Vector Forces on Tripods and mitigation

[MichaelXYZ]

Vector forces are important when using tripods in CS rescue. With a 4 to 1 or winch type system we usually don't have to concern ourselves with this. But... there are times when you don't use a 4 to 1 or winch (Insert reason here) and you will use some other MA system such as 3 to 1 off a RPM.

Well, the way I was shown to do this was to attach a change of direction pulley right under the CS entry as shown in first image.



Now my question is... What do you do if you don't have an anchor point for your CD pulley?
Can you make an anchor at the bottom of your tripod using the holes at the bottom of the legs to rig something like in the next image? Would this work or does it create other problems?

[TillamanTrk1]

extend an anchor from a near by anchor.. truck, tree, picket.... just as long as its coming from the opposing direction that your going to pull from your COD. Kind of hard to understand without looking at it.. I don't have a picture.. I wouldn't use legs of tripod as an anchor.

[MichaelXYZ]

This very issue came up last Sunday during training. First image. We had the winch, but we needed to have a backup using the belay in case of main-line failure.



Our solution was to attach a sliding beam anchor to the nearby beam and rig a pulley. Problem with this was the sliding beam anchor traveled up the beam when tension was applied to the pulley's.

[rsqman]

This very issue came up last Sunday during training. First image. We had the winch, but we needed to have a backup using the belay in case of main-line failure.

Attachment 22794

Our solution was to attach a sliding beam anchor to the nearby beam and rig a pulley. Problem with this was the sliding beam anchor traveled up the beam when tension was applied to the pulley's.

Attachment 22795

You just need a beam clamp instead of a sliding beam anchor. We can tighten ours down so it doesn't slide and it provides us with three 5,000 lb rated anchor points.

[MichaelXYZ]

All we had was the sliding beam anchor. Do you know who makes your clamp?

Was yours something like this?

[EricUlner]

a couple different options...

-Use an Arizona Vortex in an Easel A-Frame configuration. Resultant stays inside the larger footprint. If you have the money...

-If using a 4:1cd, you can remove the terminal end of the rope from the becket, add a 5th sheave, and run the rope thru and out to the opposite side of the tripod to an anchor point. Keep that end of the rope at a similar angle (or a bit larger to compensate for pulley friction) to the tripod as is the end you're pulling on has from the tripod. If you're using a 2:1cd, you'd add a 3rd sheave and do the same thing. Either MA, you're simply creating an opposing force vector, which keeps the the tripod in compresssion.

[Rescue Dave]

Was yours something like this?

Attachment 22797[/QUOTE]

We have a beam clamp just like that but frankly, we almost never use it (not to mention the thing is pretty heavy). Used it once when we couldn't get webbing around the I-beam because one flange on the beam was flush against a wall. One note when using these clamps; we like to include a "soft link" between the clamp and whatever we're connecting to it. Otherwise the 'biner can get torqued. You could also use a swivel in there but we don't carry swivels around with us.
Stay low, stay safe.
Dave

[jdcalamia]

Eric,

Any pics of this. I'm having a hard time visualizing it to understand.

[MichaelXYZ]

If I understand correctly, if... I think this might be what he is saying?

[EricUlner]

If I understand correctly, if... I think this might be what he is saying?

Attachment 22814

Yes, that's roughly what I'm saying. Put your new pulley higher in the tripod or raise your new terminal anchor a bit.