Page B–4
IronHorse® Helical Gearbox User Manual – 1st Ed. Rev. B
Appendix B: Gearbox Selection
8) Check results against original speed and torque requirements:
NOTE: Actual gearbox ratio is used from the specifications table.
a) Conveyor speed = (motor speed) / (gearbox ratio)(pulley ratio)
= (1750 rpm) / (32.02)(16.0”/8.5”) = 29.03 rpm
b) Max real torque available at conveyor = (gearbox output torque)(pulley ratio)
= (5045 in-lb)(1.94) = 9787.3 in-lb
c) Max design torque available at conveyor = (gearbox output torque)(pulley ratio)/SF
= (5045 in-lb)(16.0”/8.5”) / 1.25 = 7829.8 in-lb
The speed is very close to required and both maximum torque values are greater than the 5500
in-lb required by the load. Minor changes to pulley sizes can be tried to get conveyor speed
closer to the required 30 rpm.
9) Select a motor and check torque transmitted to the load:
From the gearbox spec tables, HGR-67-030-B efficiency = 94%
Max mechanical input power @ 1.0 SF = 4.83 hp
Max mechanical input power @ 1.25 SF
= (max input power) / (SF) = 4.83 hp / 1.25 = 3.86 hp
Max allowable motor power = 3.86 hp
The largest motor that HGR-67-030-B can accept is 2 hp.
Select 2 hp motor, and check for adequate torque at the load:
Torque = Power / Speed
[conversion factor: 1 hp = 63,025 in-lb-rpm]
Torque load =
(63025 in-lb-rpm)(motor hp)(gearbox efficiency) / (motor rpm/(gearbox ratio)(pulley ratio))
= (63025)(2)(.906) / (1750 / ((30)(16/8.5)) =
3685.15 in-lb
[insufficient torque at load]
This torque value is less than the required 5500 in-lb required by the load.
Since a larger motor will not fit on the HGR-67-030-B, select HGR-77-030-C gearbox with a 3 hp
motor.
From the gearbox spec tables, HGR-77-030-C efficiency = 90.7%
Max mechanical input power @ 1.0 SF = 6.36 hp
Max mechanical input power @ 1.25 SF
= (max input power) / (SF) = 6.36 hp / 1.25 = 5.09 hp
Max allowable motor power = 5.09 hp
The largest motor that HGR-77-030-C can accept is 5 hp.
Select 3 hp motor, and check for adequate torque at the load:
Torque load =
(63025)(3)(.907) / (1750 / ((30)(16/8.5)) = 5533.8 in-lb > 5500 in-lb
Final Selection: HGR-77-030-C gearbox 3 hp motor
Summary of Contents for IronHorse HGR-37-005-A
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