What Causes Milking

JeffGu

Well-Known Member
I'd argue that the pinching action is keeping the core and sheath from seperating very far from each other, and that the bending action of the Rope Wrench does it from above the hitch, and the Hitch Hiker does it from below the hitch... but I don't think it matters that much which side of the hitch this action happens. Either way, if you clamp the sheath and core together, the action of the hitch dragging the sheath away from the underlying core is inhibited... I use the RW and don't have the HH, but I'm not having milking issures, either. Also not having them with the ZZ/Chicane combo.

I agree that the hitch is probably grabbing the sheath and dragging it down, and the forces from a hitch might not penetrate deep enough to stop the sheath/core slippage. Also, I'm sure the devices vary a lot on how much clamping force they apply to stop slippage, which is quite probably mostly caused by the variable friction parts of the device.

I've always been convinced that there's more to this issue... why do some climbers have lots of milking and others don't, when they're using the same devices and ropes? Weight is going to be an issue, for sure, but I suspect climbing style is going to have a very important influence. I don't bomb out of trees and apply sudden, hard braking. Partly because I don't think it's good for the rope and gear, but mostly because I don't think it's going to be good for me if I make even a small error in judgement.

It will be interesting to see what other conclusions you come to, with further exploration.

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Winchman

Active Member
What kind of gloves are shown in the video? They look a lot like the Hardy polyurethane coated nylon gloves I buy from Harbor Freight for two dollars with the finger tips removed. I throw them away after five or six climbs, but they're comfortable and grip rope very well. How long does the poly coating last on those?
 

Richard Mumford-yoyoman

Well-Known Member
What kind of gloves are shown in the video? They look a lot like the Hardy polyurethane coated nylon gloves I buy from Harbor Freight for two dollars with the finger tips removed. I throw them away after five or six climbs, but they're comfortable and grip rope very well. How long does the poly coating last on those?
Look for the FOAM gloves, they are so much better then just latex coated. They last much longer and they're actually a little warmer in the winter. These are Wells Lamont and last year Costco had them in the spring, but I think you can get them on Amazon too. Yes, I simply cut off the fingertips.


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Tuebor

Well-Known Member
I have to admit, I didn't really know what milking was; the cover growing longer than the core, or the core extruding from the cover? The first rope I owned - 11 mm HTP with no eyes - had about 3" of the core squeeze out from under the cover. My drenaLine with a sewn eye had about an inch of core come out. The other dozen ropes I've used in the six years I've been climbing haven't budged an inch. I can't believe it when I read climbers complaining about "feet" of rope milking. Am I lucky? Or just too skinny?
 

Winchman

Active Member
Thanks for the info on the gloves.

I recently had to milk about thirty feet of the cover of my Samson Voyager back from the end to examine and clean a section of the core. Getting the cover milked all the way back to the end was interesting. I had tied a knot in the line before pulling the cover back, so I clamped that to a heavy piece of furniture. Then I started working from the knot to the end of the rope just using my hands. That worked well until I had only about half an inch to go. It was like I'd hit a wall. The cover wouldn't budge despite several hard pulls along the rope.

As a last resort, I started pulling small sections toward the end, working from the end back toward the knot. After several trips like that, the cover was all the way to the end. I have no idea why that worked, but it did.
 

samsquatch

Well-Known Member
I have a consequence of milking to add to the discussion, and it's scary. I don't know how it actually happened, but on my 180' Tendril the cover has milked about 1" past the core on one end. I thought, no big deal, right. Well, there is a consistent spot in the line about 20 feet from this end that feels narrow, and where my mechanical (Unicender) will only grab about 50% of the time when tending up. It's in a terrible spot because I'm always using the 0 to 50 feet on that end as my working end.
I will switch ends and the issue will go away. But just sucks, I've probably only climbed on that line ~20 times.
 

JeffGu

Well-Known Member
...that feels narrow...
I had a line like that... I spiked the line and it didn't hurt the cover, but cut about a third of the core strands. When I would descend below that spot, the core would narrow down and the cover would slip (milk), but only below that spot. I cut that whole section off, and still use the rope. It's about 115' long, now... but very much usable.
 

TreeCo

Well-Known Member
Milking is one reason I don't like eyes on the ends of my climbing rope. I melt the ends with a 200 watt soldering iron but when milking occurs the core will either pull in or push out. I just remelt the end making both the same length again. I don't believe I've had a rope that ever needed redoing or lost more than six inches or length.

Ropes with a parallel strand inner core for me it's been the inner core that out lengthens the outer core. I've seen an inch or so of milking with 1/2 inch NE Hi Vee safety blue where the outer cover lengthened.
 

Richard Mumford-yoyoman

Well-Known Member
... A new rope gets stronger with use (until it doesn’t), as the core and cover comes into equilibrium the rope will reach its peak breaking loads.
I did a lot of breaking on a particular rope and seldom could I get close to the breaking strength listed. The cover would let go at about half the listed strength, releasing the tension, then rebuild until the core would let go, again, at about half the rated strength. In practical use I suppose it provided a shock absorption quality but I suspect that only in very controlled circumstances could the actual required breaking strength be obtained.
 

Richard Mumford-yoyoman

Well-Known Member
Did they all break in the same general area?
No, some of the test were under different circumstances and this is a general observation. Some were tested over a bollard or drum, some the knot, some splices or sewn eyes. It is my feeling that there is a lot that goes into the failures and I would agree that the tension and coefficient of friction between the core and cover would certainly effect the breaking strength.
 
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