Welding Flanges onto Pipe and Bolting - Warping Issues?

[sudnak]

Hi All,

I am an artist/fabricator out of California. I am making a 30 foot tall rideable chaotic pendulum, and have some questions about flanges. Essentially, the pendulum will be held up by a tripod of 6 inch steel pipe. These legs will be around 30 feet in length, but will break apart into 15 foot sections. What I plan to do is weld a 2 foot circular flange onto the cut end of the pipe, and brace the flange with (8) 90 degree pieces of plate. This circular flange will line up with another flange attached to the next pipe, and bolt together with 8 structural bolts. Here is an image to help visualize: http://imgur.com/D7plgPD (I know its not perfect perspective, please forgive).

I plan on pre-drilling the flanges and bolting them together before welding, so I can get them lined up. The pipe, flange, and plate are 1/4 inch steel, and I am using a Miller MIG machine to put it all together. What I worry about is that when I weld it all on, the plate will warp. The bolts will then get pinched in and not come out, or if they do come out, will not be able to get back in. Has anyone had any experience welding around bolted materials?

Thanks!
Nathan
PS, for anyone interested here are some images of what the finished piece will look like: http://www.nathankandus.com/Chaotic_Affair2.html

[platypus20]

Nathan,

Yes the 1/4" thick flange will warp.

Is there a reason you are not using readily available and standard pipe flanges??

A standard weld neck flange or slip flang would be a lot stronger than the homemade one.

[Bender]

Sounds like a Burner project?

[Walker]

Weld neck flanges would give you a nice look, although slip on flanges would be easier. The are substantially thicker and wouldn't require the gusseting, though you could still put it in there for appearance. They are also going to end up being cheaper, as you don't have to make them. IIRC an ANSI 150 flange has 6 3/4" bolts. If you want more bolts go p to an ANSI 300, it has 12 bolts.
When you weld them on just hammer two of the next size bolt (7/8") through the flange on two adjacent holes, then place a level across them. Afterward, tap the bolt back out and use them to set up all the rest of your flanges (called 2 holing) http://weldingweb.com/showthread.php?t=81271

Here is a supplier out in your neck of the woods. http://www.coastalflange.com/pipeflanges.html

[Bolt]

<Cutter, please delete, thanks! >

[Bolt]

I would go with irrigation flanges, available at most any irrigation supplier. At 6 inch, (available for both 6" and 6-5/8" OD pipe) they have 8 holes for 3/4 bolts, and are about 1/2 thick. Much cheaper than ASME flanges. Weld them inside and out, and you will be good to go, warpage will be a non issue.

[digger doug]

Originally Posted by platypus20

Is there a reason you are not using readily available and standard pipe flanges??

.

Agreed, and also, why are you not sending the detail part of the design
to a "stamp holding" engineer ? who would know what parts to use, and he will
spec a approved welder, that does these things for a living.

Public involved ?

Ride-on ?

[gimpyrobb]

Ride on is what I saw. Looks like someone is going to smash into one of the tripod legs too.

[sudnak]

You all rock. Thanks for all the help! I am looking into the options you all gave now. I could not find any premade flanges before. I was dreading fabricating them myself.

[sudnak]

Hey Yall,
So, I have another question for this Burning Man monstrosity. Does anyone know of a calculator on engineering toolbox or elsewhere that can tell me the bending strength of pipe-the force one would have to put in one place to buckle the material? I am trying to compare size 8 schedule 20, size 8 schedule 40, and size 6 schedule 40. Thanks everyone.