W
Widow Shooter
Guest
was just on the weaver site...they say there were THREE FAILED bridges...wow, one is one too many, let alone 3 
IMPORTANT - Weaver's Cougar BRIDGE RECALL
B
Blinky
Guest
You know plenty. Technically, it's five hi-mod bridges that have failed. So far, no injuries or incidents. Three were Cougar bridges, two were home made but basically the problem is hi mod fiber. Just like you said, wrong application. Let's face it, hi-mod fiber is an engineered material but we approach it like it just another rope. As we start using this hi tech stuiff more and more, we need to approach it with an engineer's perspective and study the specs more. I'm guessing it would have been evident if we had.
I did try to research Vectran vs. Aramids and found that it wasn't supposed to be self abrasive but my bridge (Vectran) looked exactly like Jeremy's bridge (Technora). It's something more than self abrasion.
PCTREE
Treehouser
Glad I went away from the B line lanyards on the Wraptors......
W
Widow Shooter
Guest
I think the forces imparted on a friction hitch are not near the same in magnitude to a bridge, it is spaced out a lot more on a hitch, sure they are fine...
W
Wagnaw
Guest
The issue may not be the fibers, but more so the bend radii or radius that we subject our bridges to using a ring attachment. I started using two rings together because my sequoia bridge wore out fast after changing to a new ring a friend gave me. I since replaced the bridge and added a petzl ring to make two rings. I feel more comfortable now with the wider bend, and I have a feeling the bridge will last way longer.
PCTREE
Treehouser
John, I just switched to tenex FWIW, not due to this issue but because it grabs more reliably with my VT. Read about a dude who fell 30' who was tied in with HRC on poison ivy, VT. He hit the deck. I used to have to always "set" my hitch, now with 3/8 tenex no more. Just one less worry.
B
Blinky
Guest
That's the thing about Tenex, You don't have to think much about it.
Friction hitches are loaded way differently than bridges. The concentration of force on a bridge ring is very high, it's half your body weight focused on a few square millimeters. I use two rings, it helps some but doesn't actually change the bend radius, just separates the bend into two components.
My opinion is, use whatever you want for the material, but don't cover it. Technora won't fail catastrophically under body loads without showing a lot of wear so, as long as you watch it and replace it when starts to fray, no problem. I'm liking Polyester and webbing at this point. I don't know why my BFII bridge wore out so fast but it sounds like most don't. I would have never tried making one otherwise.
Friction hitches are loaded way differently than bridges. The concentration of force on a bridge ring is very high, it's half your body weight focused on a few square millimeters. I use two rings, it helps some but doesn't actually change the bend radius, just separates the bend into two components.
My opinion is, use whatever you want for the material, but don't cover it. Technora won't fail catastrophically under body loads without showing a lot of wear so, as long as you watch it and replace it when starts to fray, no problem. I'm liking Polyester and webbing at this point. I don't know why my BFII bridge wore out so fast but it sounds like most don't. I would have never tried making one otherwise.
wiley_p
Climbing Up
I think the smarties are going to find that the line angles play a large role in conjunction with the material used in these bridge failures.
On our friction hitches, for those of us that use high mod/high speed hitches, we have a perfect line angle, each leg bearing 1/2 of the load on 1 leg of our climb line.
Some of the bridges on the other hand, are bearing our body weight with bad line angles, we would never rig slings with angles of 60 degrees or greater. This is compounding the weight being applied to a rope fiber that does not handle abuse well.
On our friction hitches, for those of us that use high mod/high speed hitches, we have a perfect line angle, each leg bearing 1/2 of the load on 1 leg of our climb line.
Some of the bridges on the other hand, are bearing our body weight with bad line angles, we would never rig slings with angles of 60 degrees or greater. This is compounding the weight being applied to a rope fiber that does not handle abuse well.
wiley_p
Climbing Up
Since I'm to upriver to draw on the computer, maybe this will help. As the angle increases, meaning a shorter bridge, the load on the "sling" will increase. 30 degrees is a great sling angle, that has each side bearing around 54% of the load, Nobody has a bridge anymore that has that good of an angle.
B
Blinky
Guest
Line angle is definitely a factor but I'm having trouble getting my head around it. I'm thinking the longer bridge guys live and me and Stig die.
I think it's about how much force is transmitted along the length of the cord versus how much is dissipated as heat right there in that tiny little contact point between bridge and ring. I think it works like a coffee maker or demand water heater... lots of heat on a small area.
When the bridge is short, the line angle with respect to the rope anchor is large and less efficient at transmitting force. The lost efficiency is from friction and turns to heat which acts on the bridge material in a very small spot.
If the bridge is long, the angle is closer to inline with the anchor and better able to transmit the force rather than dissipating it as heat.
If I remembered anything about thermo I could figure it out but I blocked it from memory after the final.
I think it's about how much force is transmitted along the length of the cord versus how much is dissipated as heat right there in that tiny little contact point between bridge and ring. I think it works like a coffee maker or demand water heater... lots of heat on a small area.
When the bridge is short, the line angle with respect to the rope anchor is large and less efficient at transmitting force. The lost efficiency is from friction and turns to heat which acts on the bridge material in a very small spot.
If the bridge is long, the angle is closer to inline with the anchor and better able to transmit the force rather than dissipating it as heat.
If I remembered anything about thermo I could figure it out but I blocked it from memory after the final.
wiley_p
Climbing Up
I really hope not, but you get the idea.
Similar threads
