Why register? ...To Enhance Your Experience
+ Reply to Thread
Page 2 of 2 FirstFirst 12
Results 21 to 34 of 34
Like Tree1Likes

Thread: Is this safe to be used as is for work/rescue?

  1. #21
    Forum Member
    Join Date
    Jan 2012
    Posts
    76

    Default

    Quote Originally Posted by Fairfield View Post
    yup this is all around just bad. I would just love to know if someone thought this was a good plan. Never did get an answer on that.
    I don't see where you asked the question of whether it was a good plan or not. You said you thought it was bad and asked if we knew why... and then asked for deeper discussion.

    We've discussed our opinions: What is the "big reason" from your original post why YOU said no?

    To clarify, I think the basic premise of the setup is sound for the vertical reeving element of a highline. To rig for failure of the rope at the pulley with yet another rope to be managed, would probably be too complex versus the chance of it being used successfully. For a confined space, however, I would stick with an independant belay line
    I used to be DCFDRescue 2. Forum changover locked me out.

    www.rescue2training.com


  2. #22
    Forum Member Fairfield's Avatar
    Join Date
    Aug 2013
    Location
    Bucks County Pa
    Posts
    62

    Default

    Strange I wrote another reply after my last to clarify and it didn't show.....

    I was thinking out loud, The pic comes from a rope access site and to have one line like this just doesn't fly. The foundation of this I will agree is not that bad all in all. I would not use the ASAP in this spot though. knowing that the ASAP was designed to slip a given distance (in this case pushing close to the distance) and there is other mechanical devices out there that could be better fitted for this. I have never had much issue with a prusic being used here but having devices that mind them self is a huge advantage in my mind.

    Although a good talking point was brought outwith this. If the line breaks and one backup catches, will the load be outside the foot print of the A frame? I say due to the wall being (seemingly) close the resultant force will stay in the A frame. Not centered but still inside. I dont see it causing any kind of failure. If you see it different, explain why, so I can see your side.

  3. #23
    Forum Member
    Join Date
    Jan 2012
    Posts
    76

    Default

    Quote Originally Posted by Fairfield View Post
    Although a good talking point was brought outwith this. If the line breaks and one backup catches, will the load be outside the foot print of the A frame? I say due to the wall being (seemingly) close the resultant force will stay in the A frame. Not centered but still inside. I dont see it causing any kind of failure. If you see it different, explain why, so I can see your side.
    The resultant is not the load pulling downward on the A frame and the moving over a little bit in the hole. The resultant is the sum of the forces being applied. The simplest way to envision it is usually the halfway point of the angle where the rope changes direction. This is where the force is actually being applied.

    The setup in the picture works because the two pulleys on top of the A frame create resultants that cancel each other out and put the A frame into compression. When you only load one of those pulleys (an ASAP locks up), one of the resultants goes away and the system is no longer in balance. In this case with the resultant outside of the A frame legs, even while load is with in the legs.
    I used to be DCFDRescue 2. Forum changover locked me out.

    www.rescue2training.com

  4. #24
    Forum Member
    Join Date
    Jul 2006
    Location
    Southern Illinois
    Posts
    132

    Default

    Quote Originally Posted by Fairfield View Post
    ----------------
    Although a good talking point was brought outwith this. If the line breaks and one backup catches, will the load be outside the foot print of the A frame? I say due to the wall being (seemingly) close the resultant force will stay in the A frame. Not centered but still inside. I dont see it causing any kind of failure. If you see it different, explain why, so I can see your side.
    If you're using a D-carabiner to support your high directional pulley, the spine of it is the arrow pointing at the resultant. Or think of the spine as a finger pointing at the resultant, accurate to within a fraction of an inch. The resultant bisects the interior angle of the rope at the pulley.

  5. #25
    Forum Member Fairfield's Avatar
    Join Date
    Aug 2013
    Location
    Bucks County Pa
    Posts
    62

    Default

    Rescue 2, The way I see the resultant given the load being placed fully on one side of the line would still be centered fairly well inside the foot print of the A frame due to the pulley at the A frame being connected to both left and right intersecting members of the frame. This in my view places enough force to both legs of the frame to remain stable. This does not go to say though that some stabilizing rigging may need to be done before a lift or a lower is resumed (especially when approaching braking the plain of the hole) . If the pulley and its resultant force was to be close to or outside the leg of the A frame I would then see a problem.

