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donwanadi
Mar 12, 2012, 5:50 PM
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Like a quickdraw, but heavier? What is it?
[Not being an asshole]
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Skot433
Mar 12, 2012, 6:13 PM
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It's basically a stainless steel cable sling.
It's a part of my hauling rig. The link between my power point locker and my micro traxion
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csproul
Mar 12, 2012, 6:46 PM
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As long as it is strong enough....good to go. One thing to note for that application (you may already know this): That cable needs to be free to rotate some to allow the locking carabiner and the parallel plates on the mini-trax to freely move as you haul. If the plates are too constrained, the carabiner will torque the plates and can allow the rope to jump off the pulley and jam (kind of hard for me to describe without visual aids). This is one reason people generally use slings on the mini and pro-trax and do not clip them straight onto a bolt. A symmetrical carabiner is also very helpful. So hopefully that swagged cable will allow adequate rotation.
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Skot433
Mar 12, 2012, 7:18 PM
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Thanks for the input, I'm glad to be getting the feedback.
The breaking strength on the cable I used is 1,700lbs with a safe working load limit of 350lbs.
I feel that strength is adequate, figuring a max haul weight of say 200lbs, less than 60% of the safe working load giving me a 40% safety factor. My math may be slightly off but you can see my thought process....
The cable does have some easy rotation to it by nature, clearly no more than 1/4 turn... I have also made a duplicate cable with the eyes rendered perpendicular to each other in case the system tends to twist more than expected...
Thanks again for the feedback. I was afraid I would get zero feedback...
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marc801
Mar 12, 2012, 7:23 PM
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Skot433 wrote: Thanks for the input, I'm glad to be getting the feedback. The breaking strength on the cable I used is 1,700lbs with a safe working load limit of 350lbs. I feel that strength is adequate, figuring a max haul weight of say 200lbs, less than 60% of the safe working load giving me a 40% safety factor. My math may be slightly off but you can see my thought process.... The cable does have some easy rotation to it by nature, clearly no more than 1/4 turn... I have also made a duplicate cable with the eyes rendered perpendicular to each other in case the system tends to twist more than expected... Thanks again for the feedback. I was afraid I would get zero feedback...
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cobbledik
Mar 12, 2012, 7:31 PM
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Make sure to consider the extra force involved with a stuck bag. If using the 2:1 in the photo, overzealous hauling on a stuck bag can get dicey.
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Skot433
Mar 12, 2012, 7:31 PM
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This 'draw' will only be in use during the process of hauling, the haul line will of course be backed up to the anchor,
Once the haul bags reach the belay station they will be docked and this hauling system disconnected and stowed until needed for the next haul.
It is not intended for use in docking or anchoring bags to belay station.
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csproul
Mar 12, 2012, 7:32 PM
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I think I tend to agree with Marc801. That seems a little low to me. A spectra sling is rated to 22kN, much higher than your 1700 lbs. Is there a benefit to using this cable over a normal sling?
I'd be willing to bet that sling sees a lot more than 200lbs when hauling, especially if you're starting with a 200lb bag.
(This post was edited by csproul on Mar 12, 2012, 7:36 PM)
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TarHeelEMT
Mar 12, 2012, 7:46 PM
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Skot433 wrote: Thanks for the input, I'm glad to be getting the feedback. The breaking strength on the cable I used is 1,700lbs with a safe working load limit of 350lbs. I feel that strength is adequate, figuring a max haul weight of say 200lbs, less than 60% of the safe working load giving me a 40% safety factor. My math may be slightly off but you can see my thought process.... The cable does have some easy rotation to it by nature, clearly no more than 1/4 turn... I have also made a duplicate cable with the eyes rendered perpendicular to each other in case the system tends to twist more than expected... Thanks again for the feedback. I was afraid I would get zero feedback...
When you haul it, it's holding 200 lbs on the haul side and 200 lbs on the bag side. That's 400 lbs.
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Skot433
Mar 12, 2012, 8:13 PM
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I'm not using this as support for my hoisting pulley. This is simply support for the progress capture pulley, whenever the bag is in moving upward there is zero weight on this draw, the only time there are any forces on this draw is when the bag is motionless and the hauling system is being reset...
I'm not claiming to be reinventing the wheel here....
PTPP uses a frost power draw the same way I do, I simply made my own and added rope sheaths to the eyes to prevent the cable from digging into the softer aluminum of the locker.
Perhaps I will increase the size of the cable to 5/32" resulting in a 2500lbs breaking strength, or roughly 10kn... The same rating as the Frost powerdraw....
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csproul
Mar 12, 2012, 8:23 PM
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I'd definitely post this question to the people on Bigwalls.net or Supertopo, you'll probably get better responses. Also PTPP is not using a Trax, I'm pretty sure he loathes the things and refuses to use them. So his setup (Kong Block Roll, I think) would not have nearly the rotation worries that you might have with a Trax. I'm still interested though, what is the benefit over using a sling?
