# Homework Help: Torsion in Steel shaft

1. Feb 4, 2012

### togo

1. The problem statement, all variables and given/known data

Compute angle of twist of one end relative to other if a torque of 850 lb-in is applied uniformly along the length. Shaft has two flats (not just the 1 pictured!) 1.25 " is measurement across flats.

2. Relevant equations
J = C r^4

3. The attempt at a solution
I had to hand in the page with the question on it recently :(

so, here are the governing equations, need some direction on how to tackle it:

so the value of J is easily computed (table: 0.625" / 0.875" = C of around 0.93 x 0.316 = 0.294)

angle = [(torque)(length)]/[GJ])

so since there are two J values, how is this handled? thanks

2. Feb 5, 2012

### rock.freak667

I think you will need to split it as two shafts with the same torque value T. So you'd get θ1 using J1 and θ2 using J2.

The relative angle would then be θ21.

I could be wrong though as it's been quite long since I've done these types of things

3. Feb 6, 2012

### togo

ok I'll try that

although the answer is very small and would kinda be the same even if you did it wrong. So I need to know