Boiler end caps

[baldrocker]

I have noted that the majority of boiler end caps are fitted and soldered
inside the tube.
Is there any technical reason for this or is it acceptable/safe to fit
the end cap outside/overthe tube?
Thanks Guys in advance.
BR

 

[steamer]

BR,

Was pawing through KN Harris's book on boiler making and there are abundant examples of both practices. I think it is important to have the proper lap for strength with a silver soldered joint. Inside or outside will depend on the order of assembly and convienence as much as anything......beyond that it's up to you.

Dave

 

[tel]

It's much easier to get a good joint, with proper penetration, with the 'cap' on the inside. The radius on the cap forms a little dam that helps direct the solder where it needs to go.

Also, a word of caution - I don't recall the AMBSC Code allowing them on the outside, although I might be wrong.

 

[Maryak]

Tel and BR,

I my quick scan through AMBSC - Copper Boilers - It doesn't say specifically, (as far as I can tell), but all are shown with inside end plates to the barrel.

I would personally be loath to deviate from what is shown.

Best Regards
bob

 

[baldrocker]

Thanks guys
BR

 

[bentprop]

I would imagine it's a matter of shear strength.If you were to solder the caps to the ends,you only have the thickness of the shell to adhere to,obviously with the plates inside,you have much more joining area.I think it could also be very difficult to make a cap that is a good fit on the outside of the shell.Mind you,Mamod has been doing it for years.But they have the correct gear to doit.

 

[ianjkirby]

Hi all,
With deference to all those who have successfully built boilers, I would like to suggest that bentprop has hit the bullseye. Forming end caps is identical whether you wish to have external or internal caps. The only "secret" is that if you make an internally fitted end cap, you can spin it in the lathe, on its former, and take a very small clean-up cut (which will not reduce the strength of the joint), which will allow you to finish with a neat, close-fitting joint with a couple of thou clearance for the older, resulting in a good joint. To get such a good joint with an externally fitted cap is much harder.
Regards, Ian.
(Soon to retire AMBSC chairman)

 

[steamer]

Makes perfect sense to me guys....Thanks Ian!