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Thread: In need of a structural engineer

  1. #1
    Boolit Master sawinredneck's Avatar
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    In need of a structural engineer

    I want to build an overhead hoist, 8’ long that pivots with a 1 ton chainfall on it. I doubt I’ll ever lift a full ton, mostly will use it for engines, lawn mowers, things like that, but I don’t care for it failing. I know there’s many here smarter than I, so hopefully they can tell me if what I have will work or not.
    What I have,
    4” 1/8” wall pipe 7’ long.
    4 1/4” 1/8” wall pipe for the pivot, I plan on 2’ long.
    8’ long 4x4” 1/4” web and wall thickness.
    1/2” 2’x2’ plate for the base, I plan on three 1/2” anchors per side, 12 total, the concrete floor has a 16”deep, rebar enforced, 2’x2’ pillar to set this on.
    So... where’s my weak spot and how do I fix it? Right now I’m thinking the main pipe is too thin, but I honestly don’t know!
    Thanks!!
    Quote Originally Posted by sniper View Post
    Irish Proverb: Never approach a Bull from the front, a horse from the rear, or an Idiot from any direction!

  2. #2
    Boolit Master
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    to make a jib crane to lift what you want you will need to up size everything you have . the ones we had at work. they were rated at 1000 lb, they had 6 inch I beam for the main spar.

  3. #3
    Boolit Master
    Plate plinker's Avatar
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    I can't tell you what to get but I do know that will not work. We had a hoist for picking trowelers out of basements that was heavier than that and it bent over after a couple uses. those thing don't even weigh 500 lbs.

    I worked at a home where the guy had exactly what you desire and the post was probably 6-8" diameter. this was 15 some years ago and I can not recall much else but it was cool. He said he had no boys so it was all on him, hence the crane.

  4. #4
    Boolit Master sawinredneck's Avatar
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    I’ve got a broken back, I’m trying to work smarter, not harder! But I’d really like to hear from someone with numbers to back this up? I can overkill anything, but would rather know what works, why, and some basis to stand behind the reasoning.
    Quote Originally Posted by sniper View Post
    Irish Proverb: Never approach a Bull from the front, a horse from the rear, or an Idiot from any direction!

  5. #5
    Boolit Master sawinredneck's Avatar
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    I apologize if the above post came off short or rude, that is not my intention. Like many, I have a limited budget and am trying to do a lot with a little. The weather is about to kill me, my back doesn’t like seasonal changes, so I’m in, literally, screaming agony, and I won’t even bother getting into the details of the contractors I’ve gotten for my building, other than I’m not sure they can make a friggin hotdog at this point!
    If I’m short, I assure you it’s not meant towards anyone trying to offer help or advice here, so I apologize.
    Quote Originally Posted by sniper View Post
    Irish Proverb: Never approach a Bull from the front, a horse from the rear, or an Idiot from any direction!

  6. #6
    Boolit Master
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    You need to draw a sketch.
    Dimension the sketch and indicate the type of steel in each member.

    Machinerys Handbook has the info you need if you have good knowledge of trig and algebra. Look under Statics.

    Otherwise you can use a Statics textbook from your local library.
    Statics is the first engineering mechanics course in the mechanical engineering curriculum.

    No matter what the calculations say you need to proof test any lifting device.
    There are engineering standards for the proof test. I would test at 3X your maximum planned load.
    Last edited by EDG; 03-04-2018 at 05:36 PM.
    EDG

  7. #7
    Boolit Master
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    Quote Originally Posted by sawinredneck View Post
    I want to build an overhead hoist, 8’ long that pivots with a 1 ton chainfall on it. I doubt I’ll ever lift a full ton, mostly will use it for engines, lawn mowers, things like that, but I don’t care for it failing. I know there’s many here smarter than I, so hopefully they can tell me if what I have will work or not.
    What I have,
    4” 1/8” wall pipe 7’ long.
    4 1/4” 1/8” wall pipe for the pivot, I plan on 2’ long.
    8’ long 4x4” 1/4” web and wall thickness.
    1/2” 2’x2’ plate for the base, I plan on three 1/2” anchors per side, 12 total, the concrete floor has a 16”deep, rebar enforced, 2’x2’ pillar to set this on.
    So... where’s my weak spot and how do I fix it? Right now I’m thinking the main pipe is too thin, but I honestly don’t know!
    Thanks!!
    think about a portable engine Hoist

    Some are rated a 2000 lb (using the short bar) and 1000 lb using the extended bar

    I lifted the front end of a ford focus off the ground 1-2 inch using a engine hoist /from motor mounts -did not need to go up higher

    so lifting a lawn tractor would be no problem weight wise

    Ps I have used jibs at work and they were always in the wrong spot or not strong enough

  8. #8
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    Not being in the right spot is why I want a rolling gantry crane setup in the garage.

