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ARTICLE XIII.

OF PROPORTIONING THE CYLINDER TO

THE BOILER IN THE CONSTRUCTION OF STEAM ENGINES.

THE limits of this work will not admit of full directions for constructing steam engines: but the engineer must be guided by very different principles in his arrangement of a steam engine, to be wrought on the new principles already laid down, from those which should guide him, in arranging one to be wrought by atmospheric steam, where, the larger the cylinder, provided the boiler be sufficient to fill it with steam at every stroke, the more powerful the engine, while the reverse is the fact in this case, viz. The less the cylinder through which all the steam the boiler will make, is made to pass, the more powerful the engine, and the greater the effects it will produce, provided the boiler be strong enough to contain the power of the steam. Doubling the diameter of the cylinder doubles the friction, and quadruples the resistance of the atmosphere; it also quadruples the vacuum formed behind the piston, requiring to be filled with latent heat at every stroke, (see article 12.)

To show this more clearly by an example: Suppose we had an engine, on the new principle, arranged so that the boiler would supply the cylinder of 30 inches area, with steam of power 120 pounds to the inch. Then 30 multiplied by 120 is equal to 3600 pounds, the load; but suppose the friction of the piston to b( 150 pounds, added to 450 pounds, the resistance of the atmosphere, makes 600 pounds which taken from

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3600 pounds leaves 3000 pounds, the nett load the engine will carry.

Then suppose we enlarge the cylinder to double the diameter, which doubles the friction to 300 pounds, and quadruples the resistance of the atmosphere to 1800 pounds, making 2100 pounds, total resistance. The area of the cylinder, 120 inches, multiplied by 1/4 the power, reduced now to 30 pounds to the inch by the Boylean law (see articles 4 and 6) is equal to 3600 pounds, the load; from which take the increased resistance, 2100 pounds, leaves 1500 pounds for the nett load of the enlarged cylinder; just half the load of the small one. But this is supposing the Boylean law to hold true with regard to steam, and that it is a permanent elastic fluid, which it is not. When we consider that the vacuum formed behind the piston (see article 12) was quadrupled also by doubling the diameter of the cylinder, and would probably absorb all the heat in a latent state, we may safely infer, that the cylinder enlarged, would not overcome the resistance of the atmosphere and friction, and would therefore carry no load at all, provided the piston moves with equal velocity in each case.

The power of a man is equal to raising 30 pounds 2 1/2 miles per hour, 8 or 10 hours in 24; and the power of a horse is equal to 5 men, or equal to raising 150 pounds 2,1 miles or 13200 feet per hour. This has been ascertained by many experiments, and long established as data on which to found our calculations. Then, to ascertain the diameter of a cylinder and length of stroke, to produce a given power; 13200 feet per hour, divided by 60 is equal to 220 feet per

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minute, the velocity of the piston. Suppose we take 36 for the number of strokes the engine is to strike per minute; then 220 feet divided by 36 quotes 6.1 feet for the length of the double stroke, say 6 feet; that is 3 feet length of stroke, 36 down and 36 up strokes per minute to make the piston pass about 2 1/2 miles per hour.

Suppose again the piston to carry an average load equal to 50 pounds to the inch instead of 80 pounds, to make allowances, (see article 6), then every 3 inches area of the piston is equal to a horse's power.

The side of a square being 1, the diameter of a circle of equal area is 1 128/1000: therefore to find the diameter of the cylinder for any number of horse's power take the following

RULE.

Multiply the number of horses by 3, extract the square root and multiply by 1 128/1000: the product will be the diameter of the cylinder, 3 feet length of stroke, 36 strokes per minute.

The diameter of a circle being 1, the side of a square of equal area will be 7854/10000 therefore to find the area of any cylinder, multiply the square of the diameter by .7854 of a decimal and the product is the area.

To produce the power of a horse, a piston 3 inches area must move 220 feet, or 2640 inches per minute, with a load of 150 pounds; and 2640 multiplied by 3 is equal to 7920 cubic inches of space the piston forms into a perfect vacuum behind it per minute to be filled by the heat, (see article 12.) Therefore to find the power of any engine, multiply the area of the piston by the length of stroke in inches and by the number of

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strokes per minute, and the product is the space it passes through, or the vacuum it forms behind it; which divided by 7920 quotes the number of horses' power, when the piston carries an average load of 50 pounds to the inch area.

To find the number of strokes an engine must strike per minute to produce any number of horses' power, multiply the number of horses' power by 7920, and divide by the cubic inches of space the piston passes through at one stroke, the quotient is the number of strokes the engine must strike per minute, carrying 50 pounds to the inch area.

A horse can work only 8 hours steadily in 24, therefore 3 relays are necessary, and an engine of 10 horses' power will do the work of 3 times 10, equal to 30 horses.

Bolton and Watt's best steam engines, on what I call the old principle, require 1 bushel of the best NewCastle coals, from Walker's pits, (England) to do the work of a horse per day. It has been shown (article 6) that my new principle will produce at least 3 times the effect from equal fuel; one bushel of coals to do the work of 3 horses; and can be built at half the price

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COMPARATIVE STATEMENT

Of the cost of building and expense of working two steam engines, 10 years, the one on the old and the other on the new principle.

	Dolls	Dolls
Suppose an engine on the old principle to cost		10,000
Interest at 6 per cent. 10 years		6,000
Will consume about 60 bushels of coals at 33 1/3 cents, per day, 300 days per year, 10 years		60,000
		76,000
An engine of equal power, on the new principle will cost	5,000
Interest 10 years	3,000
Coals for 10 years will be about one-third the consumption	20,000
		28,000
		48,000

This difference is worthy the attention of those who wish to use steam engines.

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A TABLE

Of the areas of cylinders of steam engines to produce different powers with 3 feet length of stroke, 36 strokes per minute, carring an average load of 50 lbs. to the inch area.

Number of Horses' power, or bushels of wheat the power will grind per hour	Area in inches	Diameter in inches and decimal parts	Number of horses that the engine will do the work of per day of 24 hours
1	3	1.92	3
2	6	2.76	6
4	12	3.9	12
6	18	4.79	18
8	24	5.53	24
10	30	6.18	30
12	36	6.77	36
14	42	7.3	42
16	48	7.81	48
18	54	8.28	54
20	60	8.74	60
22	66	9.16	66
24	72	9.57	72
26	78	9.96	78
28	84	10.3	84
30	90	10.7	90
35	105	11.94	105
40	120	12.36	120
50	150	13.82	150
60	180	14.47	180
70	210	16.31	210
80	240	17.48	240
90	270	18.54	270
100	300	19.54	300

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