What level of input torque can easily be created by an average human winding a handle with their arm?

Question

I've been doing some calculations invloving torque and I'm having trouble relating my answers to real life. What amount of torque can realistically be achieved by an average person winding a handle with their arm? (ie. 5Nm? 30Nm? 100Nm?)

At 60RPM what level of torque is an average person able to input fairly easily by winding a handle with their arm? I just need a rough ballpark figure to relate my calculations to real life (ie. 5Nm, 30Nm etc.)

Answer 1

I did such an experiment in physics class once:
Cranking a ~30cm diameter pulley (mounted to a wall with a crank at the outside diameter) with a resistance band at ~60RPM I was generating about 270Watts. This was an average over one or two minutes. If you back calculate you can find how much torque I was generating.

r=15cm, theta dot = 2*pi rad/sec

Watts = 0.15 * 2 * pi * F ---> F=270/(0.15*2*pi)=286N

So the torque I generated was 286*0.15 = 43 Nm. If you are doing a homework assignment and your options are 5, 30 or 100 Nm, I would choose 30 Nm.

Torque is dependent on the lever arm, and when cranking a handle (especially a long one) the force will vary continuously throughout the cycle. Applied force will also depend on the duration over which the task is performed - obviously a person can exert more force over the short term than the long term.

Answer 2

For static torque (i.e. tightening down bolts on an engine valve head) I can generate about 450 Nm (150 ft-lb) for a very short period of time on a torque wrench. That's about my limit.

For dynamic torque it will be much less. For short periods of time (minutes) maybe 1/4 to 1/2 of the static 'limit' -- so 100 to 200 Nm would be a reasonable estimate. Some strong-armed dude might be able to keep up 300 Nm for several minutes.

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Answer 3

There's been a lot of research in this area. Look around on the internet for Human Performance Capabilities or Ergonomics...

Check this out if you are able:
http://msis.jsc.nasa.gov/sections/section04.htm
Look under strength/workload. You should be able to derive some useful info.