# Rotator drum torque

1. Jul 26, 2004

### compostguy

I am designing an in-vessel composting system - a 21 ft. long 4 ft. diameter steel tube that is mounted and spun on wheels by a hydraulic pump/turbine assembly, coupled to a 60:1 gear reduction box - the hydraulic pump will likely be powered by a small 4-5 HP gas powered motor.

My question relates to calculating the necessary torque to spin this vessel, and how to determine how much speed is altered. The vessel weighs probably 2000-3000 lbs. and will hold probably up to 2000 lbs. of compost.
How can I calculate the necessary torque to spin this? I suspect it has something to do with the circumfrence, the radius from the axis of rotation, etc., but don't really know how it all fits together.

Thanks!!!
-Colin

2. Jul 26, 2004

### KrazyIBKid

Horsepower for rotating objects:

HP = (TxN)/(5250)

where

HP = Horsepower
T = Torque (lb-ft)
N = Motor Base Speed (RPM)
----------------------------------
Torque for rotating objects:

T = (HPx5250)/N

where

T = Torque (lb-ft)
HP = Horsepower
N = Motor Base Speed (RPM)
---------------------------------- Someone please let me know if im wrong
That is what i remember from class, its a little ironic how my teacher JUST went over that with me after class, and now u ask... P.S. another ironic thing.. my name is colin too... and ur the first colin ive found to spell it the same too... just some irony for ya

3. Jul 27, 2004

### KrazyIBKid

did that help?

4. Jul 29, 2004

### compostguy

thanks!!

Thanks for the tip Colin - I don't know what the rpm and torque output will be for the hydraulic assembly but am still looking around for answers, would be nice to be able to predict that...

Weird coincidence - I went to high school in VA and did the IB program at George Mason HS in Falls Church - pretty funny! And now I'm still struggling with these little physics details!

5. Jul 29, 2004

### KrazyIBKid

Are you serious?!?! that is so weird! thats not far from where i live actually. only about a 3 hour drive at most!

we lived in the same state(within 3 hours of one another).. went to the same school program.. have the same name... Are both interested in MAth and Science(and are rather good at it)... and both joined these formums the same day.. What a coincidence ! Is it just me or is that REALLY ironic?!

Last edited: Jul 29, 2004