The Steamboating Forum

Hi Everybody

I am posting this here as we do not seem to have a section entitled Very Dumb Questions. So what is this very dumb question?

Basically I want to be able to dimension cones for soldering to copper pipe for use in compression fittings. However, I have not been able to find any technical drawings or specifications. They are almost as rare as hen's teeth to buy on internet sales sites (eg: https://www.ba-bolts.co.uk/brasscones.html), but no problem to make if you know what size.



The context is for a mono-tube boiler that I am desigining witha fellow SBA member. The 'coil' will be made up of three lengths of Cunifer pipe, 3/16, 5/16, and 3/8. The lengths will be joined outside the fire by straight compression fittings and cones. I had considered using brake pipe nuts, etc, but with a tool to do the flares at 120GBP, plus 2 other sets of dies at 20gbp plus the connectors plus the nuts it looked as if soldered cones would be much more economical. For the curious, the coils will actually be layers of 'chaos' windings with circular wooden plugs are the guides for winding. I will post up some pictures when I get a bit closer to some publishable content.

Best wishes

Pete

Hello Peter,

below the principle sketch of a 3/16" soldering nipple. It will be soldered to the pipe. To connect the pipes you will need a double-threaded nipple with different threads on the ends.

Hope it helps
Dietrich

Hi Dietrich

Many thanks for the post and diagram. That is very useful.

The assumptions I make from it are that:

1. The limiting maximium diameter of the 'tail' of nipple is the diameter of the pipe for which the comperession fitting was originally made, shown as 5mm in your drawing. Thus for my 10mm straight compression fittings that would be 10mm, the diameter of the hole in the cap screw.
2. The maximum diameter of the coned part of the nipple is limited by the inside working diameter of the screw on cap. In the 10mm straight connector I have on the bench that is 12.5mm, being slightly larger than the originally supplied olive.

I think that with those parameters plus your angles and proportions one can now design and make a cone to fit almost any 'host' pipe for almost any pipe to be connected.

Thank you very much. I now need to go back to researching bending radii as John has suggested that 3/8 pipe may not bend at the curve that I can draw.

Regards

Pete

Hello Peter,

there is a page the bending of pipes. The page is in german with a table "minimal bending radius". There you should find your pipe diameter.

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Dietrich

Thank you Dietrich

That looks a really useful site.

I have bought one of the ubiquitous hand pipe benders widely offered on eBay. After some modification because the channels were too small for the specified pipe sizes, it seems to work well, especially if the pipe is lubricated with tallow (a pot of which has been sitting in the workshop cupboard for 15 years). It is nominally 40mm diameter for its bends but slightly less for 10mm, 40mm for 8mm pipe about 42 for 6mm pipe. In all cases the channels are smaller than the specified pipe diameters due to paint and poor casting/finishing.

Regards

Pete