# how to calculate angle between pipes in 3D

Help with geometry homework please ;-)
I've got two pipes running at right angles but in different planes which I
need to connect. I'd like to use a 45degree (or 135 degree, depending on
your POV) fitting on one, and pull a bend on the other to match, but I
can't think how to work out the angle of the bend. The pipes are 22mm Cu so
not amenable to pulling back & forth by hand to get it just right :-)
Here's an ascii art
pipe A
=========\\ 135deg fitting O
Couldn't you bend a piece of 15mm to establish the angle and use that as your guide for the 22mm?
mark
OK John, ASCII art has its limits!
Pipe A is horizontal, and B is vertical? And if you extended B upwards, it wouldn't actually meet A?
You have a choice of angles, and lengths of the pipe between the bend and the 135 degree fitting. You need to bend pipe B not by an angle, but by a distance. A smaller angle, and you'll need more pipe above the bend; a tighter angle, and you'll need less pipe. Seems to me that if you put *two* joints in your pipes, instead of a bend, and dry assemble the one on the lower pipe you can swivel the nearly vertical bit around until it lines up with the other pipe, then cut to length.
Andy
Use a flexible connector.
Apologies for sidetracking your thread but it is related in that a solution could solve both problems.
Is there a flexible object which could be easily shaped to act as a template when bending pipes using a spring? We had a bendy ruler (french curve?) in technical drawing in school to help when drawing curves.
Bit of ductile 10mm copper pipe?
Coat hanger wire?
Fattish bit of T+E?
cheers, clive
Thanks, Clive.
Lateral thinking is not my strong point. The fat cable is probably the most usable suggestion. Every time I try to straighten coat hangers for alternative use, I end up nearly poking out an eye - sometimes my own. PJ
On Tue, 27 Nov 2007 21:35:09 GMT, John Stumbles wrote:
After 1/2 hour of scribbling, I think I would loose fit the 135 fitting to pipe A with a short length of 22mm long enough to reach B. Then transfer the final angle using a thin piece of metal. Assuming that pipe A and B are already in position. But I await the real answer with interest - good question...
Geo
Okay, completely OT now but wasn't a 'French Curve' one of those shaped plastic pieces made up of a whole series of curves so that you could usually find one that fitted three or more points. Usually came in sets of three and with a range of elliptical holes in the middle although interestingly the ones that I had did not have ellipses that fitted a standard isometric projection.
Andrew
There is a product which I have not seen in the merchants or used which claims certification for use on gas. Essentially the pipe is corrugated stainless coated with yellow plastic. The ends are some sort of compression joint that "bell mouth"s the pipe. There are precise rules for tightening the joints. IIRC Trac-pipe might be the name.
I came across this problem when trying to work a Keston flue pipe onto a boiler. I hoped to be able to use a couple of 135s and make a nice job. I discovered that, in fact, this problem is not always solvable with a couple of 135 fittings. I had to extend one of the pipes and use a 90 and a 135.
As drawn it looks like you may be able to use a couple of 135s
Have you ever seen a 135 compression? I haven't but I haven't looked for one either, I'd bet they'd pricey though. If you measure the ends relative to each other you can experiment with a selection of fittings in a more convenient location make up the soldered joints and then take the combined fitting to the job and use compression or just a couple of soldered ends.
HTH Best of luck.
Tsk, here's me asking on the ng and there's the answer on the wiki:
So if I understand that correctly you have say a vertical pipe, and a horizontal one running left to right, however there is a mismatch in the third axis - i.e. one is closer than the other.
You could join them with a pair of elbows and some straight extensions.
It seems as a general case if one bend anglew is determined (e.g. by a fitting) then you should always able to achieve a match by using the same bend angle on the other end, so long as you can adjust the length of one of the pipes to control the intersection point.
Yup, the bendy ruler thing is a "flexi-curve"... I do occasionally use my one of those for marking out in the workshop ;-)
Yup but you can't get arbitrary-angled fittings, so the trick is to use a standard angle (e.g. 45/135 degrees) on one end and a pulled bend of the right (i.e. correct, not 90degree) angle at the other.
I've heard of tracpipe but thought it was for longer lengths especially under floors etc; and no idea there was anything odd about connection to Cu at the ends as you describe. Maybe it's a different product?
I'm sure I'd have needed 3 * 135s since the two pipes were out of plane with each other.
Only 32mm and 40mm plastic - never in brass.
Not luck: science :-) I was dead chuffed: it all fitted like a dream - not like my normal pipe bending which is hit & miss at best (well I never had months of pulling bends on the bench in tech - it's all been on the job)
Thanks Andrew, I now recall what a French Curve looks like.
At least the name is logical. Many thanks, John, I can now search for one to help with my present project. PJ
In general you don't need arbitary angles though, I think if you use a 45 on one end, then you should be able to achieve a join with a 45 on the other as well. What needs to change is the length of one of the pipes. By doing this you can always force a point at which two matching bends will achieve the required connection.
The need for a variable angle joint on one end will only arise if you are unable to change the length of either pipe.
Thinking about this last night. Could you solve it by drawing to scale in Google Sketchup and then measuring the desired angle / lengths?
Andrew
The most convincing way to see whether this is true is to try it! Only needs a couple of 135degree fittings and 3 pieces of pipe. As soon as you try to take the pipes out of the same plane the angle between them changes from 90.
I've not tried Google's Ketchup but a bit of brain-juice revealed a straightforward answer, as illustrated with a rather lower-tech drawing package:

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