  ## 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.