    This all does not go to say I am disagreeing with when it is all ok and it is in tacked like in the pic that both resultants are equaling each other out. I do think though that this is well equaled out and important due to the raising and lowering (as to not fluctuate the force to one leg or another.

    I could very well be wrong with how I see this but am having a hard time seeing the resultant within the frame pulling the hole thing back and over. Have you seen this in this setup with a failure to one line side flip over? Or have you loaded an A frame with one leg only loaded and just not work?

    I am only guessing that this A frame is made from two ladders or to the nature due to it presumably being stable left and right from tipping over.

  6. #26
    Forum Member
    Join Date
    Jul 2006
    Location
    Southern Illinois
    Posts
    132

    Default

    Quote Originally Posted by Fairfield View Post
    Rescue 2, The way I see the resultant given the load being placed fully on one side of the line would still be centered fairly well inside the foot print of the A frame due to the pulley at the A frame being connected to both left and right intersecting members of the frame. This in my view places enough force to both legs of the frame to remain stable. This does not go to say though that some stabilizing rigging may need to be done before a lift or a lower is resumed (especially when approaching braking the plain of the hole) . If the pulley and its resultant force was to be close to or outside the leg of the A frame I would then see a problem.

    This all does not go to say I am disagreeing with when it is all ok and it is in tacked like in the pic that both resultants are equaling each other out. I do think though that this is well equaled out and important due to the raising and lowering (as to not fluctuate the force to one leg or another.

    I could very well be wrong with how I see this but am having a hard time seeing the resultant within the frame pulling the hole thing back and over. Have you seen this in this setup with a failure to one line side flip over? Or have you loaded an A frame with one leg only loaded and just not work?

    I am only guessing that this A frame is made from two ladders or to the nature due to it presumably being stable left and right from tipping over.
    To repeat Rescue2's general point... what difference does it make whether or not the load is in or out of the hole? None. The resultant bisects the interior angle of the rope thru the pulley. Correct your initial drawing to indicate this. Maybe then it will be a little less fuzzy for you.

  7. #27
    Forum Member
    Join Date
    Jan 2012
    Posts
    76

    Default

    Fairfield,

    Would you agree that this is how the force is being applied, or do you think that this thing is tied back to keep it from flying over the edge when it is loaded?

    Name:  resultant1.jpg
Views: 101
Size:  32.2 KB
    I used to be DCFDRescue 2. Forum changover locked me out.

    www.rescue2training.com

  8. #28
    Forum Member Fairfield's Avatar
    Join Date
    Aug 2013
    Location
    Bucks County Pa
    Posts
    62

    Default

    No, I see that is where the resultant is going. I understand that rule. Im not saying in the original pic that the resultant in being placed back straight down to the load. I may be being mistaken as thinking that.

  9. #29
    Forum Member
    Join Date
    Jan 2012
    Posts
    76

    Default

    Nerdy picture time:

    The interior angle of one side of your system is 73 degrees.

    Half of that (the resultant) is roughly 37 degrees, which is what the second picture represents.

    The angle you are trying to beat (be a more acute angle than) is 28 degrees.

    I argue the resultant is outside of the footprint.

    Name:  2013-11-16 08.27.43.jpg
Views: 97
Size:  24.1 KB

    Name:  2013-11-16 08.21.18.jpg
Views: 102
Size:  23.1 KBName:  2013-11-16 08.23.16.jpg
Views: 96
Size:  25.3 KB
    I used to be DCFDRescue 2. Forum changover locked me out.

    www.rescue2training.com

  10. #30
    Forum Member Fairfield's Avatar
    Join Date
    Aug 2013
    Location
    Bucks County Pa
    Posts
    62

    Default

    Nice break down of the pic. This is how I have been seeing the resultant though. Keep in mind I am not saying that the load will be raised or lowered just holding still. With that said. I have found that when a tri pod or A Frame is at a certain angle of lean that a resultant such as this will be fine. Now if the resultant was out of the foot print above ground and not at some point below the Frame or pod can still remain stable (saying it had not fallen during the shock load). Attached is a pic of a similar resultant with a slightly leaned tri pod. The block load I had sat on and had no issue with the pod going backward on its self. That being said, like I stated above I would not haul like this due to knowing it will need to have more stabilization for that. If I was to have the tri pod at a more up right stance then sure it will go over with ease. Name:  tri pod outside resultant.jpg
Views: 99
Size:  46.8 KB

    Ya I have my own Tri Pod, I love this stuff more then you all even know!

