help with pipes lengths/angles

[..DAZ..]

Don't know quite wherre to put this, so feel free to move it to appropriate section.

Please excuse my really poor drawing.
http://www.mig-welding.co.uk/forum/album.php?albumid=891&pictureid=2230 Basically I am trying to cut a piece of 4.5" OD pipe to make a chimney, but I get confused with angles and numbers so I am hoping some clever person can help me. The overall length can not be any more than 340mm from outside to outside of pipe, and I have a height of 120mm to work in. Now I know I could just make the two bends at 90 degrees, but as it is for a chimney I would rather have as much of a slope on it as possible. Is there a way for working this out or can some kind person just tell me the answers? I cant build it in situ as it would require me welding inside my house, which of course my better half would not take too kindly to. Any help would be much appreciated.
cheers
daz

 

[Hitch]

Easiest way to do it is to draw it out on the floor full size, drawer the verticle pipes
then the angle one. Take a line from at each bend, through the intersections, them measure the angle from the straight to the line, and you have your cut.

All 4 pieces will be cut the same angle.

 

[Paul.]

are you sure you mean 120mm or should it be 1200mm, how high is the spigot on the burner,

 

[..DAZ..]

it is 120mm, not much room to play with I know. There is no spiggot yet, havent got round to doing it yet. I will check measurements tomorrow and repost to make sure.
thanks
daz

 

[scarecrow]

wont the cutting angle be 45 degrees or am i missing something thing

 

[Archie]

If it really is 120mm then just go with 90º bends. You're trying to take the pipe across almost three times the distance it's going up so even if you had no vertical bit at the top and no spigot the angle would still only be 19º off horizontal. I can't believe you really only mean 120mm though. That's not even 5"....

EDIT: And that's assuming the pipe has zero thickness. In reality if it's 120mm then it'll have to be 90º since the diameter of your pipe takes up nearly the entire 120mm. So actually it wouldn't be possible as the bends will also have a height to add to the equation.

 

[jimms]

Hello
This sounds a bit like making a flue for a narrowboat, the way I do it is get a plank of wood as near to the diameter of your tube cut and screw it together at the right shape and length of what you are trying to achieve then use this pattern to make your flue, noting the bends must be as far apart as possible (as obtuse an angle) to help with cleaning and for fluing easily.
Another option is to cut flue through nearly so you can bend to shape and then fill in openings but be wary of distorting it by moving an welding.

sizzle away
jimms

 

[..DAZ..]

sorry for the late reply, been really busy the last wee while. I have checked the sizes and they are correct, I have made a bit of a balls up on the bottle size selection!!! I think I am going to have to rethink how far forward I want the stove to sit in the fireplace, or use a shorter bottle................................DOH! Thanks for all the info and tips though, much appreciated.

cheers
daz

 

[darthmojoe]

a good source of swan necked pipes about 4" is lorry exhaust pipes/tail pipes,then you only have to cut and shut the length of the straight areas,but looking at the size of your fireplace you could utilise the exhaust of a large salon car or similar. good luck

 

[scarecrow]

don't panic just yet have you though about thaiking the flu pipe out of the side of the bottle it might give you more room to work with