Compact Bulldog Bone

I don't have original arms to compare this to, but I'd speculate that these arms also keep the upper arms more horizontal than the flat lowers.

I'll try to post a pic tomorrow and maybe someone else can take a picture with the flat arms for an overlay comparison.
 
hey gordon, seth here, ive been working on the lower and upper arms as well, believe it or not they look pretty close to your e/c. Also i have been working on a tear shaped top bollard with groove to hopefully share some of the load on the bottom link. the tear drop will not spin but it might have a cam affect, making the release more progressive. I hope I get some wire EDM time this weekend.
 
Seth, I look forward to that. The teardrop bollard sounds interesting, I have experimented previously with a football shaped bollard.
 
i don't want it to spin though. think of hydraulic drum breaks. when the top arm is collapsed i believe im getting a top arm to bottom arm force applied ratio of about 20:80 which for me 200lbs, will heat up the bottom link. if i can get the distribution more evenly to say 40:60 would be ideal but i would settle for 30:70. anybody (MUMFORD) have any ideas how to measure the changing force. i get so rapped up in design i neglect to calculate actual numbers.
 
The oval shaped bollard did not spin, but I did not like the release as well. When I made an aluminum bronze sheave for my ZK1 rather than a fixed bollard, it did not seem to make much difference in the grip.
 
I wonder how far the design could improve over the next year. If I know myself, I'll probably be looking to buy a second bone this winter and complete a more symmetrical DRT system.
 
Here is the 4th batch bone with the rope installed.

IMG_1376_zpsweacbbnv.jpg
 
That is an excellent solution to a legitimate concern. You do realize that you will end up doing the same thing for the upper arms as well. The other way to remove the potential failure of a bent pin would be to not have them open and just thread the rope through like you would with a Zigzag or Spiderjack. I, as I'm sure most users would agree, love the ease of rope attachment with the opening links but I bet that a closed link BDB would be for all practical purposes, indestructible.
 
This certainly wasn't my original idea, but this is a cool way to set up the Bone Ddrt. The small prussic on the standing end of the line captures the bungee tether and keeps if from flopping around when pulling slack. Nice having virtually no sit back at all and tends great. Also the mini plate, helps to separate the lines nicely.

Also, notice that there is a 7/16" steel bollard on the outboard end of the upper friction link (Thanks Gordon). This seems to help the upper links on the bone act more like the rope wrench, putting extra friction up top. I have been using that with the 5/8" bollard on the Yale 11.7 for a month now and it works pretty darn good.

DSC00324 (480x640).webp
 
That is a good idea to have a bit of separation between the two sides of the system. Also, Mike put me on to the rubber nubs, thanks. Looks like they are holding up for you?
 
Has anyone thought of using a slick pin in the upper and lower arms, so the link would not have to be notched? It may also aid in using thicker ropes.
For myself this is the one hesitation I have with the bone. I know it's hardly likely for the open link to swing into an upright position, and even less likely for the rope to come out accidentally. However I would personally feel way more comfortable if there was a way lock or capture the swinging link. A slick pin would still allow for mid line install, with out making it over complicated.
 
evo said:
Has anyone thought of using a slick pin in the upper and lower arms, so the link would not have to be notched? It may also aid in using thicker ropes.
For myself this is the one hesitation I have with the bone. I know it's hardly likely for the open link to swing into an upright position, and even less likely for the rope to come out accidentally. However I would personally feel way more comfortable if there was a way lock or capture the swinging link. A slick pin would still allow for mid line install, with out making it over complicated.
Click to expand...
I understand your hesitation, but once you have climbed on the thing for a bit (maybe you have, the hell do I know), in my experience, that worry disappears.
I actually prefer the mechanism to the slic pins. Especally those double jobbers on the runner. Near impossible to open with cold, glove covered gorilla fingers. Those snaps are easy to operate, and even I haven't managed to open one up climbing. And I am not a finesse guy for the most part. I'm a piano mover, not a piano player.
 
No I haven't even seen one in person. Just expressing my thoughts as a potential buyer, I have some Tax return $$ on the way and looking to blow some on toys... Errr I mean tools
 
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