198 ENGINEERING ON THE FARM 



during the rainy periods and that the necessary travel is 

 at a great disadvantage. This causes the effect of poor 

 roads to be shown in the moving of each year's crop. Every 

 year there is a great rush to get the crops off before bad 

 roads set in, since the products of the farm seem to be sold 

 more in regard to the condition of the road than in respect 

 to the requirements of the market. This comes all at once, 

 and the tendency is to upset business, demoralize trade, 

 and advance interest rates, and, as only a part of the crop 

 is needed at one time, the railroads find it hard to handle 

 the grain during the rush period. They could handle it 

 more cheaply if it were shipped more uniformly throughout 

 the year, and the grain could be stored more cheaply in the 

 granaries on the farm than in the city elevators. 



Good roads make it possible to move the farm products 

 from the farm to the point of consumption as needed. The 

 cost of hauling farm products in the United States is about 

 double what it is in Europe, the comparison being made on 

 the basis of the road conditions. 



Draft and resistance. Draft or tractive force is the force 

 exerted by a team or motor in drawing a load. The axle 

 friction, rolling, and grade resistance which this force is 

 obliged to overcome are known as tractive resistance. The 

 resistance is high upon rough roads of considerable grade 

 and at a minimum on smooth, level roads. The cost of 

 transportation increases with the increase in the resistance 

 offered. The Bureau of Public Roads, United States 

 Department of Agriculture, has found that the tractive 

 force required to move a ton on loose sand is 320 pounds, 

 on the best gravel as laid for a park road, 51 pounds, on the 

 best clay roads, 98 pounds, and on the best macadam, 38 

 pounds. 



Distribution of load. The Michigan Agricultural Experi- 

 ment Station made the following experiment to determine 

 the influence of the position of the load on the wagon upon 

 the draft. A comparison was made between the draft of 



