MECH 
that ratio of the effort of the firft mover to the refiftance, 
which wil! produce the maximum of effert. 4. From this 
property it refults, that advantage may be taken of the 
weakeft breezes of wind, and to obtain a certain product 
in circumftances under which all other windmills are in 
a date of abfolute inartivity. This advantage is of great 
importance, particularly with regard to agriculture : the 
windmills employed for watering lands are fometimes in- 
artive for feveral days, and this inconvenience is more 
particularly felt in times of drought. A machine capable 
of moving with the flighted breeze muft, therefore, offer 
the mod valuable advantages. 
Smeaton^s Machine for Experiments on Windmill 
Sails. 
In the experiments with this machine, the fails were 
carried round in the circumference of a circle, fo that the 
fame effect was produced as if the wind had druck the fails 
at red with the velocity which was then given them. In 
the pyramidal frame ABC, fig. 48. is fixed to the axis DE, 
which carries the arm F G with the fails G I. By pulling 
the rope Z, which coils round the barrel H, a motion of 
rotation is given to the fails, fo that they revolve in the cir¬ 
cumference of a circle, whofe radius is D I. At L is fixed 
a cord which pafies round the pulleys M, N, O, and coils 
round a fmall cylinder on the axis of the (ails, and raifes the 
fcale P, in which did'erent weights are placed for trying 
the power of the fails, and which, being in the direction of 
the axis DE, is not afferted by the circular motion of the 
arm DG. The fcale P is kept deady by the pillars Q, R, 
and prevented from fwinging by the chains S, T, which 
hang loofely round the pillars. V X is a pendulum com- 
pofed of two leaden balls moveable upon a wooden rod, fo 
that they can be adjuded to vibrate in any given time. 
The pendulum hangs upon a cylindrical wire Y, on which 
it vibrates as on a rolling axis. 
Machine for trying the Strength of Materials. 
The piece of wood, whofe drength is to be tried, is re- 
prefented by EF, fig. 49. and the force is applied to it by 
means of the winch A, which winds up the rope B C, 
paffing over the pulley n, and below the pulley m, and at¬ 
tached to the point D of the beam E F. The pulleys 
Aide on two parallel bars fixed in a frame, held down by a 
projecting point, at G, of the lever G H, which is gra¬ 
duated like a dedyard, and meafures the force employed. 
The beam E F is held by a double vice IK with four 
fcrews, two of which are invifible. When a wire is to be 
torn, it is fixed to the crofs bar L M ; and, when any body 
is to be cruihed, it mud be placed beneath the lever N O, 
the rope BC being fixed to the hook N, and the end O 
being held down by the click which arts on the double 
ratchet OP. The lever is double from O to Q, and arts 
on the body by a loop fixed to it by a pin. Young's Nat. 
Phil. vol. i. p. 768. 
Cranes. Plate XIV, 
Of thefe ufeful machines 1 'we have defcribed feveral 
kinds, particularly that of Mr. White, of Chevening, un¬ 
der the article Crane, vol. v. p. 322. Mr. Fergufon’s 
ingenious contrivances may be fieen in his Selert Exercifes ; 
but, as the book is in the hands of almod every prartical 
mechanic, we would rather refer tc- it than extract accounts 
of thefe inventions. 
Fig. 50. reprefentsa portable crane, mounted in a wooden 
frame and ftage, which is judged to be very ufeful for load¬ 
ing and unloading carts with large heavy (tones,. It is 
moveable to any part of a (tone-yard or ground ; the frame' 
is (ufficiently wide fora cart to draw under the crane,and 
at any time it may betaken to pieces. TheVrame AAA A 
is' made of wood, is about nine or ten feet high, and about 
nine feet fquare. The w heels B X are of iren, and are 
about three feet in diameter; and the pinion D, that is 
fixed to the axis of the firft wheel B, eight inches in dia¬ 
meter; on the axis of the fecoftd wheel X the axis round 
Vol. XIV. No. 1003. 
