the vehicle is loaded and increase as gear ratio is
produce a maximum drawbar pull of 1,970 pounds
(provided, of course, that no wheels slip). Note that, if
the vehicle itself is loaded, it will tend to increase the
c. Drawbar Pull.
drawbar pull; however, at the same time, loading the
vehicle reduces the tractive factor. If, for example, a
1,000-pound load were added to the vehicle, giving a
(1) The drawbar pull is an indication of how
gross weight of 3,625 pounds, the tractive factor would
much the vehicle can pull on a trailer attached to it.
drop to approximately 0.55. This, times 3,625 pounds,
Drawbar pull can be calculated if the tractive factor and
gives a maximum drawbar pull of approximately 1,970
weight on powered wheels are known by use of the
pounds. For a vehicle having all-wheel drive, the
drawbar pull is a constant, regardless of the weight
carried by the vehicle. Note that the term maximum has
Drawbar pull = Tractive factor x
been used here; this means that the vehicle could supply
weight on powered wheels.
this amount of pull. However, in actual performance, the
vehicle is not required to supply this amount of drawbar
(2) In the vehicle under discussion (1/4-ton, 4 x
pull. The applicable technical manual for any vehicle
4 truck), it was determined that the maximum tractive
specifies the maximum trailer load to be attached. The
factor was 0.75 with a vehicle weight of 2,625 pounds.
1/4-ton, 4 x 4 truck under analysis, for example, has a
Because all wheels are powered, multiplying these two
maximum limit of 2,000 pounds trailer load on the
figures together gives the drawbar pull, or 0.75 x 2,625
pounds equals 1,970 pounds. That is, the vehicle can