Pipes & loads... will it topple over?

  • Thread starter cheebase
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Hope someone can help me. I am not versed in statics nor blessed with a mechanical vein.

I'd like to install a 1" steel floor flange in the middle of a 24"x24"x1" plywood. A vertical 15" long 1" threaded steel pipe would be connected to the flange at one end and a T fitting on the other. Another 30" steel pipe would be connected to the T at one end and a 90 deg elbow at the other. In a cantilever fashion, a 15" steel pipe would be connected to the T and another to the elbow. At midway and at the end of each horizontal pipe I'd like to place 65 lbs of concentrated load (total 130 lbs/per pipe).
All pipes will adhere to ASTM A53 (for example).

Will the pipe assembly support the whole weight?
Would the structure topple over? If so, what other base should I use?

I'd like to understand the calculation in case other pipe sizes need to be considered.

So, can anyone help me?
 

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  • #2
russ_watters
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I'm having trouble visualizing this. Can you post a sketch?
 
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I'm having trouble visualizing this. Can you post a sketch?
A really rough one, but hopefully adequate...

sketch.png
 

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  • #4
JBA
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Since 15" is the minimum distance from the center pole to the 130 lb load and the distance from the pole to the front edge of the base only 12" your load is going to overhang the front edge of the base so there is a likelihood that the the load can/will topple over. In order to prevent that from occurring you should move the mounting point of the vertical pipe to the base backward to as close as possible to the back edge of the base so that he load is located over the surface of the base rather than over its front edge. That should resolve your tipping issue.
 
  • #5
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...That should resolve your tipping issue.
Thanks JBA. It will be placed on the base like you suggested if... will the fittings and the 15" pipes (wall thickness I believe is 0.179") be able to handle the load without breakage?
 
  • #6
russ_watters
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The fittings should be fine - I'd be worried about the flange connection to the plywood.
 
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The fittings should be fine - I'd be worried about the flange connection to the plywood.
Thanks, Russ.
I was thinking of 4 bolts with oversized washers. I know there will be holes through the plywood which may weaken the base but the pulling force will be distributed over a larger surface. Or a combination of two bolts in the back (where the flange would experience the lift off force) and wood screws up front. Would that work? Or should I think of solid wood base instead of plywood?
 
  • #8
JBA
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edited dimension correction:

If you are using a threaded floor flange then it appears that the rear bolt holes are only 1 1/8" behind the centerline of the vertical pipe center.

Would an alternative of base plate fabricated by a pipe coupling welded to a larger square plate to provide a more distance from the post to the back bolts be an possible option for you?
 
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  • #9
JBA
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Using the standard dimensions for a 1" npt cast iron floor flange Flange O.D. = 3.75"; Bolt Circle Dia = 3 3/16", the loading per rear bolt calculates to 284 lbs. per bolt (with no Safety Factor).
Do these dimensions agree with the flange you plan to use; and, if so, what size bolts are you intending to use?
 
  • #10
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Would an alternative of base plate fabricated by a pipe coupling welded to a larger square plate to provide a more distance from the post to the back bolts be an possible option for you?
Originally an all welded structure was envisaged (2"x2" square tube welded to a platform, and pipes welded to the tube) but it proved to be not as economical than the pipes and fittings solution I seek advice for.
Using the standard dimensions for a 1" npt cast iron floor flange Flange O.D. = 3.75"; Bolt Circle Dia = 3 3/16", the loading per rear bolt calculates to 284 lbs. per bolt (with no Safety Factor).
Do these dimensions agree with the flange you plan to use; and, if so, what size bolts are you intending to use?
These are the dimensions as far as I can see. The holes for bolts/screws are 1/4" dia. A specimen can be seen here... What is the normal safety factor one is to use in this case? The total load will never exceed 260 lbs. In your opinion 1-1/4" wood screws are completely out of question vis-a-vis flange fastening?
 
  • #11
JBA
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As for your question about an adequate Safety Factor that depends on whether a failure of the stand could result in personal injury or significant ancillary damage. If the greatest risk of the failure or tipping of the stand is a dent in the floor then the below stated 1:37 Safety Factor is fine (apart from your wife's possible reaction); on the other hand, if a failure or tipping could result in injury to a person then a safety factors on the order of 5 to 10 on manufacturing machines, etc. are not uncommon. In that respect, you need to be aware that an impact load such as dropping, rather than setting, a load on one of the arms of your fixture will increase the fixture loading by a minimum of 2x or more depending upon the intensity of the impact.

With regard to the rear flange mounting screws, according to the below online reference (See Table 3) the pullout capacity of a #12 wood screw (major thread dia of .216") with 5/8" penetration into plywood has a pullout load of 390 lbs, based upon that, using those as rear flange mounting screws at that minimum penetration, your 284 lbs. per bolt load should be generally safe for your application for a floor damage risk level.
https://www.buildgp.com/DocumentViewer.aspx?repository=bp&elementid=3806

See the below for the screw size reference:
https://www.boltdepot.com/fastener-information/Wood-Screws/Wood-Screw-Diameter.aspx

Just to cover all issues, I cannot find any references for the safe bending moment for floor flanges (or others, for that matter); as a result, I suggest that for your own peace of mind you do a couple short height load drop tests with one of the loads while the other load in place.
 

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