716' 



The Lincoln Tractor Trials, 1920. 



[Nov., 



design are too familiar to need description. The principle is 

 to reduce the insistent weight on each square inch of the' 

 land on which the creeper stands, and also to present a very 

 large area for gripping or adhering to the ground. Eesults 

 so far have demonstrated the superiority of the caterpillar 

 tractor over the wheeled tractor on wet soils, where the track 

 machine, w^ith its low intensity of pressure upon the soil, 

 shows itself to greater advantage than on a dry light soil. The 

 wheeled machines practically group themselves in efficiency 

 more or less in proportion to the weight per square inch 

 carried, on the contact with the ground. It was clearly demon- 

 strated in last year's trials that heavy weight is not necessary 

 to provide tractive effort, and that, with efficient forms of 

 ^rip, light machines are successful. 



Many designs of caterpillar track exist, and a discussion of 

 the merits and demerits of each would require a very lengthy 

 statement. There is, however, considerable room for improve- 

 ment in the chain track itself, as well as in its supports and 

 ^inti-friction devices. The variation in resistance to haulage and 

 to work is as great as exists between one system and another, 

 not merely in static resistance to starting but in dynamic 

 resistance to haulage. There is ample scope here for investiga- 

 tion and comparative tests at the hands of any research associa- 

 tion or institute that may be established in connection with 

 agricultural machinery. 



Adhesion. — Adhesion depends for its effectiveness on three 

 conditions: (1) the amount of wheel or track in contact with 

 the ground; (2) the kind of gripping devices attached to the 

 wheels or track; and (3) the weight of the machine. The 

 second point, to which attention was drawn last year, 

 especially needs further investigation. Various methods are 

 now employed to obtain the adhesion necessary. They fall into 

 three classes: — 



(1) Angle iron at an acute angle on the rim of the wheels; 



(2) Projecting angle iron at^an acute angle to the wheels; 



(3) Variously shaped spuds or spikes. 



Each class employed at the trials seemed to do its work fairly 

 efficiently, but sufficient data are not at present obtainable for 

 comparison. There is undoubtedly considerable variation both 

 in the adhering power of and the resistance exerted by the 

 different devices, and a searching test should be carried out to 

 ascertain the effectiveness of each type. 



