Metal post project

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REA Real Estate

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May 28, 2022, 11:44:47 AM5/28/22
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Hello Maker Family 

I am seeking assistance and direction with a pipe/post project. 

I have attached a picture,
but I want to make it taller than the picture.  

Questions 
How much deeper do I need to make it go into the ground for every foot taller and foot horizontal I make it?

What is the standard pipe thickness and diameter in commercial swing frames?

Thank you 
Robelle 




Dennis

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May 28, 2022, 12:12:30 PM5/28/22
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Dear Robelle 
In Michigan the minimum depth is 4 feet below grade to reach below the frost line.

This design must accommodate turning moments as well as tilt moments of 3 times gravity, 6 times for 2x safety margin.

Backyard swing sets are designed with triangles that translate to mostly compression forces on the supports and will not withstand the forces of this design.  Some public playgrounds built with two vertical supports withstand mainly tilt forces and are built with substantially heavier tubing.

I haven't seen any materials at Home Depot, Lowes and Ace Hardware that will be strong enough.

Some basketball hoop supports may be of sufficient strength.  The cantilevered hoop has to withstand similar forces.

Dennis

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REA Real Estate

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May 28, 2022, 6:46:36 PM5/28/22
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Thank You for the information. 

I want to understand, are you saying this is Not a feasible project technically?


Knox Valleskey

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May 28, 2022, 7:01:11 PM5/28/22
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Hi,
     I'm not sure what he's trying to say, but I know as someone who has set alot of structural poles ( I work at the sign company at the end of the street) is that it's a little more complicated than just adding height and depth. 
    For sign poles to get installed a structural engineer has to go over and approve the pole and foundation the pole will bet set in to make sure it will be able to handle the weight of the sign and other possible influences on the pole, and even for poles that are 1/4" thick 4" square steel tube the concrete foundation is pretty big (like 2' diameter hole about 5' down). I don't know all the variables and equations used to say one design is or isn't good, but I know it's not simple. That being said there are local suppliers like Alro Steel that sell poles that would suit your needs. Good luck! Knox

Dennis

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May 28, 2022, 7:04:06 PM5/28/22
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Robelle,
It's feasible but may not be affordable. Materials will be expensive.

This two-sided wooden model gives you an idea of material strength required:

Knox Valleskey

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May 28, 2022, 7:04:38 PM5/28/22
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Oh, and instead of just burying a pole you may want to consider using a baseplate with 4 or 6 1" studs instead. Gives you more options with aligning the pole.

REA Real Estate

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May 28, 2022, 7:07:04 PM5/28/22
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Thank You for your input Knox. 

I am hopeful that I can accomplish this, but I want to do it the right way. 

Raiford, Jody

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May 30, 2022, 7:10:11 AM5/30/22
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"Right way" is very much in the eye of the beholder. The main considerations I'm seeing here are:

#1 Safety. Safety of both the swinging person and those around them. Your design should take into account that adults will probably use this, and not always in the smartest way, so unless you get a mechanical engineer with experience in playground equipment to design it (and sign off on it for your insurance), your going to want to overbuild for safety.

#2 Code. Cities often have code requirements for play equipment, especially if it's going in any location that might possibly be accessible to the public. Look up "attractive nuisance" for more info, and check with your local building department. They can be a little short with DIYers in my experience, but if you stay calm and persistent, you should get what you need. A local engineer or contractor, or even an architect, might help if you get bogged down.

#3 Aesthetics. It looks like you are set on a non-traditional design. Standard designs are standard for a reason, usually because they are the cheapest way to achieve a desired result. But that doesn't mean you have to do it that way! Your cantilevered design seems pretty neat, and there are certainly materials that will work. It will probably be more expensive, but if that part doesn't bother you then the sky's the limit! Just keep track of #1, safety.


You might try reaching out to places that make playground equipment, see if they could offer some guidance. You might even get ahold of their designers and have a great chat, if you're lucky!

There's also inspiration to be taken from the industrial world. Look for "jib crane" and you'll get some ideas of the material needs for something expected to support a reasonable amount of weight. Keep in mind that those are generally designed for slow loads without much swing, though. Still useful for comparison.

Good luck with it! Looking forward to seeing this come together!

And if you need help learning to weld for this or any other project (or just because fire and lightning are cool), I'm always happy to teach!

Jody




Con Vuong

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May 30, 2022, 9:36:42 AM5/30/22
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General fencing post go 4" into ground.  Since yours was will be heavier and with added weight for people swinging I suggest adding 4 corner stakes/deep scews into extra cement weights to prevent future of post leaning over.  Or do a big slab of cement. 3'x3'x8" deep at least.  I think the post will start leaning after few years use.  Especially if you have soft ground.  Best to consult someone with experience.


REA Real Estate

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May 31, 2022, 9:00:56 AM5/31/22
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Thank You Jody 

I’m really want it to be safe and cost is secondary. I wish I had the specifics so I could start. 

Everyone’s input has been helpful in clarifying my task and I am still listening.  


REA Real Estate

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May 31, 2022, 9:02:04 AM5/31/22
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Thanks 

REA Real Estate

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May 31, 2022, 9:03:37 AM5/31/22
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Hi Dennis 

I really want metal. What materials are you thinking of?

Dennis

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May 31, 2022, 10:42:21 AM5/31/22
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Robelle,
I am thinking you want metal.  I provided the photo as an illustration of the relative strength of materials required for a cantilevered swing support.  Those wooden beams are quite thick and strong.

"A" frame swing sets can get by with relatively weak supports because the majority of forces are in compression, in the direction materials are stronger.

Your design requires metal supports that can withstand lateral forces, in the direction materials are weaker.

The horizontal overhead support arm acts as a torque amplifier on the vertical support structure and its foundation for the twisting, turning and lateral forces from the swing.

A person weighing 250 pounds statically can exert 750 pounds dynamically at the swing attachment points.  A 4 foot overhead support arm multiplies the forces where it attaches to the vertical support. 

The structure may "see" torque as much as 3,000 foot pounds in the directions that the vertical and overhead horizontal supports are weakest.

The fulcurm is at ground level.  The part of the foundation that is, say 4 feet, below ground must withstand twice that force for an 8 foot high vertical support, or 2.5 that force for a 10 foot high vertical support.  All forces must be doubled for an industry standard 2 times safety margin.

Going through this "back of the envelop" analysis makes me realize some reasons I haven't seen this design in use.  It takes experience, a good understanding of physics and material strengths.  Some say the strength of materials classes are the most difficult in mechanical engineering curriculums.

It's an aesthetically beautiful design.  It takes very strong materials, but it is not impossible to do.

Roger S

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May 31, 2022, 4:59:10 PM5/31/22
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Cantilever beams have both tension (top face) and compression (bottom face). 1@

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