I don't have any X rigging rings, but based on a perhaps 1" diameter for the rope to slide over I'm guesstimating a tension ratio of 1.6 to 1.8 range. So that means 100 lbs hand side for lowering a 160/180 lb log which means a 60 or 80 lb difference up at the rigging tip. 260/280 lbs total at the tip instead of theoretical 320/360 lbs at the tip. Theoretical because a pulley runs about 1.1 tension ratio or 145/164 lbs hand side for the same 160/180 lb log, not right on double - for lowering - for raising it makes the total more than double.

Bet that's the first time anyone's quantified the tip friction load change for a rigging ring.

Edit - Crow eating time. Dr. Kane measured the tension ratio on X Rings and did a writeup:

Nov 2019 http://digimag.tcia.org/publication/?m=54984&i=629325&p=34&pp=1

He measured the forces using the Donzelli 1999 method of hanging weights on both ends of the rope and then measuring how much more force started the rope sliding. He got 1.5:1 and 0.7:1 which inverts to 1.43:1 (he slid the rope in the opposite direction) so pretty repeatable. I believe 1/2" line on large rings.

He also measured during a log drop and got a ratio of 1.2, but I question the influence of dynamics i.e. is it during a net acceleration or a net deceleration etc which is very hard to pin down on an instantaneous basis even from high speed video, which I think wasn't done.

So punchline my estimate looks high at 1.6 to 1.8 but I don't have slippery hard anodise coating data to work from.

Bet that's the first time anyone's quantified the tip friction load change for a rigging ring.

Edit - Crow eating time. Dr. Kane measured the tension ratio on X Rings and did a writeup:

Nov 2019 http://digimag.tcia.org/publication/?m=54984&i=629325&p=34&pp=1

He measured the forces using the Donzelli 1999 method of hanging weights on both ends of the rope and then measuring how much more force started the rope sliding. He got 1.5:1 and 0.7:1 which inverts to 1.43:1 (he slid the rope in the opposite direction) so pretty repeatable. I believe 1/2" line on large rings.

He also measured during a log drop and got a ratio of 1.2, but I question the influence of dynamics i.e. is it during a net acceleration or a net deceleration etc which is very hard to pin down on an instantaneous basis even from high speed video, which I think wasn't done.

So punchline my estimate looks high at 1.6 to 1.8 but I don't have slippery hard anodise coating data to work from.

Last edited: May 11, 2021