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Thread: The Holy Relic of Flat

  1. #1
    Join Date
    Aug 2016
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    Appalachian Ohio
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    842

    Default The Holy Relic of Flat

    So, a few weeks ago I bought some pine 4x6, 2x6, plywood, 4x4, eight 10" pneumatic tires, 6' of steel square tube with 1/4" walls, and a few odds and ends.

    The first thing I did was use my 4x6 bandsaw to chop the steel 4x4 into lengths, and then welded them together in various shapes. Also welded 5/8" bolts to make axles. The pine 4x4 were planed down and cut to length, and I have a portable hangman's gibbet.

    WHY? Coming up in the next installment.







  2. #2
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    Aug 2016
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    Appalachian Ohio
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    Default

    The next thing I did was make a stand using the pine 4x6 and plywood, using timber framing techniques. You can see the legs are connected to the rails with bridle joints joints, and the stringers are resting in half-lap joints in the rails. A bunch of 3/8 bolts, and the plywood to form a web to prevent racking. Then some levelers made from 1" bolts and nuts.



    Then painted safety yellow. Why? Because I got a gallon for $5 at the off-tint table. Plus, I like a colorful shop.

  3. #3
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    Aug 2016
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    Appalachian Ohio
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    Default

    So why?

    Well, I got a 3 x 4 surface plate for less than $100 (until you add in all the wood and stuff...) I needed a stand for it, and I needed a way to get it on the stand. While I could sort of brute force the smaller plates in the shop, there was no way I was going to move this without machinery.

    I got it home with a pickup truck. But the problem is that it was outside on a rock and gravel driveway. The engine hoist could barely handle it, and the tiny wheels on the engine hoist couldn't be persuaded to move on the gravel... not even empty, much less carrying around 1 ton of stone. But i thought a 10" dia pneumatic wheel could do it. Horrible Fright sells these things cheap... and I waited until they were on sale for $5 each (or maybe $4 each) and I bought eight of them. I figured distributing 1 ton over 8 wheels would keep it down to 250 pounds/wheel... which I figured was within the limits.

    So I put a chain hoist on my portable hangman's gibbet, took up the weight, lifted the surface plate and the pallet by 1/4" and then went and had coffee. I figured I'd give it some time to fail. When I came back it was still in the air, so I lifted it up about 3" and slowly moved the whole sheebang from the driveway into the shop... keeping flat 2x4's under it to cushion the blow if something failed and it dropped.

    Once I got the pallet all the way up to the edge of the stand I let it down, and then lifted the surface plate by driving something like 20 small wooden wedges under it... All I needed to do was get it up far enough to slip a nylon webbing strap under it. Once I had the webbing in place I lifted the surface plate and pallet up by an inch, and went to coffee. And a rest. This is not easy for a retiree to do this, even with tools.

    When I came back it was all okay, so I cut the straps holding the surface plate onto the pallet. Then I drug the pallet out from under the plate. That is it in the foreground.

    Then I started lifting the surface plate. Now I know some you are going to yell at me for using the blocks the weak way... and I wouldn't have done it if I had more blocks. But they aren't holding the weight of the plate. I never took the weight off of the chain hoist. I raised the plate a few inches and then added cribbing 'just in case'. I didn't really expect the blocks to hold the weight of the surface plate if something broke, but my hope was that the crumbling of the blocks would cushion it enough so that when it hit the bottom it wouldn't break.


  4. #4
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    Aug 2016
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    Finally I had it high enough. The idea of using eight pneumatic tires worked GREAT. I just rolled it over the stand, and then let it down the 1/2" it had cleared the levelers by.

    I was amazed. Something worked as designed. AMAZING.



  5. #5
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    Aug 2016
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    Appalachian Ohio
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    Here is a photo taken of The Holy Relic of Flat in place. It needs to be cleaned up, checked for level using a machinists level, etc..., but it's now my primary reference surface.

    Anybody want some small surface plates?

    By the way... the shop is the finishing stages of being remodeled. I got tired of fighting heat and cold and drafts that resulted from being in an old pig barn with no insulation. The Missus gave me a Christmas Present ... she paid for the materials to insulate it, sheath it, put in decent electric and LED lights. I also put in three double pane windows so it's not a dark hole anymore.

    I'm quite happy.



  6. #6
    Join Date
    Feb 2006
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    Phoenix
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    Default

    Sag should not be an issue the way it is supported on its permanent stand. Why does it have to be so thick?
    Allan Ostling

  7. #7
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    Quote Originally Posted by aostling View Post
    Sag should not be an issue the way it is supported on its permanent stand. Why does it have to be so thick?
    The stone is thick because thats the way they make them. I don't know why they make them that thick ...

    The wood on the stand is thick because I wanted to overbuild it. Having the stand collapse and drop 1 ton of granite on my foot would ruin my day.

  8. #8
    Join Date
    Apr 2004
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    Collierville, TN
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    Great job with the whole project; that's git'n 'er done!

    I'm sure granite surface plate size to thickness ratios for efficient stiffness were properly calculated long ago...by our forefathers that weren't encumbered with computers to complicate things. They also worked out that to prevent sag they have to be supported at the airy points. You did calculate the airy points, yes?
    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

  9. #9
    Join Date
    Jul 2006
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    318

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    Quote Originally Posted by DICKEYBIRD View Post
    They also worked out that to prevent sag they have to be supported at the airy points.
    I am quite sure you did not mean to type Airy points and that your software has done a spurious auto-correct from the Bessel points that you actually typed.

    https://www.pressreader.com/australi...82445645119709

  10. #10
    Join Date
    Dec 2016
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    Helsinki, Finland, Europe
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    3,611

    Default

    Nice tombstone.

    I'm (positively) surprised that your wooden crane didn't break. My eyeball engineering wouldn't load that 4x4 joist to more than 200kg.

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