Hoist Davit is Complete!

Steve B · 2006-05-06T23:52:18+00:00

Well, in the midst of all my other projects, I went out and in one day completed my hoist davit project for my cabin. This uses a vertical piece of 150" long 2" x 2" x .250" square tube. There is a 48" right angle leg at the top with a diagonal brace that comes in at 21" on the 48" horizontal and 150" vertical. I have used one pin at top and bottom, using a grade 8 1/2" bolt that will fit into sockets top and bottom. The lifting point is approximately 3" in from the end of the 48" top horizontal standoff.Any predictions from the engineers in the group as to bending in the middle of the 150" section with a 150# load? I really think that the maximum I would lift with this is 21 gallons of water in the winter. Mostly, less than 50# of groceries including the lift basket. Just a convenience device to keep us from making several trips up and down the steep stairs schlepping bags of groceries or "stuff".A three phase ramp is being made as we speak, conforming to ADA standards, and that will help a lot. Still, it will be nice to just pile groceries or firewood in the lift, and lift 'er up.I personally don't think it will flex enough to be a problem. When I get the base footer poured, and make a 150# test lift, I will report the actual lateral horizontal bending factor.Anyone care to guess? Winner gets bragging rights. Place yer bets, gentlemen. Will take a month or so. Going back up on the 19th, and a few days to form and pour and cure the footer. This has been an ongoing project, and it will take a while to complete. But, it's moving, at least.So much to do. So little time.Steve

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Steve B 20 years ago

"Don Foreman" wrote

If I got me sums right,

Well, just looking at it, and having hands on experience with lots of "stuff", I think it will be fine, too.

I put a picture of the cabin corner in the mailbox with the name davithoist. I am going to go out and take another of the actual contraption and post that, too. If you CAN go to the mailbox and view this picture, you will see that there is a 34' composite beam, but it only rests on 8x8 posts that are mounted directly to the deck and rafters.

This will be the weak point, pulling laterally on that beam. But, if I keep the load low, there should not be enough lateral stress to even approach critical mass. I have thought of putting in a stabilizer bar, but thought I'd wait to see how it worked first.

Steve

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Steve B 20 years ago

Pictures are in dropbox under davithoist. Four pics or so. Didn't know it was so easy to post pics. Will be doing it on future stuff to make it simpler.

On the pic showing the saddle and davit, the pin is in the saddle, you just can't see it.

On the cabin pic, the saddle will connect to the left side of the rafter end beam/porch support beam, and 2" will stick out to the left so the hole will be clear.

The base will be poured into a form plumb down from the top pin. The chalk like on the base piece is going to be the top of the concrete.

PS to Don: The top horizontal of the "gallows" is 48", not 36".

Steve

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Steve B 20 years ago

"Steve B" wrote

The chalk

Durn spellchecker. Supposed to be "chalk LINE".

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glyford 20 years ago

Don't forget to type up a ".txt" file to go with it, notepad would work fine. Put "hard" carriage returns at the end of every line for best readability. This is so it won't get flagged as a possible virus and deleted... --Glenn Lyford

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wfhabicher 20 years ago

Uhhhhh, guys,

How does one access the dropbox? Usta know, posted there myself..But, time catches up.

Thanks,

Wolfgang

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Steve B 20 years ago

formatting link

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wfhabicher 20 years ago

Steve,

Thanks for the link. Had a look.

I think your design is OK. The horizontal force at the top of the post is quite small, about 1/3 of the vertical load.

My only concern is that you welded to a structural bolt (SAE Grade 5 or

8 slewing pin bottom, and top?). For lifting / hoisting stuff this is a no-no since welding screws up the heat treatment. Too rapid cooling would make the bolt steel brittle, and the bolt head could snap off at embarrassing or dangerous times! I'd re-think that detail. Other than that it looks ok.

Wolfgang

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Steve B 20 years ago

I had thought about that, and intend to make the fit as tight as possible between the two receiver holes. I was going to stack a couple of washers, and put some grease on them.

This unit will see very light use. It will travel about 180 degrees each time, and be used about 50 times a year. I was not thrilled about the bolts, but I wanted to keep the pivot point on center. I figure that I will keep an eye on it, watch for wear, and if I have to, beef it up.

BTW, I will do the first test load with 150#, and measure the side deflection at 75" up from bottom. I think it is going to be Gawd awful strong for lifting 50# at a time.

It's just that the first test load will be about June.

Steve

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Ecnerwal 20 years ago

The tricky thing about brittle failure is that it could quite easily take the 150 lb test load, work fine on the 50 lb loads for a while, and then snap at 25 lbs one day, with essentially no warning. While the 50 lbs might not do any significant damage, what's the hoist pole going to hurt when it lands, if it breaks free?

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Steve B 20 years ago

Nothing important. People. Propane tanks. Dogs. Cars.

I see your point.

Steve

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Hoist Davit is Complete!

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