# SRT setup with Unicender



## the Aerialist (Jan 21, 2011)

I've been putting together an SRT setup based around a Unicender. The reason I chose the Unicender was so that I could use the system for working the tree once I get up there, and can also descend without equipment change. Not that I'll be giving up on my Lockjack and DRT, but will try to also incorporate SRT into my climbing routine. 








The aluminum mallion at the top connects to my chest harness to advance the Unicender as I stand on the rope with my foot ascenders.

Note the pulley I integrated into the Unicender for working to advance my CMI foot ascender and CMI rope grab and footloop (not shown in photo).


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## treefaller25 (Apr 23, 2011)

Aerial Arborist said:


> I've been putting together an SRT setup based around a Unicender. The reason I chose the Unicender was so that I could use the system for working the tree once I get up there, and can also descend without equipment change. Not that I'll be giving up on my Lockjack and DRT, but will try to also incorporate SRT into my climbing routine.
> 
> 
> 
> ...


 I am looking at the unicender now for myself and understand the function of it,I am curious about the rest of your set up.Is it possible for some more pictures?


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## rmihalek (Apr 23, 2011)

Aerial Arborist said:


> I've been putting together an SRT setup based around a Unicender. The reason I chose the Unicender was so that I could use the system for working the tree once I get up there, and can also descend without equipment change. Not that I'll be giving up on my Lockjack and DRT, but will try to also incorporate SRT into my climbing routine.
> 
> The aluminum mallion at the top connects to my chest harness to advance the Unicender as I stand on the rope with my foot ascenders.
> 
> Note the pulley I integrated into the Unicender for working to advance my CMI foot ascender and CMI rope grab and footloop (not shown in photo).


 
I'd definitely like to see the complete set-up with the connection to the foot ascender.


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## imagineero (Apr 24, 2011)

it's not a bad setup, but these types of ascension systems need the fine details to be spot on or they become very cumbersome to work with. If you're going to use static cord between the pulley and the leg loop/ascender then the length is critical or the system becomes very inefficient. You can make the length tunable by using a prussik in there, or a whoopy sling. You've got to be careful that you dont end up with too many snags for stubs to catch on.

My preference would be to experiment a bit with different thicknesses of bungy cord there. I think you'll end up with something around 8~10mm bungy to get the right compromise between stiffness and stretch. The bungy there will give you more freedom to make different step heights, and will probably stow better when you remove the ascension part and go on to descending. For the same reason I would probably try a bungy link between the unicender and the chest harness, otherwise you are on a limited tether and may find yourself constantly undoing that very slow 'quicklink'. Since the attachment between chest harness and unicender isn't critical, I'd be inclined to use a very small non screwgate karabiner there - it doesnt carry any load. 

The key to the success or failure is how quickly you can transition from ascension to descension in this type of system. If it takes time then you will waste a lot of time in the tree, even if you are quite an efficient forward thinking climber and plan your route out carefully. These systems seem to do pretty good on removals where you are working from the ground up (but then why on rope? you're going to spike it) but go less well on pure rope work like deadwooding and trims where you are constantly switching between up and down, working the canopy all over the place. The losses inherent to the double rope system seem to win out over SRT because of the seamless transitions between up/down until you start talking very tall trees.

I've been experimenting lately with a 2:1 system using a ratcheting pulley at the top. I shot my TIP with a bigshot, then haul the pulley/rope up with a line that I tie off at the base or wherever. This gives me the advantage that I can rig a gri gri at the base to be lowered off in the event of an emergency. The pulley ratchets, so its very efficient going up and you don't have the losses inherent in natural crotching with friction at the top. I use a shunt with a bit of 2mm cord prussik to slack tend on my tie in side. It works surprisingly well. When descending, the pulley locks and has grip faces that give a claimed 10:1 mechanical advantage. It's probably not that high, more like maybe 5:1, but what this means is that I need very little effort for a controlled descent, so shunt style devices which really have no variable friction only an 'on/off' work quite fine because it takes hardly any effort to control the lower off. This system would work equally as well with the range of prussik knots. I've only used this system a few times in the last month because most of my work is removals.

I've been experimenting with the same pulley as a lowering pulley due to the mechanical advantage it gives guys on the ground. It has a couple of downsides. Firstly it takes 1/2" rope max. That's not really so bad I guess. The second is the 700lb conservative safe working load, breaking strength is 2800lbs. 700lbs SWL means realistically that you can only lower a branch weighing about 150~200lbs max because the load is double at the pulley, and you get some dynamic forces in there too. If you are dropping something any sort of distance then you might as well make that figure 100lbs. This is way way less than most of my other pulleys that are rated at closer to 20,000lbs and take rope up to an inch. It might work out well for smaller jobs where it's just one groundy and me, taking small branches hanging over a roof for example. I dont feel the safety margin is high enough.

Shaun


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## Saw Dust Smoken (May 16, 2011)

*ascending*

Unicender to tnp fairly simple. Any movement on horizontal angle without weight of rope. No rope self tailing.
What system \ climb style to avoid this probem? Any pictures of system you use?


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## Saw Dust Smoken (May 17, 2011)

*any users*

Maybe more hype than real use? Ive messed with this unicender several months. Their are other mechanical devices easier to use! Maybe Im missing something here? But again no pictures?


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## Saw Dust Smoken (May 18, 2011)

*more info*

Dave in Montana talks about the uni. Find some more info on other tree forums. Use the search department. Happy climbing!


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## the Aerialist (May 22, 2011)

*SRT put aside, back to DRT for actual work ...*



rmihalek said:


> I'd definitely like to see the complete set-up with the connection to the foot ascender.



The Unicender SRT project was shelved once work started coming in. One of my climbers likes the Unicender (DRT) and has used it a lot, but I went back to the LockJack, and this week bought a SpiderJack and like that even more.


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