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OT : Overbending a Stainless Exhaust Elbow

TheBigLebowski

New member
I have a couple of 45 degree exhaust elbows made from 2.125 OD 16 gage Stainless steel. I need to add about 10-12 degrees of overbend to them to get the correct alignment.

I tried to make up a set of solid forms to use in a hydraulic press (this method works for solid bar) - but because the tube is hollow it kinked up pretty badly at the initial contact points instead of bending.

Has anyone had any luck bending pipe like this without a mandrel? I already ordered a new set of elbows up, if bending it is a no go maybe I should make the new set of pipes shorter and machine an adapter to go between the elbow and muffler.

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blcksmth

Member
Pack it full of dry sand before the bend. Last century method was to fill with molten rosin. After cooling do the bend and then melt out the rosin.

Bob
WB8NQW
 

Garwood

Active member
Buy a 90, cut it off where you need it and weld back together.

Or, like me, have a neighbor that owns a mandrel bending company.
 

TheBigLebowski

New member
Just tried to bend the spare one by inserting tight fitting round stock in each end and packing the middle with sand; still kinks up pretty badly.

It looks like it's either going to be cut and weld or machine an adapter.
 

007Rob

New member
Buy a 90, cut it off where you need it and weld back together.

Or, like me, have a neighbor that owns a mandrel bending company.

This would be my choice, or a couple pie cuts on the elbow would probably work fine for ~10 degrees
 

Demon69

Active member
Just tried to bend the spare one by inserting tight fitting round stock in each end and packing the middle with sand; still kinks up pretty badly.

It looks like it's either going to be cut and weld or machine an adapter.

To bend with dry sand:-
cap one end (weld up a disc)
fill with sand
cap the other end
hold in a pipe vice
fire up the biggest rose bud you have
heat and bend as you like

like this is pretty similar to how mike the pipe used to do it back int day
 

CalG

Active member
To bend with dry sand:-
cap one end
fill with sand
cap the other end
hold in a pipe vice
fire up the biggest rose bud you have
heat and bend as you like

like this is pretty similar to how mike the pipe used to do it back int day

You will need to show us all how to cap those ends and keep the dry sand packed inside.

I've seen it on a small long piece, but never on a 90... Just too difficult to pull off.
 

Demon69

Active member
You will need to show us all how to cap those ends and keep the dry sand packed inside.

I've seen it on a small long piece, but never on a 90... Just too difficult to pull off.

To cap the end just cut a disc out of some sheet or squish the end and weld if you've length to play with.
To keep the sand dry? Bring it in out the rain and keep the cats out of it :D
Seriously though, they sell dry paving sand over here in 25kg bags.

If you struggle to get a bend going or as getting it as tight as you like you prolly dont have enough heat. A reflector (bent sheet attached to handle) to place behind the area youre heating.

Ive limited experience (headers I couldnt afford to be made att) but I saw the maestro at work once, putting shape into a 3"ish piece o pipe with a torch flame nearly big as he was, he was short but still lol.

Edit:- Sorry I misread, tired here. Weld up one end, fill with sand and tamp it down, top up as needed then weld the top cap on.
I remember being shown a large bore 180 section bent tight that was flame bent, but Mike was the man back in the day.
 
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TheBigLebowski

New member
By the time I learn how to do that well enough to produce a semi acceptable result, I will probably have ruined $300 of stainless tubing.
 

boslab

Active member
I’d have said cerro but that size solid cerro bar would take some tonnage to shift at a guess, ive seen assorted bend boxes on eBay, cut as required and lobster back it as it’s a net reduction cut what you have as eloquently suggested as cut and shut!,(calg) it doesn’t seem visible anyhow, I don’t know why I’m even replying as all I’m doing is repeating the combined wisdom of the collective ( gives me a nice cosy feeling being part of a collective even if I’m a faulty drone)
Merry Christmas fellow collective
Mark
 

GregSY

Active member
I once saw a photo of an old Italian exhaust header made back in the days before mandrel bending. They made it by welding 1" length of straight pipe, each with an angle grind, to get the bends they needed. It was a work of art.
 

Limy Sami

Active member
I once saw a photo of an old Italian exhaust header made back in the days before mandrel bending. They made it by welding 1" length of straight pipe, each with an angle grind, to get the bends they needed. It was a work of art.

AKA ;- cut and shut Greg
 

Homeshopblob

New member
SS is notoriously difficult to bend. I pretty much gave up and just buy prebent pieces from Burns Stainless and cut and weld then together. I tried packing it, heating it, etc, it's so tough it just folds together into kinks even in bending dies unless you use a mandrel and pull it over the mandrel while bending it.
I have successfully packed mild steel tubing for bending just by shoving rags in the ends to keep the sand in place, welding caps on is unnecessary and can be hazardous because caps will allow pressure to build up and burst the hot pipe. The sand won't move if you keep it in place with a tight fitting rag and have a few inches of length past the ends of the bend to fill. If you want to be fancy, cut a wood plug and pond it in. I've taped the rag on to keep it from falling out.
I saw a very nice Formula Ford header built from 4 pieces of (steel) tubing, the builder in GB heated the packed tubes over a coal forge fire and bent them around tree stumps.
 








 
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