Bullring rigging device idea

surveyor

Well-Known Member
The copper stay pipes started at 90 degrees from what is shown in the video, but they did not work there to keep the tail on the device. My thought is to make the stays thicker and curved towards the black ring, leaving just enough space so the rigging rope would mid line insert. All parts shown would be welded, with the ring and central cross member made monolithic by CNC milling, with the bollard cut and welded to the cross member, with the stays welded on the ends of the bollard. The 4 wear positions would be if you inserted the bight from one side or the other, and if you flipped the girth on the ring from top to bottom.
 

Tom Dunlap

Here from the beginning
Administrator
Brilliant.

Have you read Carroll Basset from BMS paper about friction?

I could see a problem with too much friction on the bollard when yarding up the working end to the climber. Carroll’s solution was to round over the corners of his bollard. Plus, stainless is pretty slippery
 
Last edited:

Tom Dunlap

Here from the beginning
Administrator
After my first view on my phone and time to think about the device the issue of unloaded friction might not be as important because of the design.
 

*useless info*

Well-Known Member
Very nice!
.
i would think would want close enough access to device to whip on/off last turn for lowering/retrieval: but far overhead c/would be problem as say
.
Bottom half of ring supports downward loading of top half and gives friction arc points; center bracing handles side forces produced enroute .
.
Ultimately must insure remains self balancing thru our BS.
.
Strong aluminum will be light, and like copper a very 'jealous' metal grabbing heat from neighbor, that cook evenly and make great heatsinks, including for this work.
(vs. bark arcs to tear on rope, and be thermal insulator to massive heat conversions.)
In a shop if 1 side of steel gets hot, have more time to get off other side before getting burnt than if is aluminum for sure!!
.
Very nice considering at conception to build as more functional flip when bottom route worn reducing own sales.
>>If outer ring wear shows as the greater concern some more position variance can be seen and given per control leg is lesser wear point than load would think
>>Also control leg angle doesn't need to be straight 'down'/inline to hit the primary wear point squarely like load leg
>>this would happen Naturally if load leg routed thru pulley, branch, krab etc. not directly under support causing unit to line up load leg same inline between laod and support, but control leg again not on primary wear point.
.
Any (f)utility in continuing initial rope pass back under ring and around to finally lock back under capstan?
>>perhaps would then invite thicker cross member , really as spacer for pathed
.
These are things i'd consider as watching this and categorizing facets of this gem:
fave: jrre.org/att_frict.pdf showing for friction brakes in rescue ; src for:
work: Exponential Brake Force Increases per added degrees: compared in different materials flat then radial CoF
Biggest take away, larger capstan gives same friction per 180 arc, and this is all about the arcs.
Extends to:
i think ALL of rope work can be based on 180degree arc counts in att_frict as a base
>>cumulatively applied like as bollard type/radial or rapell rack/linear type builds
>>the same formulae base is used for calculating compounding interest
>>the formulae is similar to what math nuts call the most beautiful formulae in math
To my 180degree units:
>>a straight line is actually, simply arc_0 (x180) to keep math/model tidy as shorthand
(straight line is just extension anyways, can still be slanted to leverage higher tension tho)
>>rope/flexibles only support on the inline axis>>straight line or arc back around to same axis, reverse direction
>>can be taken further as actually based on 90 degree geometry and other half, but 180 is 'most usable form' so shorthand to there usually
>>matches source work theory doc.
 
Last edited:

Jonny

Well-Known Member
Cool idea, looking forward to the finished product :)

I’m not seeing any reason it wouldn’t work as a traditional basal lowering device, like porty, as well.
 

surveyor

Well-Known Member
Hello all, Thanks for the input. I am considering increasing the ring and cross member dia. a bit, and going with all Aluminum alloy 7075, with the bollard having 1/2" thick wall thickness, and the stays being a full 1" dia.. After talking with a fabricator today, I think the stays should be angled back towards the ring, leaving about a 1" gap where the stays near the ring. I have not read the Carroll Basset article. The exponential brake article also looks helpful, Thanks.
 

*useless info*

Well-Known Member
About as dense as steel but no weldie, 6061 compromise.
Larger rounds allow softer rope arcs; but counter-intuitively same friction by this math; then also add strength and weight as device. Standard aluminum not as weight nor strength dense as steel. So must be thicker to match steel strength. Over all strength to weight still favors steel even if 2.5x heavier per volume than aluminum. 7075 resolves but not as friendly.
.
Can bring choices closer to cost, heatsink and CoFs
Nylon on steel shows higher/ more frictive CoF than nylon on aluminum.
 
Last edited:

surveyor

Well-Known Member
I'm thinking that a 1/2" thick walled bollard would be strong even with 6061, then also increase the thickness of the ring and cross member.
 

surveyor

Well-Known Member
That is what I am thinking also. I would like to make the OD of the ring 7" dia., with a 2.5" dia. bollard. When you say 1/4 cleats, do you mean the stays, 4 on each side?
 

SomethingWitty

Arkansawyer
I'm thinking that a 1/2" thick walled bollard would be strong even with 6061, then also increase the thickness of the ring and cross member.
Man. Yes.
Half inch wall is absurdly strong. Have you seen the aluminum bollard for the GRCS?
It's welded so probably heat treated 6061?
 

evo

Well-Known Member
That is what I am thinking also. I would like to make the OD of the ring 7" dia., with a 2.5" dia. bollard. When you say 1/4 cleats, do you mean the stays, 4 on each side?
like the stein units... yes.. It's best of the climber is controlling the load for it to be fine tuned as much as possible... What is the mini porty's diameter?
 

*useless info*

Well-Known Member
Devil's advocate shotgun:
.
Playing workflow backwards;
Shows soft sling attachment;
lots of hangs like this i'd prefer krab attachment link to then soft sling/rope as most modular utility of fewest links
.
But this could mar 1 reversible side with metal to metal, especially steel krab to softer alum device, that then might not want to be friction path if no longer smooth/moving this to non-reversible.
.
Envision hang sling in choke with enough room to invert device on to girth choke?
Float from rope to ground (extra support loading then)?
short round or eye2eye(less self equalizing and more dedicated wear points) sling girthed to krab to sling or rope sounds busier/more linkages; but cracks egg.
.
Other thing been trying to see is pre-tensioning options
>>if attachments high and low with some kinda Evo rope guides at those positions could hang from krab and have mini pulley for pre tension on opposite end, but then too busy while working if can't take out of way before lowering.
>>could throw 3/8" thru lower ring between load and control legs and pretighten, but then remove, so 1 shot charlie if device is remote from climber
>>want this metal clear from denting brain bucket or contents, so probably out of climber reach in lots of scenarios
>>perhaps could say climber stand on load to set, sit to cut but reduces some other plays on the board position wise for device
But conceivably could put rope on device, climber hang on control leg /perhaps stand on foot cam or even loop to it) and reach over and pick up on load leg(or further out on flexible load) for rope purchase, then paste rope tight to device high side with hand and putt on extra friction turn then and sit, and go for what ya know.
>>Fair workflow, but specific position of device to be close enough and yet far enough to not dent your coconut on loading.
.
Start up cost$ aside (yeah right.. ) ;
could envision bear and puppy sizes like some Portys.
 
Top