الفهرس 
Materials and mithodOnly 14 pages are availabe for public view
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Abstract
Total costs can be divided into two categories fixed cost and
variable cost Fixed cost is composed of the following five
elements :
depreciation, interest, taxes, housing and insurance. Variahle
cost includes the following labor to operate the machine, fuel and
lubricants, and repair and maintenance costs. The distinction
between fixed and operating costs is clear for all machinery wh ich
are important components of total costs.
The objectives of this study were as follows:
I-To develop a statistical equation to predict the repair and
maintenance cost for both tractors and combine harvesters
under Egyptian conditions.
2- To evaluate the developed equations with the current available
equations.
Data were collected from 11 Governmental Stations of
Agricultural Farm Mechanization Centers. The data included 58
tractors, 55 combine harvesters. The records were kept for hours
of working for each year and repair and maintenance cost for same
years and initial list price of machine.
Tractors were purchased in the period from 1983 to 1986
with total recorded accumulated hours per tractor ranged from
580 to 10260 hours. The percentage distribution for tractors was
10.34 %, 44.83 0/0, 13.79 %, 13.79 %,17.25 % for Ford,
Romanian, Nasr, Hinomoto, Kubota tractors, respectively. On the
other hand, 22 tractors had nine- year old, 10 tractors ten years old.
26 tractors 11 years old.
Combines harvesters were purchased in the period from
1984 to 1990 with records accumulated hours per combine ranged
from 288 to 2204 hours. The percentage distribution for combines
Kubota RX 2750, Kubota RI 40 Yanmar CA 32 M89 , Yanmar
CA 32 M92 was 10.90/0, 54.55 %, 12.73 %,21.82 % of the total,
respectively. On the other hand, 6 combiners seven- years old, 7
combiners five- years old, 30 combiners three- years old, 12
combiners three- years old.
”Cuvefit software” program used to select the best fitting
equation for all types was found to be of the same formula of the
form:
Using this program 10 order to derive equation constants and
analysis of variance .
Table (22) Shows the constants of tractors. data analysis.
Table (23): Shows the constant of combines data analysis.
Table (22): Constants of tractors data analysis.
Models Constants R2
a b _~
Ford Y = 0.0000008X 2.1895 0.98
0.0000008 2.19
Romanian Y = 0.00005X 1.726 , 0.97
0.00005 1.726
Nasr Y = 2.3e-12X 3.7299 0.97 I
2.3e-12 3.7299
Hinomoto Y = 6.7e-17X 4.7993 0.91
6.7e-17 4.7993
Kubota Y = 0.000008X 1.9939 0.98 -
0.000008 1.9939
I General Equation
i
Y> 0.00004X 1.7461 0.84
I
II 0.000042 1.7462
Table (23): Constants of combines data analysis.
Models Constants R2
a b
Kubota RX 2750 Y = 0.0000007X 2.5219 0.99
0.0000007 2.5219
Kubota RI 40 Y = 0.00005X 1.8543 0.99
0.00005 1.8543
Yanmar CA 32 M89 Y = 0.00000003X 2.9311 0.98
0.00000003 2.9311
I
Yanmar CA 32M92 Y = O.OOlX 1.3452 0.99
0.0014 1.3453
General Equation Y = 0.00000015 X 2.7274 0.99
0.00000015 2.7274
1- The power model Y = aX b IS predicting repair and
maintenance costs because it is very closed to the actual
values.
2- from general equation for tractors repair and maintenance cost
reached to 405 % of initial list price after 10000 hours of use.
3- from private equation for tractor types repair and maintenance
cost for Nasr tractors were higher than from others tractors
and Hinornoto tractors were less than from other tractors.
4- from general equation for combines repair and maintenance
cost reached to 150 % of initial list price after 2000 hours of
use.
5- from private equation for combine types repair and
maintenance cost for combines Kubota RX 2750 were higher
than from other combines but repair and maintenance cost for
combines Yanmar CA 32 M92 were less than from other
combines.
6- Private owners of farm tractors and combines harvesters in
Egypt do not keep complete records for their mach ine’ s
expenditures.