Mo:
I discussed all designs with Jack Sobon before I built them.
The gin pole is a direct copy of the ones from Richard Babcock's book. The windlass was a direct copy of one from another book that Jack Sobon showed to me.
It is my understanding that you divide the diameter of the circle created by the end of the handles by the diameter of the drum to get the ratio. So if you decrease the size of the drum you would increase the ratio. But there is a trade off in doing that. The circumference of the drum gets smaller too. That means you'll wind up less line with a smaller drum.
We found this to be a problem when we used the windlass to pull parts of a covered bridge out of a river in southern NH. The block and tackle setup was three pulleys in one block and two in the other. That makes it a 5 to 1 ratio. So with 1 hundred pounds of pull out of the block you could lift 500 pounds of bridge. But the line moves very slow and not very far because it had to go through all the pulleys.
I just measure my drum and it is 7" in diameter and the handles are 98" long so that's a 14 to 1 ratio.
In the pictures I posted above, I was lifting two 8x8x16 timbers. They were eastern white pine, and not green but not dry. I figured they weighed about 249 lbs each. 249 x2 = 498 lbs. Going through my blocks, which are two pulleys each the ratio is 4 to 1. So to lift 498 lbs I need to pull the line at 124.5 lbs. Connecting the line to the windlass reduced the force by 14 so 124.5 / 14 = 8.89 lbs. Very easy to try the windlass at about 9 lbs pressure.
Now someone told me to add a friction drag load to the total due to the line going through all the pulleys. And that this load could be as much as 40% of the total loads. So doing the numbers again 498 x 40% = 199.2 -- 498 + 199.2 = 697.2 / 4 = 174.3 / 14 = 12.45 lbs. Again very easy to turn the windlass at 12.45 lbs of pressure. I actually lifted both beam by turning the windlass with one hand on one handle, and I took a picture of the timbers up off the sawhorses with the other.
And if you wanted to break it down even further and use all four handles with four people that would be 12.45 / 4 = 3.1125 lbs of force on one handle.... Very easy for about anyone to turn.
I was told to only lean the gin pole off of vertical not more than 20°. But in the picture I posted we let it lean way over. This was intentional as we were trying to break something to see if it would fail. I wanted it to break here in my yard where no-one could get hurt if it was going to break, instead of on raising day with the crew all around the frame.
We put twice the intended load on the setup and it didn't fail.
We used it to raise a frame here in my yard one day, and it worked great.
If you need any more info please feel free to ask, and if my numbers or assumptions aren't correct, please let me know.
Jim Rogers
