CHAPTER XI.

MISCELLANEA.

Useful hints. To find the area of the safety valve of a boiler.—To find the pressure upon each square inch of a safety valve.-To find the weight on every square inch of a valve where the weight is hung to it.-To find a weight to hang on a valve to resist a given pressure.-Steam engines.Horse power. To find the nominal horse power of a condensing engine.Of a high pressure engine.-To find the indicated horse power. To find the commercial horse power.-Shafting.—To find speed of second motion shaft.-To find speed of a belt or rope driven power.—Testing cotton.Card clothing; conditioning.-Oil paint to be avoided.-Covering iron cylinders.-Twist; to find the proper amount.-The twist of slubbings and rovings.-Counts of yarn. Cotton yarn measure.-Avoirdupois weight used for cotton yarn.-French system of numbering yarns.—To reduce English to French nos.- -To reduce French to English nos.-Strength of yarns; table showing; means of ascertaining.--The strength of the cotton fibre utilized in yarns; American cotton yarns; Egyptian.-Filaments in cross section.-Twist for doubling of yarns.

S the prescribed limits of this work have already been considerably exceeded, only a few useful hints can be given upon matters that could not easily be incorporated under any particular heading in the previous chapters, or that were overlooked at the time. These consist mainly of practical rules or directions that will be found useful in the various departments of the mill. No pretence whatever is made of covering the whole ground, nor indeed of doing more in this respect than briefly supplementing the deficiencies of professedly practical essays treating of cotton spinning. For calculations and practical rules regarding the various changes in the different departments, the reader is referred to one or other of the numerous treatises already well known.

To find the area of the safety valve of a boiler.-Multiply the square of the diameter of the valve by 7854.

To find the pressure upon each square inch of a safety valve.-Multiply the area of the valve by the length in inches of the short end of the lever for a divisor; the total length in inches of the lever, multiplied by the weight upon it in pounds, will give a number which, divided by the first, will yield a quotient showing the pounds pressure upon each square inch. This rule pre

sumes that the valve and lever are balanced by a counterpoise, and that the only acting weight is that upon the end of the lever. When the valve and lever are not balanced, but contribute their weight to press against the steam, to find if the pressure upon the valve is equal to the pressure of steam against: multiply the area of the valve by the pounds pressure per square inch in the boiler, and the product will be the pressure of steam against the valve; then multiply the pounds weight upon the lever by its length in inches to the fulcrum, and divide the product by the number of inches in the short arm; to the quotient obtained add the weight required to balance the lever, and the sum will show that the pressure upon the valve and the pressure against it are in equilibrium. The weight to balance the lever may be found by applying a spring balance to the lever at the point where it presses on, or is jointed to, the valve. The actual weight of the valve must be added; or if it is attached by a joint to the lever, it will be weighed at the same time as the lever.

To find the weight on every square inch of a valve where the weight is hung to it.-Divide the weight by the area of the valve, and the quotient will be the weight upon every square inch of the valve.

To find a weight to hang on the valve to resist a given pressure.-Multiply the pressure per square inch by the area of the valve, and the product will be the weight required.

Steam engines. The capabilities of steam engines are measured by a standard, the limit of which is a horse power. This is a force capable of raising 33,000 pounds

one foot high in one minute; or 1,000 pounds thirty-three feet high in one minute; or, again, the exertion of a force of 33,000"foot-pounds " per minute.

Horse power. There are three forms in which this is expressed nominal, indicated, and commercial. Nominal horse power is the oldest form, and is now rapidly becoming obsolete. It is based upon the area of the cylinder, but takes no cognizance of the steam pressure and speed of piston. It is derived from data met with in the experience of Watt and his immediate successors the early engineers.

To find the nominal horse power of a condensing engine. -Square the diameter of the cylinder in inches, and multiply this by 7854, and the product will be the area. Divide this by 22, the number of inches area for one horse power, and the quotient will be the nominal horse power of the engine.

