Boxing/punching bag stand project

[paleos]

TL;DR Summary

Engineers from the construction/materials science type fields shed some advice on this project. What's the simplest design for building a punching bag stand?

Criteria: freestanding, not bolted down (i.e into floors, walls, ceiling, et), stable, least corrosion & health/safety concerns, support 200lb bag, and minimal cost. So far it seems best solution is a pull-up bar design: 2 posts with support legs but joined with a 15ft pipe, 2in+ thick (stainless steel, titanium, or other steel type)

 

[berkeman]

Summary:: Engineers from the construction/materials science type fields shed some advice on this project. What's the simplest design for building a punching bag stand?

Criteria: freestanding, not bolted down (i.e into floors, walls, ceiling, et), stable, least corrosion & health/safety concerns, support 200lb bag, and minimal cost. So far it seems best solution is a pull-up bar design: 2 posts with support legs but joined with a 15ft pipe, 2in+ thick (stainless steel, titanium, or other steel type)

Welcome to PF.

Can you say more about what you think the best solution is, and why? What forces will be transmitted to the mounting points, and how can you optimize the longevity of the structure?

 

[paleos]

Thanks so much for your response and thanks for the welcome :).
I'm not so great with that kind of technical detail/knowledge. But I can say that its around 150-200lb bag that will be getting punched and kicked so I'm guessing the main forces involved would be approx 200-1000psi. I know that certain steel grades and thickness levels, like a 2inch or more gauge steel galvanized pipe (~15ft in this example) would be able to hold that kind of weight in the center, but I'm not sure for how long and with these forces regularly applied to it. Seems titanium and stainless steel would be better (in strength and corrosion resistance) but obviously cost more, but just trying to see what's the minimum I can get by with without compromising the integrity of the structure and therefore the quality of the experience.

 

[paleos]

also importantly the design should allow for the bag to be circled freely/unimpeded like most designs for punching bag stands are (because they are held up by a pillar with a hanger or a wall mount, therefore offering less than 180-270 degrees of contact area). So that's why the best designs I can come up with so far are like a gymnastics balance beam, except the legs are like 10ft tall and the balance beam is 15ft so hanging the bag from the middle would allow free circling underneath, and could stand on its own without being bolted into something or grounded in concrete, if needed can be moved around too, and its so stable :0. But as far as I've looked they don't make balance beams with legs that tall and if they did I'm guessing it would cost a lot more then just getting a bunch of threaded metal pipes to join one another and form a look alike of that kind of design.
Sorry if I've written in too much length, is that normal for this forum? I just felt bad for not being descriptive enough initially.

 

[Lnewqban]

Welcome, paleos!
What affordable materials and fabrication capabilities (welding, cutting, drilling, etc,.) do you have available for this project?

A structure similar to the ones for swings in playgrounds comes to mind, although a 2” steel pipe seems to be too weak for 15 feet horizontal and 200 lbf hanging midpoint.

Please, see:
https://www.physicsforums.com/threads/calculating-bending-stress-for-pipes.847953/

 

[paleos]

Welcome, paleos!
What affordable materials and fabrication capabilities (welding, cutting, drilling, etc,.) do you have available for this project?

A structure similar to the ones for swings in playgrounds comes to mind, although a 2” steel pipe seems to be too weak for 15 feet horizontal and 200 lbf hanging midpoint.

Please, see:
https://www.physicsforums.com/threads/calculating-bending-stress-for-pipes.847953/

View attachment 275057

View attachment 275060

View attachment 275061

Thanks so much for your reply!
I am open to using any kind of material that can fit the criteria I listed. Examples like aluminum ibeams (like a portable gantry crane), or aluminum truss, or schedule 80 3inch pipe gauge steel galvanized or titanium.
I like the second pic you got there and the fact that the load is distributed to two points instead of one in the middle; I'm assuming that helps decrease chances of overbearing the pipe?
Could I do something similar for my build and how would I know if that build type would be supportive enough for my build?
Thank you for your tips :)

1) https://www.bodysolid.com/commercial/spracb/spr_power_rack_connecting_bar#gallery1-9

2) https://www.google.com/imgres?imgurl=http:/%2Fwww.aluminumstagetruss.com%2Fphoto%2Faluminumstagetruss%2Feditor%2F20190715171527_63422.jpg&imgrefurl=http%3A%2F%2Fwww.aluminumstagetruss.com%2Fsale-3166139-customized-aluminum-truss-lighting-truss-stands-for-truss-led-screen.html&tbnid=ElPum8BEU6VuKM&vet=10CCAQMyh2ahcKEwjAoPW4mvHtAhUAAAAAHQAAAAAQBA..i&docid=9cqkrk7aXf1DQM&w=680&h=509&q=truss%20lighting&client=firefox-b-d&ved=0CCAQMyh2ahcKEwjAoPW4mvHtAhUAAAAAHQAAAAAQBA

3) https://www.amazon.com/dp/B00CEY9VJG/?tag=pfamazon01-20

4) https://www.spanco.com/products/gantry-cranes/aluminum-gantry-cranes/

 

[Lnewqban]

The material selection also depends on the easier and more economic way to assemble the structure (bolts, welds, etc.).
The originally discussed 2-inch steel pipe will not permanently deform, but it will bend around 2.5 inches down at midpoint due to the weight of the bag alone.
Pipes are not good at resisting bending loads, I-beams and trusses are better.

Please, see how to calculate for bending:
https://www.engineeringtoolbox.com/beam-stress-deflection-d_1312.html

Since the structure is not going to be anchored down, it needs to have a broad base along the smallest footprint.
The total weight of the structure should also be considered, as it may need relocation by one or two persons.

The bag is going to oscillate when punched and kicked; therefore, the projected vertical angle should remain within the base footprint at all times.
The bending beam should resist some lateral bending for the same reason.

 

[Dr Transport]

look at something like this for your design, all you need is some weights to keep it from toppling over when punching it

 

[berkeman]

look at something like this for your design, all you need is some weights to keep it from toppling over when punching it

View attachment 275377

The bag didn't render quite right in the drawing, did it? It looks like it is behind the left diagonal support, but it's meant to be in front of it between the two outstretched floor members, right?

 

[Dr Transport]

yes, that was an image from amazon.

 

[Raynomurn]

I like the idea from the OP. Has someone made a stand like this?

 

[Fra]

I exploited a coincidence where I put up a full 170cm heavy bad that is around 60kg. I found a corner in my home (junction between 3 rooms), so I have a small supporting corner and still 270 degrees free angle. So you can essentially kick or punch from both left and right, except I have to change position a bit to not slam the legs around the other door post, but it works, so you get to train footwork as well ;)
And I hang the bag on a hinge that was for a door (that i removed). So the bag is kept upright by a door hinge (that accidently was at perfect height) and supported from a wall. It can withstand any force even from jumpkicking, however it's not entirely ideal as it has too much resistance (more than an opponent). And I would have likey more space around it, but it's the compromise i ended up with. Better than nothing. Just just punching however, it works well. To make up for the too hard resistance against the wall, you can use softer gloves to compensate, to save your joints. Kicking needs more playroom around the bag.

/Fredrik