GRCS strength Demo Sat June 5

F

frans

Location
healdsburg, CA
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
 
trebuchet.gif


The calculations can be ported over from the medieval catapult launching of a car on fire. A Trebuchet was used to send a flaming Cadillac flying across the field at night.

Here's a 1 1/2 minute video file that is 4 mb in size. Trebuchet car launch movie.
 
I forgot to mention I also have a Hobbs device which we will be setting up exactly the same way for each drop test.
We will begin with a drop of 5' and then go up from there.
Frans
 
There are a couple other ways to break a lowering device ,besides dropping junk cars on them. Do you want to break it , and where do think it will break ?
 
I dont want to just break the lowering devices. that would be be too easy.
Ideally, I want to apply successive loads that increase in weight on the ratcheting mechanism of each device. Overall I hope the test will stress both of the capstans attachment points to the base plate but also test the durability of the pawls or dogs of each device. Then increase the shock loading until something in the loweing devices gives away. If any point in the rigging fails then we will strenghten the failed point and continue.
 
Frans,you don’t have the balls to break a lowering device . Why drop a couple cars , i don’t get it . Why not do “real sceanarios” or is that too scary? Cut a piece and see what happpens , the device is only half the equation. School time.
 
Udate on: GRCS/New Hobbbs strength Demo Sat June 5

Ouch Riggs, have you ever met me before? why say a thing like that?
Spent all day today setting up and doing the tests.
We began with using an approx 3,000 lb. euc. log. It was about 8' long and 3' thick so the weight is just a guess but we will have it weighed and be able to supply an exact figure.
We used 5/8" & 9/16" inch lines to begin with because we wanted to show how the rope failes under real world conditions. For both devices the rope failed first at the capstan because of thermal heat breakdown. When we put approx. 10' (feet) of slack and let the log fall into the 5/8" line the rope failed at the marl- a clean snapping break.
Both devices seemed to experiance no problems with the pawls, baseplates etc.
On the first test of the day we had the GRCS mounted on the tree. The euc. is 90" Dia. so we had to cut "pads" for both devices to rest on, the tree just did'nt have any curve to it.
We mounted the GRCS incorrectly and it slid up the trunk digging a deep 4" deep groove in the trunk as it went up the trunk. When this happened the hinged portion that holds the strap bent slightly.
After that we positioned it correctly and experianced no problems with either device.
The New Hobbs worked just fine, no problems at all.
The chunk we were dropping was raised to maybe 40', and dropping 35' so it would "hit" the rope and stop.
I am real impressed with both devices and think they are everything both manufactures say they are.
Tomorrow we will begin the car drop test using heavier line. Ran out of time today what with setting up and running the lighter line testing.
We did extensive filming. I'll try to post at least a picture of the car drop.
Folks who helped today:
Sam Noonan
Robert Phillips
Ken Johnson
Me
Greg Liu
Gerry Baranek
and others not known in the tree world
Many thanks to all for making this first day a success and working so hard on this project


I'll post more when we are through tomorrow.
Thanks
Frans
 
Re: Udate on: GRCS/New Hobbbs strength Demo Sat Ju

Thanks for the update.

I expect to see the results of tests on one of the reality TV shows later this summer :)
 
Re: Udate on: GRCS/New Hobbbs strength Demo Sat Ju

</font><blockquote><font class="small">In reply to:</font><hr />
Both devices seemed to experiance no problems with the pawls, baseplates etc.

[/ QUOTE ]


Sounds like you have tested the GRCS with the winch attachment. Will you also test the GRCS with the bollard?

Mahk
 
Re: Udate on: GRCS/New Hobbbs strength Demo Sat Ju

(did not test the bollard, wanted to test the weaker part of the GRCS system)
Well after many hours and lots of laughs we finally got the tests done.
Yesterday and this morning we dropped tested a Euc log measuring approx. 8' long by approx 3' thick.
First we dropped the log using a 5/8" &amp; a 3/4" line.
The log was dropped about 10'-15' into a 2" load line.
THe big line accepted the shock loads just fine and so did both devices. But the smaller lines failed either at the marl or at the drums (almost a friction/thermal break)
Interesting because we always hear about knots reducing the strength of a rope by +/-50% and now we saw this first hand. But by allowing the load to run a little the ropes failed at the drum.
We had a little trouble with mounting on such a big stem because the straps extended out from the devices without being able to cinch very well.

