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Support angle for steel rack

  1. Feb 10, 2016 #1

    DaveC426913

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    I'm building a clothing rack that swings out of the way. It's ideally made of 7/8" (or possibly 1") stainless steel tube, with 1/16" thickness and will sit on a 3" bearing (lazy susan) that supports 200lb. The top is firmly attached to a stud in the sloped ceiling. It needs to hold up something more than 50 lb (5 feet of clothing).

    There is a support bar that starts about 18" above the clothing bar. I'd like to position the support bar correctly to balance the load on either side.

    I have no idea how to determine the optimal point of support to balance the load (minimizing risk of collapse). It will obviously be between 30" (midpoint) and 60" (endpoint) from the upright.


    closet-rack.png
     
    Last edited: Feb 10, 2016
  2. jcsd
  3. Feb 10, 2016 #2
    For all purposes I'd position it at or very close to the very end between 45'-55' . You will have two load bearing points on the vertical rod, the weight at the farthest end of your horizontal rod will impart its maximum pressure on the vertical rod right at the joint 18 inches down so the farther out you put your angular support rod the less pressure you will have at the end of the horizontal joint. You want it to support a load like a crane or counter leaver long gate.... if the top and bottom of your vertical rod are securely fastened then you shouldn't have a problem supporting 50lbs at any point on that rig. 1/16 tubing is very strong
     
  4. Feb 10, 2016 #3

    DaveC426913

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    Thanks. I hadn't really thought about the strain on the upright. I assumed it would be on the bar.
    Maybe I should place a very short angled support underneath the horizontal bar to distribute the load on the upright. (Has to be short, or it will waste valuable clothing rack space.)

    I want it strong. I've struggled for years & years with movable clothing racks. Ikea racks just fold like a cheap lawn chair under the weight.
     
  5. Feb 10, 2016 #4
    If you are welding it you could add a triangular gusset underneath the horizontal, I'd use 1/8 plate stainless, for best results you'd need to tig it with 316ss 1/6 filler wire at low temp, after you tack it keep most of your heat on the plate steel and "wash" the filler over on your tube steel, weld all the way around and try to prevent it from "sugaring" ( getting porosity) on the inside of the tubing. You could (purge pipe weld) it and you wouldn't have to worry at all about any porosity. You shouldn't have a problem with it supporting quite a bit of weight, I bet at least 100 lbs or more.
     
    Last edited: Feb 10, 2016
  6. Feb 10, 2016 #5

    DaveC426913

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    Not a welder. Going to use stainless steel marine handrail fittings.
    mRAzDV0TdI6jvX7NGyZ3khg.jpg
    I'll have to drill points to secure them against the load, the little set screws normally used to grip tubing won;t be enough.
    I sure hope that doesn't compromise the tube's strength.
     
  7. Feb 10, 2016 #6
    Screws shouldn't if you are using mechanical fixtures and hardware, I wouldn't put a counter leaver on the bottom, even a short one, it would be a waste of steel and could cause the horizontal to bear the load more in the middle in front of the bottom counter leaver. A gusset would just spread the load over a wider area giving the horizontal tube a bigger foot print, thus giving it a better weight distribution on the vertical load bearing tube. I'd put the counter leaver almost to the top of the vertical touching the connecting point at the top if possible to spread the load over a greater area.
     
  8. Feb 10, 2016 #7

    DaveC426913

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    All right, no underbrace then. That'll save me 20 bucks in fittings.

    Just bought a couple of 3" lazy susans to act as bearings top & bottom.
    41TE0WcXjvL._SX342_.jpg .
    Would've liked them smaller but this is all Lee Valley Tools had.
     
  9. Feb 10, 2016 #8
    As long as you have a way of attaching the tubing on center of your bearings they should work.
     
  10. Feb 10, 2016 #9

    DaveC426913

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    Yeah, it's just that it'll be a disc 2√3 inches across.
     
  11. Feb 10, 2016 #10
    If you can, I'd go with a bigger diameter upright, since it's going to be pretty long that will be the 'flimsy' feeling part of it (it'll be about 6-8 ft high right?)
    If you have a bigger upright, you could get a 1" hole drilled into it to hold it

    If you support the horizontal section by it's end, you could use aircraft cable to hold it up, the angle of the wire would even keep the horizontal section pressed into the vertical.. and using just 1/8th aircraft cable I'm quite certain you could easily hang 100 lbs off the end.

