strength demo of the GRCS 6/5/04

[Frans]

Well we finally have all the preparations in place to conduct a drop test using the GRCS.
Saturday June 5 in Healdsburg, CA we will take either a Cadillac Eldorado, or a economy compact car and drop it into the GRCS at different heights 40',30' & 20'. Or maybe just once, after all the shock loads will be extreme and who knows the device may just explode!
We are using a big 'ol Euc. owned by Foppiano Vinyards for this test.
The rope used for 'catching' the car just above ground level is a 2" double braid mooring line.
We have an International with a low boy to bring the car to the site. (the car is a training vehicle used by the Geyserville fire dept.) The truck will be used to raise the car into position, we will cut the rope and let er drop.
The entire event will be filmed using the skills of Gerry B. and three other filmers to record from multiple angles.
This tape will be used to help compile a video for demoing the GRCS at trade shows and the like.
Does anyone know how to determine the exact shock loads for me?
I can supply the weight of the cars used cause we will weigh the truck and trailer without the car and then with the car.
Any help would be welcome...
Frans

 

[rbtree]

Let me get this right, you're planning to drop a max weight 5500 lb Caddy a minimum of 20 feet onto a 110,000 lb rated line? Are you going to let the line run? If not, you'll be right at the tensile strength of the line. I doubt if the GRCS or its sling could withstand the load. And what are you using for an overhead anchor? I hope a 200000 lb rated sling and block.....Oh my! But wait, how could you get a 2 inch line wrapped enough times to supply the needed friction? Your test is destined for failure...either that, or I'm missing something. Maybe you're planning to give it 20-40 feet to stop, applying tension right away. Now that I could see working, but with a max size 1 inch rope, of synthetic fiber, like Samson's Validator ll, rated 80,000 lb tensile at 1 inch.

Edit, The GRCS can't accomodate any line over 3/4 inch.

You better stick with the econo car!

By the way, my GRCS sling is already torn, after only 5 weeks of use..maybe 10 times we've used it. What's up with that, I wonder?

 

[rbtree]

Ok,I'm thinking more now. You're attaching the 2 inch line as a backup, but using a regular rigging line that the GRCS can accomodate.

I'm not a pro math calculator guy, but if a 5500 lb car drops 2 feet and is snubbed, it will apply 11000 lb of force, and I think 22000 lb to the anchor. But if you let it run 40 feet, and it reaches max velocity at 10 feet, then you are able to start slowing it down, just a guess would be that the max forces exerted on the line and GRCS could be kept under 20-30,000. Maybe I'm wrong in that guess, perhaps a good rigger can get the load to start slowing down right away. If so, if he is able to control the speed, peak forces might be less. But if he has to bring the load to a stop after 20 feet, more load will be applied than if he has 40 feet to work with.

The Arbormaster team, with their extensive use of dynamometers, would know how much force is applied to a line, given the load, it's initial freefall, and distance it is let run before it stops.

Graeme McMahon would be the other guy who oughta be consulted, as he's dropped 2.5 ton euc leaders into rigging. He used to use 2-2.5 inch line, wraps taken in the tree. He has sometimes remotely detonated the limbs with explosives.

 

[SilverBlue]

It’s absolute insanity! Besides we lost all our Eldorados during the great senior retirement rush to FL last year. Now we are importing these from Dousman Wisconsin, everyone has one down there, more practical and easier to tie down.

 

[rbtree]

So that's why you use Caddy pads...

 

[SilverBlue]

 

[MasterBlaster]

Whut the heck iz that thing, Rob?

 

[SilverBlue]

Wisconsin's answer to the mad cow/
anyways all bow to the The Ayatolla Of Rock'n Rolla

 

[a_lopa]

it seems like insanity to me,dropping a caddy from 40' just to see what happens.rb im pretty sure the ropes that graeme used on that particular job were made in nz by du-pont, kevlar and were throw away after one use as there integrity couldnt be trusted,well thats what he told me anyhow.graemes bro is a mathimatician and works out some of graemes riddles that need solving,he would be the one to ask for sure

 

[Frans]

more info RE caddi/drop

The 2.5" double braid will be the one to arrest the fall of the car. A smaller line will be used to hoist the car into position.
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.
The rigging point will be a natural crotch, with a half wrap down to the GRCS. The car will be hoisted up using a 3/4" double braid running through a block above the 2.5" load line.
I will minimize as much as possible any tight bends in the 2.5" Db. braid so no knots connecting the load line to the car. We are thinking of taking a clove hitch around the middle of a log and attaching the log to the car with two 3/4" chokers. One just in front of the rear wheels and one just behind the front wheels extending around the entire car and over the ends of the log.
Whadda think?
OH I FORGOT THE HOBBS WILL ALSO ENDURE THIS SAME TEST, USING THE SAME SET UP, THE SAME TREE, etc. (unless of course we tear apart the euc. on the first test)
Both the GRCS and the Hobbs are about the same vintage, used for the same type of work throughout their lives so should be fairly matched.
The GRCS is one of the first made. I think #7-9 not sure will have the exact manufacturing #s from Greg G. on the demo video.
We dont care if these devices are destroyed, we are after really hammering them both and seeing which one will cut the mustard.
I am tired of hearing that one is stronger than the other and really want to put this question/issue to bed.
AND PROVE IT!
Frans

 

[Tom Dunlap]

The place that I have my temp housing has cable TV. That means that I've been doing some surfing and getting caught up on the various "makeover" and reality TV shows. The house/car makeover shows give me the willies most of the time. They do some pretty weird things sometimes. Then there is American Chopper where the dog fights between Dad and Paulie are as entertaining as the bike building.