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ptlong2
Mar 12, 2012, 8:34 PM
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Skot433 wrote: I'm not using this as support for my hoisting pulley. This is simply support for the progress capture pulley.
If it blows while hauling 2:1 you'll get sucked up into the other pulley but at least you won't lose the bag. However you can't safely switch over to 1:1 hauling with this arrangement without some amount of re-rigging. On top of that the strength of your cable sling depends on your swages. How have you tested them?
Those little knit cozies on the ends are very cute looking.
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Skot433
Mar 12, 2012, 9:05 PM
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The benifit over using a regular sling is not having to double or triple up the sling to shorten it, it also eliminates the rubbing friction of sling in sling (when doubled or tripled) also eliminates having to inspect said sling for wear caused by shortening it, lastly it minimizes the CF factor of cramming a shortened sling onto the power point locker....
I have tested the strength of the swages by pulling apart several of these cables using a ton and a half chain come a long.. Each cable was tested until it broke, every cable tested broke in the center between the two swages, not once did the cable part in the eye, nor did a single swage slip... These results lead me to conclude that the 'draw' is equal to full breaking strength of the cable used to construct it....
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csproul
Mar 12, 2012, 9:15 PM
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Gotcha, thanks. In that case, as long as it's strong enough and rotates enough...looks good to me. I'll let you figure out what is "enough" since it would be pure theory on my part.
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TarHeelEMT
Mar 12, 2012, 9:58 PM
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Interesting. If it works, it works.
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Skot433
Mar 12, 2012, 10:13 PM
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I'll put it to the real test the first week of April... I'll post a report and some pics of it in action.
Thanks again everyone for the input and feedback.
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ptlong2
Mar 13, 2012, 12:37 AM
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Skot433 wrote: I'll put it to the real test the first week of April... I'll post a report and some pics of it in action.
It's going to work under normal conditions, you already know that. The question is whether it is a weak link and riskier than using a FROST draw or a sling. One outing hopefully won't test that.
I usually clip a loose draw to the haul line to protect against the remote possibility of hauler failure. Is there any reason you couldn't do the same?
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Skot433
Mar 13, 2012, 4:09 PM
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I would simply use a FROST power draw if I didn't have the capability to make my own...
I constructed my own using the same techniques and materials, with the small addition of 'cozies' added to each eye to prevent my draw from digging into the softer aluminum of the power point locker.
I have increased the size of the cable used to 5/32",
I'm using 7x19 stainless steel cable for increased rotational flexibility,
The cable has a rated breaking strength of 2,700lbs,
Well over the the 22kn of standard slings,
I'll also be using two of my draws for redundancy...
Effectively doubleing the breaking strength....
My power point locker will blow before this ever does
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csproul
Mar 13, 2012, 4:18 PM
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Skot433 wrote: I would simply use a FROST power draw if I didn't have the capability to make my own... I constructed my own using the same techniques and materials, with the small addition of 'cozies' added to each eye to prevent my draw from digging into the softer aluminum of the power point locker. I have increased the size of the cable used to 5/32", I'm using 7x19 stainless steel cable for increased rotational flexibility, The cable has a rated breaking strength of 2,700lbs,
Well over the the 22kn of standard slings, I'll also be using two of my draws for redundancy... Effectively doubleing the breaking strength.... My power point locker will blow before this ever does
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Skot433
Mar 13, 2012, 4:33 PM
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Sorry.... It should read like this...
I have increased the size of the cable used to 5/32",
I'm using 7x19 stainless steel cable for increased rotational flexibility,
The cable has a rated breaking strength of 2,700lbs,
I'll also be using two of my draws for redundancy...
Effectively doubleing the breaking strength,
Well over the the 22kn of standard slings....
My power point locker will blow before this ever does
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ptlong2
Mar 13, 2012, 8:42 PM
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Skot433 wrote: I have increased the size of the cable used to 5/32", I'm using 7x19 stainless steel cable for increased rotational flexibility, The cable has a rated breaking strength of 2,700lbs, I'll also be using two of my draws for redundancy... Effectively doubleing the breaking strength, Well over the the 22kn of standard slings....
Now it sounds like overkill!
If it were me I'd just spend the $5 on a FROST draw or a 6" sling, but homemade gear is cool.
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Skot433
Mar 13, 2012, 10:15 PM
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Total material cost: $0.85 each
Time to construct: 10 min each
Über cool factor: PRICELESS.
HahhHa.
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dan2see
Mar 14, 2012, 4:45 AM
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Skot433 wrote: Total material cost: $0.85 each Time to construct: 10 min each Über cool factor: PRICELESS. HahhHa.
Go for it, Skotty!
Cool trumps!
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