30 MACHINERY 



MACHINERY. 



Nominal horse-power (N.H.P.) is a general or vague 

 term used to indicate the size of the engine and means the 

 power given out when worked at a pressure of about 30 lb. 

 to the square inch. 



Indicated horse-power (I.H.P.) refers to the total power 

 exerted on the piston by the steam or the exploding gases in 

 the cylinder as tested by an indicator. It is usually 2£ times 

 the 'nominal.' Brake or effective horse-power (B.H.P.) 

 is the net useful work transmitted by the driving shaft 

 through a band which acts as a ' brake ' to the motion of the 

 fly wheel. It represents the ordinary working power of an 

 engine, and runs about f of the I.H.P., or l£ times the 

 N.H.P. 



One horse-power = raising 33,000 lb. one foot high in 

 one minute or — 33,000 foot pounds = 33,000 units of work. 

 The heat unit, i.e., the energy required to raise 1 lb. of water 

 1° Fah. is 744 ft. lb., to raise 1 lb. of water 1° C. requires 

 1,390 ft. lb. 



1 lb. of coal yields 14,000 heat units. 



1 lb. of kerosene oil yields 20,000 heat units. 



The modulus of an engine is the proportion of motive 

 power which is given out as useful work : in ordinary farm 

 machines it is about a half, the other half being used up in 

 overcoming the resistance of the machine itself. 



In an oil engine about 60 per cent of the heat is dissipated 

 by the cooling jacket, 25 per cent escapes by the exhaust and 

 only about 15 per cent are ultimately available for transmit- 

 ting power to other machinery. 



Half a pint of oil is supposed to be required per B.H.P. 

 per hour. 



Water Lifting. 



Water lifted in one hour by various machines. 



Picottah (3 men — 2 on beam) ... 14 ft. 2.735 gallons. 



Mhote 38 ft. 1,523 



Oil engine : 3" pump and 3* H.P. 25 ft. 12,800 

 engine. 



The co-efficient of utility is the amount of useful work 

 done in one hour, expressed in foot pounds, divided by the 

 weight of the animal in pounds, and represents the vertical 