We dropped the car using the big line and let some slack in the system.
The Hobs took the load and bent within the channel iron on the base by about a 1/8" inch. The capstan still ratcheted fine.
The GRCS took the load but the bottom of the base plate lifted under the load away from the tree and the rope yanked off the outer part of the capstan in a sucking/pulling action not a shearing pull as we wanted.
The base plate on the GRCS was not harmed at all. The base pulled out easily with no pinching in the rails. The ratchet action of the core mechanism was not affected.
The Hobbs is one stout device that handled loads far in excess of any device or rope manufacture's guidlines.

The GRCS lifted the '79 Volvo station wagon (rated at 4300GVWR) by cranking up on the drum with the handle and the rope did not slip from the jaws.
Over all both devices seem to be the same strength, One will lift easily huge loads, self tail, lighter because of it's component assembly. The other is easy to operate, very strong, less expensive.

Overall I have come to the opinion that both devices have a place in the tree industry. One is not stronger or better than the other, just different devices.

I have changed my tune about the Hobbs and am here to say it is just as good as the GRCS.
The movie will be assembled by Gerry B. once we get all the different tapes to him. I'll let folks know who are interested and see about making copies.
Loads/weights, distances dropped and other details will have to wait until we get all the facts together.
This is just advance details
Thanks
Frans
 
Re: Udate on: GRCS/New Hobbbs strength Demo Sat Ju

Frans,

Interesting to hear about the results. Is there any chance of having you post some still pics of the bent tools? I'm sure that I'm not the only one who is anxious to see some.

Tom
 
Re: Udate on: GRCS/New Hobbbs strength Demo Sat Ju

A few more thoughts on the GRCS &amp; the Hobbs...
I still think the GRCS is by far the more versatile of the two. For me I really need to be able to have one man operate the device not two like the Hobbs, and because of always working in tight areas I really need to be able to lift loads. So even tho I dont have any bad things to say about the Hobbs' construction, the GRCS still rules in my book. I suppose if you are only dumping wood all day long and never need to raise loads, attach the device to your truck, and have a crew that does not under stand load factors then the Hobbs is for you.
Frans
 
Re: Udate on: GRCS/New Hobbbs strength Demo Sat Ju

Frans ,I hate to be the guy who says "what the ?" but I guess I have to be"that guy". i had a lot of experience with devices , and the last place I'd go is a car lot. Matter of fact I do tree work, video taped some stuff. Seems like you went out with the Don Blair gang and changed your mind on the Hobbs. in Cars &amp; trucks the manufacturars and dealers don't conduct the test on vehicles, outsiders do. Did you test the idiot factor? Anybody ready for a Easty Coast test? trees though , what we use them for and attach them too, we'll put a couple trucks on there too...sorry Frans but , I don't get it .
 
Re: Udate on: GRCS/New Hobbbs strength Demo Sat Ju

I did change my mind on the Bobbs. I am very impressed with the construction. It is one strong device.
However I really dont have any use for it. There are so many different things I can do with the GRCS I just dont see why anyone would buy a Hobbs.
As for the idiot test well, you where not there so you could not check up on me.
All I can say is each test was doubled, one for the hobbs and one for the grcs, on down the line.
All the footage will be assembled into a dvd and will be available soon. Maybe you will be interested to view our results at that time.
The car was used for the shock and awe value. Believe me it looks better seeing the grcs pick up a Volvo station wagon (3000lbs)three feet off the ground than a piece of wood. In my mind anyway. The same goes for drop testing.
Trust me I dont have any allegiance toward a paticular manufactuer. If I feel someone is producing an inferior or unsafe product I will turn on them like a rabid dog :)
-think Kong lowering device-

Frans
 
Re: Udate on: GRCS/New Hobbbs strength Demo Sat Ju

I had to use that Kong device in Italy two weeks ago. Let me tell you, the GRCS is better in many ways (opinion). I guess that if I had never used the GRCS before, then maybe I might be impressed, but I have-so I'm not. It's just not as well thought out.

Although I have limited time with the Hobbs, I like it better than the Kong too, but I like the GRCS the best. Especially when you have to use the crank.
 
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