Copper pipe to tube plate

[Tony Bird]

Hi,

In the next few months I will be making four model boilers all of which will use the same diameter tube. Three of them will be vertical and the other horizontal all will be gas fired, the vertical boilers will have ceramic burners the horizontal one a poker burner.

The boiler barrels will be made from 54mm (2.1/8”) OD copper tube which has an ID of 52mm (nominal 2”). Looking for some material to make the boilers tube plates I came across some 19mm (3/4”) thick wall 1.97mm (5/64”) copper pipe. This pipe when opened up should just be long enough to make the tube plates from. Pi times 19mm gives the answer of just less than 60mm but the thickness of the saw blade and twice the thickness of the material will have to be subtracted from that which gives a rolled out length of the tube of 55mm. In fact the pipe rolled out to a bit over 54mm which is just enough to make the tube plates.

As there were to be several boilers made steel rather than a wooden former was made for the tube plate. The diameter of the former was the ID of the boiler minus twice the thickness of the material of the tube plate and I add about .050mm to the result so the diameter of the former came out to 49.5mm. This will give a flange height of about 3mm due to the stretching of the material during the forming.

Photographs taken of making the first of the tube plates needed.

001. As eight tube plates are needed the hacksaw depth stop was set up to cut the tubes to length.



002. The tubes were machined to a length of 55mm.



003. The tubes were split along their length.



004. The tubes were annealed.



005. The tubes were flattened out and were marked out for the diameter of the former and for the maximum diameter possible on the sheet, this outer line would become the cutting line.



006. The disc was cut out.



007. Some steel rod was machined to 49.5mm to make the former and a radius formed on its end.

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008. The other end of the former and a shoulder turned on it and was centred.



009. The annealed copper disc was held to the former using double sided tape.



010. A start was made on forming the flange of the tube plate.



011. It wasn’t found necessary to anneal the tube plate again the flange being formed in one go.



012. The end of the flange being machined while held on its former.



013. The completed tube plate.



014. Test fitting of tube plate in a boiler barrel.



I hope this is found interesting.

Regards Tony.

 

[modeng2000]

Yes Tony, very interesting as usual.

John

 

[crueby]

Nicely shown - I would not have thought of starting with tube stock like that.

 

[stevehuckss396]

Very cool. Looking forward to more.

 

[barnesrickw]

Thank you. I will use this method.

 

[Tony Bird]

Hi,

I would not have thought of starting with tube stock like that.

If the tube plate is to be the same thickness as the boiler barrel I often use an extra section of the barrel tube to supply the material for the tube plate. Opened out it is large enough sometimes to make three tube plates.

Regards Tony.

 

[charlesfitton]

Hi,

Opened out it is large enough sometimes to make three tube plates.

Regards Tony.

3.1416...

f

 

[kquiggle]

Great idea - I learned something new today! Thank you for sharing.

 

[jschoenly]

No not sure what the rule of thumb is, but the flange looks a little short on that end cap. I'm used to seeing something like 2 -3 or even 3-4 times that material thickness for the joint length, this is where the strength comes from. Anybody else have a rule they go by?

Don't get me wrong, nice forming job done! I don't at all mean to criticize the work as you did a great job and nice pictures, just asking about the joint strength.

 

[mcostello]

Most excellent!

 

[Tony Bird]

Hi Jared,

No not sure what the rule of thumb is, but the flange looks a little short on that end cap. I'm used to seeing something like 2 -3 or even 3-4 times that material thickness for the joint length, this is where the strength comes from. Anybody else have a rule they go by? Don't get me wrong, nice forming job done! I don't at all mean to criticize the work as you did a great job and nice pictures, just asking about the joint strength.

I don't know of any rule of thumb regarding the depth of flange on tube plates if they are going to be hard soldered into the barrel. A lot of model boilers just have plain discs hard soldered into their barrels. I suppose if the boiler is to be riveted there probably is some legislation that would apply. If there is a rule of thumb regarding the depth of flanges of tube plates it would be interesting to know it. I don't think there is here in the UK.

Regards Tony.