Pendulum rigging

Some interesting rigging work from Graeme McMahon.

http://sherbrooketreeservice.com/wp-content/uploads/opposing-pendulums/opposing-pendulums-arborage.pdf

Fascinating, he really is in a different league.

Clever stuff.

It's the precision that impresses me

It must have been a bit like cutting on a crane job. The lump would idealy stay where it was initialy. I think you could have used a Gcrs instead of the chain block winch but having the dynometer in the system looks fantastic.

I think most companys would strugle to accurately explain there rigging in terms of the forces involved. Good article.

Engineer+mathematician+arborist = legend rigging!

cool bit of work, makes the rest of us look like ameteurs!

I think you could have used a Gcrs instead of the chain block winch but having the dynometer in the system looks fantastic.

Out of interest, how would that work?

Good question, Angus....Now that you bring that up, I see that using the Tirfor's attached to the main line via a prussic, and the dyno between the tirfor and its anchor is a logical method to determine the amount of line tension to apply.

It was that article where I first heard of Graeme (well, the version of it that ran in a US arb publication anyhow.) Back then, I thought he used two Hobbs as the lowering devices. At that time, it was before Greg had invented the GRCS.

I was and still am way impressed with that job, and how Graeme employed such technically advanced rigging, down to the specially made sheaves for the blocks, special rope order, the calculator in the tree for the trip function calc.....and on and on!

It was a thrill to meet Graeme not long after, at the 2002 ISA conference. Plus, he came out to my jobsite, strapped some of our gaffs on over his tennie runners, asked what the heck the toy 335 Husky was that I handed him to brush out a 130 foot doug fir (well down to 90 feet, which we craned for log sales later) then showed us his 20 minute video in the customer's house, prior to driving off to the airport for the trip back home.

clever stuff indeed. nice one as usual

Out of interest, how would that work?

Use the Gcrs as a winch to apply the tension to the line.