994 



ANNUAL REPORT OF THE 



Oft. Doc. 



ruts dry and rigid. Kuts worn smooth by use, and free from dust 

 and loose dirt. Koad in what would be termed fair hauling condition 

 for narrow tired wagons. Narrow tires were run in old ruts in ad- 

 vance of the broad tires. Broad tires practically filled the ruts in 

 four trips or two runs. Length of runs, 400 feet. Trials made No- 

 vember 10, 1890: 



Narrow tire, 



Broad tire 



Difference in favor of narrow tire, 



127.0 



133.6 



6.7 



In this case the ruts were 2^ inches deep and the disadvantage 

 at which the broad tires operated was comparatively slight. In 

 the first run there was a difference of but 18.4 pounds or 14.2 per 

 cent. In the second run the order was reversed and the disad- 

 vantage caused by the rut was so far eliminated as to enable the 

 user of the broad tire to draw his load over this road with less effort 

 than the user of the narrow tire, the difference being 5.2 pounds, 

 or 4.4 per cent, in favor of the broad tire. It is to be further noted 

 that the use of the broad tire in the track of the narrow tire in the 

 first run did not so increase the draft of the narrow tire as to cause 

 this, since there was a slight reduction in the draft of the narrow tire 

 in the second trial after the broad tires had been used as compared 

 with the first run before they had been used. Clearl}-, therefore, a 

 rut of this depth would be of little consequence. 



For several weeks in the spring the ruts on din roads are usually 

 considerably deeper than those in the foregoing trial and on that 

 account these results were not considered sufficiently reliable to 

 form the basis for a general conclusion. Therefore these additional 

 tests were made : 



Clay road, dry, cut into ruts by narrow tires in the ordinary course 

 of travel. Surface of road, hard. The narrow tire ruts were an 

 average of 8i inches deep with smooth, rigid walls well apart so 

 that the side friction on the narrow wheels was slight. The bottoms 

 of the ruts were comparatively hard and smooth. On each side of 

 rut was a ridge of loose, dry earth or baked clay about 2^ inches 

 high. Length of runs, 400 feet. March 27, 1807. 



