Lobster bends - I'm doing something wrong.

[Ashh]

Hey guys,

I'm turbo-ing my 2t/3t combination that resides in my TA22. At the moment I'm up to the intercooler piping.

I've got my powerhacksaw set to 11.5ish degrees, which should then mean that I should get 90 degrees out of four pieces correct? (2 sections with one angled side and two with both sides cut at angles).

However I'm not getting anything near that and it's supremely frustrating because I need to get on with this job. What am I doing wrong??

Cheers
Ash

[Hen]

The way you've described it you only have three joins. A-B, B-C and C-D (where A and D have one angled end while B and C have two). Each join is around 23 degrees and so you should end up around 69 degrees total.

Add an extra piece, or take it up to 15 degree cuts. I think that's getting a bit extreme though, so I'd rather more slices.

Hen

[Ashh]

Nah I'm using 4 pieces
A-B, B-C, C-D and D-E

still doesn't seem to come out to 90 though.
I might try 7.5 degree cuts?

So frustrating! I'm cutting these on a powerhacksaw so they *should* be pretty accurate angles.

[ta22fan]

Ash - I think Hen is correct. 5 pieces (A,B,C,D,E) means 4 joints. 4 pieces (A,B,C,D) means 3 joints. With 4 pieces (3 joints) - you'll need 30 degrees per point, so 15 degree angle on each side. 5 pieces, 22.5 degrees per joint, so 11.25 degrees on each side.

[Fantapants]

the easiest way to do this is to draw it out properly on some decent sized paper. there are good tutorials on youtube and such as to how to do the drawing. that will get the numbers and such right in your head...

[Fantapants]

yes you are also only using 3 joins as such...

[Ashh]

Ahhh officially retarded..
alright I think I'll switch to 15 and 3 joins (then things are exact angles and hopefully this will start working..)

Thanks for the help and the patience with a newb

[V-Na]

Your total bend is the sum of all the bends.

In this case you have 6 equally angled cuts producing the bend and four members, call them A, B, C and D. Let theta_XY denote an angle between two adjacent members X and Y:

theta_AB = 11.5 deg + 11.5 deg = 23 deg

Similarly theta_AB = theta_BC = theta_BD

theta_total = theta_AB + theta_BC + theta_BD = 11.5 deg * 6 = 69 deg

You should have cut each angle at 90 deg / 6 = 15 deg.

[mattysshop]

is it not feasable to obtain tight radius (1D) stainless 90's??

tube sales
sandvik

just a few of the big name suppliers you should be able to get some from very easilly..

[Ashh]

@v-NA : Cheers for the maths. I got myself confused and divided by the number of parts not by joins.

@mattysshop: I'm making the piping out of aluminium. It is possible to get bends (though I didn't find any that tight, they were around 2-3D) but it was expensive and I just bought my tig welder and want to practice aluminium welding. not sure if I regret that decision yet haha

[midnight_purple_GA70]

[mattysshop]

Go doughnuts for sure..

unless your really good with a TIG, ally lobster bends look VERY messy..

[jfallen]

^^What he said^^

[dnegative]

Go doughnuts for sure..

unless your really good with a TIG, ally lobster bends look VERY messy..

If they are cut perfectly and you keep the bead small they look good, if your saw is not accurate they will look shit.

[Ashh]

Yeah they're not looking great but I'm getting some nice beads down. Their serving a double purpose as to actually give me some practice on the TIG with ally. I probably will remake it in the very distant future when I start trying to push the setup for maximum power but that's a long way away.

I didn't even know you could buy doughnuts. That would have worked really well! Damnit! haha