Rigging Research Part Deux

[Matt Follett]

Hey Folks,

Another article out this month in Arb News... this time looking at the effects of mass/aerodynamic damping in a rigging situation!

Much of what we know about damping in the crown comes from wind/tree interaction research, and although much of the work has used a mechanical input such as a "pluck test" pull and release, there has not been a lot of work looking at specifically rigging.

So this is just a start!

Here's a link to the other thread here, with some of the data collection methods discussed.

https://www.treebuzz.com/forum/threads/rigging-research-results.46427/

We used the robot groundie again and strain gauges and accelerometers and tension load cells in the rope... and got cool data!

Basically we worked our way up a live ash tree, dropping a pseudo top, recording motion, then removing a limb, and do it again!

Here's the poor subject tree.



This time due to the long slender nature of the "top" instead of the plywood hinge to line up the piece, I made up this mid-evil "piece chucker" to align the top and control its flight path.



Poor tree... but hey, science right?



and some raw data...

Top graph is the strain in the stem, bottom is the load in the porta wrap.


And of course... the relevant analysis.


Soooo!!!

We see a nearly 35% reduction in stem strain through leaving those 2 small upper limbs!!! And 20% leaving one small limb that was less then 1/3rd the diameter of the "top"!!!

Remember that % number is this case specific... but this really points to leaving a few limbs on the stem below you on a negative rig.

Check out the article if you have access. and I'll be happy to chat shop here when I can!

Climb safe!


Matt

 

[theatertech87]

Hey Folks,

Another article out this month in Arb News... this time looking at the effects of mass/aerodynamic damping in a rigging situation!

Much of what we know about damping in the crown comes from wind/tree interaction research, and although much of the work has used a mechanical input such as a "pluck test" pull and release, there has not been a lot of work looking at specifically rigging.

So this is just a start!

We used the robot groundie again and strain gauges and accelerometers and tension load cells in the rope... and got cool data!

Basically we worked our way up a live ash tree, dropping a pseudo top, recording motion, then removing a limb, and do it again!

Here's the poor subject tree.

View attachment 82425

This time due to the long slender nature of the "top" instead of the plywood hinge to line up the piece, I made up this mid-evil "piece chucker" to align the top and control its flight path.

View attachment 82426

Poor tree... but hey, science right?

View attachment 82427

and some raw data...

Top graph is the strain in the stem, bottom is the load in the porta wrap.

View attachment 82428
And of course... the relevant analysis.

View attachment 82429
Soooo!!!

We see a nearly 35% reduction in stem strain through leaving those 2 small upper limbs!!! And 20% leaving one small limb that was less then 1/3rd the diameter of the "top"!!!

Remember that % number is this case specific... but this really points to leaving a few limbs on the stem below you on a negative rig.

Check out the article if you have access. and I'll be happy to chat shop here when I can!

Climb safe!


Matt

Did you mean to say (this really points to leaving a few limbs "below" you). Or did you mean above?

I see the benefits of the energy dampening of the branches but I only see headache and hassle of brush getting hung up if you leave them below your rigging point

 

[Jonny]

@Matt Follett can you link the article or is it a paid subscription/ members only thing? I found stuff from part 1 of your study.

Thanks for sharing your work.
Can totally feel the difference a little brush makes when standing on the spar, but cool to see it in recordable evidence.

 

[Matt Follett]

Did you mean to say (this really points to leaving a few limbs "below" you). Or did you mean above?

I see the benefits of the energy dampening of the branches but I only see headache and hassle of brush getting hung up if you leave them below your rigging point

Hi,

I do mean below.

I have been practising this for years... and teaching it, and have some ardent followers Finally we have some data to back it up. With a bit practice it's easy to pick a few limbs to leave. It's really effective on those tall slender stems, when you are way up, and that's when the big bending moments happen too, so it's doubly effective.

This is me circa 2007... I have used the video version of this in class to demonstrate. The groundie locked it up and I'm willing to bet I would have been chucked off my spikes if those limbs were not below and behind me. As it was, I just laughed it off, smiled, and kept going.



And here's a photo montage from a colleague who has this down to an art, both as a climber and a bucket/spider operator. ( I used this montage in the the Arb News article, Thanks Jimmy!)

 

[Matt Follett]

@Matt Follett can you link the article or is it a paid subscription/ members only thing? I found stuff from part 1 of your study.

Thanks for sharing your work.
Can totally feel the difference a little brush makes when standing on the spar, but cool to see it in recordable evidence.

Hi Jonny,

The current year arb news is subscription based, part of an ISA membership (past years available free online). But I'm happy to share the relative info here and wherever.

International Society of Arboriculture > Publications > Arborist News

www.isa-arbor.com

I'll slowly start to fill the gaps.

 

[theatertech87]

Hi,

I do mean below.

I have been practising this for years... and teaching it, and have some ardent followers Finally we have some data to back it up. With a bit practice it's easy to pick a few limbs to leave. It's really effective on those tall slender stems, when you are way up, and that's when the big bending moments happen too, so it's doubly effective.

This is me circa 2007... I have used the video version of this in class to demonstrate. The groundie locked it up and I'm willing to bet I would have been chucked off my spikes if those limbs were not below and behind me. As it was, I just laughed it off, smiled, and kept going.

View attachment 82433

And here's a photo montage from a colleague who has this down to an art, both as a climber and a bucket/spider operator. ( I used this montage in the the Arb News article, Thanks Jimmy!)

View attachment 82434


View attachment 82435

View attachment 82437

That makes sense and not at all what I was envisioning by "below"

I do that too, but mainly to dissipate the energy from a top swing, so it can't travel just the stem if the tree and hit a house or something similar.

 

[Bart_]

Matt, a cool auxiliary part to present would be climber video of the jiggle behaviour of a leader(s) or the main stem as the last limbs/dampers disappear. I turned a Linden into a tuning fork just the other day as I took off the last branches. It was noticeable enough to grab my attention when I wasn't consciously thinking about it.