BALANCING 429 
ank pin, 30 Ibs. Distance between centre lines of cylinders, 74 inches. 
Jistance between planes containing centres of gravity of balance weights, 
59 inches. Distance between planes containing centres of gravity of crank 
arms, 62 inches. Determine the balance weights to be placed in the driving 
sls at 3 feet radius. All the revolving parts and two-thirds of the recipro- 
rts are to be balanced. 
‘ e the data of Exercise 5 as applying to an inside cylinder engine with two 
sairs of wheels coupled, together with the following additional data, Radius of 
_ wheel cranks, 11 inches. Distance between planes of motion of coupling-rods, 
6 feet 3 inches. Distance between planes of rotation of wheel cranks, 5 feet 
2inches. Weight of each coupling-rod, 270 lbs. Weight of each wheel crank, 
ine iow the weight of the portion of the crank pin within it, reduced to 
pel 
Determin 
es radius, 120 lbs. Weight of each overhanging crank pin, 30 Ibs. 
a e the balance weights in the driving and trailing wheels, at 2 feet 
_ 6 inches radius, to balance all the revolving parts and two-thirds of the recipro- 
eating parts, one-third of the reciprocating masses being balanced in the 
* wheels, and one-third in the trailing wheels. 
___ 8. Determine, from the following data, the balance weights for an outside 
linder locomotive with two pairs of wheels coupled. Stroke of pistons, 26 
inches. Distance between centre lines of cylinders, 75 inches. Distance be- 
_ tween planes of motion of coupling-rods, 67 inches. Distance between planes of 
revolution of balance weights, 60 inches. Distance between planes of revolution 
_ of cranks, 60 inches. Weight of reciprocating parts per cylinder, 350 Ibs. 
_ Weight of one connecting-rod, 225 lbs, One-third of weight of connecting-rod 
_ to be considered as reciprocating with cross-head and two-thirds as revolving 
_ with crank pin. Weight of one coupling-rod, 230 lbs. Weight of one crank pin 
_ within coupling-rod, 15 lbs. Weight of one crank pin within connecting-rod, 
121lbs. Weight of one crank’ with part of crank pin within it, reduced to 13 
inches radius, 90 lbs. Centres of gravity of balance weights at 26 inches radius 
in driving wheels and 27} inches in trailing wheels. All the revolving and two- 
thirds of the reciprocating parts to be balanced, the balance for the reciprocating 
parts to be in the driving wheels only. 
9. Find the difference between the maximum and minimum pressures on the 
rail of a driving wheel of the engine in Exercise 7 when the speed is 60 miles per 
hour, the diameter of the wheel being 7 feet. 
10. Calculate the difference between the maximum and minimum pressures 
on the rail of a driving wheel of the engine in Exercise 8 when the speed is 
50 miles per hour, the diameter of the wheel being 6 feet 1 inch. 
11. The piston of a single cylinder direct-acting engine has a stroke of 
_ 2feet. The weight of the reciprocating parts is 300 lbs., and these parts are to 
be balanced by two bob-weights driven by cranks of 6 inches radius. The lines 
of stroke of bob-weights are 5 feet apart, and the line of stroke of the 
n is between the lines of stroke of the bob-weights and 2 feet from one of 
m. Determine the weights of the bob-weights. 
12. A, B, and C are the parallel lines of stroke of the pistons of a three- 
cylinder engine. B is between A and C, and is 25 inches from A and 80 inches 
from C. Each piston has a stroke of 24 inches. The reciprocating parts in the 
line A weigh 210 lbs. Find the weights of the reciprocating parts in the lines 
Band C, and show how the cranks must be placed so that the reciprocating parts 
_ of the engine may balance one another. 
13. The diagram (Fig. 699) shows the crank shaft of a three-cylinder triple 
expansion engine for a torpedo boat. ‘The cranks make equal angles with one 
ff sete oe 
, et - _ ie  -_ 
Fig. 699. 
another. The reci rocating parts connected to the crank pins A, B, and C 
weigh 150 lbs., 160 lbs., and 260 lbs. respectively, and they are to be balanced 
by bob-weights in the planes X and Y. ‘The one bob-weight in the plane X has 
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