Curving a Steel Pipe for a Helical Stair - Need Advice from Experienced Fabricators 2

[Jay_]

Hello all,

I hope everyone is doing well. I am currently working on an exciting project that involves curving a straight 355mm outer diameter steel pipe with a thickness of 16mm. The objective is to transform it into a curved pipe that will eventually take the form of a spiral, serving as the main beam for a helical stair.

Unfortunately, we do not have access to a specific pipe curving machine for this particular task. However, I believe that with the collective knowledge and expertise of this engineering forum, we can come up with some clever solutions.

So, I'm reaching out to all experienced fabricators in this community for your valuable opinions and suggestions. If any of you have successfully curved steel pipes without using a pipe curving machine, I would greatly appreciate hearing about your techniques and methodologies.

Please share your insights, ideas, and any alternative approaches you might have. Your contributions will be instrumental in helping me find an efficient and effective solution for this project.

Thank you in advance for your support and expertise. I'm looking forward to engaging in a fruitful discussion with all of you.

Best regards,

Detailing is a hobby,

 

[phamENG]

Not a fabricator, but just a thought: what about building a temporary form that you can bend the tube around? Use induction heating to hot bend the tube around the helix? Wouldn't be easy, but may be workable? It may even reduce some of the residual stresses from cold working.

Do be sure you're using round HSS (A500 or A1085) and not pipe (A53 or similar).

Link

 

[SnTMan]

Hire it out to a tube bending company. One example, I'm sure ther are others...

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[LittleInch]

Creating a helix from straight pipe is far from easy.

The radius you need to bend to you will need a bending tool.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Jay_]

Thank you, everyone, for your responses and suggestions. I appreciate your input and the collective knowledge we have here. Let me address each of your comments individually.

phamENG: I like your idea of building a temporary form to bend the tube around. Induction heating could be a viable method for hot bending the tube into the desired helix shape. It would be challenging, but it might help reduce residual stresses from cold working. I will explore this option further.

SnTMan: Hiring a tube bending company is indeed an option worth considering. They specialize in bending pipes and may have the necessary equipment and expertise to accomplish this task efficiently. I will research tube bending companies in my area and explore this avenue as well.

LittleInch: I understand that creating a helix from straight pipe is not an easy task. As you mentioned, a bending tool is typically required to achieve the desired radius. Since I don't have access to a specific pipe curving machine, I'm looking for alternative methods that might achieve a similar result. However, if none of the alternative approaches work out, I will consider acquiring or renting a suitable bending tool.

Once again, I want to express my gratitude for your insights and suggestions. Your contributions have given me some valuable ideas to explore. If anyone else has additional thoughts or alternative approaches, please feel free to share them. Together, we can find an efficient and effective solution for this project.

Detailing is a hobby,

 

[LittleInch]

Differential heating and cooling / quenching on one side compared to the other can bend pipe.

Or heat the whole pipe then quench one side. Not sure which way it bends but a bit of trial and error...


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[robyengIT]

what I don't understand is "why ?". IMHO you have to bend the pipe with a correct "pitch" so that the steps can be fixed at such pre-defined pitch, so to have equal steps and not different one from the other. Looks like to me quite crazy (my opinion as site engineer/designer, not fabricator)

 

[JStephen]

That's 14" pipe at 5/8" wall, so pretty beefy stuff.
There aren't many people that can roll it period, much less to a helical shape.
I see magazine ads from one or two outfits that can do that, I'm thinking one is in Chicago.
I'd say, either contact someone that can form it properly, or change configuration altogether.
Just measuring the helical shape would be a challenge.
You may be able to use heat distortion to shape it, but trying to get adequate bend, and also making it uniform in two directions, is going to be a major challenge.
It might actually be easier to work with rectangular tubing of similar size.

Edit: The place in Chicago:

https://www.cmrp.com/

 

[robyengIT]

further to my previous post, if I don't misunderstand, you would like something as shown below, but in helical shape.

I think this is coming from a deformed steel plate, rolled to circular shape, welded longitudinally and then chrome plated, but the outer max diam is approx 120-130 mm and thickness 2 or 3 mm.
Sorry, no hope (for me)

 

[LittleInch]

I think what the OP wants is like this but instead of a steel plate wants a pipe?

Maybe a a central support and then treads coming out from both sides?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[robyengIT]

or something like this

 

[phamENG]

robyengIT - that looks like a trap designed to trip you and behead you...

Pretty neat, though!

 

[LittleInch]

Does the central pole also act as a laundry chute?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[dvd]

Years ago, I built a spiral staircase and had a boiler shop roll the handrail. It was amazing - very low tech - they rolled the proper length of tube (spiral length plus additional) to the 2-d (plan view) diameter and then hooked onto the two ends with come-alongs and stretched it to the required height.

 

[CANPRO]

Jay, how do you plan on attaching the treads to the helical pipe? I'm thinking you'll need a sizeable jig to hold the pipe while the treads are placed with some precision. What kind of tolerances are you expected to achieve? No doubt this is difficult, but I think first step would be to conceptualize how this is all going to come together and then plan on where you can make up for tolerances and hide imperfections from the bending and fabrication process.

 

[bugbus]

I had the following in mind from the OP's description. They do this a lot with rollercoasters. I bet there are fabricators who do this sort of thing all the time.

 

[Just Some Nerd]

curving a straight 355mm outer diameter steel pipe with a thickness of 16mm

I feel like creative solutions for this requirement is not a great idea....at the very least you'd want a fabricator who already does this stuff so you can guarantee the shape, since the purpose of using this giant helical tube seems aesthetic and nobody likes to look at an asymmetrical piece of work

 

[JStephen]

Forming pipe for roller coasters, etc:

https://youtu.be/5jY2a7MFATc

I downloaded Swebend's brochure, and if I understand right, they go up to 5" pipe. The spiral-bend essentially is rolling to a radius while simultaneously rotating the pipe.
I found this video on hot-forming large pipe to a (flat) radius:

https://youtu.be/Dc16UtLp7eQ

Several years ago, on a bike ride, I went by Turner Industries up in Paris, Texas, and they had a bunch of wrought ells, etc, roughly 48" size, on trailers awaiting fabrication or transport. That video may be their shop, I didn't see anything to identify it. Looking on Turner Industries' website, they list hot-bending up to 54" diameter pipe.

 

[3DDave]

JStephen, The second video includes spraying an ID for bendtec onto a pipe. Apparently they are in Duluth MN.

For CAD models it was sometimes easiest to create arc segments of 90 degrees or so and assemble them with a twist - seems like the same could happen here - planar bends and then weld them with the desired amount of twist to get the helix. The length of the arc sets the smoothness of the helix.

I do like the Swebend system.