FARM MECHANICS. 155 



526. A farmer adjusts a 45-inch doubletree so that 

 a colt which he is breaking may pull but one-half as much 

 as the older horse. What is the length of the colt's end 

 of the doubletree? 



Effect of Speed on Pulling. 



The standard quantities are: 



1. Rate, 2.5 miles an hour. 



2. Size of horse, 1,200 pounds. 



3. Pull, 120 pounds. 



4. Days work, 10 hours. 



5. Rate of work, 4-5 of a horsepower. 



If speed is increased a horse is able to pull less during 

 10 hours ; if diminished he is able to pull more. Experi- 

 ence indicates that speed between three-fourths of a mile 

 and four miles an hour, when continued for 10 hours, 

 may be estimated by the following relation : 



Standard speed X standard pull = changed speed X 

 changed pull. 



527. A 1,200-pound horse works for 10 hours, walk- 

 ing at the rate of two miles an hour. How many pounds 

 pull may be expected of him ? 



Process : 



2.5 X 120 = 2 X pull to be determined. 

 300 -^ 2 = 150 pounds pulling force. 



528. A 1,200-pound horse walks three miles an hour 

 for 10 hours. What pull may he exert ? 



529. A 1,600-pound horse walks four miles an hour 

 for 10 hours. What pull may he exert? 



