9bells

Gentlemen,

I have a question that I think I know the answer to, but wanted to run it by you guys...
I have to make a tight radius bend, you can't buy it this tight.
4" stainless has to turn on it's OD.
The question:
Is it best for LOOKS to cut and cheat the existing bend, or is it best to just pie the tube like I've done with Ti?
Money is not an object, at all.
I want the cleanest looking tight radius fabbed 90 that can be made without a CNC.
Help is much appreciated.

Chris

Flashmn

I think pie cuts would look better than cheating the bend, plus if I understood the shape correctly, I would assume the pie cut version would flow better.

CRMB

Chris you can buy 4" OD on a 4" radius stainless donuts. Why not go that route?

ToxicFabrication

Chris, I wouldn't cheat the bend. I think a bunch of very low angle pie/miter cuts is best. If it cant fit, then go jdm, Canadian style of course.

9bells

It was dropped on me last minute today, I had 4" stainless and 4" Aluminum, so I said sure.
Get the current piece off(3.5") and realize its really tight with a 6" radius on 4".
I was just thinking that if you cut some pies out of a bend and weld it back together, it wouldn't have those flat spots between the welds.
I'm going to have to do it the hard way I guess and try just a few cuts of each to see how it looks.. Good thing is there is no budget, just make it pretty.
Thanks for the help guys, I'll check back a little later. Got some other stuff to do tonight, start on this first thing in the AM.

h2.4

I never liked cheating, I would prefer pie cuts.

Captain Bondo

I would pie cut the bend. Saying you'd rather pie cut than cheat the bend is not the right line of reasoning here. It's all "cheated". But, if you pie cut a piece of tube that is already bent to begin with, you just need less pie cuts, and/or less aggressive pie cuts.

As long as the pieces that are cut are uniform it'll be about the same aesthetically either way.

And yeah, a donut might be the ticket here.

Tjabo

But the pie cuts really function differently on a bent piece than a straight piece, don't they?

I'm having some trouble envisioning the way they both work, but I *think* the cross-sectional area is maintained better on piecut straight than on reduced radius curved piece, isn't it?

RickyLee53

You waste more doing pie cuts in a bend as you can only use them the same way. Unless you just cut a few 5 degree cuts out, but then you've just cheated the bend really.

If its a 4" bend with a 6" radius though, thats just a straight forward 1.5 CLR?

9bells

I went with pie cuts, 6 degrees per cut. Looks decent.

Ricky,

I was referring to the bends I had on hand. The 6" radius is the smallest I buy.
Post pics later. Just gonna finish my coffee, the go and give her a light polish to get rid of fab scratches and get the whole thing to a fairly even satin look. It's a 69 Camaro.
Thanks for all the thoughts and comments guys. Cutting the bend would have been harder to do, not sure what it would have looked like.

swapshop

I have to do this too only with 3 inch pipe for intercooler hot side charge, they dont make a bend in the tight degree that i need so ill have to fab somthin that looks good as well ... please post pics very interested to see thanks

9bells

It turned out ok. Just a few quick pics. Gotta run out for some clamps. The guys sent it here with smaller tubing and some ghetto clamping that isn't big enough for the new tubing.
It's a holiday here, so only a few places open.
More pics when I get back...

Tjabo

Wow, that is the best looking sectioned bend I've ever seen. I think the small weld beads and precision take it to a different level than what I was expecting to see.

CTD-Fab

Nice! I like the finish and I think that definitely looks better than a cheated bend. The other nice thing about pie cuts is the ability to make some very smooth complex bends. 6 degrees is the same i like to use also

9bells

Pics in my thread, but I'll post them here too.
Here is the bad boy 4" CAI on the Camaro.
Nice car, worth too much for anything but very careful.



Old set-up with 3.5" and polished aluminum

New piece mock-up

Slight adjustment and stainless piece made


Make note of how the mount covers the coupler.

SovXietday

Wow, what are you using to cut your pipe? It's friggen perfect!