New product for Figure 9 users

[Dutch]

I made three anchors last night and had one revelation. I start with 3/16 stock and made one as we planned. It picked up 300 pounds with no problem.

Then I tried a 569 pound mold. It almost got off the ground lifting one side up. Then the rope slipped. I tried wrapping it many different ways but it always slipped. So I put a half hitch to see if the hook would carry the weight. It picked it up no problem. It weighs 5.22 grams.

It got me thinking about having the long stem so it doesn't pull to one side. Then it hit me, put the support hole above the weight bearing hook. That is esentially what the figure 9 does too.

That took off about a gram as you can see.
I still had to put a half hitch in it to hold 569 pounds though.

The BPL coreplus is very slippery plus I had a round slot instead of a V making it easier to slip. Here are the two showing scale.

I then made one out of 1/8 stock just because I wanted to see something break. It broke at the base of the stem but almost picked up the mold. The base of the neck was 1/4" wide. Here is a picture of all three after I broke the 3rd.

By this time the rope was in very bad shape. I am going to order the rope that WBG suggested and try more weight, but I think the 3/16th is strong enough. I held the mold up for an hour and a half with no fatique. I am sure if I used the HH spectra the line would not have slipped at all. Even so I don't think we really put 569 pounds of pressure on the supports. the weight of me never distorted the coreplus the way this was stretched and tearing. On the third version (the one that broke) I had more of a v instead of a rounded hole to see if it would slip. It did and I had to tie it again so it would take the full weight. I have to order some new large figure 9s so I can test the strength of them. All in all I think it was really a success. The best breakthrough I had was making the stem off center so the supporting hook and the hole are in line. At 4 and 5 grams they are light enough. What am I gonna do with all the webbing I bought for Speer?

[schrochem]

This is awesome Dutch!
I've been waiting for your report....
It's great that you access to tools to test this stuff. I'm going to get a hold of some 3/16" and see what I can make.
I like how you found the 'offset' to hold a nice line.
I think more weight could be saved (and possibly make it stronger??) by making the neck shorter.
Also, how important do you think the 'hooks' are at the tips of the anchor? Could that just be straight like I drew in post#167?
This is pretty darn cool!

[warbonnetguy]

you are the man dutch.

that is awesome. did my wrap slip too? the one in the top pic looks different than mine. i did figure it would eventually slip with enough weight though.

so, a stem made of 1/8" alum and 1/4" wide almost held 569#? that's pretty amazing.

i think by "leaning" the stem like that, you are creating more leverage on the stem, which might make it weaker (i'm no engineer though) but, SCH is right, if you get rid of the tilt, you can make the stem shorter, and save more weight, but at 4g whose even counting anymore.

looks like the 3/16 is the way to go. could you test some of these stronger ones including the nine to failure? i think alot of people are concerned about the strength, and the common idea is that a 200# guy can put at least 400-500 lbs on his support ropes due to the sag angle of the hammock.

if you can test to failure, could i send you a couple to break? if we all make a couple designs with signifigant differences and break them all, it would be easier to find the design with the best strength to shape ratio.

hey, does your shop have the ability to cut these things out without having to do it manually? like a water jet cutter or similar?

i'm surprised about the line slipping at 569, but not during bodyweight bouncing.

conventional wisdom says that the angle of the hang can cause the force on each rope to be more than double the weight of the occupant. then when you figure in bouncing, that 569 should have been reached or at least close by me or turk or whoever did some bounce testing, and nobody reported rope slipping.

i wonder if the forces on the hammock and the suspension are indeed less than everyone thinks?

for a while i've been trying to figure out a way to test the actual load for different amounts of sag. so far the best i've come up with is using "screamers" on the hammock. they are special runners designed to rip their stitches when loaded to a certain weight, absorbing force as they rip, reducing the impact force of a climbing fall. once they are activated and the stitches rip, they become just a regular loop runner. pretty ingenious idea.

they have several different models which are designed to activate at 400# and 600# i think. it would be interesting to see what sag scenarios would generate 400 and 600 lbs of force from a regular weight person.

check them out here: http://www.yatesgear.com/climbing/screamer/index.htm#1

listed forces are in kn. 1kn~225# (i think).

i'm going out to buy some 3/16" alum.

[schrochem]

Well i just got back from buying a 12' bar of 6061 3/16" aluminum. $12
There is a shop just behind my building that sells all sorts of stuff.
They also have a CAD plasma cutter.
So if we ever figure out a nice design we could have them cut out many of these from a sheet. We can supply a design made in a editing program (I have photoshop) and that makes things precise and easy.

As far as the loads on the hammocks, spreader bars, etc. I always wondered if anyone had access to a large fish scale. Like the one they string up the big salt water fish. I figure if you put that in line with the suspension, it give you an idea what kind of force is being pulled.

[Rapt]

I can create a CAD file of any design you'd like... It may take a week or two for me to fit it in between my "real" work, but I'd be happy to help out once you've decided what you want.

And yes, putting the "curve" in the shaft of the "anchor" increases the stresses on it, on the inside. It increases the bending moment on it.

I suspect that with some care in wrap styles we could find a wrap that works and centres the load on a "straight" tab style. Or something like that....

[warbonnetguy]

just got back from colorado iron and metal. i had to choose between 1/8 and 1/4. they didn't have 3/16. i got one foot of the 1/4". i figure i can make the device narrower since it will be thicker. it's also 6061 alum i believe. 60 something anyway.

hey SCH, wanna sell me a couple short pieces of your 3/16"?

[Rapt]

Hey guys I did up a sketch (drawing).

Assuming the thickness is .188" (3/16), the anchor estimated weight is 5g. I figure failure strength is somewhere around 1000-1500lbs with 6061-T6. (Wet finger calculations of weakest section... no time to do full analysis.)

I have a PDF that I attached.

[warbonnetguy]

Rapt,
thats amazing how you can do that and calculate the strength based on dimensions and type of metal!

looks like a stem that short is gonna have alot of tilt, and need steeper hooks. the hooks themselves look a little long for 3-4mm line.

what do you think about this?

p.s. my drawing may have exaggerated the amount of tilt a little though.

[schrochem]

just got back from colorado iron and metal. i had to choose between 1/8 and 1/4. they didn't have 3/16. i got one foot of the 1/4". i figure i can make the device narrower since it will be thicker. it's also 6061 alum i believe. 60 something anyway.

hey SCH, wanna sell me a couple short pieces of your 3/16"?

Sure, no problem. I have 12' of it! It is 1.25" wide.
How much you want?
Btw schrochem is just an old internet name I came up many years ago. It's a fusion of my last name (Schroeder) and job (chemist), so just call me Scott

[schrochem]

Hey guys I did up a sketch (drawing).

Assuming the thickness is .188" (3/16), the anchor estimated weight is 5g. I figure failure strength is somewhere around 1000-1500lbs with 6061-T6. (Wet finger calculations of weakest section... no time to do full analysis.)

I have a PDF that I attached.

Sweet, looks nice.
I have 3/16" X 1.25"
Maybe I'll try this out tonight, but I doubt I can come anywhere close to getting those measurements.