Compact Bulldog Bone

Sorry I tried to find a pic of a lady with a bulldog and a bone by her side, yelling at a guy in a tree on spikes. No dice. Google is so finicky . LOL. But I thought the ear muffs were a nice touch. :)
 
I've found my favourite bdb setup and am posting it for general consideration.

14169695574921283337854.webp

And from another angle:
1416970200257-1728164768.webp

I attach the caribiner to the hydra pulley on my bridge and the tether to my chest harness.

It advances effortlessly attached to the chest harness.

There is a caution however: if you pull back hard with your back while the tether is attached to your chest harness, the bdb will slip. This phenomenon was mentioned by someone else (sorry can't remember who it was) earlier in the thread. I don't find it alarming in anyway
and to stop the slip just stop pushing back.
 
something looks different about that CBDB treegongfu. still needs the safety mod (nubs). did you do something to modify the clip-in point?
 
Treegongfu unless you bounce through the trees like the ninjas in kungfu flix ,which i wouldnt put past you ,I'd fix that bone up a bit. For safety!
 
That is very interesting Gavin, and is something I have not tried exactly as you are showing it. I have sent Gavin top arms with nubs/handles, in order to facilitate a fix, but evidently the parts are very slow to arrive. If too much load is transferred to the top of the spine, say if the climber was incapacitated, then I think it would release, so please be careful. The spacer aluminum washers are there to stabilize the joint at the spine from side to side movement and it looks like you could add a washer on either side of the shackle to accomplish that.
 
macswan said:
So if you became incapacitated during ascent, and flopped backwards? Would the bone slip a bit, then set. Or would it slide down the rope unchecked?
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treegongfu said:
It would set. To make it slip you have to rigid.
Click to expand...

I reported on this earlier and with my setup I had to have a foot ascender engaged on the rope, lay back with my legs locked straight and my entire body fairly straight to have the BDB not grab. If you were incapacitated, your knees would bend, your body would not remain straight and the BDB would grab exactly as it should. After figuring out the exact set of circumstances required to have this happen, it does not concern me at all.

Still loving the BDB.

Edit: I suspected the Rope Runner would behave the same way so I gave it a try this afternoon and it will slide and not grab under the same conditions. Again, the only way I have this happen is to have may weight on a foot ascender, hold the rope above either device and lean way back keeping my legs and body straight.
 
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I did as Gordon suggested and instaled the thinnest washers I cld find on either side of the shackle. They fit but it was too tight so I removed one. Not sure if that slight offset is significant.

The slipping is similar to what gmcttr is describing but more pronounced: I think.

It occurs as Gordon said "when too much load is transferred to the top of the spine"

When i go limp in my harness there is load both on the saddle and on the top of the spine-they share the load and there is no slipping at all.

If I put my feet above my head and hook them over a branch it transfers more load to the top of the spine and it slips.

If I play dead my feet get dragged off the branch as I continue down until they swing free and the balance point is restored. No more slipping.

The length of the chest tether relative to the length of the bridge-pully-carabiner-bdb connection plays a role in this and the shorter the chest tether the sooner pullback will start to transfer load to the top of the spine.

Hope that isn't too long winded and is clear.


Gavin
 
gmcttr said:
I reported on this earlier and with my setup I had to have a foot ascender engaged on the rope, lay back with my legs locked straight and my entire body fairly straight to have the BDB not grab. If you were incapacitated, your knees would bend, your body would not remain straight and the BDB would grab exactly as it should. After figuring out the exact set of circumstances required to have this happen, it does not concern me at all.

Still loving the BDB.

Edit: I suspected the Rope Runner would behave the same way so I gave it a try this afternoon and it will slide and not grab under the same conditions. Again, the only way I have this happen is to have may weight on a foot ascender, hold the rope above either device and lean way back keeping my legs and body straight.
Click to expand...
I was only asking cuz gongfu has changed the attachment point for the chest harness. I was unsure if that would change the mechanics of the apparatus
 
Treetopflyer said:
Anybody using static ropes through bdb like a sterling htp or kermaster
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I tried new Sterling HTP Static 11mm with the BDB today and it was a no go. I had the large bollard in and it would not consistently grab. Mostly just a quick slide to ground only controlled by holding upward pressure on the upper arm. It was strange...climb up a bit, sit back and it held. Descend any and it would not grab.
 
gmcttr said:
I tried new Sterling HTP Static 11mm with the BDB today and it was a no go. I had the large bollard in and it would not consistently grab. Mostly just a quick slide to ground only controlled by holding upward pressure on the upper arm. It was strange...climb up a bit, sit back and it held. Descend any and it would not grab.
Click to expand...
Thanks for the quick review ..I don't care for running 11mil for my hands,but I do like a more static feeling on rope while climbing , I'm a solid 200pounder and can make a not so bouncy rope seem like it is , and by the sounds of it the bdb doesn't care for 11 mm either,I bet the 12mm or 13mm statics would be performer's . I'm sticking with Yale 24 strands 11.7 mm and they perform flawlessly for me with large bollard. Love my 24 xtc...and I really love my bone . Anybody even goes near it on the job and I ggggrrrrrrrrrrr.! Try and touch it and I snap! Luckily for me this Dogg climbs so its not near the masses for long .. Put it on and away we go!
 
That is a very good explanation Gavin of the way the Bone is affected by the upper attach point and the length of the tether attached to it, thanks.

Great video Eric! and thanks also to Kevin and yourself for promoting DRT. Maybe you should get a red line also : )

It would seem that the range of ropes the Bone likes is approx. 11.5- 13mm depending on rope type and climbing weight. For a 11mm line it helps a bit to have no grooves on the inner sides of the arms and to be a lightweight.
 
I am currently backordered. I have a new batch of parts scheduled to arrive tomorrow. The bottleneck is the corrosion resistant links, I have used all the available stock my vendor has. They are saying they should receive new stock in next week. We shall see. I have considered making Bones with stainless steel links, but they would likely wear faster than the high carbon steel links I prefer.
 
You've got a winning design. I'm thinking you should stock the back bone component as a separate item, since that's about all that will wear on this device. Mine show wear at the lower bollard pinch point. I'm thinking that a user could get 4 surfaces out of this by flipping it around as wear gets to the tipping point. Should also determine what that tipping point is...
 
Eric I have made a smaller (wish)Bone using size 60 links. but is not really that much lighter and does not tend slack as nicely.
I still have a big Bulldog Boss(bone) made from size 80 links, but at 26 oz. it is more like a boat anchor.
I don't have a picture of the (wish)bone but here is a picture of a small OAR using size 60 links that will give you an idea of the size.
IMG_0797_zps74db58ec.jpg
 
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