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Author Topic: Instead of a typical fish-mouth notch. What do you think of this idea?  (Read 4117 times)

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Offline Nutz4sand

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Instead of a typical fish-mouth notch. What do you think of this idea?
« on: July 14, 2009, 04:08:54 PM »
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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Offline Nutz4sand

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #1 on: July 14, 2009, 05:52:06 PM »
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.

 
« Last Edit: July 14, 2009, 05:54:18 PM by Nutz4sand »
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Offline Yummi

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #2 on: July 14, 2009, 06:22:40 PM »
Seems to me you just created two stress risers and significantly weakened the red tube.
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Offline Nutz4sand

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #3 on: July 14, 2009, 06:27:10 PM »
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. 
« Last Edit: July 14, 2009, 06:30:47 PM by Nutz4sand »
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Offline Boostinjdm

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #4 on: July 14, 2009, 08:34:32 PM »
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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Offline fabr

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #5 on: July 14, 2009, 08:40:09 PM »
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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Offline Boostinjdm

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #6 on: July 14, 2009, 08:43:55 PM »
Quote from: Masterfabr on July 14, 2009, 08:40:09 PM
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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Offline Nutz4sand

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #7 on: July 14, 2009, 08:45:46 PM »
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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Offline Boostinjdm

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #8 on: July 14, 2009, 08:50:42 PM »
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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Offline fabr

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #9 on: July 14, 2009, 09:10:29 PM »
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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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

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 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Offline Nutz4sand

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #10 on: July 14, 2009, 09:14:23 PM »
Quote from: Masterfabr on July 14, 2009, 09:10:29 PM
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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Offline fabr

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #11 on: July 14, 2009, 09:36:42 PM »
For your concerns NASCAR ,I THINK, requires a tube within a tube for high shear force areas of the cage.
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"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

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magnum4598

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #12 on: July 14, 2009, 09:53:30 PM »
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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Offline BDKW1

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #13 on: July 14, 2009, 11:59:23 PM »
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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Offline Boostinjdm

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Re: Instead of a typical fish-mouth notch. What do you think of this idea?
« Reply #14 on: July 15, 2009, 01:28:07 AM »
Quote from: BDKW1 on July 14, 2009, 11:59:23 PM
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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