A NIC S. _ €93 
which the rope coils is fixed. Now the (lone being corded 
and hooked at the end of the rope that coils round the bar¬ 
rel, the workman turns a winch on the axis of wheel C, 
and raifes or lowers the weight according to the direction 
in which he turns it. The advantage in point of power 
is in proportion as the'produrt of the radii of the wheels 
to thofe of the pinions. 
Fig. 51. is a reprefentation of a crane-carriage which 
Mr. Gottlieb conceives to be very ufeful in moving large 
Hones in quarries, where carts and horfes cannot be con¬ 
veniently or at all managed. Its principle is evidently 
clear from a bare view of the figure. It confifts only of 
two fets of crane-wheels applied to the twoietsof wheels 
belonging to the carriage ; fo that two men, one at each 
winch, A, A, turning the pinions and wheels round, (hall 
adt upon the carriage-wheels and move it along. By their 
both turning forwards or backwards, the carriage goes ac¬ 
cordingly; but, if they turn contrary ways, the carriage 
will be turned round, or partly fo, as may be wanted. 
The pinion B is fix inches in diameter, which turns the 
wheel C of three feet diameter, on the axis of which is 
fixed the pinion D of one foot diameter, which works into 
two wheels E, E, of three feet fix inches diameter, that 
are fixed upon the carriage-wheels, and give motion to 
the whole machine. 
Fig. 52. is a jib for a crane. The nature of this inven¬ 
tion, for which we are indebted to the ingenious Mr. 
Bramah, may be eafily underflood from a bare infpertiotx 
of the figure, which reprefents a jib attached to the wall 
of a warehoufe. The jib turns on a perforated axis or 
pillar. The rope by which the weight is railed, after pafs- 
ingover two pulleys, goes through the perforated axis, and 
is conducted over another pulley to the barrel of the crane, 
which is not reprefented in the figure. In jibs of the 
common conftrurtion which turn in two folid gudgeons, 
the rope pafies over the upper gudgeon, and is confined 
between two vertical rollers ; but the bending of the rope 
occafions a great deal of frirtion, and produces a conflant 
effort to bring the arm of the jib into a pofition parallel 
to the inner part of the rope. 
A very good kind of crane, which requires no framing 
over ir, is reprefented in the Frontifpiece to this volume. 
It turns round upon a ltrong vertical beam, moving be¬ 
tween rollers fixed in the floor of the wharf, and going 
down below that twelve or fourteen feet, where it works 
on a pivot. The beams of the jib are mortified into the 
beam ; the wheels are mounted in a frame formed by two 
call-iron erodes bolted to the beam, one on each fide; the 
barrel is one foot diameter ; the great wheel has one hun¬ 
dred teeth, and is four feet diameter; the fiecond wheel 
has thirty-one teeth ; and the lali pinion feven leaves. The 
winches can be applied to any of the wheels for different 
powers, when it is ufed oh the barrel, or fecond wheel ; the 
others are put out of gear by Aiding their (pindles end¬ 
ways. The barrel and pulleys (houlcf always be grooved, 
though this is not fu(Hciently attended to by mechanics. 
The tongs by which logs of timber are taken up with this 
crane are worthy of attention, as the greater weight they 
bear the better they hold. 
Fig. 53. is a portable cellar-crane, a machine very ufe¬ 
ful to wine-merchants, brewers, &c. in drawing up and 
letting down ca(ks full of wine, beer, &c. It Caves the 
troub'e and inconvenience of horfes ; and in many places 
can be ufed where horfes could not. A, A, are two wooden 
props, about fix feet in height, and jointed together like a 
ruler at B. They are connsrted to each other by an iron 
round bar C, and wooden bar at the bottom D. The 
iron prongs EE faften the uprights fteauily to the edge 
of the cellar; F is the axis round which two ropes are 
coiled, the ends of which are faflened to the two clamps, 
G, G. On the axis F. is fixed the iron wheel H, of three 
feet in diameter : in the teeth of this works the pinion I, 
of about fix or feven inches in diameter, and is turned by 
the handle at K. It is evident, from a.bare infpection of 
the figure, that, when the two ropes are dipt over the cans, 
8 O upoa 