While I've been watching these shows I've wondered what it would be like to have the arbo-reality show. What would it look like? I think Frans has written the pilot episode Having Jerry there to tape means that it will be arbo all the way!

Be sure to do some math first though. How do you plan on triggering the drop? What kind of self-portection are you going to have? Underground bunkers? Sand bags?

Tom

 

[Lumberjack]

And we wonder why they cost so much ?

How about yall just send them to me?

Didnt I read that the GRCS is rated to 20,000 pounds MBS?

Instead of killing a tree for no sensable reason, how about this.

Get some 3/4" double braid and wrap it in both devices, take one and attach it to the tree, and the other to the semi. Use blocks to get the rope angles correct. Then pull until one breaks.


The rope will break before you cold stop a car that has fallin 20'. If somehow it doesnt, then the tree is coming over and/or the friction device is gonna explode.

Think, 5000 # caddy falling 6 feet (end of practical measuring w/ this formula) is 35000 pounds, 15k pounds over the GRCS MBS.

3k pound car 6' is 21k pounds. THIS IS 6' NOT 20' it aint gonna make it.

Stupid waste of time and money, use a test that is more practical.

Not to mention that the natural crotch will melt the rope more than likely.

Plus, after shockloading the tree like that, whos gonna get the block down?

Somehow doesnt seem too smart to me.

 

[Lumberjack]

Originally posted by Tom Dunlap
How do you plan on triggering the drop? What kind of self-portection are you going to have? Underground bunkers? Sand bags?

Tom

They are cutting the 3/4" rope they used to pull the car up with.

Another thing, however you attach it to the car, its not gonna survive many 20 drops to a hard bottom. Think about duke of hazzard(ing) a car down a 20' drop with no ramp to catch your landing.

Friggin stupid soundin the more I think of it.

 

[rahtreelimbs]

Why not use a crane for your rigging point?

Carl brings up 2 good points: why possibly weaken/destroy a perfectly good tree, and who is going to retrieve the anchor point?

 

[Frans]

O.K. So we will start slow and low with our heights. I told you all I was seeking weight estimates.
They told Columbus it was "stupid" to try to find a new world, but what happened?
The ropes and gear can break, melt, explode whatever who cares? I dont. I dont tell you how to spend your money... Most of the gear, the peoples time, the car, etc. has been donated.
The tree is slated for removal by us, so what difference does that make?
It will be fun, informative and vastly amusing- what do you look for in tree work? Drugery? I dont, I like to streach my horizons, and above all have a blast and learn.
The first time you set up a speed line, was it fast to take the branches and wood down? Did it take a long time to set up? was it frustrating?
Is your skill level improved by the learning you did? Are you a better arborist as a result of your learning? Or are you still in the "stone age".
H@ll This will be an "event" and we will share it with all. What more could you ask for?
This will all be recorded and shown at trade shows. Seems to me I am really doing a service to the industry as a whole and supplying a source of amusement.
Any constructive items to add?
Thanks
Frans

 

[Lumberjack]

No crane operator in there right mind would let you drop a car or anything on them.

Maybe start out at 5 feet and work up. If the rope is tied below the friction device then the device wont take the full load, tie it off 90 degrees or so to either side.

What I was thinking about the rope melting, it will loose strength in the lower heights, and assuming you are using 1 anchor point nand not moving it up, that would put the first wear 40' up the rope, what are you gonna do if it toasts it, cut the rope?

 

[NeTree]

Are you kidding?

Add a 12 pack, and you gots quality entertainment, if nothing else!

Bring it on Frans, we gotta see that video when you're done!

 

[rbtree]

Franz,

I'm sorry, but something is not right here. Number one, did I understand you correctly, did you really say the 2.5 inch db will be used on the GRCS? Come now, you can't really be considering that, when even one inch line cant be wrapped enough times to achieve necessary friction to control heavy loads.

If that is what you're planning, the wraps won't hold, and the tied off rope will catch, breaking the GRCS...

You'd better go to some Amsteel Blue....two problems there it's near zero stretch and slippery hand. Samson's Validator SK would be better. The only way you'll succeed in this test (without breaking things the first try) is to use small line, and manually control the drop, as normal. Slam dunking a car after a 20 to 40 feet is sheer lunacy.

You should get this software from Arbormaster! I'd like to know how they came up with this 20000 lb figure! Seems mighty high! But I do remember some higher than expected Dyno readings, when I took their 6 day seminar.
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Young Carl, with your very limited experience, you are spot on in your observations.

 

[Joe]

Originally posted by Frans

H@ll This will be an "event" and we will share it with all. What more could you ask for?

That one actually gets some useful information from the ordeal and it stays free.

This will all be recorded and shown at trade shows. Seems to me I am really doing a service to the industry as a whole and supplying a source of amusement.
Any constructive items to add?
Thanks
Frans

You really need professional input for this experiment.

KC has stumbled across a method you may be able to use to create more applied force to the devices without killing the ropes 1st. The 2:1 setup checked out for me. When pullies were added, his #'s didn't quite jive with his given solution.

You will be able to generate more force to the devices by building a mechanical advantage rig between the device and the rigging point. You'll get more force from a smaller drop. Friction in the rig will be a factor that'll need to be considered.

Joe

 

[Lumberjack]

I have that software, but I didnt see a caddy on the tree species.


I am wondering how you will make an attachment to the car that can withstand the force.