Calculating Worm Gear Strength With ANSI

Based on the fixed-end beam calculation. Includes the majority of effects.

Dynamic Load

Fd = Ft2 Kv

where:

 

F t2

Poisson's ratio (material value)

  

circumferential force factor

 

v 2

gear circumferential speed [ft/min]

Allowable Bending Force

Fs = Sn b2 py ≥ Fd

where:

 

S n

limiting bending strength (material value)

 

b 2

gear width

 

p

gear pitch

 

y

form factor (Lewis factor)

Allowable Contact Force

Fw = d2 b2 Kw ≥ Fd

where:

 

K w

limiting contact strength (material value)

 

b 2

gear width

 

d 2

gear pitch diameter

Increase of Temperature Check

Qmax ≥ Pz

where:

 

P z = P (1 - η + 0.3)

lost power

 

Q max = C A (t max - t 0 ) / 33000

heat conducted away in oil

 

t max - t 0 = 120° F

allowable temperature drop

 

A

gearbox surface, which conducts away the heat, A ≈ 0.3 a 1.7 for well ribbed gearbox

 

C

transfer of heat factor, C ≈ 0.0356 n 1 + 20 for the gearbox with fan and bottom worm

Parent page: Worm Gears Calculation Formulas