AGRICULTURAL ENGINEERING. 997 



AGRICULTURAL ENGINEERING. 



Influence of width of tire on draft of wagon, H. J. Waters 

 (Missouri Sta. Bui. 39, pp. 165-206, figs. 14). — Experiments on this sub- 

 ject are reported in detail, with numerous figures and diagrams. The 

 results are summarized as follows: 



"Numerous tests of the draft of wide and narrow tired wagons have been made 

 at this station during the past two years on macadam, gravel, and dirt roads, in all 

 conditions, and on meadows, pastures, and plowed fields, both wet aud dry. The 

 draft has been determined by means of a self-recording dynamometer. The net load 

 was in every trial the same, viz, 2,000 lbs. Contrary to public expectation, in a 

 large majority of cases the draft was materially less when tires (i in. in width were 

 used than when the tests were made with tires of standard width — 1£ in. The fol- 

 lowing is a summary of the results: 



"(1) On macadam street, as an average of the 2 trials made, a load of 2,518 lbs. 

 could have been hauled on the broad tires with the same draft that a load of 2,000 

 lbs. required on the narrow tires. 



"(2) Gravel road. In all conditions of the gravel road, except wet and sloppy on 

 top, the draft of the broad-tired wagon was very much less than that of the narrow- 

 tired wagon. Averaging the 6 trials, a load of 2,482 lbs. could be hauled on the 

 broad tires with the same draft required for a load of 2,000 lbs. on the narrow tires. 



"(3) Dirt roads. («) When dry, hard, and free from ruts and dust 2,530 lbs. 

 could have been hauled on the broad tires with the same draft required for 2.000 

 lbs. on the narrow tires, (b) When the surface was covered with 2 or 3 in. of very 

 dry, loose dust, the results were unfavorable to the broad tire. The dust on the 

 road in each of these trials was unusually deep, (c) On clay road, muddy and sticky 

 on the surface and firm underneath, the results were uniformly unfavorable to the 

 broad tires, (d) On clay road, with mud deep and drying on top or dry on top and 

 spongy underneath, a large number of tests showed uniformly favorable to the 

 broad tire. The difference amounted to from 52 to 61 per cent, or about 3,200 lbs. 

 could have been hauled on the broad tires with the same draft required to draw 2,000 

 lbs. on the narrow tires. In this condition of road the broad tires show to their 

 greatest advantage. As the road dries aud becomes firmer, the difference between 

 the draft of the broad and narrow tires gradually diminishes until it reaches about 

 25 to 30 per cent on dry, hard, smooth dirt, gravel, or macadam road, in favor of the 

 broad tire. On the other hand, as the mud becomes softer and deeper, the difference 

 between the draft of the 2 types of wagons rapidly diminishes until the condition is 

 reached when the mud adheres to both sets of wheels; here the advantage of the 

 broad tire ceases entirely, and the narrow tires pull materially lighter, (e) Clay 

 road, surface dry, with deep ruts cut by the narrow tires in the ordinary use of the 

 road. In every trial the first run of the broad tire over the narrow-tire ruts has 

 shown a material increased draft when compared with that of the narrow tire run 

 in its own rut. The second run of the broad tires in the same track, where the rut 

 is not deep, completely eliminated this disadvantage, aud showed a lighter draft for 

 the broad tire than the narrow tire showed in the first run. Where the ruts were 8 

 in. deep, with rigid walls, 3 runs of the broad tire in its own track over the ruts were 

 required to eliminate the disadvantage. Three runs of the broad tire over this track 

 have in all cases been sufficient, however, to so improve the road surface that both 

 the broad and narrow-tired wagons passed over this road with less draft than the 

 narrow tires did in the original ruts. In addition to the saving or draft, the road 

 was made A-ery much more comfortable and pleasant for the users of light vehicles 

 and pleasure carriages by the few runs of the 6-in. tire. Summing up all the t< sts on 

 dirt roads, it appears that there arc but three conditions on which the bioad tires 

 draw heavier than the narrow tires, viz: (1) When the road is sloppy, muddy, or 



