COST AND UTILIZATION OF POWER ON FARMS. 49 



Table 35. — Unpaid labor used in repairing tractors. 





Labor used (days). 



Tractors on which 

 specified amounts 

 of labor were 

 used. 





2-plow 

 tractors. 



3-plow 

 tractors . 



o ; 



49 

 41 

 47 

 16 

 10 

 11 



28 



i... 



29 



2 



17 



3 



12 



4 



9 





9 







Average investment = 



Nearly all of the men who spent more than one or two days on 

 repair work gave their machines a general overhauling during the 

 year. 



The value of this labor at $5 per day has been included in the cost of 

 operating the tractors Five dollars per day, or 50 cents per hour, is 

 considerably higher than the value of ordinary farm labor during the 

 year of investigation, but is considerably lower than the prices charged 

 by regular experts and repair men. On the average this charge 

 amounted to $8.55 for the 2-plow tractors, $9.45 for the 3-plow trac- 

 tors, and $9.06 for all tractors. 



Interest. — Interest is charged at 6 per cent on the average invest- 

 ment. The average investment has been found by the rule: 



first cost X (years of service + 1 .) 

 years of service X 2. 



This is the generally accepted formula for determining the average 

 investment in equipment where a fraction of the first cost is charged 

 off each year for depreciation. The interest charge when computed 

 on this basis is slightly greater than when computed on one-half of 

 the first cost. 



The average interest charge for the 2-plow tractors was $34, for 

 the 3-plow $47, and for all tractors $40. 



Fuel and oil. — The average amounts of fuel and oil used per day 

 by the 2-plow machines at the different drawbar operations are given 

 in Table 36 and the amounts used by the 3-plow tractors in Table 37. 

 The fuel and oil required per day by the 3-plow tractors was consid- 

 erably greater for every operation than that required by the 2-plow 

 machines, but this was offset by the greater number of acres covered 

 per day by the larger machines (see Table 12), so that there was 

 practically no difference in the requirements per acre between the 

 2-plow and the 3-plow machines for any of the operations. 



