Forklift Truckload Ratings.

TM 38-400/NAVSUP PUB 572/AFMAN 23-210 MCO 4450.14/DLAM 4145.42

continued overload are damage to lift mechanism,

b. Flammable material.

Electric-powered fork

excessive tire wear, and strain on the truck frame.

trucks, spark-enclosed type, will be utilized for the

handling of flammable material such as paint, oil,

4-21. Warehouse Tractor Load Ratings.

gasoline, and flammable gas.

c. Fume

absorbing

materials.

Certain

a. Warehouse tractor capacity is stated in pounds

commodities, particularly fresh fruits and vegetables,

drawbar pull, which is the motive force exerted at the

will absorb and become tainted by the fumes from

coupling. The drawbar pull and pushing power of the

gasoline or diesel engines. Electric power is required to

tractor is figured on the basis of the engine torque, drive

handle these commodities.

ratio, weight, and the traction of the tires. Although this

d. Gasoline-and diesel-powered MHE. These are

pull is not the maximum load weight the tractor will

best suited for outside applications and, in most cases,

draw, since under ideal conditions a tractor can pull a

can provide greater lifting, pulling, or pushing power

load equal to 20 times its drawbar pull, the maximum

than electric-powered MHE.

normal load weight should not exceed 10 times the

drawbar pull which will allow for all technical and safety

4-20. Forklift Truckload Ratings.

factors.

(1) Tractive effort and resistance. Tractive

a. The fork truck pivots on the center of the drive

effort is the motive force (measured in lbs) exerted at

axle; therefore, the weight of the load ahead of the front

the drive wheels of a tractor to overcome the resistance

wheels must be counterbalanced by the weight of the

to motion. Tractor resistance is the result of rolling

truck. In accordance with the principles of leverage, the

friction between the wheels and the surface, expressed

ability of the fork truck to lift a load depends upon the

in pounds per ton of gross weight of tractor. The type of

length of the load (the distance of its center of gravity

surface over which the tractor is to travel has an

from the center of the front axle of the truck) and the

important bearing on tractive resistance. The following

weight of the load. The capacity of the fork truck is

table of road resistance shows the comparative road

stated in inch-pounds, which is the rated pounds

resistance of some of the more common types of road

capacity of the truck multiplied by the distance from the

surfaces:

center of the front axle to the center of the rated load

Table of Road Resistances

selected by the manufacturer. In general, trucks are

rated by pounds and the distance from the heel of the

Type of Road Surface

Resistance in

forks to the center of gravity of the rated load (for

pound per

instance, 4,000 lbs at 24-in load center). To determine

ton

inch-pounds capacity, add to load center the distance

Asphalt (hard) ..............................

from the center of the front axle to the heel of the forks,

Brick (glazed) ...............................

which can be obtained from the manufacturer's

Brick (poor) ..................................

specifications or by measurement, and multiply the sum

Brick (smooth) ..............................

by the rated load weight.

Clay .............................................

200

b. An example of the forklift truckload ratings is as

Concrete (poured) ........................

follows: Assume a rating of 4,000 pounds at 24 inches,

Concrete road ..............................

with a measurement of 15 inches from the heel of the

Granite blocks ..............................

forks to the center of the front axle; result:

Gravel road ..................................

4,000x(24+15)=156,000 inch-pounds. To determine the

Ice and snow ................................

maximum weight which may be placed on a pallet of

Macadam ......................................

given size, assuming uniform weight distribution on the

Macadam (poor) ...........................

pallet, add half the dimension of the pallet parallel to the

Sand (loose, 3 in deep) .................

330

forks to the distance from the center of the front axle to

Sand road ....................................

275

the heel of the forks and divide the sum into the inch-

Snow (hard) .................................

pound capacity of the truck. To complete the example,

Snow (soft) ...................................

the maximum weight on a 40-by 48-inch pallet is

Tarvia ...........................................

156,000 divided by (15+20), which equals 4,457.

Wood blocks ................................

However, the load weight may not be in excess

Wood planking .............................

of the weight of the rated load stated by the

Wood planking (sticky surface) .....

manufacturer. If the dimensions of the pallet used,

(2) Grade resistance. Grade resistance is the

parallel to the forks, is less than twice the rated load

resistance for movement on a grade, to be added

center, the rated pounds capacity is the capacity of the

truck; therefore, the maximum load would still be 4,000

pounds. Bending of the mast channels as the load is

raised, plus forward tilt action, will reduce the capacity of 4-60

elevated loads by as much as 25 percent. Overloading

of fork trucks is strictly prohibited. Among the effects of