Chaplain242
Branched out member
Have used the Kong, but how did the Simond perform?
rope stretch when falling on MRS vs. SRS
- Thread starter climbstihl
- Start date
Have used the Kong, but how did the Simond perform?
I think this has been answered before. Jan_ almost had it but goofed. Pretend each rope is a spring, linear or not for now doesn't matter. SRT lets "Basal" anchor at your position. DRT of course you're anchored at your position. Nastiness = stiffness of system i.e. drop onto a chain and the instant force spike and instant stop = crunch. Have an undersized 1/4" line and it'll stretch like spaghetti and stop as soft as ever if it doesn't break. So our line is somewhere in the middle. Take your weight, be it static or weight plus inertia, put it in the SRT system. You stretch it over (length up+ length down) with weight W. Take your DRT system, you load the rope with 1/2W and have two ropes in parallel holding you up. So each rope stretches half as much PER LENGTH as the SRT and the length holding you is 1/2 as long as the SRT length. So you stretch it distance wise 1/4 as far as the SRT system. The SRT up leg and down rope stretch distances add to each other. So its 4x harsher. And you can de-harshen SRT more by being half way up the tree and a basal anchor so its more than 2x SRT rope in line, maybe it works out to 6x harsher like that. And you can de-harshen it even more by routing your multi tip through some springy branches. And SRT de-harshens even more because when the basal leg does it's stretch it skids over the tip(s) and dissipates some fall energy. Pretty damning or enlightening view of falling between SRT and DRT depending on which one you do.
Our ropes don't have much non-linearity at low loads to really affect the result especially 4x or 6x system rope spring constant.
Only SRT "fall" I took was a stupid twig stub I couldn't miss with my rope and as I went up it snapped. I had multi tip, I dropped a couple feet and landed on my Haas and Pantin, my hands bonked my forehead during the instant the rope was slack. I stopped for a second and kept going, no biggie.
Our ropes don't have much non-linearity at low loads to really affect the result especially 4x or 6x system rope spring constant.
Only SRT "fall" I took was a stupid twig stub I couldn't miss with my rope and as I went up it snapped. I had multi tip, I dropped a couple feet and landed on my Haas and Pantin, my hands bonked my forehead during the instant the rope was slack. I stopped for a second and kept going, no biggie.
- Location
- Retired in Minneapolis
Early in the life if this thread I trotted down the ‘rope stretch’ rabbit hole One side trip took me to a discussion in the construction crane world. Arbos think of wire rope as non stretch. The discussions I found were just the same as we have but many orders of magnitude smaller
Same tune, different key
Same tune, different key
- Location
- Retired in Minneapolis
You can read more on Gary Storrick’s website
*useless info*
Participating member
- Location
- usa
In parallel view, one of my counterintuitive benchmarks is,
Dynamic load hit into single line gives more elastic response than same everything but into pulley on load.
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Also another standard example is ropes of same material and manufactured that are served with diameter/strength as only difference. Thus model: when load impedes more on strength , get more elastic response; as consistent theme.
.
Just as in electronics,
Where parallel resisters give half resistance
>>and doubles in series.
Parallel legs elastic response is reduced
>>and series elastic lengths increases elastic response.
In usage of same amount of rope or resistors to loading forces.
(In other ways view elasticity like system stabilizing capacitor, cleaning peaks and drops more)
.
Climbing is just another example with more sensitive load of 1 or 2 support leg dampening response.
Any relief of stretch or slip allows to dissipate force / friction conversion, along with force dampening of wood support and branches made to move yet hold etc.
Each like steam relief valve allowing relief of peak forces to reduce internal pressures thru system .
Dynamic load hit into single line gives more elastic response than same everything but into pulley on load.
.
Also another standard example is ropes of same material and manufactured that are served with diameter/strength as only difference. Thus model: when load impedes more on strength , get more elastic response; as consistent theme.
.
Just as in electronics,
Where parallel resisters give half resistance
>>and doubles in series.
Parallel legs elastic response is reduced
>>and series elastic lengths increases elastic response.
In usage of same amount of rope or resistors to loading forces.
(In other ways view elasticity like system stabilizing capacitor, cleaning peaks and drops more)
.
Climbing is just another example with more sensitive load of 1 or 2 support leg dampening response.
Any relief of stretch or slip allows to dissipate force / friction conversion, along with force dampening of wood support and branches made to move yet hold etc.
Each like steam relief valve allowing relief of peak forces to reduce internal pressures thru system .
Chaplain242
Branched out member
Was hoping for an ‘at home’ report from an arborist that has used one mainly because of the type rope used...
The Simond plate is from a via ferrata set, one of the last ones of the rethreadable type that were for sale, everyone has gone to the sewn ripper ones. Works as good as the Kisa, but was bulkier to store with two sections of rope. Finding the right size rope, or cord is a challenge, it has to slide through on a fall but not when normal weight is on it during work. The first device I tried was PMI‘s PED, normally used for building escape. Again, worked great, it’s low break strength didn’t seem like it mattered, as the cord should slide through with slightly more than my body weight. It’s back to its original use, going to see how useable it would be for a hands free descent.
