MA vs VR

[Leroy]

I

 

[DSMc]

Your not going to like the answers so why keep asking the same question?

 

[DSMc]

Are they climbing forums?

 

[Tuebor]

The MA for a hauler on the ground is 2:1.

The MA for the climber is 3:1.

The video John posted on the other thread explains it perfectly. It's all about the frame of reference. When the climber is pulling the load, the reference point is the climber, and the top pulley becomes a moving pulley in relation to him.

 

[DSMc]

And the VR changes from a 2:1 to a 3:1 also.

 

[Tuebor]

A stranger on another forum is hardly any more credible than any of the strangers on this forum.

Meanwhile...

Tie a alpine butterfly in your tail and clip it to your harness. You are now suspended by three legs of the rope, each supporting 1/3 of your weight: 1/3 on the leg from your canopy anchor to your BDB, 1/3 on the leg from the BDB to the revolver hanging from your ascender, and 1/3 on the leg from the revolver to the AB at your harness. Using my previous example of 180 lbs, each leg is supporting 60 lbs. Grab your tail and unclip the AB. Now your arms are holding that 60 lbs...the 60 lbs that it would take to hoist your 180 lb body. MA = 3:1

 

[DSMc]

Or, since you brought it up, VR is the distance traveled be a machine. In our case a climber. A 50' tree will take 100' of line to reach the ground in a DdRT system. Set an SRT system with a haul back and you will need 150' to reach the ground.

 

[Tuebor]

In this video, I set a canopy anchor and a Futura/Revolver combo at the tree. Using my Runner, I walked out 15' from the Revolver. I marked the tail next to the Runner (the spot where I would start pulling when I haul myself back) with a pink string. Then I start pulling the tail to haul myself (the Runner) all the way back to the top. I had to pull 45' of rope to get me 15' back to the "top".

 

[JeffGu]

Richard Delaney explains exactly what you are asking in THIS video.
Richard Mumford explains it in THIS video.

In the second video, Richard actually uses three digital scales to show that the mechanical advantage is indeed 3:1 for the climber (the weight divides by three instead of two).

 

[Tuebor]

I'm sorry, but the the people replying on other forums are incorrect.

 

[Tuebor]

Yes, the proof that DdRT is a 2:1 MA.

Now add a pulley.

Sent from my SM-N920T using Tapatalk

 

[Tuebor]

Yes, Mike I am. Lol, I could never have come up with the answer from scratch so I have to take what's claimed by the industry in general and work babkwards to see if the numbers work out to my satisfaction. Cudos to you for questioning this concept and not blindly accepting it!

Sent from my SM-N920T using Tapatalk

 

[JeffGu]

Whew! I guess I can call off the intervention!

 

[Richard Mumford-yoyoman]

http://physicshelpforum.com/general-physics/12183-mechanical-advantage-question.html

I took a quick look at the link...
"Sorry, but I do not understand what you mean by, "if the I were the load, tied into this system, ..." ?"
Maybe "being" an engineer does not give the, perspective, to understand the question. Maybe why most of the answers out there were irreverent.