How would you....

[Rubberdown]

My wife has this welding project she wants me to do. I need a form for half a sphere about 4 foot across to use to create a sphere shape. How would you guys create that? Not looking to spend a gazillion on a thing that may not turn out well anyway.

Thanks

Ryan

[Tyler's Outdoor]

Need a little more info about what you're wanting the final product to be.

[Rubberdown]

Lots of railroad spikes welded roughly in T shapes that will ultimately end up as a sphere. Was going to make it in two halves so it isn’t so heavy I can’t move it. Think a globe made of railroad spikes or something.

[Tyler's Outdoor]

I would just cut a sheet of plywood into a 4' semi-circle and then use that to clamp your spikes to and make one semi-circle, then keep intersecting that one with more semi-circles until you have a hemisphere.

[JonBoy]

Just thinking out loud here...

If you had a box, say 4 1/2' x 4 1/2' x 2 1/2' filled with sand, following Tyler's suggestion if you cut a single 4' semicircle out of plywood and then used it to carve the hemisphere into the sand (by rotating it) you could use that as a negative to cast a form that you would use to weld on top of. Not sure what medium would work best to fill the form...spray foam/gap sealer?...

[Philip-TX]

buy a tank head, lay em in it and weld 'em up

[TXBRASS]

buy a tank head, lay em in it and weld 'em up

winner!

[pontiac]

I had to go back and RE-read your project description.
I thought you said a wedding project.

[Maxx85]

We had that idea years ago, and even tried to start it, but too bad we had too many competitors in our area, so it didn't work as we were expecting...