FARM MOTORS 329 



Maximum Capacity of the Horse. The maximum effort 

 of the horse for a short time may exceed his own weight. In 

 an actual test a horse weighing 1550 pounds and pulling on 

 traces at an angle of 27 degrees with the horizontal exerted a 

 pull of 1750 pounds. A draft horse may exert an effort of 

 about one-half his weight while walking at a speed enabling 

 him to develop, for a short time, as much as four or five horse- 

 power. Such trials must be of short duration and be followed 

 by periods of rest. 



The fact that the horse is such a flexible motor, being able 

 to develop power much in excess of the normal rate, is cer- 

 tainly a great advantage for traction purposes, where the load 

 is constantly changing because of the condition of the surface 

 and the varying grade. Yet this fact often accounts for a 

 serious overloading, resulting in an injury to the horse. 



Amount of Service. The horse on the farm does not do 

 continuous labor. Investigation in Minnesota indicates that 

 the average farm horse does not labor for more than 1000 

 hours per year. The useful life of a horse is usually regarded 

 as ten years. 



The Size of Teams. A well-trained horse will direct his 

 effort at the command of his master; yet the manageable 

 team for field work cannot well exceed four horses. A capable 

 driver can drive a four-horse team practically as well as a two- 

 horse team and manage almost any of the implements requir- 

 ing four horses. It is true that larger teams than four horses 

 are in use, but the difficulty connected not only with the 

 driving but with the harnessing and hitching will likely pre- 

 vent any general increase of the size of the field team beyond 

 four horses. As many as 32 horses have been driven by one 

 man, but the assistance of several others is required in har- 

 nessing and hitching. In driving these large teams, which 

 are used principally on the combined threshers of the large 



