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Discussion Starter #1
Just thought I'd throw this up here.
There's not a lot on the internets about this.
Some.
Not all in one place.
But enough that I think I'll give it a try.

Hopefully when I'm done, it'll be a nice synopsis of all I've learned.
And, yeah, this is a project in process and not a retrospective presentation. So updates may be slow depending on my motivation.

I trolled craigslist for a long time and picked up a used metal chop saw (carbide blade not the abrasive kind) for the project.
39419_3_400x400.jpg

To be continued...
hopefully
 

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Discussion Starter #2 (Edited)
Why am I doing this?
The modified stock exhaust I'm using chokes down to less than 1" at various spots in the exhaust and I feel it is limiting high rpm power. Great torquey engine. But flat on top.
Also, the stock exhaust limits ground clearance on right turns. I'm going to reroute for more clearance as well.

If you buy pre bent mandrel tubing you are limited to a couple and sometimes only one radius bend. With pie cuts not only can you make any radius you want, you can vary that radius within a single bend as well.
And because it's another skill that I want to learn.
 

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Discussion Starter #4 (Edited)
Tig. I'm pretty decent at it. I don't own a mig.

Steel for my first attempt. I'd rather not add the complexity of purging the tubing.
 

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Never heard it called pie cut, was always called lobster backed when I worked in fabrication, always wanted to make my own exhaust and will do one day, good luck and I look forward to the updates.
 

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Discussion Starter #6
Ok. So first the theory.

I want small enough segments so that the result looks decent rather than some sort of kids Lego toy.

10 segments per 90 degrees should be plenty. This means 9 degrees per segment.
Since each pie cut or segment is cut on an angle at each end, then each side is 4.5 deg.

I set the chop saw with a protractor to cut at 4.5 degrees. Hopefully.

To set the centerline radius of the "bend" created by these segments I'm going to use an online program that calculates the width of the cut. I'll use solidworks to print up a cutting template.

The biggest thing about cutting these segments is that the cuts must be made alternating +4.5 and -4.5. And the tube held in the exact same rotation for each cut.

Right now I'm trying to figure the best way to make the cuts and ensure the tube is kept in the right rotational position.

Pics to follow...
 

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Discussion Starter #7
Oh btw, can someone tell me what I like pie and CR.net have to do with one another?

Please.....
 

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Discussion Starter #9
Here's a link to a post with the link to the excel program that calculates the width of cut for a given tube diameter and center line radius.
Tube pie cut calculator

Screenshot of the above
piecut.jpg
 

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I have not tried to bend a pipe that way, but when I do a pie cut, I try to finish each weld and then planish the seam to flatten it and remove any dags on the inside. You welding is undoubtedly better than mine, so maybe not an issue for you.
 

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Discussion Starter #13 (Edited)
Next up was to measure the approximate centerline radius (CLR) of the initial header bends of the stock exhaust.

I traced the initial portion of one of the header pipes on a piece of paper, drew some reference lines and it's about 3.5".

My tube diameter is 1 3/8".

plugging this into the excel program, I get 0.6570949267". Which is the length of the long side of the tube after the cuts are made on both sides.

for example picture from the internet.
piecutsm-1024x683_large.jpg

I'll put this in solidworks and print out a paper template to wrap around the tube to help with the cut.
 

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Discussion Starter #14
I have not tried to bend a pipe that way, but when I do a pie cut, I try to finish each weld and then planish the seam to flatten it and remove any dags on the inside. You welding is undoubtedly better than mine, so maybe not an issue for you.
We'll see... But I know exactly what you mean.
It has to do with heat input. You get the heat right then you have adequate penetration without that burn through and all that sugaring or oxidation on the back side (or inside in this case).
Welding in short segments and allowing it to cool under good gas coverage is a technique they use with Ti.
Pulsing is also very effective in reducing heat input into metals. If I can't get it quite right, I'll pulse it.

It all comes down to practice, practice, practice.

And fit up. You could weld these without filler (autogenous) if the fit up is perfect.
 

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If you purge the inside of the tube with argon the inside will look as good or better as the outside of the welds.
 

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Discussion Starter #17 (Edited)
I purchased a parts bike from a guy who welds for a living.
He was showing me the welded exhaust cans he grafted onto the stock pipes. I asked about welding and welders. He told me you really don't need to spend $$$$ to go red or blue these days(lincoln or miller).
He had this really small DC only Everlast tig that he said worked fine. At work he uses all miller.

So I did my research and bought a digital inverter DC everlast tig with a nice wide range and pulsing capability.
Its made in china, I think, so you have small quality control iissues sometimes. Haven't had the need to pursue customer service so can't comment there. If not for a slight flickering of the lights on the panel after 2 years of intermittent use, it would have been perfect for me.
Super stable low amp starts. Enough power to weld what I need. Enough adjustability for me to weld thin walled tubing and sheet easily. Pulse capability, 2T and 4T operation. Foot pedal might be a touch lower quality but perfectly serviceable. Bought a smaller lighter torch with a gas lens for the frame welding work.

I knew I would probably upgrade in the future to AC tig and aluminum welding but I wanted something to practice on. Make sure if tig welding was something I really wanted or was able to learn.

My next welder will probably be the Italian made(?) HTP invertig 221.

There are others, too. Great time for the "hobbyist" welder.
 

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I've had Lincoln Tig square wave welders, and 3 Lincoln Migs. Now have a Hobart, and find its a much higher quality machine for about the same money.


Sent from my iPhone using Tapatalk
 

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...

Right now I'm trying to figure the best way to make the cuts and ensure the tube is kept in the right rotational position.

Pics to follow...
Hi, my left side doesn't work so well, so I don't have your skill of TIG welding, but I wish I did. On keeping the right rotational position, if a length of flat steel, say 1 inch by an eighth, or even a length of light angle, was placed longitudinally underneath the tube and welded at the non cut end, it might work. It's just a thought.
 
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