Motor Stall or Rope Snaps

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Main Question or Discussion Point

We have a winch that lifts a load weighing 25kg up a shaft 30m deep. A 2mm Dia wire rope goes up the shaft over a guide pulley and down to the winch reeling drum. There is a load cell on the guide pulley.

The question is this. "If the load cell fails and the load being lifted gets snagged on the steel work as it is lifted will the wire rope break before the motor gearbox on the winch stalls / trips out?"

Wire Rope 2mm Diameter with a Breaking Load of 230kg

Winch Drum 300mm Diameter.

I'm still trying to get the information on the Motor / Gearbox but if someone could point us in the right direction as to what formula we could use to calculate this and also what specific information we would require for the Motor / Gearbox. Thanks in advance for the any help provided.
 

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  • #2
stewartcs
Science Advisor
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We have a winch that lifts a load weighing 25kg up a shaft 30m deep. A 2mm Dia wire rope goes up the shaft over a guide pulley and down to the winch reeling drum. There is a load cell on the guide pulley.

The question is this. "If the load cell fails and the load being lifted gets snagged on the steel work as it is lifted will the wire rope break before the motor gearbox on the winch stalls / trips out?"

Wire Rope 2mm Diameter with a Breaking Load of 230kg

Winch Drum 300mm Diameter.

I'm still trying to get the information on the Motor / Gearbox but if someone could point us in the right direction as to what formula we could use to calculate this and also what specific information we would require for the Motor / Gearbox. Thanks in advance for the any help provided.
A sketch of the system would be nice for clarity.

Assuming my visualization of what you are describing is correct, you'll also need the locked-rotor torque for the motor (I presume it is electric). That torque divided by the drum radius will approximate the tension in the cable. Specifically, you'll need the distance from the axis of rotation of the drum to the point where the cable leaves the drum. The closest wrap will give the maximum value since the radius will be the smallest there.

Thus, as long as that value is less than the breaking strength of the cable, you should be fine. Of course this assumes you are not concerned with the load on the guide pulley.

Hope that helps.

CS
 

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