TOPIC:

Porche... First off LUVv this freakin post and data... Thanks!

Question, Would the deformation be the same if multiple passes where incrementing pressure each pass was accomplished?

I see curved risers in these images ...

OMR, THAT will be the next subject of experimentation. At some point today I'll put a virgin piece of 1.5" in and see what happens when I halve the amount of tension on the center die for each pass. So instead of 3/8 of a turn on the die, I'll go down to 1/8-3/16 of a turn per pass.

You mus work for HFT for the more I review this post the more eager I get go and buy that roller...

Damn I love that store....

I definately do not work for harbor freight
Suffice it to say that less pressure on the die per pass did not reduce the amount of deformation. Here is the third piece of 48" 1.5" dia. tubing to give its life for science

The amount of deformation was approximately the same at .046" down to 1.454" in diameter.

This result was obtained using 1/8 of a turn on the die for each pass. I have also learned not to get too concerned about the z axis roll in the tube. Once you get enough curve in the piece, it gets fairly easy to guide the piece through while rolling it to keep it straight. Any off center bending gets straightened out in a few passes. I do try to keep it as straight as I can from the start by lining up the weld seam on the tubing with the top edge of the dies and keeping it as close as I can through the roll.

Since rolling in smaller pressure increments did nothing to change the deformation of the tube, I decided to fill the next piece of tubing. Now the first thing we need is caps, like these 2" disks cored out of 18 gauge steel-

I welded one on the end of a fresh piece of tubing and welded the pilot hole closed

Then I welded the other side on but left the pilot hole open

The common practice is to fill the tubing with sand, but I thought I'd try the hydraulic route first. I recall from high school science class that fluids are non compressive, so I thought hey, why not fill the tube with water and weld it shut? It turns out to be alot harder than it sounds I could not actually get the tube to seal because the water boils in the local area of the weld creating steam, and the steam makes a pathway out of the weld before it can cool enough to contain the pressure. It turned out to be a never ending, loosing battle that I gave up on after 30 minutes of thinking I was smarter than the physics involved. I don't think I lost alot of water in the tube, but it doesn't take much to give the tube airspace to deform, so we'll call tube test #3 the same as empty tube #2. There's a reason everyone uses sand, I just had to figure out why the hard way

I took tube #3 further through the roller just in case the water filling added some support

It didn't

I was hoping the water filling in this tube would help prevent deformation despite any loss of water during the failed sealing process and leakage during rolling. Due to this false hope, I rolled this tube much further than the first 2 tubes.

I was wrong

Here is 1.5" tube #3 with the stock 4:2 primary header tube laid on top of the test piece. The radius of this roll is a hair over 10.5 in.

Here, the deformation on a 10.5" radius roll is .085"

This represents a 5.66% change from the original o.d. Lets see how much tighter we can make this radius before things go to hell, shall we?