Are two Three to One MAs in fact a Six To One MA?

For a long time it was accepted that having two Three to One Mechanical Advantages hauling on a load would equate to a Six to One Mechanical Advantage. We did some testing with CrackerJack Rescue to see if this was true.. Turns out.. It isn't. (Watch at 1080p to see the notations on the white board)
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[@VisinskiRadoviBeograd]

I'd like to hear Richard Delaney on this presentation.

[@NorthWashOutdoors]

Great explanation :)

[@jasonmcmillan6598]

SADLY- this video is necessary. thanks for doing it

[@legnip]

And let's not forget...3' of rope hauled through a 3:1 moves your load 1'. 6' of rope hauled through a 6:1 moves your load 1'.

[@mikekollross8810]

That was my thought. A side x side has the same pull on each setup as a 6:1 but without the length of pull needed for a 6:1

[@yair3k]

How are you monitoring 2 load cells in the app, I can only monitor 1 at a time?

[@ianbrown_777]

If people still have trouble seeing why there is no advantage, they could think of replacing both 3:1s with fixed ropes. If the theory is that paralleling systems halves the effort, the theory must work for ANY MA so by that thinking, 2 1:1s should do the same. Clearly anyone can then see that they don't.

[@tkmfischerman2582]

Two 3:1 MA's = 6:2 then...? And 10:2 for the 5:1, and so on right?

[@michaelstepp8883]

So the smaller pulleys do increase friction in the system. For rescue certification minimum pulley size should be 4 times the diameter of the rope so it’s not a sharp change of direction, example a 1/2” rope need a minimum of a 2” pulley. Secondly the more parts put into a system makes more friction and more equipment needed so we wouldn’t usually build two systems side by side anyway. We put one system built onto another just like you did with the 6:1 set up you did, and when one system is acting on another you multiply them together - the friction lost in the system. An example there like you did here a 2:1 acting on a 3:1 is a 6:1 system if a 3:1 acting on another 3:1 you have a 9:1, same as a 4:1 acting on another 4:1 you will have a 16:1 then whatever friction is lost in the system. And finally if you do build two separate systems side by side one person is not pulling both systems you will have someone working one system and someone else working another system so you are getting additional mechanical advantage because each person is pulling less weight than with a single system. Yes total load is the same but each system is assisting the other thus it does add to them. In your example one system had 36lbs on it and the other had 40lbs which is less than one system with a load of 74lbs on it. So again yes added together they are providing the same amount of work for the effort but the effort is split in two systems with two people pulling the load instead of a single system single person doing all the work so I disagree with the way it was added together.

[@MegaCbgames]

in that last case, what do 2 separate 3:1's have for an advantage over one 3:1 with 2 persons pulling on it?

[@moomastico]

@@MegaCbgames you maintain tension in both lines so there's much less of a shock load if one fails.

[@ZebulonJakub]

Wait science? Hahahha i thought folks knew this