296 FARM MOTORS 



and around a cylinder at each end of a platform. Power 

 is derived from a pulley placed upon a shaft passing 

 through one of the cylinders. Fig. 200 illustrates a tread 

 power for three horses with the horses at work. Some 

 aprons are made in such a way that each slat has a level 

 face. This tread is thought to enable the horse to do his 

 work with less fatigue because his feet are more nearly in 

 their normal attitude. 



Owing to the large number of bearings, the matter of 

 lubrication is an important feature in the operation of a 

 tread power. Lubrication should be as nearly perfect as 

 possible in order that little work will be lost in friction 

 and the efficiency of the machine may be increased. The 

 bearings should not only have due provision for oiling, 

 but they must be so constructed that they will exclude 

 all dirt and grit. 



419. The work of a horse in a tread power. A horse at 

 work in a tread power lifts his weight 'up an incline 

 against the force of gravity. The amount of work ac- 

 complished depends upon the steepness of the incline and 

 the rate the horse travels. If the incline has a rise of 2 

 feet in 8, the horse must lift one-fourth of his weight, 

 which is transmitted to the apron and travels at the same 

 rate the horse walks. Working a i,ooo-pound horse in a 

 tread power with a slope of I to 4 is equal to a pull of 

 250 pounds by the horse. This is much greater than is 

 ordinarily required of a horse, but it is not uncommon to 

 set the tread power with this slope. If a horse weighs 

 i, 600 pounds and walks at the rate of two miles an hour, 

 work will be done at the rate of 2.13 H.P. At the same 

 speed a i,ooo-pound horse will do 1.33 H.P. of work. 



It is often true that a horse will be able to develop much 

 more power when worked in a tread power than when 

 worked in a sweep power, but he will be overworked. 



