Compact Bulldog Bone

treegongfu said:
Ive found that attaching a tether between the top link and the upper-arm friction link is better than attaching it to the top link.

It provides optimal tending, allows for a shorter tether and is less prone to slipping.

View attachment 29359 View attachment 29358
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Very interesting! Thanks for posting that up. Tending from the top (and I've only gone to the top link) makes a world of difference.

My thought with your mod is that if you got the tether attachment on those upper arms to be lower (holes for tether pin are centered in the stock, but I'm imagining them lower), would leaning back actually try to engage the upper arms, but give that magical tending capability as well?
 
Interesting, That hole placement would work as David's mod for his Vortex rope also!
 
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oceans said:
would leaning back actually try to engage the upper arms
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That does seem to be happening Oceans, and I believe explains the decreased tendency to slip.

I think Mike discovered that with his ring coming out the top many posts ago, I just didn't understand it at the time.

You know David's pic at the top of page 48 with the arms extending out beyond the spine? That may work as a tether point and leverage the arms up when loaded by the tether. I'm going to give that a try.

There is another way to increase the leverage. I think it works a little better but is less clean.

I'll put it together and take a pic.
 
Yes. Gordon. Those were David inspired mutilations to begin with. :)

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This seems to further diminish slipping by increasing the leverage and even seemed to increase the force required to release the bone when short tethered. I tried one other variation and would need to test it again to be sure that this particular variation was the one that had that effect.
 
treegongfu said:
Yes. Gordon. Those were David inspired mutilations to begin with. :)

View attachment 29360

This seems to further diminish slipping by increasing the leverage and even seemed to increase the force required to release the bone when short tethered. I tried one other variation and would need to test it again to be sure that this particular variation was the one that had that effect.
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If that works, I will certainly be drilling a small hole across the upper arms and threading through a thin bolt to which I would girth in a soft connection. I like!
 
I've just read the BDB and RR threads and started wondering about possible differences in performance between the two devices.

It appears that there probably is no performance difference and the choice could be down to whether you would like the top arm facing away or towards you. This would be only be an ergonomic preference I suppose.
Does anyone have enough experience on both to be able to express an opinion?
Thanks.
 
The bone does have the edge there.

Beyond that. I have found them to perform equally. I honestly can't choose one. I feel some affinity for the bone because I had it before most people, but that is sentimental rather than functional.
 
I see that you can put a key ring directly through the extra holes in the upper arms. Then you have a handy ring to clip the tether to that stands up nicely. This would also work as a clip in point for self tending the Bone with the standing end of the line on the bridge DdRT (as shown with a prussic on page 5)
 
Nice work, treegongfu! I still like my strap and ring attachment as it doesn't interfere with the BDBs movements. One thing I think you guys are missing is that anything that causes the BDB to tilt back towards the climber, reduces the clamping force at the spine by negating the leveraging force of the lower arms. So even if you forced the top arms to engage, releasing the spine grip will still cause the BDB to slip. I think it is best to just avoid the problem by only pulling up while slack tending during a rope walk.
 
OK, I tested out my tilt theory of my last post and it doesn't appear to be a significant factor in releasing the lower arm. I still however, can't find a tether location that will absolutely guaranty not to release with backward pressure.
 
David. I'm afraid you are correct. I stupidly didn't take into account differences in rope. I get roughly similar results when all three configurations are tried on the same rope. I was getting more grip with tachyon and comparing the results with cougar blue.

I feel like an idiot:(
 
I really should try doing more testing before I post but it's 10 below zero out and I keep wimping out. I do think that the location recommend by treegongfu is going to work out best. It seems that midway between the links is the sweet spot.
 
David, thanks :)

I'm going to extend the arms out the back like in your mod pic and try a tether there.

If that doesn't work I will stop messing with Gordon's amazing creation and just enjoy climbing on it.
 
One word of caution with attaching a tether to the top arm with the rear portion of the of the arms sticking out proud of the spine, and that it is it could impede the free upper movement of the top arm as you sit back.
 
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