## FORCE and TORQUE CALCULATION

## FORCE and TORQUE CALCULATION

(OP)

Hi,

Not done this sort of things since college days.

Some input would be much appreciated.

Please refer to the attached .pdf. The diagram is a schematic drawing only.

In order to determine the weld size, I need to calculate the force (N) at the diameter of the welds (888mm).

The inner flange is driven by a 250 kW motor which has a rotational speed of 42 rpm.

Given that motor power Kw=(T*rpm )/9552.4 where T=Torque (N m).

T=(kW*9552.4)/rpm T=(250*9552.4)/42 T=56859.5 N m

I calculate that the force at the weld diameter to be:-

force at weld=56859.5*((888/2)/1000)

force at weld=128062 N

I deduce that the welds will be in shear.

Not done this sort of things since college days.

Some input would be much appreciated.

Please refer to the attached .pdf. The diagram is a schematic drawing only.

In order to determine the weld size, I need to calculate the force (N) at the diameter of the welds (888mm).

The inner flange is driven by a 250 kW motor which has a rotational speed of 42 rpm.

Given that motor power Kw=(T*rpm )/9552.4 where T=Torque (N m).

T=(kW*9552.4)/rpm T=(250*9552.4)/42 T=56859.5 N m

I calculate that the force at the weld diameter to be:-

force at weld=56859.5*((888/2)/1000)

force at weld=128062 N

I deduce that the welds will be in shear.

## RE: FORCE and TORQUE CALCULATION

Also, please consider whether you have any thrust or acceleration in the application.

I used to count sand. Now I don't count at all.

## RE: FORCE and TORQUE CALCULATION

If the view you show is a section the force on a circular weld or weld's will be more like a shear stress not a force.

Remember - More details = better answers

Also: If you get a response it's polite to respond to it.

## RE: FORCE and TORQUE CALCULATION

So shear stress is app. 5,7 N/mm2 which is a low value.

## RE: FORCE and TORQUE CALCULATION

As suggested by SANDCOUNTER, I am doubting the size of the force 128062N.

Take it a stage further from jlnsol:-

Circumference at the weld = 888*PI = 2789.7

Shear strength of weld material is 285N/mm2

Bearing in mind there are 2 welds.

So, area of weld required = 128062/285/2 = 224.7mm2

Width of weld = 224.7/2789.7 =0.08mm

All this of course is assuming that the motor is stalled by a force resisting rotation and no safety factors applied to the weld size.

## RE: FORCE and TORQUE CALCULATION

omega = 2*PI*n/60 = 2*PI * 42/60 = 4,398 rad/s

power is 250.000 Watt

torque is P / omega = 250.000 / 4,398 = 56844 Nm

force is torque / radius = 56844/0,444= 128027 N = 128 kN

## RE: FORCE and TORQUE CALCULATION

But yes you've discovered that welding is very strong.

Remember - More details = better answers

Also: If you get a response it's polite to respond to it.

## RE: FORCE and TORQUE CALCULATION

throatdimension, not the leg.Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

## RE: FORCE and TORQUE CALCULATION