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CALCULATING THE POWER CAPACITY of TUFNOL GEARS


The following formulae have proved suitable for determining the power transmission capacity for TUFNOL gears produced with the standard 20° pressure angle.

 

Power Capacity (S.I. Units)

P= 0.00314 * fw' * y * V' * S' * m

where P= power transmission capacity in kW

fw' = face width of gear in mm

y =  a factor, depending on number of teeth (see Table 14)

V'= pitch-line velocity in m/s

S' = safe working stress for TUFNOL gears depending on speed in MPa

m = module

The safe working stress for static load should be taken as 42 MPa and the values of S' are derived from the equation

            S' =        42 *( 0.75/(1+V') + 0.25)

 

Power Capacity (Imperial Units)

hp =       ( 0.000095 * fw *  y * V * S ) / dp

where:

hp = horsepower capacity

fw = face width of gear in inches

y =  a factor depending on number of teeth (see Table 1)

V = pitch line velocity in feet/min (calculated from V = 0.262 x  r.p.m. x pitch dia. in inches).

dp = diametral pitch

S = safe working stress for TUFNOL gears, depending on speed, in lbf/in²

The safe working stress for static load should be taken as 6000 lbf/in² and the values of S are derived from the equation:

                                              S = 6000 * (150 / ( 200 + v )+ 0.25)

By adopting 42 MPa (6000 lbf/in²) as the static stress figure, a considerable factor of safety is obtained, particularly for the fine weave grades such as Carp and Lynx brands.

In abnormal stall or excessive overload situations, the laminated gear will usually strip without causing undue damage to the metal gear or other parts of the equipment.

There is no general formula for calculating the power capacity of bevel gears produced from TUFNOL laminates, as each case requires individual consideration. Our Technical Advisory Service will provide assistance in such cases.

Table 1

 

Number of teeth

y value

16

0.094

17

0.096

18

0.098

20

0.102

21

0.104

23

0.106

25

0.108

27

0.111

30

0.114

34

0.118

38

0.122

43

0.126

50

0.130

60

0.134

75

0.138

100

0.142

150

0.146

300

0.150

Rack

0.154

Speeds. In general TUFNOL laminates have greatest power capacity when operated at a pitch line velocity from 600 to 6000 feet per minute (3 to 30 metres per second). Speeds above this may require special consideration but, at very low speeds, torque or tooth loading should be taken into account in assessing suitability.