To find the nominal horse power of a high pressure engine. Find the area of the cylinder as before, and divide by 11, and the quotient will be the horse power.

To find the indicated horse power.-The area of the cylinder, the number of pounds pressure per square inch on the piston, and the speed of the latter, or the distance it travels per minute, multiplied together for a dividend, and divided by 33,000, will give for quotient the indicated horse power the engine is exerting.

To find the commercial horse power.-Deduct one-third from the indicated horse power for friction of the engine and shafting, and the remainder will be the commercial horse power available.

Shafting. To find speed of second motion shaft.-Multiply the number of teeth in the spur wheel of the engine by the number of revolutions it makes per minute for a dividend, and for a divisor take the number of teeth in the driven wheel upon the second motion shaft; the quotient will be the revolutions per minute of the latter.

To find the speed of a belt or rope driven pulley.—Multiply the number of revolutions of the driver by its diameter,

and divide the product by the diameter of the driven pulley. The quotient is the number of the revolutions of the driven pulley.

Testing cotton. Of late years cotton has been greatly adulterated, and spinners have suffered correspondingly heavy losses from this cause. Sand and water are the two chief ingredients used for this purpose, either separately or in combination, and it is therefore desirable to ascertain the specific amount of each adulterant. Nearly all the former is left in the opener, intermediate, and finisher lap machine, but the latter evaporates, and hence has received the name of the invisible loss. It is too often, however, confounded with the former. In testing, therefore, let the parcel of cotton, after being carefully weighed, first be exposed for several hours spread open in a room the temperature of which is equal to the maximum temperature of the rooms through which it will have to pass in the working processes. Weigh again, and the loss will be the weight of water that has been evaporated. Next proceed as directed in a previous chapter.

Card clothing. It has long been a recognized fact that the quality of yarn produced in a cotton mill depends more upon the proper treatment of the material in the carding process than in any other. The most conscientious care is required in this department, and the process of carding should also be guided by an intelligent conception of its requirements. The cotton may be good, and the carding engines the best, yet the product may be quite unsatisfactory. In such cases it will often be found to originate in a defective condition of the card clothing arising from its unintelligent treatment. Cylinders and rollers are often covered with cards that have not been properly conditioned, when, though put on tightly, they soon become flabby and loose. This is owing to the temperature of the room in which they work being so much higher than that from which they were brought. In order to prevent this occurring, all cards should be exposed for several days and

nights in a room the temperature of which is equal to or slightly higher than that of the room in which they will have to work. They should not be taken from here until wanted for use. India-rubber card clothing has to a great extent superseded leather, and this sort requires special treatment. When kept in stock, exposed to a low temperature, it becomes stiff and hard, and if examined would be found to have shrunk considerably. If a cylinder fillet be measured in this condition by stretching it over a long table with a considerable strain to get the fullest possible length out of it, and the same be conditioned and measured again, it will be found to have become practically two or even more feet longer. Were such a fillet put on in its unconditioned state, however tightly it might have been wrapped, the change of temperature would give it the extra length, which would go to slackness, and thus induce endless trouble and bad work. The proper way to deal with cards of this description is to condition them in a room where the temperature is five to ten degrees higher than the room in which they will have to work, by which they will become perfectly flexible and soft. Next, before using, let them be exposed for three or four hours in a temperature the same as that in which they will work. They should then be wound on the cylinders or rollers under a moderate and perfectly uniform strain; and after having been fastened at each end they should be left for an hour or two before the intermediate nailing is proceeded with, in which time the card will have settled or beaded itself into its ultimate position. After this has been done, there will be a slight and uniform contraction, which will bring the card into the best condition for producing highclass work and ensuring durability.

No oil paint of any kind, in any way, or under any circumstances, should be laid on the cylinders before nailing on the clothing. The application of oil paint to cylinders before nailing is a highly dangerous practice, and where india-rubber cards are in question cannot be