Explanation of forklift terms
Load capacity and load center
The load capacity of a forklift truck varies depending
on the horizontal distance between the vertical
surface of the forks and the center of gravity of the
load. A forklift truck is equipped with a load chart
indicating this relationship between the distance and
the load capacity. The X shown on this load chart is
called the load center, and the Y which corresponds
to the X is the maximum load capacity.
Dimension
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Maximum fork height
The maximum fork height denotes the height from the ground to the upper surfaces of the
forks when the forks are raised to their highest position with the mast positioned vertically.
Free lift
The free lift is the maximum lifting height of the forks with the mast position remaining
unchanged.
Overall length
With forks:
Without forks:
The length from the front end of the forks to the rear end of the truck body.
The overall length minus the length of the forks, i.e., the length from the
vertical surface of the forks to the rear of the truck body.
Overall width
The maximum width of a forklift truck with the steering wheel set in the straight ahead
position.
Overall height
The height to the top of the forklift truck. The mast overall height is classified in two
categories: mast extended overall height when the forks are fully raised and mast lowered
height the forks are fully lowered. The mast lowered overall height must be compared to the
height of the overhead guard. This dimension is essential when judging whether or not a
forklift truck will be able to pass through and entrance to a building or some structure.
Wheelbase
The horizontal distance between the centers of the front and the rear axle.
Front overhang
Distance from the front axle center to the vertical surface of the forks.
Rear overhang
Distance from rear axle center to rear of the truck body.
Tread
Distance between the center of the left and right tires on the same axle, or in dual-tire models,
the distance between the centers of the left and right dual tires.
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Turning radius
The radius of the locus drawn by the extreme outward side of
the truck body when the forklift turns either right or left at the
minimum forward speed with the steering wheel turned
completely is called the “outside minimum turning radius”.
The radius of the locus drawn by the inner front tire is called
the “inside minimum turning radius”.
Right angle (90°) stacking aisle
The right angle stacking aisle denotes the minimum width of
an aisle in which a forklift truck is able to load and unload after
completing a 90 degree turn.
Right angle (90°) intersecting aisle
The minimum turning radius indicates the sharpness of a turn,
but it does not indicate how large a space is required to make
a turn. The right angle intersecting aisle is defined as the
minimum width of aisle which intersects at right angles
through which the forklift truck is able to pass. The catalog
data is for a non-loaded with the forks set at their widest
position.
Fork length
The length from the vertical surfaces of the forks to the front end of the forks.
Floor height
The height from the ground to the upper face of the floor board.
Step height
The height from the ground to the upper face of step.
Seat height
The height from the ground to the upper face of the seat when the operator [90 kg (199lbs)] is
seated.
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Head clearance
The head clearance from the under face of overhead guard to the upper face of seat when the
operator [90 kg (199lbs)] is seated.
Counterweight height
The height from the ground to the top of the counterweight.
Backrest height
The height from upper of the forks to the top of backrest.
Maximum fork spread
The distance of outer forks when the forks are moved on the outsider notches of carriage.
Minimum fork spread
The distance of outer forks when the forks are move on the inside notches of carriage.
Maximum ground clearance
The height from the ground at the position
where the clearance from the ground is
considered minimum, except the elevating
portion of the loading device and around the
wheels.
C1:
C2:
C3:
under mast
under power unit
under frame
Grade clearance
The angle (α) between the plane contacting the front tires and passing the front lower end of
the mast and ground is called the “Approach angle”.
The angle (β) between the plane contacting the rear wheels and passing the rear lower end of
the forklift truck and ground is called the “Departure angle”.
The angle (γ) between the lane intersecting on the underside parts of the body where the first
plane is tangent to the front tires and the second plane is tangent to the rear tires is called
“Ramp brakeover angle”.
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These angles are essential for assessing the ability of a forklift truck to climb over an obstacle
on the ground when traveling.
Approach Angle
Departure Angle
Ramp break-over Angle
Performance
The performance of forklift truck is changed by road surface and oil temperature of the
transmission or reduction gear etc.
The value on this handbook shows on the concrete or asphalt road and oil temperature as
below.
Engine oil:
Transmission:
Torque converter:
Reduction gear:
Hydraulic tank:
more than 50o C (122o F)
more than 50o C (122o F)
more than 80o C (176o F)
more than 50o C (122o F)
more than 40o C (104o F)
Lifting/Lowering speed
The speed of the forks as they move upwards and downwards is expressed both for their
loaded state and unloaded state. The lowering speed has been limited (reduced) to prevent
both vehicle instability and damage to the load which can result from sudden drops caused by
the weight of the load.
Travel speed
The maximum truck speed when the accelerator pedal is fully opened.
Drawbar pull
The forklift truck is often used as a tractor for a
trailer or other equipment. In such instances, the
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maximum traction varies according to the engine torque, reduction gear ratio, road surface
and other factors. It also varies largely depending
on whether or not the truck is loaded.
Gradeability
The “Gradeability” indicates the ability of the
forklift to ascend a slope. This ability differs
depending on whether it is loaded or not. The unit
of measuring the Gradeability varies from
manufacturer to manufacturer. The conversion
table given below may be utilized for comparison
purposes. The Gradeability of Tailift forklift trucks
is normally expressed in tangent percent (tan 0%).
Gradeability Conversion Table
Degree
(0)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Fraction
(B/A)
1/57.2
1/28.6
1/19.1
1/14.3
1/11.4
1/9.5
1/8.1
1/7.1
1/6.3
1/5.7
1/5.1
1/4.7
1/4.3
1/4.0
1/3.7
1/3.5
1/3.3
1/3.1
1/2.9
1/2.7
1/2.6
1/2.5
1/2.4
tan 0%
(B/A)
1.8
3.5
5.2
7.0
8.8
10.5
12.3
14.0
15.8
17.6
19.4
21.3
23.1
24.9
26.8
28.7
30.6
32.5
34.4
36.4
38.4
40.4
42.4
sin 0%
(B/C)
1.8
3.5
5.2
7.0
8.7
10.5
12.2
13.9
15.6
17.4
19.1
20.8
22.5
24.1
25.8
27.5
29.2
30.9
32.5
34.2
35.8
37.4
39.0
Degree
(0)
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
9
Fraction
(B/A)
1/2.2
1/2.1
1/2.1
1/2.0
1/1.9
1/1.8
1/1.7
1/1.7
1/1.6
1/1.5
1/1.5
1/1.4
1/1.4
1/1.3
1/1.3
1/1.2
1/1.2
1/1.2
1/1.1
1/1.1
1/1.1
1/1.0
tan 0%
(B/A)
44.5
46.6
48.8
51.0
53.2
55.4
57.7
60.0
62.5
64.9
67.4
70.0
72.7
75.4
78.1
81.0
83.9
86.9
90.0
93.3
96.6
100.0
sin 0%
(B/C)
40.6
42.2
43.8
45.4
47.0
48.5
50.0
51.5
53.0
54.5
55.9
57.4
58.8
60.2
61.6
62.9
64.3
65.6
66.9
68.2
69.5
70.7
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Weight
Truck weight: Total weight of a forklift truck without load.
Gross truck weight: The truck weight plus the
maximum load. In a forklift truck the gross
truck weight also includes the weight of an
operator.
Weight distribution: The weight of a truck in
both an unloaded and loaded state is
distributed to the front wheels and rear
wheels.
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