102 POWER AND THE PLOW 



angle are usually placed so that the rear end of one comes 

 opposite the front of another to make the circumference more 

 continuous and reduce jolting. Some firms use pressed steel 

 plates which, when attached, form a continuous succession of 

 corrugations clear around the wheel. This is claimed to pass 

 over soft ground without tearing up the surface and still prove 

 efficient in gripping hard roads and wild sod. One firm has 

 a peculiar crow's-foot grouter, while several use sharp spikes, 

 either conical or pyramidal in shape. The English tractors 

 sold in this country and Canada are not ordinarily provided 

 with such sharp cleats, using instead flat strips of steel put on 

 at an angle with narrow spaces between. They prove efficient 

 on good roads rather than in field work, and separate mud lugs 

 are provided for emergencies. 



STEERING WHEELS 



The majority of tractors have two steering wheels in front, 

 though there is a respectable number of three-wheeled types. 

 The three-wheeled tractor will turn in a somewhat shorter 

 radius, but the four-wheeler with the weight carried on a ball 

 and socket joint has practically a three-point support and is 

 less affected by minor irregularities in the ground surface. 

 The front wheels are usually built up, with a raised collar 

 shrunk on the tire to prevent lateral slippage. A few wheels 

 are made, however, with steel spokes cast into an iron hub 

 and rim. 



STEERING MECHANISM 



The steering mechanism usually operates on the front wheels, 

 though some attempt has been made to guide through the 

 drivers, and on one light traction cultivator a single steering 

 wheel is placed in the rear. In the majority of tractors a chain 

 is attached near either end of the front axle, after being 

 wrapped several times around a horizontal shaft, which is 

 rotated by a worm gear and steering wheel. The entire axle 



