I wanted to throw this question out there as a poll of sorts. I recently taught a class and got into a discussion of using a 3:1 MAS or a 4/5:1 MAS in a horizontal operation. I find this to be a debate a lot. I'm a big fan of the 4/5:1 block-tackle in any application. I think the system overall is neater and why use the power of a 3:1 when I can harness the power of a 4 or 5:1. When I ask why they prefer a 3:1 in that application usually it stems back to : Thats how I was taught" Then I do my best to convert them.
So what are your thoughts on this? Shout them out loud and proud!
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Thread: MAS Poll 3:1 or 4:1 Horizontally
12-11-2010, 10:02 AM #1
MAS Poll 3:1 or 4:1 Horizontally"Training Prepares You...For Moments That Define You
12-11-2010, 10:12 AM #2
4/5:1, but I always hear the same about the 3:1 too....
12-11-2010, 10:57 AM #3
- Join Date
- Nov 2006
- N. Ridgeville, Ohio
We use the 3:1 for horizontal due to the fact that it is easier to make it adapt to areas easier. Ie: changes of direction or mulitple anchors for longer runs of pulling areas. The 4:1/5:1 lends itself to cleaner use in the vertical world. Plus, the 4:1/5:1 is not as user friendly when having to lengthen the ropes for longer systems. If I have to go 150' for a lay, then I would need a 600' rope with a 4:1. I can accomplish the same task with a 300' or 400' rope just as easily. The big thing that we try to teach, is not to get stuck using what is packed in the systems bags the same way all the time. Think outside the box. If the system is more efficient for the application use it. If not, rethink and adapt. Trying to use the same system all the time is foolish. We tend to teach the 3:1/5:1 method for quick and easy addition of MA if needed. Not a whole lot of hardware is need to convert to the 5:1 and it can be done very quickly.Jason Brooks
IAFF Local 2388
12-11-2010, 02:40 PM #4
Safe to say they both have there place and time.
12-11-2010, 07:37 PM #5
The stroke of the system really does become a factor when using a 4/5:1 MAS. I just go the route of piggybacking the system onto the main line,this allows for any change of direction needs (pulleys) ahead of the MAS and also eliminates the need to use 750' rope on a 600' haul. Bottom line...it's just my preference.
Mike Donahue"Training Prepares You...For Moments That Define You
12-11-2010, 10:26 PM #6
- Join Date
- Nov 2006
- N. Ridgeville, Ohio
12-12-2010, 04:00 AM #7
i tend to gravitate to the 3:1/5:1/9:1 progression. most guys are pretty comfortable with that. we regularly gang on an aztek (4/5/11/12:1) for raise then lower operation or knot passing. my observations are that most guys i've worked with are most comfortable with the 3:1 based systems and that 4:1 systems have more head scratching going on than the 3:1. they shouldn't but they do since there are dead legs, ganging on issues with length to the edge, knots in the system, etc...
personally i'm fine with any of the systems as long as they are efficient, the team is comfortable with them, and they get the job done easily and in a timely manner.
12-12-2010, 10:12 AM #8
- Join Date
- Jul 2006
- Southern Illinois
Stick hinted at it with the "dead legs". But no one has mentioned that except for instances of a straight shot in space to the rescuer, such as through a manhole, even MA systems are typically ganged on to the main. Such then requires a "slacker" on the main taking the dead leg through the PCD. If you're down on human resources, you might want to consider an odd system, inline with a PMP at the ratchet, and put the slacker in the haul team.
12-16-2010, 05:31 PM #9
- Join Date
- Mar 2010
- eastern WA
If we have sufficient main line left after the lower, we build the MA out of the main line itself in the simple 3:1 to simple 5:1 to compound 9:1 progression. The first COD pulley (a PMP) at the main line anchor gets the ratchet (3-wrap Prusik) for progress capture.
It should be noted that other simple odd-MAs (e.g. 7:1, 9:1, 11:1 etc) can easily be built out of the main line, at the expense of many pulleys and possibly too much friction, even when using pulleys with high efficiency. We’ve found that the simple 5:1 is about where it starts not paying to add more pulleys. Anyone else?
If we have insufficient main line left after the lower, we use a ganged MA. We put progress capture (3-wrap Prusik with PMP) on the main line to avoid the “dead leg” effect during raises and, of course, to allow resets of the ganged MA. It should be noted that a ganged MA can be ANY MA that one can dream up. As has been pointed out, even-MAs are most commonly used in ganged systems, but any MA, even or odd, can be used. We typically use a simple 4:1 or a compound 6:1 in ganged systems, and we build our ganged systems out of an extra full length rope rather than a pre-rigged jigger (see last paragraph below).
As has also been pointed out, it takes an additional person to operate the progress capture for a ganged system. If you’re short on personnel but have plenty of main line left over, just build your MA out of the main line itself as described in the first paragraph above.
Also, for situations requiring a very short raise (e.g. pickoffs in which the subject is loading a fall arrest system), we have also simply built an MA jigger out of the loose end of the main line, ganged it onto the main line, did the small raise, de-rigged the MA jigger, and then continued the lower. We’ve tried many different MAs in this fashion: simple 2:1, simple 3:1, simple 4:1, simple 5:1, and compound 6:1.
I don’t like pre-rigged jiggers for ganged hauls because they have very limited throw distance. I prefer to rig my ganged systems out of an extra full length rope. In this case, the throw distance is only limited by the distance between the MA anchor and the inside edge of the safety zone. In my humble opinion, pre-rigged jiggers are meant for very short raises or for guying applications, and they do excel in those applications.
These are my preferences for flexible and efficient raises.
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