strength demo of the GRCS 6/5/04

[rbtree]

Re: more info RE caddi/drop

Originally posted by Frans
The 2.5" double braid will be the one to arrest the fall of the car.This double braid will be wrapped as many times as possible around the GRCS then tied off to the base of the tree with a little bit of slack.
The point being to really try to make the GRCS take as much of the load as possible.
!
Frans

Given this scenario, if I understand correctly, the LD's will take little load, as the wraps won't even begin to hold....nowhere near enough room on the drum to generate required friction. All that will happen is the wraps will slip, until the termination knot causes the line to become tight. Little of the load would be felt at the LD. (more on the Hobbs as it has room on the drum to handle a larger line) Please show me where I'm wrong.

I like the idea of testing the LD's to the point of failure, but the test must be designed realistically. Perhaps, if you're not planning on using dynamic loading, then simply tie off the rope to the LD, let er drop. But do some calculations to keep the first drop's shock load to a reasonable figure, like 20K-30K lb, and work up from there.

 

[ORclimber]

Frans, If you want to break a ratcheting bollard too, I've one to donate.

 

[kowens]

hey yall! meet me at the locial pub and we will come up with a
way to reall blow this thing apart

 

[kowens]

give me time to smoke one first

 

[kowens]

OH!i got a better idea lets get together with the guys in chainsaw
forem maby they can figure a way to cut some logs for us and
we CAN DO IT RIGHT

 

[kowens]

OR MABY SOMEONE HERE CAN CUT ONE BIG ENOUGH WITH THEAR ZUBAT

 

[kowens]

heres a better one find a tree to remove
2.buyrigging software figure 1000lb log.drop it 10ft onto the grcs
with zubat 3 TESTS IN ONE

 

[kowens]

3. MAKE SPONSERS PAY FOR PARTY

 

[kowens]

i forgot the rope thats 1 more sponser
MORE BEER

 

[Kneejerk Bombas]

The strength of the strap was mentioned, that is the first thing that would break, if you want my opinion. The little rubber things would be next on the list.
If both those held, the rope would slip.
All this would happen long before a car was dropped from ten stories up, or whatever.

 

[Frans]

Carl where the heck did you think I would have a Crane involved?
I dont know where you got that. Out of the blue maybe

The whole point is to not blow up everything right away ( sigh).

So I will start low maybe 5' and we will record every drop with weight factored in.

The load line is spliced so I'll slip it over the capstan.

1/2" choker cables will hold the car w/ clevis and such

Frans

 

[rbtree]

Originally posted by Frans
Carl where the heck did you think I would have a Crane involved?

He didn't, Rich Hoffman suggested it....none too practical of course, as a crane and shock loading go together like a fish and a bicycle.

So now you plan on simply looping the spliced eye of the load line around the LD's capstan...Might as well, as you can't wrap a 2.5 inch line and achieve much braking.

Carl, my GRCS has 4500KG WLL stamped on it, and I think 2000 lb SWL in another location.

6 feet might be too much for an initial first drop...better start with 2 feet. Of course, the natural crotch and half wrap will absorb some of the shock load.

 

[Lumberjack]

Rogger:

9000# SWL? I dont think the strap would like that one bit!. 2000 sounds much better in my eye. I just need to go out and buy mine through JPS and be done with it. Heck if I could stop spending on other stuff I would be set with the GRCS and a crane. Spent 850 on a Remmy 870 this Sat, and i want a AR-15 to go with it.


The natural crotch will take alot of the force I bet. If you could tie the load line off 90 degees to the side, the GRCS will take all the load that makes it past the crotch.

Frans:

Are you going to use the capstan or the bollard?

 

[a_lopa]

why dont you run rope throu a block/pulley keep the weenies happy

 

[Lumberjack]

I guess I am a weenie?



Anywho, a 2.5 inch block (and a sling) has to be really exspensive. The sling would be crazy high, as would the block (which would support 2 times the shockload without becoming a projectile). But, it would make everything smoother.

 

[a_lopa]

and i get told crotches are old school

 

[Lumberjack]

Originally posted by aussie_lopa
and i get told crotches are old school

Uh, it is, but I still use them when it is faster, more convienent.


Is this gonna be a debate too?

 

[a_lopa]

no

 

[a_lopa]

well said,but if they do this it may snap whole head out or up root the tree,depending on strengths.espesially shock loading its hard to determine what outcomes there looking for.should attach it with 100t hurc alloy chains all round then you will see results

 

[Crofter]

I have seen films of stunts that were so hopelessly doomed, that rather than focus positive attention on the industry it made every viewer think all associated were a bunch of goofs. I think Rocky and others advice good. Get some expert advice to make sure a reasonable match of components is made so that a number of increasing, successful drops can be made before initial failure.

Frank