Hauling ratchet zed cord and pulley sheave diameter

I just read through the 2:1 hauling ratchet thread and got warned off replying to the old one, so I'll post here a new topic since its a different direction anyway...

In the past I've heard people advocating the use massive pulleys for wall hauling, as the flex of the rope around small sheave diameter pulleys costs quite a lot in efficiency, despite the quoted 'efficiency' rating of the bearings etc. (Here is someones backyard experiment on diameters).

In the zenith-of-efficiency 2:1 setup from Skot and Mark, the pulleys are actually pretty small, which seems unexpected. I read somewhere that the ratio of pulley sheave diameter:rope diameter is the factor why big pulleys are favoured, up to a point. I wonder if the small zed-cord diameter and the rope flexibility in these setups from Skot and Mark, is negating the benefits of bigger pulleys and making it feel so efficient.

I'm guessing that the zed cord diameter and flex-characteristics (as well its stretch-resistance, obviously) are actually super important. It'd be very interesting to see some side-by-side tests if someone has the means to do it, or hear any experiences. Some of those ropes are available in a series of diameters, and there are stiffer or more-flexible alternatives in these things so theres a good experiment there.

Not carrying bigger pulleys is always appealing, and if scaling down the cord allows this thats pretty cool.

Also with regards to those thin spectra/aramid cords snapping, you've gotta expect the spliced/sewn terminations to be a lot stronger.. I wonder how many snapped at the knot for the people who snapped em.

Pulley efficiency (disregarding the bearing aspect) is basically a function of cord diameter to sheave diameter. BUT this is related to the bending resistance of the cord which is a function of the extensibility of the material and the coefficient of friction of the filaments in the cord. 

A cord will also have higher resistance  as a dynamic rope of the same diameter as the twists in the core of the dynamic rope extend easier as does the crimp in the filaments.

That is mostly how I was thinking about it. 

The efficency of the whole hauling operation in general might be reduced with dynamic rope though, as a bunch of work must be done to take the stretch out of the rope.

The bending resistance of the cord must also be more complex than its linear stretch (extensibility, if this is what you mean) characteristics. The braiding of the rope must play in here: Different dynamic, or static, ropes can have completely dissimilar resistance to folding/bending while still retaining highly similar linear stretch characteristics.

Larger pulleys will be more efficient,  but only marginally.  The swivel pulley I use is available in larger diameter sheaves, but they are also way heavier.  I use the Omni Block 1.1 with a 3/16” diameter Technora braided cordlette with a high temp wear resistant sheath.  
Mark and I have hauled massive loads with this system. We hauled over 300lbs on our ascent of Genesis hauling 2:1 every pitch. Mark isn’t exactly the biggest guy and he had no issue.

To me one of big wall climbings biggest appeals is the ability to tweak your set up in a million ways…. I’ve done the same pulley, cord, biner and progress capture mash up everyone does.  The haul set you all know I use is the result of Marks 40 years of experience combined with my mechanical and technical rigging experience and our experiments on the wall.  
My haul kit is by no means the end all be all. If you find a configuration of components that works great for you, that’s the haul kit you should use.
 I think Marks original intent with sharing our kit was to give people a list of parts that make a great kit, in hopes of saving people time and money going through dozens of configurations like I did.   We all know how expensive kit can be!! 

I actually once used a Dyneema sling as my Z cord to mitigate the bending resistance of cord. I probably achieved a greater level of efficiency but the percentage was certainly minuscule.

The system and components Skot and I are using make a really, really good system. There is simply not going to be more than a couple percentage points of efficiency to be gained in more exotic Z cords or pulleys.

Like Skot said, he and I enjoy tinkering with it and like I’ve said in the past, there are many ways to skin the big wall cat. Ultimately, the techniques and toys YOU like are the way to go.

No worries :D I know you guys have climbed tons of walls, I read the other thread and Mark’s trip reports etc for years.

I was just interested in why that setup is so efficient. I’m sure someone will work it out.

steve barratt wrote:

No worries :D I know you guys have climbed tons of walls, I read the other thread and Mark’s trip reports etc for years.

I was just interested in why that setup is so efficient. I’m sure someone will work it out.

I think a large part of the efficiency is the ball bearing sheave, the swivel above the pulley, which allows the pulley to orient itself to allow a clean pull (the Zed doesn’t rub against the pulley side frame) and the fact that it’s compact and easily deployed.  I think all of those things equal a haul kit that works incredibly well across the vast array of anchor configurations and features found at belays,  ie ledges, corner, overhangs….  
I just works great everywhere.   

steve barratt wrote:

I was just interested in why that setup is so efficient. I’m sure someone will work it out.

Jim Titt wrote:

Pulley efficiency (disregarding the bearing aspect) is basically a function of cord diameter to sheave diameter. BUT this is related to the bending resistance of the cord which is a function of the extensibility of the material and the coefficient of friction of the filaments in the cord. 

A cord will also have higher resistance  as a dynamic rope of the same diameter as the twists in the core of the dynamic rope extend easier as does the crimp in the filaments.

I'm sure someone will. 

Hahaha!  It is great to see that the Canadian English Zed Cord has made it with you Merricans!
Yann Camus has cut a skinny triple-length sewn sling and used it as a zed-cord. It's flat, and no stretch. He swears by it, although I haven't tried it.

I only ever use a 7mm perlon cord, and it works for me.

The most important thing is to have two high efficiency pulleys in the system, with the more efficient of the two on top. Forget size, diameter - just look at the efficiency in % and choose that way.

And practise!  You must practise to get it as efficient as possible!

Peter Zabrok wrote:

Hahaha!  It is great to see that the Canadian English Zed Cord has made it with you Merricans!
Yann Camus has cut a skinny triple-length sewn sling and used it as a zed-cord. It's flat, and no stretch. He swears by it, although I haven't tried it.

I only ever use a 7mm perlon cord, and it works for me.

The most important thing is to have two high efficiency pulleys in the system, with the more efficient of the two on top. Forget size, diameter - just look at the efficiency in % and choose that way.

And practise!  You must practise to get it as efficient as possible!

*practice *practice.  

Silly Canuck…..    haha.   

Skot Richards wrote:

*Claim credit for what Chongo brought into the bigwall game *Claim credit for what Chongo brought into the bigwall game.  

Silly Canuck…..    haha.   

FIFY

I credited Chongo in my book with the invention.  You own my book, and you know this. 

Peter Zabrok wrote:

I credited Chongo in my book with the invention.  You own my book, and you know this. 

And yet your post here says........

Peter Zabrok wrote:

I credited Chongo in my book with the invention.  You own my book, and you know this. 

*In Fabio and my book.  

FIFY.