CHAPTER XIIIi 
TRACTORS 
Tractors are used by the logging industry as a substitute for 
animal draft for skidding, for hauling logs loaded on wagons 
and trailers, and also for trailing logs in slides. Comparatively 
small and isolated tracts of timber, which do not justify the build- 
ing of a railroad often present an opportunity for tractor logging; 
also stands which are too light for profitable logging by steam 
machinery, especially if the timber is not too small and the char- 
acter of topography or bottom are unsuited to animal logging. 
Logging by tractors is more destructive to the timber left on the 
area after cutting and to reproduction than animal logging, but 
it is less destructive than power logging machinery. 
The limited knowledge of tractors and their proper use has 
retarded the success of this type of equipment on many logging 
operations. Many breakdowns could be eliminated if competent 
drivers only were hired and they were made financially interested 
in the continuous productive run of the machines. 
The crawler type- of tractor has proved to be better adapted 
to logging work than the wheeled tj^pe, because the latter often 
is useless on sandy, soft or loose forest soils, on wet clay, and on 
snow and ice, since it has a tendency to mire on soft and to slip 
on hard road surfaces, while the former gives satisfactory results 
when operated on such bottoms, due chiefly to the large area of 
traction contact with the ground surface. Tractors are not 
adapted to very rough topography, but in some cases they have 
been operated successfully on adverse grades as high as 15 per 
cent or more, and hence they may be substituted for logging 
^ Prepared by A. Koroleff. 
* Crawler tractors also are knowTi under the names of "track-layers" or 
"caterpillars" but these names may lead to misunderstanding because "cater- 
pillar" is an exclusive trade name for tractors made by the Holt Manufac- 
turing Co., while "track-layer" also is a term used to designate a machine 
used in the laying of railroad tracks. ' 
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