Calculate the pressure on a reel/drum 1

[azrom]

I have this winch-reel (540mm wide, Diameter=800mm, cylinderer wall thickness=10mm) that is to be pulled by a wire. The maximum braking load on the winch is 4.3 metric tonnes (42kN).

My task is to check the reel against buckling. I can determine the buckling if I know the relevant pressure on the reel/cylinder wall.

How can I determine the design pressure on the reel if only the braking load is known?

 

[kelowna]

Not much information!
I would tend to assume that the maximum braking load is also the maximum tension on the wire (or cable).
From the tension on the cable, you can get very easily the force of the cable against the reel and therefore the pressure.

 

[GregLocock]

Yes, and each layer of the wire will add a further compressive load.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[azrom]

Thankyou for your input!

I agree that each layer would add more compressive load on the reel. But I would also gather that this pressure isnt constant or equal for each layer. So a simple addition of (layers x force per layer) may be wrong? I would guess that the latest layer would carry most force - but that is only a guess.

I would also guess that the load distribution around the reel isnt constant either. Any tip on anyone having a study or formulas for wire/cable problems would be appreciated!

 

[GregLocock]

Yes, as you add each layer (at constant tension) the total pressure on the reel increases, at a non linear rate. The outer layer of the reel is at full tension, but compresses the inner layers, so they detension slightly.

The important parameters I found were the coefficient of friction of the cable, and the ratio of the radial to axial stiffness of the cable, and the radial stiffness of the cable and the reel.

In my case, from memory, I found that the load on the reel did not increase after we got 7 layers on there. However that was a pretty unusual cable.




Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[kelowna]

You have to be carefull there. If you take the friction coeficient of steel to steel, you can determine the loss of pressure per turn and then determine how many turns you need before the tension on the cable reduces to cero, ...BUT, and big but, it depends on the winching operation. Say that you start with an empty drum and you start reeling in under tension. Then all the layers of cable are equally tensioned even if after finish reeling you de-tension the cable.

Regards