belt tension and bearing load

[nnjunger]

I am trying to run a simple calculation for bearing load on a motor bearing, and have evidently not done enough calculations in a long time, because I keep getting unrealistic answers. My system is pretty simple, I have a motor, belt driven to a machine. The sheaves are 14" drive, 12" driven, 12 each of a 5VX1250 belt, tensioned to 5/8" deflection at 12#. My question is simply what the effective load on the motor bearing is. Sorry for the simple problem, but I guess I need more sleep.

 

[Barry1961]

Will need more information. The horsepower of motor and distance from bearing to center of pulley. Besides the stactic tension you will add the belt pull which will be the torque at the drive shaft divided by the drive pulleys radius.
Example:
100hp at 1750rpm=3600in-lb/7" would be 514lb of belt pull if motor was under full load.

Hope this helps.

Barry1961

 

[nnjunger]

300 HP, 1800 RPM, the pulleys are approximately 42" on center, the distance from the bearing center to center of the pulley is approximately 9"

 

[Tmoose]

It depends in part on the stretchiness of the belt. The bigger belt catalogs have static tension in lbs per strand necessary to transmit a certain amount of power with various sized sheaves. Also the algebra necessary to figure the overhang's effect on the bearing loads.

The GAtes HD drive design manual is available here -

http://www.gates.com/catalogs/index.cfm?requesting=ptcatalog&location_id=524#cat

page 214 has info to calculate "tension per strand."

The belt manufacturer's engineers will print out detailed calculations for your set-up.