alluminium pipe bends?

[Tim.duncan]

Hey guys

i have just bought my first ae86 (first toyota to tell you the truth!) and it had no engine so I'm in the middle of putting it all together. which leaves my sorry arse on the train every moring to get to work. While on the train i have lots of time to read car mags and this is my question

Most cars in the mags are running fmic and when ever there is a bend in alluminium pipe they have welded along the outside of the bend?? why do fabricators do this? have they cut out a section and made the pipe smaller by bending it in and rewelding it? I have seen it alot in my mags and was curious?
can any one explain this to me?

cheers guys

[balistic]

Generally those tight bends are made from two halves welded together, coz its easier to manufacture that way.

[Jonny Rochester]

The bends you buy are often a completed circle. Two halves of a donut.

[Jonny Rochester]

I think most people with a turbo Sprinter would still end up catching the train anyway, for various reasons. Even after its "finished".

[choom78]

coz sand bending pipes is oldskool and getting whole sections mandrel is for a 1-off is expensive. Using donuts gives flexibility.

[driftke70]

two halves of a donut tigged together give you a larger range of choice in the bend you want, you can buy or make them in different radii and are alot easier than guessing angles without a visual to compare etc.

personally ever since i have been around motocross i have always loved the lobster shell look, especially on raw steel expansion chambers.