  9. #9
    Boolit Master
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    I second the advise to get a portable engine hoist. They come with a rated capacity, are very handy, can be taken to remote locations, and can usually be found at sale prices if you are not in too much of a hurry. I have even seen one modified to mount on a farm tractor three point hitch. Get one rated for more than you think you need, it will come in "handier". One down side, your friends may want to "borrow" it "often".
    Getting old is the best you can hope for.

  10. #10
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    JonB_in_Glencoe's Avatar
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    If I was gonna tackle a project like this, I'd start by searching out as many designs and/or commercial units as possible. I searched a bit, it seems your 4" pipe is way undersized.

    This 1 ton floor mount Jib crane uses 12" pipe (they include specs and PDF drawings).
    https://shop.bohlco.com/products/gor...ne-fs300-12-w8

  11. #11
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    Not a ton at the end of it.... You might be rated at 250 pounds max. I'd bet dollars to donuts, you would see a flex if I grabbed end and hung from it and I'm only 160 pounds.....
    Either buy or make a rolling hoist or an h frame. torque is too much and while it is nice to pivot out of the way, you have to keep the whole side wall clear to use it and that isn't practical for most of us. HF for this..... Yeah I know, but it will work as needed. Heck, roll outside is you need the space.

  12. #12
    Boolit Master sawinredneck's Avatar
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    I have other means to use for the rolling hoist, a skid steer and engine hoist. I want this 1’ each way inside the door, the plan is I can unload from my truck or trailer and then just pivot it around to set whatever on my welding table.
    This will also be the door I plan to work on mowers, pull the mower in, wrap the chain and I can lift it to take blades off, etc., engine hoists suck for this, I’ve tried!
    Where I plan to put it is out of the way, wastes little space but is still in a convieniont location for my needs. Believe me, I’ve spent months laying this shop out for the best utilization of space I can. I wish I had the money to make it twice the size, 30x31’, but I’ve got to work within my budget.
    So it sounds like I need a much bigger pipe!
    Quote Originally Posted by sniper View Post
    Irish Proverb: Never approach a Bull from the front, a horse from the rear, or an Idiot from any direction!

  13. #13
    Boolit Master
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    An 8' long horizontal reach attached to a vertical pipe that has a 2' x 2' base plate bolted to a concrete floor sounds a little iffy to me. The downward force applied at the end of that beam is going to translate into a lot of twisting force at that floor plate. In a perfect situation, I would have welded that plate to the vertical pipe and set under the concrete slab before the floor was poured. That's no longer an option.
    A surface mount on top of the concrete floor relies heavily on those anchors around the perimeter of that floor plate. The anchors on the side of the boom have little or no load but the ones on the plate opposite of the boom will be subjected to a lot of tension attempting to pull them out of the floor.

    Using round pipe for the horizontal boom and vertical support also runs the risk of buckling that pipe. You could gain a lot of strength on the boom by welding a truss to the top of the pipe. The upper section of that truss would be in tension and the vertical sections of the truss would be in compression. The vertical support is a bit more of a problem because the load must be able to rotate around the vertical support (to swing the boom side to side). I would want to spread that load over a fairly large section of that vertical member to avoid buckling near the joint.

  14. #14
    Boolit Master
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    I may come across as very rude. Not trying to be rude,m just honest. I am a Registered Civil Engineer and I wouldn't touch your project wit a ten foot pole. You are going about it backwards. Design your hoist for your 1000lb load and see what your MINIMUM sized members are. Now does what you have work? If it doesn't call some lift companies. Based on what I have seen at my mechanic's there are companies that make exactly what you want. It may be out of your price range but it is what you need. To try to design to existing materials or a fixed budget creates things that fail.

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