Calculate Forces at A & B in Steel Wire Tractor Pull

[raymanmusic]

Homework Statement

https://dl.dropboxusercontent.com/u/11241083/tractor.png
How do I calculate reaction forces at A and B? We pull with a force F2 = 300 N on the steel wire. The steel wire goes two and a half times around the axel wheel.

d = 38 mm

D = 200 mm

a = 100 mm

b = 120 mm

\sigma_{w} = 256 \frac{N}{mm^{2}}

K_{t} = 1.5

\eta_{k}=0.7

\mu=0.2

Correct answers:
F_{A} = 13.3 kN
F_{B} = 6 kN

 

[SteamKing]

What have you tried? This seems to be a very straight forward problem.

Why don't you try something that can be checked and discussed?

Hint: Pretend the power take of shaft (a-b-d) is a beam with two supports and the load from the sheave is cantilevered over the end of this beam.

 

[raymanmusic]

What is the force at the end of the shaft? Is it the same as F2=300N? I sum moment at point B to try to find reaction force at A.
https://dl.dropboxusercontent.com/u/11241083/New%20Document20140407191616593.pdf

 

[SteamKing]

What is the force at the end of the shaft? Is it the same as F2=300N? I sum moment at point B to try to find reaction force at A.
https://dl.dropboxusercontent.com/u/11241083/New%20Document20140407191616593.pdf

Look at the left figure, the one showing how the line goes around the sheave. You are given F2, so make a FBD of the sheave to see what load the shaft sees.