CHAPTER LXI 



THE STEAM TRACTOR 



A steam boiler and engine mounted upon skids or on a 

 truck to permit them to be moved from place to place make 

 what is called a portable steam engine. If an engine be pro- 

 vided with means of ready control and with gearing for trans- 

 mitting the power to the traction wheels, thus enabling it to 

 propel itself forward over the ground and perhaps pull a load 

 after it, the outfit is called a steam traction engine, or a steam 

 tractor. The latter term has come into use recently. 



The steam boiler and the steam engine have been dis- 

 cussed under separate heads. This chapter will be devoted 

 to a discussion of the features of the steam tractor other than 

 the boiler and the engine. 



The Mounting of the Boiler. There are two general types 

 of mounting for the steam tractor boiler. One has a frame 

 connecting the traction and steering wheels in such a manner 

 as to form a truck sufficiently strong to support the boiler. 

 As now generally manufactured this is called the under- 

 mounted tractor, but a general name for this style of construc- 

 tion is frame mounted. 



Again, the boiler may be used as the frame for the engine 

 and the truck, in which case the gearing is attached to the 

 boiler by brackets or flanges riveted to the boiler. This 

 construction, called top mounting, is in more general use, but 

 is criticised by some because the boiler is subject to the 

 stresses produced in transmitting the power from the engine 

 to the traction wheels. When the traction wheels are 



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