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majid_sabet
Jul 26, 2007, 7:17 AM
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Allright slackers, now it's your time to take your slacking test.
So, what kind of mechanical advantage we got here( if any) ?
[URL=http://imageshack.us]
(This post was edited by majid_sabet on Jul 26, 2007, 7:21 AM)
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irregularpanda
Jul 26, 2007, 8:42 AM
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1- do you even slackline....?
2-oh wait, it's obvious that you don't from this picture.
3- nevermind, it's useless to respond to dumb posts when I'm drunk.
4- slackline on a rig like this, it'll be funny. I promise.
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slacklinejoe
Jul 26, 2007, 3:49 PM
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A simplified look at this fools errand:
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areyoumydude
Jul 26, 2007, 3:58 PM
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No, carrying a big rock while slacking does not give you a mechanical advantage.
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quadfire
Jul 26, 2007, 4:00 PM
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areyoumydude wrote: No, carrying a big rock while slacking does not give you a mechanical advantage.
Majid just becasue you got banned from the other forums doesn't mean you can wander in here
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kr0g3r
Jul 27, 2007, 8:41 PM
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thats a big tire, not a rock...
and ummm who can slack while holding a tire over their head?
i think i'll try it this weekend on my trip. i'll bring back pics for you if it happens.
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knieveltech
Jul 27, 2007, 8:56 PM
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majid_sabet wrote: Allright slackers, now it's your time to take your slacking test. So, what kind of mechanical advantage we got here( if any) ? [URL=http://imageshack.us][IMG]http://img444.imageshack.us/img444/9692/untitled1ix0.jpg[/IMG]
Finally! After all the anchor pics of mine you crapped up with arrows (copyright violation btw, my photos, my server, NOT public domain), it's my turn. That rig is a total clusterfuck! Extraneous hardware, unnecessary third tree, etc. But the worst offense: no army man in the diagram.
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shockabuku
Jul 27, 2007, 9:02 PM
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majid_sabet wrote: Allright slackers, now it's your time to take your slacking test. So, what kind of mechanical advantage we got here( if any) ?
Slackers:
In Majid's defense this is completely in keeping with his normal behavior. He doesn't climb either but continues with these "discussion prompting" items in the climbing forums as well.
Take note to either upload the killfile that JT512 has produced presumably in Majid's honor; make sure Majid's posts are always quoted so they aren't lost (for posterity's sake); or otherwise ignore, insult, or argue with Majid.
I'll go away now.
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summerprophet
Jul 27, 2007, 9:23 PM
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Ummm, hopefully no mechanical advantage at all.
That would imply that you are moving the anchors.
(oh and a prussic on a slackline is a bad idea, your "sliding V" anchor wont work very well slacking, a tree growing directly out of a boulder is a pretty bad idea, and truck tires make for shitty hula hoops.)
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jdouble
Jul 27, 2007, 10:38 PM
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WHAT??????? Not a single red or green arrow in that picture. Yes, a car tire was included, but still I am going to have to call it out.
We have a Majid copy cat troller on our hands.
It was only a matter of time.
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shockabuku
Jul 28, 2007, 1:41 AM
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summerprophet wrote: Ummm, hopefully no mechanical advantage at all. That would imply that you are moving the anchors.
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coldclimb
Aug 6, 2007, 9:43 PM
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I think it looks like 2:1, but with a whole lot of unnecessary friction. 
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slacklinejoe
Aug 6, 2007, 10:12 PM
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I guess I shouldn't have been so subtle as it seems no one got it. What has been posted is an example of a fool's tackle. Instead of a 2:1, it's a 1:2, i.e. you have to pull 200 lbs 1 foot to lift the 100 lb weight 2 feet.
With friction knocking it down to "why the hell don't I just lift the damn thing by hand".
The fools tackle reduces the MA however has the advantage of increasing the distance lifted at a faster rate. Usually completely useless but if a system has a high amount of torque it can be used to speed up lift rates in certain systems - none of which can I envision a use in climbing or slacking.
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slacklinejoe
Aug 7, 2007, 8:19 PM
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What is shown last is what is commonly referred to as a primitive system, i.e. webbing drapped over carabiners to form a primitive block and tackle. It does not have pulleys or rollers however as long as the end you pull on is tucked inside on each turn it reduces the friction from what would be unusable to somewhat helpful since the top web is sliding over webbing that while moving not at the same pace, is moving in the direction it is going. While that helps reduce friction somewhat the overall result is actually a 1.3:1 instead of the theoretical 3:1 MA when you account for firction. My numbers come from a Search and Rescue study which I have quoted several times on this site that evaluates the effect of friction within different pulley systems. Most people seem content to throw around numbers like 4:1, 9:1 and such and never consider system efficency, which radically reduces theoretical MA down significantly.
Since theoretical MA for rope and webbing is the same I can't exactly answer your last question. Real MA however will vary depending on a lot of things: slickness of webbing, texture of carabiner, bend radius of carabiner and even down to humidity and dirt on web.
There are some slackline systems which put rollers within the system such as the Slack Jack. Unfortunately I do not have the efficency numbers for products such as it. In that example they advertise as a 6:1 however when I built a surpisingly similar device and tested it 4 years ago it ended up closer to an effective 2.5:1. Again, though lots of things would vary the actual MA even if the theoretical MA was the same.
Pulleys are also used, and often offer significantly more efficent rigs than primitive or small roller systems as long as they have large sheaves. Unfortunately these are often costly, cumbersome and require removal afte rigging (softpointing) as they add tons of weight to the setup making for lots of counterbalancing.
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majid_sabet
Aug 7, 2007, 8:41 PM
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Joe I know the biner system, I am talking about the new toy on the image above the biner photo.
What is that thing ?
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