buying copper for boiler makeing

Dave

Edited By David Haynes on 14/02/2012 22:23:36

hi all again the barrel is nearly done just a couple more bending sesions then we should be there as mw said the next thing is the long join down the boiler tube, im guessing that a strip of copper the same as the boiler is used and rivited in a zig zag patten alternating side to side. will 1/16 copper rivets be ok to do this and how wide should the strap ideally be?

many thanks once again mike

Hi

When riveting for silver soldering should you stop short of completely closing the rivet in order to maintain a few thou gap the for silver solder to flow between the joining surfaces.

I understand it's important to maintain a few thou gap to get a sound joint?

Nigel

ah ok so the strip goes on the inside i imagined it going externally il look in to the solder and when i can il make an order as for the staying well i will go for the best method, iv been looking in to the copper for the back head it calls for 13g would 2mm be ok as the fittings wont be screwed straight in i will be making bushes 2mm is .337 smaller then 13g i can get a small peice big anougth to make he back head as i dont have the money or the need to buy a big 300x300 sheet

many thanks mike

ok MAJOR muck up riveted the boiler togethor ready for soldering and after all that work it seams its come out 3/16'' bigger so an external diameter of 3-3/16'' im not gonna remake the thing now i know were it went wrong so im gunna try my best to work round the problem bigger tube plate bigger smoke box on and on and on admitally the boiler shell does look nice just went a teeny weeny bit wrong oh well hopefully i can make it work =(

mayby it will work mayby it wont if not it can live on my shelf

well that was reasonbly sucsefull for my first time at flanging a plate....... yes i started the tube plate and to my surprise has come out rounder then the boiler barrel so not all bad never done it before so im fairly happy wih myself solder and flux is on order going to get some fire bricks next week so should be getting the seem brazed up i must admitt with the little patiance i have im doing very well hehe

will soon be purchsing the tube for the boiler tubes haveing trouble finding 3/8 24g i can easily get 20g that is 0.355 smaller wall thickness would this be much of a problem? also im going to fit bushes in the tube plate for the stays and cant really afford to buy a foot so was wondering would anyone have a few inches of sutible material i will gladly pay for a few inches probley arround 1/2'' diameter should do

on a side note i have some meteral that is 3/8 and should do the job now it was sold to me as bronze but im doubting it as it machines like copper and has the look of copper is there and shure fire way of telling what it is i made two bearings for a little model i built and they wore out very quickley of running so also makes me belive it may be copper

thank you mb1

Thank you David for your occasional edits where threads go askew!

Contact Joe at Macc Models, he will sell you everything by the half inch if needed.

hi thank you iv got to order some bits from macc models anyway so il have a ask when i do, as for the tubes would 20gauge be ok

regards

hi...20g is 0.9mm, thats the same as the stuff in b&q (wall thickness) its critical limit is about 600 psi so in theory its strong enough, but i would go thicker if i could - bottom line is it will easily pass for your requirements

Hi Michael,

what exactly are you worried about? 20g is thicker than 24g, so are you concerned about the reduced internal diameter (0.305" as opposed to 0.331" ) reducing air flow?

Terry

Edited By Terryd on 29/02/2012 04:16:19

Hi Nigel.

according to (British Standard) 2871 - Dimensions and Working Pressures the maximum working pressure of 10mm x 0.6mm thick standard half hard copper tubing is 7.7N/sq mm which is around 1116 psi (annealed 0.8mm wall thickness has limit of 8.2N/sq mm).  Allowing for a safety factor of 2 that would be about 600psi as you say. However that is internal pressure which causes a tensile force in the tube (I've forgotten the formula to calculate exactly after so many years ). In a boiler tube the pressure is external, inducing a compressive force in the tube wall which means that the tube can withstand a much greater pressure. So Michael should be ok with 20g (0.91mm).

Best regards

Terry

Edited By Terryd on 29/02/2012 05:21:27

Hi again Michael,

don't forget that BS EN standard copper tubing 10mm dia tubing is 0.6mm thick which is very close to 3/8 (9.3 mm) x 24g (0.559mm),

Terry