Not really model engineering related but I suspect someone here may have
the expertise or have come across this:
In modern motorhomes/caravans, the LPG regulators are mounted on the
vehicle, rather than the gas cylinder. A pig tail (rubber or stainless
steel) is then used to connect to the LPG cylinder (or cylinders,
possibly by some change over arrangement). Most people use Propane and
the cylinder end tends to be a 'POL' connector but there are others,
including a 21.8 LH thread generally known as the Butane connector,
although it is used for Propane as well !
The other end, ie the regulator (end, we can ignore any change over
arrangement), is most commonly known as a W20 although sometimes an M20.
I'm trying to find out want kind of thread the W20 is.
Looking on the 'net, it seems the W20 and M20 aren't the same but will
'mate' well enough, even for gas- the thread isn't part of the seal,
that is via a washer (rubber I assume).
The M in M20 suggests a metric thread and while the W could, perhaps,
suggest Whitworth, I thought the normal shorthand was BSW, plus I've
never heard of a metric Whitworth thread.
The 'nut' part of the female fittings all, at least all that I have
seen, have small notches in the edges.
Others, like myself, who have investigated this from the
motorhome/caravan world seem to have lacked the expertise in threads etc
to nail this mystery. While we can, and do, tend to simply buy the
correct fittings etc, I'd like to get to the bottom of it.
Can anyone help, please?
(Things get even more complicated if you want to connect to an European
gas cylinder as some have different connectors on the top but that is
another can of worms. You can't get UK gas cylinders in Europe.)
3 years ago