To reduce load another spider gear is usually added

allows the two wheels to turn at different speeds. To reduce load, another spider gear is
usually added on top meshing also with the two side gears and rotating in the opposite
direction as the other spider gear.
2. Overall Gear Ratio: Driven/Driver = 15/10 = 3:2 or 1.5 Clockwise

Data/Exercises:
Exercise 1
Gear
Specification/Par
t Number
Gear Type Number of
Teeth
Pitch
Diameter
Diametral
Pitch
Gear Ratio
for the Pair
H2472 Spur 72 3” 24 4:3
H2496 Spur 96 4” 24
L112Y Bevel 24 1.5” 16 1:1
L112Y Bevel 24 1.5” 16
H1616R Helical 16 1” 16 2:1
H1632L Helical 32 2” 16
Speed Gear Pair 1 Actual Velocity
Ratio
Theoretical
Velocity Ratio
N1 N2
4 18 13.5 1.33 1.33
6 42 25.5 1.47 1.33
8 54 36 1.50 1.33
Speed Gear Pair 2 Actual Velocity
Ratio
Theoretical
Velocity Ratio
N3 N4
4 12 12 1 1
6 30 30 1 1
8 36 36 1 1
Speed Gear Pair 3 Actual Velocity
Ratio
Theoretical
Velocity Ratio
N5 N6
4 18 6 2 2
6 30 15 2 2
8 39 18 2.2 2
Overall Speed Ratio = 18:6 or 3:1
Exercise 2
Speed reducer driven by 1750-RPM electric motor directly connected by a coupling.
Conveyor operates 3-10 hours per day and head shaft speed will be 36 RPM.
Calculations indicate that 2000-inch pounds of torque needed at conveyor head shaft.
1. What is the service factor?
a. 1.25
2. What is the overall drive ratio?
a. RPM Driver/RPM Driven = 1750/36 = 48.61
3. If belt drive used for secondary reduction, what is the ratio of worm gear
reducer? Belt drive ratio is 1.215.

a. Drive Ratio/Belt Drive Ratio = 48.61/1.215 = 40
4. What is the actual torque at the reducer output shaft
a. Torque/Belt Drive Ratio = 2000/1.215 = 1646.1
5. What is the normal torque?
a. Actual x Service Torque = 1646.1 x 1.25 = 2057.63
6. What is the selected size of the reducer based on mechanical rating?