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Tube notching for wing bars


white90
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I did it the hole saw method when i did my roll cage - took bluddy hours!!!

When I did my roo bar i just did it with the grinder. Much much quicker and the results are the same - just keep trial fitting it until its perfect.

Abrasive flap wheel in the grinder is best I found.

HTH

Jon

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Tube notching can be really easy: a 90 degree tube notch is in fact a tube straight cut twice at 45 degrees. Have a look at a notched tube and this is a very close approximation of the shape. This is how I did all mine. It needs a bit of fettling afterwards, because this method assumes 0 wall thickness, which you obviously havent. if the angle is not 90 degrees, say 45 dgrees, the cutting angle will be 22.5 and 67.5 degrees and so on. once you get the hang of it, its easy! (as usual..).

Daan

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I think there is a certain amount of confusion here.

As I understand it, everyone is talking about the same thing, but using different words for it. Notching / fish-mouthing / birds-armpit / elephants-genitalia... whatever, it's the curvy bit at the end of one tube which allows it to butt up against another tube perpedicular to it with no gaps.

Daan (et al) is right - the answer is: Yes! It can be done with 2 straight cuts. I was gonna suggest you use a chop saw if you have no notcher etc. It can come out pretty perfect if you get the 2 angles right - maybe a quick clean up / fettle with a grinder, and just weld it on! :)

Al.

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Cheers, I dont hear this very often and I wasnt going to start a row over it, because I dont care. But, yes with so many things simple is best.

Daan

No you're absolutely bang on - I think it's hard for a lot of people to visualise how a straight cut through a bar results in a lovely curved notch that butts up against another tube perfectly, but it sure does - I've done it myself.

Practice a bit though, or use a calculator - if you are doing wonky angles the cut often needs to be at a pretty unintuitive angle...

If I can be bothered, I'll post a link to the thread on Pirate about it... Don't hold your breath...

Al.

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OK Daan, sorry for misunderstanding. I've still got my 2D head on though, I don't understand how you can get the proper 'sine curve' profile into a round tube with 2 straight cuts. In my head, that'd be the way to join a tube to some triangular bar - as I see it you need to project a circle onto the pipe (as viewed from the side).

Cue a 1980s diagram in Paint (I hired an 8 year-old to help me with this part)

Solidworks.jpg

Is it just a case that 2 straight cuts is near enough to tidy up with a grinder and make up the gap with an unsteady hand on the welder? I'm not saying I don't believe you, I just don't understand it and it's bugging me now.

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Think about it....

Take tube and make two 45° cuts in an X (as viewed from above) such that you end up with a point on the end of the tube rather than a triangular notch in it. Now turn the tube through 90°. What shape is the notch? I say it's semi circular.

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I'm with you - I've edited my diagram.

Solidworks.jpg

The issue was that I was making two cuts as the blue 'wedge' shows (and getting a much worse approximation), not as the purple plane represents. Like I said, I just didn't have my 3D head on... :) Cheers guys, esp Mark (it hurts to say that) for the clear explanation.

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