DESIGN PROCEDURE OF HELICAL GEAR

STEP 1: Calculation of Gear Ratio

Use i=N1/N2=Z1/Z2

STEP 2: Selection of Material

If the material is not given select a suitable material from

STEP 3: Calculation of Gear Life

If the gear life is not given assume the gear life as 20,000 hrs. PSG.8.5

STEP 4: Calculation of Initial Design Torque

[Mt] = Mt х K х Kd

Kd х K = 1.3 (initially assume the symmetric scheme from PSG 8.15

Ko = 1.5 (assuming medium shock or medium load from table)

STEP 5: Calculation Of Design Bending Stress [σb] and Design Contact Stress [σc]

To find [σb]: Refer the formulaPSG.8.18

To find [σc]: Refer the formulaPSG .8.16

STEP 6: Calculation of Centre Distance (a) Refer the formula

STEP 7: Selection of Number of Teeth (Z1 & Z2)

If not given assume Z1 = 20

Z2 = i х Z1

STEP 8: Calculation of Module (m) Refer the formula

PSG.8.22 for helical gears

PSG.8.13 for helical gears

STEP 9: Recalculation of Centre Distance(a) Refer the formula PSG8.22 for helical gears

STEP 10: Calculation of b, d1, v and ψp

b=ψхa

d=mхZ

v = ∏ х D х N / 60

ψp = b / d

STEP 11: Selection of Suitable Quality of Gear

Refer for ψ refer PSG 8.14 table 10

PSG.8.16 table no 15

STEP 12: Recalculation of Design Torque [Mt]

[Mt] = Mt х K х Kd х Ko

K = Refer the value from

Kd = Refer the value from

Ko = Refer the value from the table

STEP 13: Check for Bending Stress

STEP 14: Check for Contact Stress

PSG.8.15 table no 14

PSG.8.16 table no 15

Refer PSG. 8.13A for helical gears

Refer PSG.8.13 table no 8 for helical gears

STEP 15: Calculation of Basic Dimensions of the Gear Pair Refer the formulas PSG.8.22.