Torque calculations for axial loading. 1

[fakeringing]

Hi guys,
How do you calculate the torque required to turn an axial load on the shaft. For example, the shaft is in a vertical position and a weight of 100lbs placed on top of the shaft, how would you calculate the minimum torque for the shaft to rotate?

 

[hydtools]

Use f= m * aa, if you ignore friction.

Ted

 

[Jboggs]

Depends on how much angular acceleration you want, how much friction must be overcome, and the moment of inertia of the entire rotating mass. All must be quantified to calculate the torque.

 

[rb1957]

the general equation (for tightening a screw thread) is T = F*d*k. k = 0.2 is generally used to account for friction, thread ramp, etc.

but your question seems to be a little different ... a shaft with a mass sitting on top. how does the shaft interface with the rest of the world ? a flat surface ?? so the torque is over-coming the friction of the face-to-face contact ? or is the shaft threaded into the base-plate, and you're trying to lift it (against the load) ?

nothing to do with F = m*a, IMHO

another day in paradise, or is paradise one day closer ?

 

[hydtools]

fakeringing, search for power screw solutions.

Ted

 

[hydtools]

Look here:

http://www.roymech.co.uk/Useful_Tables/Cams_Springs/Power_Screws_1.html

Ted

 

[tygerdawg]

Simple.
Torque = [mass moment of inertia] x [angular acceleration of the assembly]

MMI can be manually calculated using standard MMI primitive formulas found in 1000's of places or developed from your solid model CAD program.
angular acceleration ~ [change in velocity] / [change in time to achieve that velocity]

Upsize it for friction, etc.

Websearch the Smart Motion Cheat Sheet in pdf format, it has the formulas you need.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[chicopee]

What is supporting the shaft and how is the shaft held in a vertical position? Also what mechanism is involved in turning the shaft?