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is hung on to the arm, subtracted from the length between the centre of the ball and the centre of suspension of the arm.

To find the weight of the centre-weight. Find the vertical height by the above rule, both for a centre-weighted governor and for a simple governor, both at the same speed, then multiply the weight of the two revolving balls by the vertical height thus found for the centre-weighted governor, and divide the product by the vertical height thus found for a simple governor, which will give twice the weight of the centre-weight plus the two revolving balls, then subtract the weight of the two balls from that result, and divide the remainder by two, which will give the weight of centre-weight required.

The diameter of the revolving balls for governors like Fig. 30 should be equal to about 4th of the vertical height from the plane of revolution to the centre of suspension of the arm.

200 to 300 revolutions per minute.

The speed of these governors is from

Example of the rules for Centre-weighted Governors.-A governor like Fig. 30 revolves at 260 revolutions per minute, the weight of the balls is 3 lbs. each, the weight of the centre-weight is 84 lbs., required the vertical 1875 height. Then ='71 x '71='504, vertical height,

260

and ·5 (6+168) = 87, and 87

6

145 inches, vertical

height. Taking these particulars to find the centre-weight,

=

then 145×6 87 and

87 5

= 174, 174-6=168, and

1682 84 lbs., the weight of centre-weight required. Centre-weighted governors are in some cases fitted with a spiral-spring on the spindle, to assist the weight, as shown in Fig. 32.

Fig. 32.-Governor, with

Centre-weight, assisted by a spiral-spring.

Shifting-Eccentric Governors.-This type of governor, shown in Fig. 33, regulates the supply of steam to the cylinder by controlling the cut-off valve. It is fixed on the crankshaft of an engine and the movement of the centrifugal weights shifts the eccentric a certain angular distance, and alters the point of cut-off of the steam by the valve. The gravity of one weight neutralizes the other, and the centripetal force is derived from spiral-springs. To steady the action of the eccentric, and prevent irregularity of its motion,

Fig. 33. Shifting Eccentric Governor.

a dash-pot is frequently attached to the arm which carries the centrifugalweight as shown in Fig. 34.

Ball's governor, shown in Fig. 35, has a spring, s, placed between the dash-pot and the moving part of the governor, for the purpose of obtaining

D

This governor

stability and efficient adjustment of the long spring, D. efficiently regulates the supply of steam to the varying conditions of the load.

Oil Cylinder

Fig. 34.-Shifting-Eccentric Governor, with Dash-Pot.

S

Fig. 35.-Ball's Shifting Eccentric-Governor.

PROPORTIONS OF HIGH-PRESSURE NON-CONDENSING STATIONARY STEAM - ENGINES.

The Proportions of Steam-Engines are generally determined by empirical rules dictated by experience, consequently there is great diversity of practice, and the proportions adopted by different engine-makers vary considerably. Illustrations of several of the most generally-used types of engines, and empirical rules for calculating their proportions in detail, are given in the following pages as representative examples of average good modern practice in the construction of stationary steam-engines.

A Horizontal Stationary Non-Condensing Simple Steam-Engine of well-known design and strong construction, with all working parts easy of access, and admitting of ready adjustment, is shown in Fig. 36. The bed is of box-pattern. The crank is shrunk and keyed on the shaft. It is formed on a cast-iron disc having a counter-weight to counter-balance the weight of the crank, crank-pin and connecting-rod-end. The crosshead slide-blocks are fitted with four slide-bars. The length of the stroke is equal to twice the diameter of the cylinder. The engine is fitted with a high speed governor and an equilibrium throttle valve. Engines of this type are usually made of the following sizes and weights.

Table 3.-SIZES OF HORIZONTAL NON-CONDENSING SIMPLE STEAM-Engines, AS SHOWN IN FIG. 36.

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[graphic]

Fig. 36.-Horizontal Stationary Non-Condensing Steam-Engine.

A Horizontal Stationary Non-Condensing Simple Steam-Engine of another type and lighter construction is shown in Fig. 37. The frame is girder-shaped. The crank-shaft-bearing, guides for slide-blocks, and front cylinder-cover are all cast in one piece with the frame. The crank is a polished and balanced disc, shrunk and keyed on the shaft. The length of stroke is generally equal to about 1 times the diameter of the cylinder. The engine is fitted with a high-speed governor and an equilibrium throttlevalve. This type of engine is usually made of the following sizes and weights. Table 4.-SIZES OF HORIZONTAL NON-CONDENSING SIMPLE STEAM-Engines, AS SHOWN IN FIG. 37.

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The Weight of Horizontal Non-condensing Simple Steam-Engines by different makers varies considerably. Taking the average of a number of each of the above types of engines by different makers, as a basis, the weight of engines of each of the above types may be estimated approximately by the following rules :

Weight of horizontal engines with fly-wheel complete, as shown in Fig. 36. (diameter of cylinder in inches)2

Weight in tons =

36

For the weight in cwts. use 18 as a divisor instead of 36.

For instance, the weight of a horizontal non-condensing simple steamengine, as shown in Fig. 36, with cylinder 12 inches diameter and 24 inches stroke, may be estimated at (12 × 12 inches) ÷36=4 tons.

Weight of horizontal engines with fly-wheel complete, as shown in Fig. 37. (diameter of cylinder in inches)2

Weight in tons =

46

For the weight in cwts. use 23 as a divisor instead of 46.

For instance, the weight of a horizontal non-condensing simple steamengine, as shown in Fig. 37, with cylinder 9 inches diameter and 14 inches stroke, may be estimated at (9 × 9 inches) 46 =1'96, or say 2 tons.

The General Proportions of Steam-Engines of the type shown in Fig. 36, together with useful practical data, are given in the following pages. The proportions also apply to other types of engines, and with slight modifications to all kinds of steam-engines. It is usual in practice to make the proportions of most of the details of engines proportional to the diameter of the cylinder. In designing an engine the first thing to be determined is the speed of the piston.

[graphic]

Fig. 37.-Horizontal Stationary Non-Condensing Steam-Engine.

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