Compact Bulldog Bone

joezilla11 said:
What if... where ur chest harness comes together in the front, u girth hitch it together with some bungee and a biner if that makes sense.
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Makes good sense! I just used a small petzl Ange I had to complete harness and its snag free nose which brought me to bungee the bone instead . I like that thought as well though Joe.
 
joezilla11 said:
What if... where ur chest harness comes together in the front, u girth hitch it together with some bungee and a biner if that makes sense.
Click to expand...
I used a micro oval screw link on one side of the Loop 8, connected to the eye of a dog snap. The dog snap clipped to the other side of the Loop 8 to hold it on, and a mini biner hung from the eye of the dog snap. This made for ultra easy on/off of the harness and the biner hung nice and centered.
 
oceans said:
You know, sometimes the bit of kit just lying around serve as great ingredients for new projects. Give it a go and let us know! I only thought of the ring as a means of not allowing the bungee loop to fall down inside the ingenious mechanismic awesomeness of the Bone's internals.
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No doubt it will go down under top arms when taking on /off . I tried it a few times and maybe a bit longer would be better for that issue. What is cool about the bungee there is you can stretch it over top arm and see the difference from in between arms to the backside . I'll see which position tends best for me tomorrow .
 
DSMc said:
I am starting to think that a bungee system might be the safest on the BDB. As stated, you don't want whatever you use to interfere with the proper sequence of engagement. Even with a soft link, if there is no stretch it can create a problem.
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Im thinking this was my seed that was planted to grow and brought me to the bungee to the bone idea as well.
 
Couple of random thoughts.

One for the neck bungee tetherers a possibility to avoid the choke hazard:
nochokeNeckTether.png


Sorry about my crappy doodle - but the point is to have a length of webbing around your shoulders (under your pits) with rings or tied loops at each end. Put the bungee through the rings and then over your head. The webbing will stop the bungee choking you if it gets hung up on something behind you.

Then Tylers mod got me thinking about the bone dynamics. For clarity I've butchered someones picture - sorry I forgot whose (that was a whole page ago!)

BoneAnnotated.png

The bone as two levers - one 'fixed', the other semi-floating (dynamic). Both are releasable, although we tend to use the top one, so I've called that the (C)ontrol arm and the lever distance C. TC is the Tending Control distance

Decreasing C gives for more power/MA to TC - so thats why even a shorter TC still has plenty of power.

S is the (S)pine length and to be honest - I've not worked out how its length will really affect the dynamic of the Bone, except in concert with C. Ie make S longer and C would have to be longer too. But as S is approximately 2*C... its length has half the effect.

A is the (A)nchor lever distance.

I'm wanting the bone to work well on my 11mm rope (11.7 seems great, but the 11 is not firm enough and I get slippage)

I think that increasing A would increase the leverage on the rope between the Anchor arm and the spine locking it more... Looking at it again - I'm going to try flipping the anchor arms around and see how it goes.

Increasing A might allow for a decrease in C so giving more power to the arm (ie less C more TC)
 
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Sorry for the spam but I just did a couple of 25m climbs using my old SA-Responce LSK (its the same as http://www.ebay.co.uk/itm/11mm-LSK-...s_Climbing_Mountaineering&hash=item1c4ae86abd) and I'm delighted to say that with the Anchor arms flipping around and the 19mm bollard sleeve with my full cold weather climbing weight... zero creep.

I still want me some Cougar blue but I can at least use my nice long line SRT again.

And something else happened which I had hoped for: it became a _lot_ smoother. Control is lighter and really nice, although you can't do "drop like a stone" descents any more. I think this is because the Anchor lever now has greater MA and is taking more of the load. The top/control arm now has less load and is therefore easier to opperate. This is true for my other LSK too which is nearer 11.7mm.

:bananahappy:

Hopefully Gordon isn't going to pipe up pointing out I just did something really stupid... (But I was climbing DSRT - the second on a hitch as a backup but always with some slack...)

There is also something comforting that less load is on the spine and top arm - more of the load is closer to the anchor (me!) Less to go wrong surely?
 
Paul, you've posted a great deal here, so I just want to clarify what I've gathered from reading it all.

So, what you've done is flipped the lower arms, end for end, to increase 'A', installed the 19mm (3/4" bollard), and you've achieved the positive results described above.

If that's the case, then it's a non destructive way of adjusting the Bone for different lines. Good on you for conducting that experiment. Now I can truly see the need for multiple holes drilled into the arms (upper & lower) for ultra fine tuning along with the various bollard sizes.

