Curve ball for men of maths

[treedave]

I've had a request from a friend to advise him on the suitability of a proposed zip wire set up. I've given him the benefit of my experience, but it's not enough - he wants numbers. Namely, peak loads on anchor points for a known load (say 85 kg) at the mid point of a 200 metre zip wire.

I've been able to find ways to calculate a force for the load and the turning moment (Newton metres) at the anchor. But what force will the anchor experience when the load is at the mid point of the wire?.

 

All help / pointers / answers will be gratefully received,

Yours from Geekland,

[Mr Ed]

We need Treespydie!

[bob]

this may come with the rigging research due out soon august i think but not sure

[Tom D]

I am no mathmatician but i did cs41 last year and i remember chatting with the instructor who explained that he and a friend had done exactly this calculation. The forces are massive, quite how massive or how to measure them i dont know. I could ask if you dont get any luck on here.

[Dean Lofthouse]

It's same priciple as a crowbar I would imagine. The higher up the tree the longer the crowbar/leverage forces at the bottom of the tree must be huge, but I would imagine no more than the forces of the wind blowing the huge Canopy/sail.

 

Just set the thing up, find the lardyarsest person you can find and pay him twenty quid to have a go.

 

I'll have a do, that's part of the thrill, is the fear of the first go whther it will hold or not

[treedave]

(1)It's same priciple as a crowbar I would imagine. The higher up the tree the longer the crowbar/leverage forces at the bottom of the tree must be huge, but I would imagine no more than the forces of the wind blowing the huge Canopy/sail.

 

(2)Just set the thing up, find the lardyarsest person you can find and pay him twenty quid to have a go.

 

(3)I'll have a do, that's part of the thrill, is the fear of the first go whther it will hold or not

 

(1)You can get round the height = lever issue by running the line via pulleys (imagine pulleys at the top of the towers in the image below - yes, I know its a bridge!)

The line is secured to ground anchors at either end, the up slope at the lower end acts as a brake for the flying person.

 

(2)Yep, done that, and to add insult to injury they slammed the doors on his feet in an attempt to get the ambulance away quickly!.

 

(3)Dean, I can reserve you the first test spot if it goes ahead - you'll just have to carry 4 bags of sand (in the interests of science you understand:001_tongue:).

[Dean Lofthouse]

Would be my pleasure Dave

[A_lopa]

We need Treespydie!

 

What the hell are you on about Ed??

[Bundle 2]

Treespydr is an arborist/climber from the usa who appears on the Treebuzz web based forum.... He is known to go "off " on one now and again as it pertains to the mathematical principles and calculation dynamics of tree work scenarios...It can be a little worrying sometimes I think but mostly its just funny!!!!

[Quickthorn]

I'll have a go...

 

It will depend on how far the rope deflects once the load is on, but if the rope deflects an angle A to the horizontal under the weight of the load L, the tension in the rope will be L / (2 x sinA)