MIL-T-62735 Trucks And Truck Tractors: Modified Commercial, General Specification ForThis specification covers general requirements for the classes, models and types of modified commercial trucks indicated in the specification title above and in 1.2 below. This specification is intended only as a document to be referenced in detail specification sheets that must, as a minimum, cover detailed truck body requirements and specify the model and class required from table I.

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MIL-T-62735

6.3  Performance prediction.  SAE Truck Ability Prediction Procedure calculations and calculations for low speed and maximum geared speed will be required by the contract.  The SAE Work Sheet Item 1 should include the chassis manufacturer's model number, engine model number, drive axle(s) model number and gear ratio(s), tire size, and vehicle type, class and model.

6.3.1  Conditions and factors used in calculations.  Unless other conditions are cited in the contract, calculations should be made for normal atmospheric pressure, normal ambient air temperature, and still, dry air.  The factors to be used in predicting truck ability (see 3.2.2) are established as follows for the corresponding SAE Truck Ability Prediction Procedure Tables:

80 km/h (50 mph) performance requirements:

Table 1                                          -  Tire Factor.   This factor must relate to the size of tires furnished by the contractor in accordance with this specification.

Table 2                                          -  Altitude Factor.   1.00

Table 3                                          -  Rolling Factor.   1.613

Table 4                                          -  Area Factor.   For truck tractor, use factor 0.223;

for all other trucks, use factor 0.173. Table 5                                          -  Velocity Factor.   250.0

Table 6                                          -  Altitude Factor.   1.00

Table 7                                          -  Chassis Friction Horsepower.   Use applicable power

unit GVW (to nearest, higher, 454 kg

(1,000 pounds)) and the engine speed (to nearest

100 rpm) which is required for 80 km/h (50 mph) geared speed.  For GVW and engine speed beyond range of this table, factors shall be extrapolated.

Table 8                                          -  Grade Factor.   0.75

Table 8A                                       -  Correction Factor.   Not required. Table 9                                          -  Road Factor.   0.0

69 km/h (43 mph) performance requirements:

Table 1                                          -  Tire Factor.   This factor must relate to the size of the tires furnished by the contractor in accordance with this specification.

Table 2                                          -  Altitude Factor.   1.00

Table 3                                          -  Rolling Factor.   1.315

Table 4                                          -  Area Factor.   For truck tractor, use factor 0.225;

for all other trucks, use factor 0.173. Table 5                                          -  Velocity Factor.   159.0

Table 6                                          -  Altitude Factor.   1.00

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