    I'd weld it.. for a 50 lb load you'd hardly need a brace.
     
  12. Feb 11, 2016 #11
    If you plan on using screws to fasten the fitting to the pipe, self tapping screws would work good, just don't strip them.
     
  13. Feb 11, 2016 #12

    DaveC426913

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    Nope. Its only 5'6" high (due to sloping roof).


    I've considered cable. I don't think it'll look as nice. Also, it doesn't provide any torsional rigidity as I rotate the structure.
     
  14. Feb 12, 2016 #13

    JBA

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    I would suggest running the top diagonal to the end of the rod and then determining the rod center point deflection by analyzing it as a simply supported beam with a 100 lb distributed load to see if you need to place an intervening vertical member between the rod and the diagonal at that center point to prevent excessive rod center sagging under load.

    As for the vertical support, resolve the diagonal end load into its vertical and horizontal components at the the horizontal rod end; and, then determine the vertical pole"s required diameter by analyzing it as a simply supported beam with the horizontal load component as a concentrated lateral load at the horizontal beam connection point height. This will also give you the horizontal reaction forces on the bottom turn table and the top pole socket connections.
     
  15. Feb 12, 2016 #14

    DaveC426913

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    Yes I Will Um Definitely Do All That. :nb) :nb) :nb)

    Do I utilize the Rockwell Retro Encabulator to do that?
     
  16. Feb 12, 2016 #15
    That's actually not a bad idea, adding a mid angular support to the top counter leaver would distribute the load more evenly on the horizontal tubing. It wouldn't have to be a ridged support. A cable or banding material would work fine. Really anything you find aesthetically pleasing you could actually make an ornamental (S) piece to place in the middle. You could bend it out of some thin flat or square stock, just heat it and bend it to the shape you like, attach it to the leaver and the horizontal with some tap screws. Decorative touch with form and function.
     
  17. Feb 12, 2016 #16
    With the (S) in the middle of it you could name it the super lazy Susan encabulator next gen unconventional clothing storage system or S.L.S.E.N.G.U.C.S.S for short....:woot:
     
  18. Feb 12, 2016 #17
    Also......been thinking about it, when the rack has some weight on it depending on the pivot point and how level you can make it....it may tend to swing out in the middle of your closet or where ever you are placing it. Just a suggestion,...once it's built add a bolt (ferrous metal) to the end of your horizontal tubing. And mount a decent size magnet (cabinet latch magnet) or an old speaker magnet where you want the end of your rack to stay. That way you will have a a way of holding it in place and out of the way. Just a thought.
     
  19. Feb 12, 2016 #18

    JBA

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    Does that mean you could use a bit of guidance or assistance in the analysis process?
     
  20. Feb 12, 2016 #19

    DaveC426913

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    Its 'stowed' position is not actually against anything. It sits parallel to an inner rack, and is moved away (out into the open) so we can get at the inner rack.

    But I think your idea has merit - I should have thought of the risk of the device 'wandering'. I'll incorporate something at the base or head of the upright.


    I certainly don't have the chops to do that.

    Question though: is it necessary? Hopefully, I've over-engineered it.
     
  21. Feb 13, 2016 #20

    Merlin3189

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    The only issue to consider (for positioning the tie), is the bending of the horizontal member.
    Both the thrust of the horizontal member against the vertical pole, and the horizontal component of the tension in the diagonal support (again trying to bend the vertical pole) are independent of the position of the diagonal support. They are determined by the load on the horizontal and the 18".
    The tension in the diagonal decreases as its angle to the vertical increases, but once you are half way, you're within 10% of the tension at the end.

    My guess is (as yours) to have the tie 2/3 to 3/4along the horizontal, with the cantilever equal to or slightly less than half the beam, but I'm really not familiar with beam calculations. Psychologically I think you will put heavier items near the vertical support and lighter items towards the end, so perhaps the cantilever will tend to have a lower load than the beam and 2/3 is the right spot.
     
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