O.k. here is the situation:

A rotating clothes dryer, with a rotational diameter of 2.7m, caries a load of 30kg. I need to find out what torque is required to rotate the clothes dryer from the centre shaft.

Can anybody help me with any relevant equations?

thanks, joe.

Torque = force x distance

30 kg is a mass, so you have to convert to a force via F=ma

The 30 kg is located the radius away from the center.

This sounds like a homework problem and I'm treating it as such.

Get the units right. A torque wrench may typically have units of ft-lbs in the English system, but remember that lbs is a unit of force not mass.

The SI unit of force is the newton which is equal to 1 kg/s^2.

So, your answer will be in the hypenated unit newton-meters

well its part of a design problem really, I need the reqired torque to rotate this clothes dryer up to 10 RPM (so I can select the 'right' gearbox for the applicattion.

When converting the mass into a force, I wouldn't know which area to use in the equation... might it be better if instead of rotating a 30kg mass we were rotating a 294.1995008592 N weight?

(if that conversion is right, I used an online calculator) =S

Yep, that sounds about right. F = 30 kg * 9.8 m/s^2

Here are some other equations: Torque - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Torque)

Remember to take into account the drum too, since most of the drum is located at the outer edge.


and this one: Electric Motors - Introduction to Electric Motor Acceleration Time (http://www.electricmotors.machinedesign.com/guiEdits/Content/bdeee1/bdeee1_2.aspx)

you can treat as a thin cylinder.
t=i x a

I =moment of inertia=mr2
If you want add weight of drum you can suppose 20 kg,total wt=50 kg.

I=50 x (2.7) x 2.7
I=364.5kg-m2
a=2xpixn/60=2x3.14x10/60=1.0466rad/sec2

t=364.5 x 1.04=382 n-m
if you want to know power

2xpi xnxt=383x2x3.14x10/60=399.9 watt=400 watt (0.53 hp)

something is always better than nothing so we may choose most nearest equvalent case.