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AGRICULTURAL ENGINEERING 



frame under which the load is driven; the lifting is done with 

 either ropes or chains running over pulleys above and back 

 to a windlass below. The overhead type is the simpler of 

 the two, but is a little inconvenient to move. Ropes are 

 cheaper than chains, but are less durable. 



Nearly all of the various devices known for heavy lifting 

 are used with fairly good success, such as the worm gear, the 

 screw and nut, the hydraulic lift, the rack and pinion, and the 

 windlass. The worm gear with windlass is one of the most 



Fig. 181. A portable farm elevator mounted on a truck and equipped 

 with a folding hopper and a low-down dumping- jack. 



common and most satisfactory. As a usual thing, a rough- 

 cast worm gear is not a lasting part of a machine, and if port- 

 able elevators are to be put in constant use no doubt greater 

 refinement would be necessary at this point. 



The pump and cylinder, or the hydraulic jacks, are built 

 with lifting chains extending down to the hubs of the front 

 wheels, or with the cylinder placed directly under the front 

 axle. In the latter type the piston rod has a yoke at the top 

 which engages the axles and raises the entire front end of the 