  11. #31
    Forum Member Fairfield's Avatar
    Join Date
    Aug 2013
    Location
    Bucks County Pa
    Posts
    62

    Default

    Name:  forces outline.jpg
Views: 92
Size:  55.5 KBSo this is the break down from the floor of as close to the original picture I can get. The resultant hits the ground at 7 inches from the rear load bearing leg (and will like your picture shows eventually be outside the foot print below grade). There is 31 inches of space from front to rear and 17 inches of space left and right to work in. Not to say you cant make the 31 inches more if you are bringing the load up and out toward the front two legs centered. Now with this set up I had shock loaded the system with the concrete and also myself. The tri pod had wanted to move a bit but not enough to flip over. Keep in mind I had not anchored the legs down in any way. The tri pod is a Miller and the leg in the rear was set to the second hole up and the front two at the lowest setting. This gave a small amount of lean like the original pic shows.

    Again to haul with this setup would not turn out to great for anyone, but the discussion is would a load that has survived a shock load to one side be stable with this resultant?

  12. #32
    Forum Member FiremanLyman's Avatar
    Join Date
    Dec 2009
    Location
    Texas
    Posts
    948

    Default

    Quote Originally Posted by Fairfield View Post
    Ya I have my own Tri Pod, I love this stuff more then you all even know!
    Hell my wife gets frustrated when I repack my task force gear in the living room when my team goes to stand down. I am going to show her this!
    Fairfield likes this.
    ~Drew
    Firefighter/EMT/Technical Rescue
    USAR TF Rescue Specialist

  13. #33
    Forum Member
    Join Date
    Jan 2012
    Posts
    76

    Default

    Quote Originally Posted by Fairfield View Post
    Again to haul with this setup would not turn out to great for anyone, but the discussion is would a load that has survived a shock load to one side be stable with this resultant?
    If it has survived a shock load, then you'll probably be able to haul on it. But we're playing a guessing game based on a drawn diagram.

    I think the A frame would not flip, but instead try and move towards the anchor.
    I used to be DCFDRescue 2. Forum changover locked me out.

    www.rescue2training.com

  14. #34
    Forum Member Fairfield's Avatar
    Join Date
    Aug 2013
    Location
    Bucks County Pa
    Posts
    62

    Default

    Yes move toward the anchor first. That is what I have always found to be the case. Although due to the legs being staked to the ground that movement toward the anchor in my experience has turned into the energy flipping or trying to flip the rig. Due to both sides of the Frame being anchored down though I don't have to much concern. This is all saying we are not maxing out the load capacity for the Frame. If this was the case I can see the top twisting or being damaged in some way. Similar to having a tie back line go from an anchor to a leg directly on a Tri Pod, you will eventually bend the leg.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Does anyone work for Dekalb county fire rescue in ga?
    By Mickeymantle in forum Hiring & Employment Discussion
    Replies: 0
    Last Post: 10-19-2013, 07:08 PM
  2. Nice Bit Of Cross-Border Rescue Work
    By MalahatTwo7 in forum Firefighters Forum
    Replies: 0
    Last Post: 04-12-2011, 07:40 AM
  3. Rescue work temporarily halted at German ice rink
    By RspctFrmCalgary in forum Firefighters Forum
    Replies: 2
    Last Post: 01-05-2006, 09:41 AM
  4. Tech. Rescue Work Sheet
    By BC White in forum Specialized Rescue
    Replies: 2
    Last Post: 08-21-2000, 08:32 PM
  5. Ron Goes to Work for Plano (TX) Fire/Rescue
    By rmoore in forum University of Extrication
    Replies: 0
    Last Post: 06-13-1999, 02:45 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts