end of the .bolt is guided by paffing 
through a piece of wood, 6, fixed into the-great (baft, 
and the upper pafl'es through an arm ol the wheel; the 
lever, 3, has a weight, 4, which always tends to pulh up 
the bolt Y through the wheel into the drurn ; N L is the 
great lever, turning on the centre vi, and felting its end 
N, upon the forcing-bar 5, which goes down through a 
hollow in the lhaft A, and bears upon the little lever 3. 
The 
