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

  1. #26
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    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.

  2. #27
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    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
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  3. #28
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    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.

  4. #29
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    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.

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    Name:  2013-11-16 08.21.18.jpg
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  5. #30
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    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
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    Ya I have my own Tri Pod, I love this stuff more then you all even know!

  6. #31
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    Name:  forces outline.jpg
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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?

  7. #32
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    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!
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    ~Drew
    Firefighter/EMT/Technical Rescue
    USAR TF Rescue Specialist

  8. #33
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    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.
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  9. #34
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    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.

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