shock absorber for rigging?

[MOG]

thinking about this the other day.

 

so when you rigging knots set and dress for snatching etc. how about between the pulley and log Marlin spike or two?

 

i know this would extent the lenght but would bite and load and bite and load. what are your thoughts? been yet to try it out was just a idea and i dont do rigging much anymore but miss the thinking of it.

 

cheers mog

[Ben Saxton]

Must be hard just doing crane work

[Rupe]

Might they not release and over tighten, never to come undone again?

 

I think the bollard/skilled groundie are the best/only shock absorber needed, plus the increase in length (as you mention) might mess up the groundies control.

[Pete Mctree]

I can understand your train of thought.

I know some people use "screamers" & I can see there benefits in a tight spot where a load cannot run & deceleration is required

 

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Miscellaneous Tree Rigging Slings

[MOG]

yeah i know Ben but thats only in Winter, in summer i dont wear chainsaw pants and just prune trees. well today i smashed out a huge beech emergency job over the street with police stopping traffic and forester clearing up. ;p

 

anyways yeah i guess similar to those's screamers but free and you would still have the original strength of the rope but less force? i think if you dont tighten the Marlin spike too much by had it should pop out no worries ay. only one way too find you, you riggers should give it a bash and let me know what happens, not much i guess but less force. i try and work some out too.

[Rupe]

I'll give it a go if I get a chance, but if you don't tighten the spike much then it will open easily and achieve nothing (maybe make the shock loading worse) and if you over tighten it might not open at all.

 

Yes, thinking about it, dropping an extra few inches of line into the drop might increase the shock, or maybe it will step the shock out into separate sections. Easier to manage it in one go I think.

 

My mind has to envisage stuff!

 

 

 

 

 

 

So, I've now figured that shock loading will be the same but separated into"steps" the number of steps and if you exceed the force for each knot then you move onto the next step, depending on the number of spikes you put in. So as the shock increases the next spike un does from the rope and the rope goes slack, as it takes up the slack the next load of shock is applied.

 

I don't think this will absorb any shock, all it will do is delay it and let it out in steps which might be hard for the groundie to control. ,???

 

Just thinking out loud. It's worth trying.

[felixthelogchopper]

Have to say, I think it would be a nightmare for the groundie.

[Swampster]

I agree with Rupe in so much as whatever energy is absorbed pulling the loop on the marlin through, it'll be lost as an advantage when the hitch finally unravels and the line is then shock loaded.

 

 

Personally i use different size groundies as required.:-)

[Tony.Price]

The friction created by the rope slipping through the hitch would cause excessive heat damage in the rope and, lengthen the drop. A Skilled groundy could let it run over the same distance using a rotating bollard such as GRCS to take up slack when in free fall before loading occurs.

 

Not tested, but my interpretation of what you are describing

[WeeDee]

I don't think the final shock load will be the same as the initial one.

In effect, the energy of the falling piece is being given to each knot's undoing - by the final knot, some of the energy has been already 'shared out'.

I am picturing the same effect as in a tightly formed daisy chain - as the load pulls the daisy chain out, there a series of drops and jerks - thus regulating the rate of load dispersal over time (something that a groundy does but in a different way).

In practice, I think the difficulty would be in the guessing of the knot's tightness in changing conditions.

Of course, this is all perfect in my head - maybe not outside it.