5 replies to this topic

[pete_dl]

Has Ultra high molecular weight polyethylene (Dyneema) been used for haul ropes ? If not, what are the disadvantages?

Thanks,
Pete.

[Aussierob]

I tnink the elogation is away too high, it wouldn't get traction on a bullwheel liner and wouldn't resist the compresive force of a grip.

[aug]

pete_dl, on Mar 13 2009, 01:35 AM, said:

Has Ultra high molecular weight polyethylene (Dyneema) been used for haul ropes ? If not, what are the disadvantages?

Thanks,
Pete.

UHMW polyethylene. a close cousin to polypropylene... In a way, yes it has been used . Most ropes with a fibre core now use polypropylene fiber for the core of the wire rope. The solid core ropes are using plastic ( for core). Fatzer is using solid polyethylene rod.

This post has been edited by aug: 13 March 2009 - 06:43 AM

[Splicer]

Actually, Fatzer uses a high-density polyethylene rod wrapped with a low-density polyethylene sheathing. When the rope is being closed during production, propane heat nozzles heat the low density outer sheathing which allows the softened material to extrude out through the valleys and create a strand to plastic wire imprint. The extruded plastic provides a barrier between the strands in the valleys reducing inter-strand contact and keeps the strands evenly distributed. All of the wire rope manufactured were forced to design low stretch ropes to accommodate the short (less expensive) tension terminals put out by the lift manufacturers. Fatzer’s calculated rope stretch is about .15% x the rope length within the first 2 years. The short terminals and low stretch ropes created a whole new set of issues. After the first initial factory stretch period and subsequent shortening happens, this leaves the tension carriage close to the front. If or when splice repair becomes necessary, due to the low rope stretch design, there is no available carriage left. Worse case scenario, remove the splice and patch in a section (yuk). So the idea is to keep the tension carriage back as far as possible after the initial factory stretch splice to save available tension carriage for a future splice repair. Hard for operators to do when it has been driven into our heads for decades to shorten as much as possible so we don’t have to splice again.

[aug]

Splicer, on Mar 13 2009, 09:40 AM, said:

Actually, Fatzer uses a high-density polyethylene rod wrapped with a low-density polyethylene sheathing. When the rope is being closed during production, propane heat nozzles heat the low density outer sheathing which allows the softened material to extrude out through the valleys and create a strand to plastic wire imprint. The extruded plastic provides a barrier between the strands in the valleys reducing inter-strand contact and keeps the strands evenly distributed. All of the wire rope manufactured were forced to design low stretch ropes to accommodate the short (less expensive) tension terminals put out by the lift manufacturers. Fatzer’s calculated rope stretch is about .15% x the rope length within the first 2 years. The short terminals and low stretch ropes created a whole new set of issues. After the first initial factory stretch period and subsequent shortening happens, this leaves the tension carriage close to the front. If or when splice repair becomes necessary, due to the low rope stretch design, there is no available carriage left. Worse case scenario, remove the splice and patch in a section (yuk). So the idea is to keep the tension carriage back as far as possible after the initial factory stretch splice to save available tension carriage for a future splice repair. Hard for operators to do when it has been driven into our heads for decades to shorten as much as possible so we don’t have to splice again.

Thanx Mr. Splicer, You are a wealth of information. Aug

[Walt Askier]

pete_dl, on Mar 13 2009, 04:35 AM, said:

Has Ultra high molecular weight polyethylene (Dyneema) been used for haul ropes ? If not, what are the disadvantages?

The main disadvantage of the high tech fiber cordage is that it's very easy to cut vs. steel. I can pull out a knife and slice a half-inch thick piece of Dynema (or Vectran, Spectra, Technora, etc.) Not so with steel. Abraision resistance (or lack thereof) is another disadvantage.

The breaking strength may be equal to or greater than steel, but there are other failure modes to consider.