GENERATING MECHANICAL POWER 81 



hungry condition. This calls to mind the necessity of 

 arranging a brake to stop the wheel to let the dog off. 

 When the wheel is running light, the dog cannot let go. 

 A spring brake to wear against the iron tire of the 

 wheel is the most satisfactory. The brake may be 

 tripped and set against the tire automatically by a 

 small lever and weight attached to the underside of 

 the wheel. When the speed is too fast the weight 

 swings out and sets the brake. When the speed slack- 

 ens the weight drops back towards the center and re- 

 leases the brake. When the speed is about right the 

 weight swings between the two spring catches. 



BULL TREADMILL 



On dairy farms it is common to see a valuable pure 

 bred bull working a treadmill for exercise and to pump 

 water. Sometimes he turns the cream-separator, but 

 the motion is too unsteady for good results. Tread- 

 mills for this purpose are very simple. The mechan- 

 ism turns a grooved pulley which propels a rope pow- 

 er conveyor. The rope belt may be carried across the 

 yards in any direction and to almost any distance. 

 Bull treadmills consist of a framework of wood which 

 carries an endless apron supported on rollers. The 

 apron link chains pass around and turn two drumhead 

 sprocket-wheels at the upper end and an idler drum at 

 the lower end. The sprocket-wheel drum shaft is 

 geared to an auxiliary shaft which" carries a grooved 

 pulley. A rope belt power conveyor runs in this groove 

 and carries power from the bull pen to the pump. 



Bull tread powers usually have smooth inclined 

 lags, because a bull's steps on the tread power are 

 naturally uneven and irregular. This construction 

 gives an even straight tread to the travel surface. To 



