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Haul Rope Twist


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#1 teachme

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Posted 10 March 2016 - 08:55 AM

Hi,

A few years ago I read about a problem with early fixed grip lifts where the haul rope wanted to 'twist' as it went through the bull-wheels. I can not remember the actual issue though but I do remember it was a serious issue in lift design at one point. Does anyone know the actual issue or can point me to a source that describes it? Also, what solutions were developed?

Thanks,

TME

#2 JSteigs

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Posted 12 March 2016 - 07:10 AM

If it's at the bullwheel then the rope probably isn't in the same plane as the bullwheel. Meaning it isn't coming in straight. Place a smart level (or bubble level if you don't have a smart level) on the bullwheel, then raise or lower the guide sheaves to make the rope match what you have at the bullwheel. Do this for both incoming and outgoing guide sheaves. If you want to check if the you are still getting twist, with the chairs off draw a stripe with soap stone or a marker before it comes into the bullwheel, run that part of the rope around the bullwheel and see if it's still straight.

#3 MoltzVT

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Posted 20 March 2016 - 11:11 AM

Large heavily loaded breakover towers running in or out can induce twist as well, using flagging tied to the rope will allow you to watch the tails as they twist. Replaced a haul rope on a lift with a gauge change, it was a triple turned into a quad with a gauge change for the smaller wheels top and bottom. The old rope did not have an issue but the new rope gripped the liner edges a lot better and twist built up to a point the chairs hung badly as it neared the drive. Carriers actually moved forward as the tension of the twist overcame the grip force. Learned a lot about rope twist that fall.

#4 Lift Dinosaur

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Posted 20 March 2016 - 12:47 PM

As already stated, haul rope twist is induced into the rope by the cable rolling on both sheave liners and bullwheel liners. Here are some slides that show how this occurs.
Hope this helps.
Dino
Attached File  1 Haul Rope Roll.jpg (260.51K)
Number of downloads: 123Attached File  2 Haul Rope Roll.jpg (548.13K)
Number of downloads: 122
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