MIL-T-14521 Trestles, Motor Vehicle Maintenance And Storage \(Vehicle Support Stands\)

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MIL-T-14521E

and the trestle examined for damage and for permanent deformation in accordance

With 4.4.2. Following the examination and measurements. the operability of the

rat} and pawl mechanism shall be verified. Evidence of cracked welds or other

damage: permanent deformation in excess of the limits specified (see 3.5.4 and

3.6.2): failure of the rack and pawl mechanism to operate freely throughout

it's entire adjustment range: or any tipping, overturning, or movement of the

trestle shall be cause for rejection (see 3.5.2). The above test shall be

repeated with the saddle and column of the trestle fully retracted (a total of

four load tests shall be performed. )

4.4.5 Proof load test. The trestle shall be positioned in the testing

machine with the saddle and column fully extended. A proof load equal to 1.5

times the trestle's specified capacity shall be applied to the saddle for a

time period of one hour, as depicted in Figure 4. The proof load shall then be

removed and the trestle examined for damage and measured for permanent

deformation in accordance with 4.4.2. Following the examination and

measurement, the operability of the rat} and pawl mechanism shall be checked.

Evidence of cracked welds or ether damage: Permanent deformation in excess of

the limits specified (see 3.3.4 and 3. 6.2): or failure of the rack and pawl

mechanism to operate freely throughout it's entire adjustment range shall be

cause for rejection (see 3.5.3). The above test shall be repeated with saddle

and column fully retracted.

4.4.6 Functional test. After the completed trestles have been painted and

the paint has dried, the trestles shall be tested for proper operation of the

rack and pawl mechanism. The test shall consist of raising and lowering the

saddle by hand. allowing the pawl to engage each tooth of the rack in turn. At

each increment of saddle height adjustment. an attempt shall be made to

dislodge the pawl by pushing on, shaking, and turning the saddle. When the

saddle is fully extended, the trestle shall be lifted by the saddle. Failure

of the pawl to automatically engage each tooth of the rack as the saddle is

lifted: ability to dislodge the pawl from the rack through any movement of the

saddle other than straight up: separation of the column and saddle from the

base when the trestle is lifted by the saddle; or inability to lower the raised

saddle shall be cause for rejection (see 3.6.2 and 3.6.3).

4.5 Production test and test methods. The tests 4.5.1, 4.5.2, and 4.5.3

shall be performed in the order given and in accordance with the sampling plan.

Tests 4.5.1 and 4.5.2 shall be performed in accordance with the requirements

of 4.4.1.

4.5.1 Off-center loading test-production. The following test shall be

performed on each end, in turn, of the trestle saddle. The trestle shall be

positioned in the test machine with the saddle and column fully extended. A

load equal to the trestle's specified capacity shall be applied to the saddle

for a time period of approximately tne seconds, as depicted in Figure 3.

The load shall then be removed and the trestle visually examined for cracked

welds. permanent deformation and other damage. Following the examination, the