Torque to turn with no acces to the centre of rotation 3

[Deaks]

If I need to measure the torque to turn a device but I can only apply a torque wrench to a bolt at 150mm radius, is there a way of calculating the relationship between the wrench and the dvice?

 

[hydtools]

How far is the bolt from the center of rotation?

Ted

 

[hydtools]

R = distance of bolt to rotation center
w = length of wrench handle
F = force applied to wrench handle
T = torque measured at the wrench
M = moment or torque applied to rotation

M = F*(R+w)
T = F*w, F = T/w

Subsitute F into equation for M
M = T*(R/w + 1)

Only if pure torque were applied to the bolt would the distance of the bolt from the rotation center make no difference.

Ted

 

[zekeman]

This is not that simple.

You first get the torque reading; next, you get the force, F at the bolt, but it is actually a force vector perpendicular to the torque wrench arm.
So the device sees a force F times the perpendicular distance from the force vector and the line from the bolt to the centerline plus the measured torque.

Mathematically,
T =Tmeasured+F#Xr#
where F# is the force vector and r# is the offset vector and

F#Xr#= F*r*cosine@

@= angle between the arm and the line from the bolt to the device centerline
And the amplitude of F# is F, or

T=Tmeasured+F*r*cosine@
F=Tmeasured/arm length

Note , if the arm is perpendicular to the line from bolt to centerline, the measured torque and the actual torque would be equal. and at the other extreme they would add.

 

[dinjin]

We used a long flat bar and captured two bolt heads 180 degrees
apart. Whatever the radius is of the bar from the center of
the bearing, you can use a fish scale and pull it perpedicular to the bar. The torque would be the fish scale value times the
radius.

 

[chicopee]

Alway draw diagrams when such problems arise. See my JPEG attachment for your answer