What are the dangers of using SRT?

[tree-fancier123]

Surely Ddrt and srt load the anchor point the same amount? As in both instances the load is secured at each side of the anchor therefore subjecting the anchor to double the load this only being reduced by the angles each side of the rope intersects the anchor. Similar to when deciding where to place a rigging anchor? Or am I missing something?

 

Be gentle folks I can be a bit thick at times.

 

if its a top anchor srt then only a single leg has weight on it, base anchor same forces as ddrt yes

[Old Mill Tree Care]

if its a top anchor srt then only a single leg has weight on it, base anchor same forces as ddrt yes

 

 

That's wrong.

Top anchor applies the same load wether it's SRT or DDRT.

Base anchor for any system doubles that load, (prior to the installation of a redirect).

[tree-fancier123]

That's wrong.

Top anchor applies the same load wether it's SRT or DDRT.

Base anchor for any system doubles that load, (prior to the installation of a redirect).

 

ok good - I stand corrected, going to have to research this a bit now, thought I had my head around the physics of it, obviously not

[Old Mill Tree Care]

ok good - I stand corrected, going to have to research this a bit now, thought I had my head around the physics of it, obviously not

 

 

Ok. The load is doubled while you are base anchored and ascending on the opposite side of the stem. Therefore the anchored side of the rope is vertical and your side of the rope is vertical.

When you arrive at the top (or near) and move out through the crown, the load alters but you then have to consider some lateral forces as well as the compression force.

Multiple redirects help to solve this problem but one must always consider the forces on every redirect.

[Marc]

ok good - I stand corrected, going to have to research this a bit now, thought I had my head around the physics of it, obviously not

 

Old Mill covers the basics principals of it, it is as simple as a base anchor doubles the load. There are just so many variables and other points to consider, one being how the force is applied, whilst ascending you are compressing which is more favourable, as you move out you begin to apply lateral force only the force is reduced if your still base anchored due to deflection so you no longer apply 2 times the load.

 

If installing from the ground you can ensure your line is deflected this will also spread/share the loads through deflection.

 

On Friday I climbed a very drawn leaning Oak I kept my base anchor to work off base tying to a tree further back reducing the load on my anchor and had my rope taking half wraps around limbs ensuring friction/tension as when you move and let slack into your system it can sag which can be a pain when working on a base tie when wanting to weight your system again as the slack can drop down to your base tie without you the climber realising.

 

Most of the time I top tie, not to reduce forces just to prevent all that unwanted sag and movement and so as to not have support/load bearing leg of my line on another part of the crown.

 

I climb very simple with few gadgets, do not use fancy redirects, I base tie with a running bowline (or snake anchor) then top tie for work and use a hitch with rope wrench nothing else.

 

It's that simple, much like a Prussik and cambium saver.

Edited November 6, 2016 by Marc

[johnanderton]

Richard Mumford does a good video on forces/angles YouTube or treebuzz .. Some actual forces put on limbs are not wot you'd expect but in real word srt work climbing being able to make multiple anchors in skinny trees is where srt shines .... Yes it's nice to keep simple set ups but re- directs makes for perfect work positions & that's wot we are looking for )

[Marc]

Richard Mumford does a good video on forces/angles YouTube or treebuzz .. Some actual forces put on limbs are not wot you'd expect but in real word srt work climbing being able to make multiple anchors in skinny trees is where srt shines .... Yes it's nice to keep simple set ups but re- directs makes for perfect work positions & that's wot we are looking for )

 

John I do us redirects, just not often and when I do they are simple natural redirects, choked sling with carabiner or cow hitch with a bight.

Having climbed with conventional doubled rope system and a hitch climber for most of my climbing I never struggled for good positioning and used redirects often here to, the good thing with DdRT is the ease of popping out your friction saver and moving it, a HitchClimber also shines with the ability to triangulate or redirect the whole system to the other side of the tree without having to climb up and over.

 

Both systems have merit, and both can be simple or as complex as you like.

 

I personally have quite a collection of gear but have found the longer I climb the less I need and most is now redundant and sits under a workbench gathering dust.

[tree-fancier123]

found this about forces on anchor points - i had to sign up and log in to treebuzz to be able to view the slide from Petzl

Petzl preliminary research | The BuzzBoard

'when climbing SRT od Ddrt system the force applied to the top anchor is approximately 50% greater than the weight of the climber

 

When climbing on a SRT with a base anchor, the force applied to the Primary suspension point is approximatly 50% greater than the force applied to the top anchor when climbing on an srt or ddrt system

 

falling on an SRT with base anchor will genertate a longer free fall and deceleration compared to falling on a srt and Ddrt with top anchor.

 

falling on a Ddrt system can generate 60% to 70%higher forces on a top anchor point (and on the climbing system and climber) compared to the forces generated on a primary suspension point when falling on a SRT with a base anchor.'

 

I wondered if the force on a top anchor when ascending ddrt is different when using natural crotch compared to a pulley saver, then decided life is too short to get bogged down with the details

[Marc]

So yes Tree Fancier it appears a base tied SRT puts substantially less force than a top tier DdRT, along the lines of what I posted there are lots of variables including more rope to absorb energy also more favourable loading.

[tree-fancier123]

the Petzl research seems to say base tied puts less force on the anchor point in the event of a fall (probably coz of more rope to bounce into), but in normal ascent base tied does load the anchor point more than canopy anchor, the figures they give for percentages I don't doubt will be adjusted over coming years when they get out there again with the load cells and other gadgets