Page images
PDF
EPUB

Friction of the parts of Engines.-The amount of pressure upon the piston, expended in overcoming friction, appears, on an average, to be not more than 1 lb. to the square inch, in well-constructed engines. The difference in loss of power from this cause, between beam and direct action engines, is found by experiment to be inconsiderable.

Mr. Tredgold's Estimate of the Distribution and Expenditure of the Steam in an Engine.

IN A NON-CONDENSING ENGINE.

Let the pressure on the boiler be

Force required to produce motion of the steam

in the cylinder will be..........

Loss by cooling in the cylinder and pipes........
Loss by friction of piston and waste........
Force required to expel the steam into the at-

10.000

0.069

0·160

2.000

mosphere.......

0.069

Force expended in opening the valves, and

friction of the various parts.

0.622

Loss by the steam being cut off before the end

[blocks in formation]

Let the pressure on the boiler be..........
Force required to produce motion of the steam

in the cylinder ............

Loss by cooling in the cylinder and pipes........
Loss by friction of the piston and waste...

10.000

0.070

0.160

1.250

[blocks in formation]

Loss by the steam being cut off before the end

of the stroke........

1.000

Power required to work the air-pump............ 0·500

[blocks in formation]

Steam-power required to drive various kinds of Machinery.

A series of experiments instituted by Mr. Davison, at Messrs. Truman and Co.'s Brewery, gave the following results:

1st. That an engine which indicated 50 horses' power when fully loaded, showed, after the load and the whole of the machinery were thrown off, 5 horses', or one-tenth of the whole power.

2d. 190 feet of horizontal, and 180 feet of upright shafting, with 34 bearings, whose superficial area was 3300 square inches, together with 11 pair of spur and bevel wheels, varying from 2 feet to 9 feet in diameter, required a power equal to 7·65 horses.

3d. A set of three-throw pumps, 6 inches in diameter, pumping 120 barrels per hour, to a height of 165 feet, 4.7 horses.

4th. A similar set of three-throw pumps, 6 inches

in diameter, pumping 160 barrels per hour, to a height of 140 feet, 6-2 horses.

5th. A set of three-throw pumps, 5 inches in diameter, raising 80 barrels per hour, to a height of 54 feet, = 1 horse.

6th. A set of three-throw "starting" pumps, pumping 250 barrels of beer per hour, to a height of 48 feet, 4.87 horses.

7th. Two pair of iron rollers and an elevator, grinding and raising 40 quarters of malt per hour, 8.5 horses.

8th. An ale-mashing machine, mashing at the time 100 quarters of malt, = 5.68 horses.

9th. Two porter-mashing machines, mashing at the time, 250 quarters of malt, 10.8 horses.

10th. 95 feet of horizontal Archimedes screw, 15 inches diameter, and an elevator, conveying 40 quarters of malt per hour, to a height of 65 feet, 3.13 horses.

Steam-engines for Cotton-mills.-With a mean pressure on the piston, with low pressure steam, of 5 lbs. per circular inch, each circular inch will drive three spindles of cotton yarn twist with the machinery. For mule yarn, add 15 to the number of the yarn, and multiply the sum by 26, for the number of spindles for each circular inch of piston.

Or, one-horse power will drive 100 spindles with cotton yarn, and machinery. For mule yarn, add

15 to the number of the yarn, and multiply by 8, for the number of spindles for each horse-power.

Economy of Steam-jackets.-The following Table presents the results of three experiments made in France to ascertain the economy of steam-jackets to the cylinders of engines, in the consumption of fuel. In the 1st, the steam first entered the jacket round the cylinder, and passed from thence into the cylinder. In the 2d, the steam entered the cylinder directly, without passing into the jacket. In the 3d, the steam entered both the cylinder and jacket directly, by means of separate communications between them and the boiler. The result shows an increase in the consumption of fuel of nearly five-sevenths, in the 2d experiment, over that in the 1st.

[blocks in formation]

1 43 15 1482.7 8387-1 3.82 2.57

233 30 1982.12 11111·59 3.5

!

3 32 30 1469.5

2.55

0.26 34.28 193.9 5.66 0.28 | 58.16331·7 5.61

7822-23 3.5 2.73 0.24 45-22 240-7 5.32

| 45·22|240·7 |

13*

MARINE ENGINES.

The following Dimensions are given by Mr. Russell, for the Cylinders of Marine Engines of various

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

The improvements in Marine Engines have of late years been various and extensive. Those in oscillating and direct action engines have far exceeded previous calculation. In recently constructed war-steamers with screw-propellers, the whole machinery is placed seven or eight feet below the water-line, and the screw is driven by direct action at the rate of 45 revolutions per minute.

« PreviousContinue »