DTSFab.com (Desert, Trail and Sand)
The Machine Shop => Welding/Cutting/Bending/Forming => Topic started by: Nutz4sand on July 14, 2009, 04:08:54 PM
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Out working on stuff in the garage and looking at my notcher while I work on my bender stand. I started thinking about this below.
I am busy on other stuff but may try to actually do one of these tonight. But for now I just have a quick "paint" drawing to show what I am thinking about.
Insead of the usual fishmouth we all know of like the top one in the picture below.
What if you use the hole saw to actually cut grooves in the tube its meeting. Then the tube thats NORMALLY fishmouthed will fit in it and practically lock in place. The weld area around the outside remains pretty close to if not the same for strength. But the tube cannot slide even if the weld breaks.
Granted this would be a little tougher to assemble some designs of some parts as it would have to be fitted and not jsut slid into place like a fishmouth. BUT in some places this may be a great strength addition.
The only thing I might question is if the tube you bore into with the saw would be weakened once the weld was completed VS one that had a fishmouthed tube around it. It seems like the welded tube would give it the strength back?
Maybe this type of joint already has a name? Anyone ever try this? Thoughts?
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Here is a view from the top I whipped up.
Just bore a hole in the red tube with a notcher then the blue tube would slide in. The green area represents the area that will be out of sight INSIDE the red tube (on the sides anyway) when the joint is kissed together. The top of the blue tube would still be on top of the red tube just like a normal fishmouth.
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Seems to me you just created two stress risers and significantly weakened the red tube.
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I thought of that Yummi. But the way a holesaw cuts they would not be perfectly square cuts and once you ran a weld around the entire outside area any stress area should be relieved and covered.
Maybe not. Thats why I am asking for thoughts on it! : ]
I think I am gonna make one here in the future and weld it up then put it in the 20 ton press just to see what happens. Just gotta figure out what way to push on it. To do it right would be to make a few and try heavy loads in different directions.
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welding all the way around will do nothing for the inside of the cut. The cut will act like a crack and spread. A press may not reveal the extent of the problem, but I assure you that many cycles on a buggy will result in failure.
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I think boost is right. the red tube is still cut and connected together by the sides of the blue tube. Loses a lot of tensile strength in the red tube and will fail more easily.I think anyway.
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I think boost is right.
I think fabr is right for once. ;)
A bend test won't show it's weakness unless hit at just the right angle, which may or may not happen in a specific application. It's going to be the constant cycling that kills it.
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Being you weld all the way around (just like a normal fishmouth) I thought that the sides of the blue tube would hold the reds integrity. Maybe I got too many fumes from the cutting fluid I used all day.....
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The weld would help it, but would not overcome the fact that you intentionally weakend it by leaving exposed saw marks on the inside.
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THe tensile is also lost one way or the other as the pull on the red tube would be transferred through the easily deformed blue tube sidewalls. In a low stress area I'd say it would be fine and quick assembly. Likely several places it COULD be used with no issues at all.
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THe tensile is also lost one way or the other as the pull on the red tube would be transferred through the easily deformed blue tube sidewalls.
Yah the more I look at it the more I think that too.
Better for the blue tube not going anywhere but for the loss of the reds integrity prolely aint worth it.
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For your concerns NASCAR ,I THINK, requires a tube within a tube for high shear force areas of the cage.
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hey nutz i think it will make a stress point in the tube for a crack to start
and with the nothcer i use its so fast it should matter to try it any other way
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Extra weight without any real gain.
Drill a hole in the wall of the tube thats being intersected. Less weight with now real downside but several upsides.......
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Extra weight without any real gain.
Drill a hole in the wall of the tube thats being intersected. Less weight with now real downside but several upsides.......
I think the extra weight would be negligible. If you are that worried about weight, take a crap before playin or skip that cheeseburger....
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Out working on stuff in the garage and looking at my notcher while I work on my bender stand. I started thinking about this below.
I am busy on other stuff but may try to actually do one of these tonight. But for now I just have a quick "paint" drawing to show what I am thinking about.
Insead of the usual fishmouth we all know of like the top one in the picture below.
What if you use the hole saw to actually cut grooves in the tube its meeting. Then the tube thats NORMALLY fishmouthed will fit in it and practically lock in place. The weld area around the outside remains pretty close to if not the same for strength. But the tube cannot slide even if the weld breaks.
Granted this would be a little tougher to assemble some designs of some parts as it would have to be fitted and not jsut slid into place like a fishmouth. BUT in some places this may be a great strength addition.
The only thing I might question is if the tube you bore into with the saw would be weakened once the weld was completed VS one that had a fishmouthed tube around it. It seems like the welded tube would give it the strength back?
Maybe this type of joint already has a name? Anyone ever try this? Thoughts?
I like the idea, but to offset the extra time required to slot the second tube for fitment, I would use gorilla glue to attach the tubes to one another.....
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Heheheheeee!
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or skip that cheeseburger....
Now thats just not gonna happen. It's going to have bacon on it as well. This is why I drill holes in the walls of the intersected tubes.........
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Now thats just not gonna happen. It's going to have bacon on it as well. This is why I drill holes in the walls of the intersected tubes.........
sounds like its your lil american gastric tubes which need drillin...... ::)
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sounds like its your lil american gastric tubes which need drillin...... ::)
That's what Vodka is for, keeps the artery's nice and clean.......
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That's what Vodka is for, keeps the artery's nice and clean.......
Is that why Rusians never got sick (oops, nah that was the KGB firing squads wasnt it....)?