Heres what happens when a pulley is shockloaded.
- Thread starter rangerdanger
- Start date
TreeCo
Carpal tunnel level member
Re: Heres what happens when a BBS is shockloaded.
[ QUOTE ]
what in hades name were you doing dropping limbs off that pulley? thats a lightweight rescue pulley!
sorry no offense.
[/ QUOTE ]
I agree but that pulley is rated for 16K LBS.
No pulley is going to function properly if is not connected properly to the rigging. Hanging a heavy duty rigging block off of an open pear connector would have resulted in a rigging failure, too. It's obvious the damage to this pulley is from the pear connector opening and the whole load hanging off of one cheek plate.
The pulley is not to blame for this rigging failure!
[ QUOTE ]
what in hades name were you doing dropping limbs off that pulley? thats a lightweight rescue pulley!
sorry no offense.
[/ QUOTE ]
I agree but that pulley is rated for 16K LBS.
No pulley is going to function properly if is not connected properly to the rigging. Hanging a heavy duty rigging block off of an open pear connector would have resulted in a rigging failure, too. It's obvious the damage to this pulley is from the pear connector opening and the whole load hanging off of one cheek plate.
The pulley is not to blame for this rigging failure!
- Location
- Connecticut, USA
Re: Heres what happens when a BBS is shockloaded.
A couple of points I'd like to make.
1. Running a rope over a shackle , under load, is allot different from bending a rope around a tight radius in a static situation, such as a knot. The dynamics of a moving rope around a tight radius are that the fibers on the outside of the turn have to stretch. The tighter the bend, the greater the stretch, thus causing much more wear in the rope. This is why manufacturers specify the diameter of the sheave that each of their different ropes should be run over. The lower the percentage of stretch the larger the diameter of the sheave required. That is why the load rating of a rope changes with the radius of the bend, the tighter the bend(smaller radius) the lower the load capacity.
If the rope has any particles of dirt in between the fibers stretching will cause the fibers to slide back and forth across the sharp dirt particles. This will accelerate the wear in a part of the rope that is difficult to check. Always keep your ropes clean.
2. I run an arborist supply store and am sure to tell anyone buying a pulley, such as the CMI, that it should only be used in an overhead rigging situation. Any time the load has to be dropped onto the lowering rope it is essential that a block be used. For any of the various reasons mentioned. Used under these situations the CMI pulley is an excellant tool and will give a long and satisfactory service life.
3. As was mentioned earlier, but bears repeating, a block, pulley, and the sling suspending them see twice the load of the actual weight of the piece, in a static situation. In a dynamic situation the loads can skyrocket.
4. The best equipment in the world, used incorrectly, won't work as advertised. Make sure that you understand how a piece of equipment is supposed to be used. And, just because you had seen it used that way once, does not mean that is the correct way it should be used. Education is key.
A couple of points I'd like to make.
1. Running a rope over a shackle , under load, is allot different from bending a rope around a tight radius in a static situation, such as a knot. The dynamics of a moving rope around a tight radius are that the fibers on the outside of the turn have to stretch. The tighter the bend, the greater the stretch, thus causing much more wear in the rope. This is why manufacturers specify the diameter of the sheave that each of their different ropes should be run over. The lower the percentage of stretch the larger the diameter of the sheave required. That is why the load rating of a rope changes with the radius of the bend, the tighter the bend(smaller radius) the lower the load capacity.
If the rope has any particles of dirt in between the fibers stretching will cause the fibers to slide back and forth across the sharp dirt particles. This will accelerate the wear in a part of the rope that is difficult to check. Always keep your ropes clean.
2. I run an arborist supply store and am sure to tell anyone buying a pulley, such as the CMI, that it should only be used in an overhead rigging situation. Any time the load has to be dropped onto the lowering rope it is essential that a block be used. For any of the various reasons mentioned. Used under these situations the CMI pulley is an excellant tool and will give a long and satisfactory service life.
3. As was mentioned earlier, but bears repeating, a block, pulley, and the sling suspending them see twice the load of the actual weight of the piece, in a static situation. In a dynamic situation the loads can skyrocket.
4. The best equipment in the world, used incorrectly, won't work as advertised. Make sure that you understand how a piece of equipment is supposed to be used. And, just because you had seen it used that way once, does not mean that is the correct way it should be used. Education is key.
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