Awesome! Maybe if all the information gets compiled and agreed upon, Gordon could be making these in a 1 size fits all (following adjustment) construction with a manual to describe configurations...or a chart that allows the user to find their point on the graph based on weight, climb line, etc...
 
I have tried previously moving the teardrop anchor outboard as you describe, but on my ropes it did not seem to make any discernible difference, and it caused the spine to tip a bit more when loaded. Be aware that you are putting more stress on the lower arm at the narrow point now that you have turned it backwards and it is 1/2" further from the fulcrum pivot hole at the spine.
 
Paul, again, thanks for setting up the photo with pivot point diagrams.

So, has it been said that shortening 'C' will raise the angle of the Spine and put more friction into the lower Bollard? That appears to be one of the results, along with less MA in the upper arms.
 
Paul Hedderly said:
...There is also something comforting that less load is on the spine and top arm - more of the load is closer to the anchor (me!) Less to go wrong surely?
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Nice work! The reduced force to initiate a release with the upper arm is, as you say, because the lower arm is applying more force. Expect to see increased wear on the spine contact point. One of the many things that I like about the BDB is the potential to easily replace worn out parts.
 
oceans said:
Paul, you've posted a great deal here, so I just want to clarify what I've gathered from reading it all.
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Oceans sorry again for the brain splurge!
oceans said:
So, what you've done is flipped the lower arms, end for end, to increase 'A', installed the 19mm (3/4" bollard), and you've achieved the positive results described above.
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Yes exactly.
oceans said:
If that's the case, then it's a non destructive way of adjusting the Bone for different lines. Good on you for conducting that experiment. Now I can truly see the need for multiple holes drilled into the arms (upper & lower) for ultra fine tuning along with the various bollard sizes.
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The counter argument is that more holes = weakness.
The counter counter arguments are that more holes = lighter, and that the stress/strain (one each side of the hole) is mostly at the points where the pivots are active - so inactive holes are not problem.

oceans said:
Awesome! Maybe if all the information gets compiled and agreed upon, Gordon could be making these in a 1 size fits all (following adjustment) construction with a manual to describe configurations...or a chart that allows the user to find their point on the graph based on weight, climb line, etc...
Click to expand...

Yea that could be quite fun. I don't climb enough, or have many ropes to do it though.

oceans said:
Paul, again, thanks for setting up the photo with pivot point diagrams.
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No problem! I should have used L and U instead of A and C in hindsight.
oceans said:
So, has it been said that shortening 'C' will raise the angle of the Spine and put more friction into the lower Bollard? That appears to be one of the results, along with less MA in the upper arms.
Click to expand...

I would clarify or correct that a little to say that shortening C:
1) Moves the friction towards the centreline reducing the upper arm friction and therefore increasing the load on the lower arm
2) Increases the MA of the upper arm control because C is shorter with respect TC.

The second point is the reason Tyler has got good control even shortening the top arm as far as I can see.



surveyor said:
I have tried previously moving the teardrop anchor outboard as you describe, but on my ropes it did not seem to make any discernible difference, and it caused the spine to tip a bit more when loaded. Be aware that you are putting more stress on the lower arm at the narrow point now that you have turned it backwards and it is 1/2" further from the fulcrum pivot hole at the spine.
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Yes there is more torque+stress on A. And there will be more wear on the spine - but I have one that can be inverted... :)

I may try shortening C also and see if that does the trick for me with the lower arms back in their proper place.

Gordon do you think there is a significant risk associated with flipping the lower arms? If money and time were no object some proper destructive testing would be fun.

The more I play with and ponder this thing - the more amazed I am by it. To have such a flexible device using simply machined stock and lightly modified off the shelf parts is brilliant.

I even used it to belay a few days ago - worked great ;)
 
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I think the risk is increased 50% as you have half again as much load now on the anchor side of the lower arms. It would be better if the arms were purpose built with full dimension arms on the anchor side.
 
Paul Hedderly said:
Gordon do you think there is a significant risk associated with flipping the lower arms? If money and time were no object some proper destructive testing would be fun.

The more I play with and ponder this thing - the more amazed I am by it. To have such a flexible device using simply machined stock and lightly modified off the shelf parts is brilliant.
Click to expand...

Destructive testing could be fun AND informative.

A resounding agreement with the second statement in the quote above!
 
Also want to add that this thing should be slipping before anything breaks while on-line. Testing would be good to see how this acts.
 
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