I WAS never happy with the automatic drain cocks fitted to my engine, but equally was not keen on levers and cables to operate plug cocks. All too fiddly. I soon realized that both Peter King and Chris Orchard had steam operated drain cocks on their respective Simplex locos, and these seemed to be a sensible way forward.

The design was known as Ockadee drain cocks, involving a small conical piston within the body of the unit to seal the escape of water and steam from the cylinder when held in place by steam from a valve on the backhead. Peter very kindly lent me the shaped ‘D’ bit to machine out the bodies, and a set was quickly manufactured and fitted. The tricky bit was lapping the little conical pistons into the valve body to get an acceptable seal. In operation they were far more effective than the automatic versions, but required dismantling, cleaning and re-lapping at fairly regular intervals. All part of the constant maintenance regime that we are faced with when running steam engines.

During one of my trips to France, I spotted some unusual looking drain cocks fitted to a number of Decauville type engines, and soon realized that they were steam operated. A few discussions using my very best technical French, and the learning of some new terms such as “purgeur” for a drain cock, a copy of the design from the ‘Confrerie des Amateurs de Vapeur’ (CAV) newsletter was produced.

Back in the workshop, a few doodles converted the design to ‘pouces’ (inches) and a start was made on the lathe. A quick foray onto eBay found the PTFE sheet required for the membrane.

End result is a very satisfactory set of drain cocks. The design is not visually compatible with UK locomotives with outside cylinders, but for inside cylinder mainline designs, or maybe larger locos based on narrow gauge designs, does not look out of place. I have tried to sketch out a compatible version for outside cylinders, but the little grey cells have not come up with one yet.

To operate the cocks, a steam valve that vents to air when closed is required, similar to a steam brake valve. These are easily made, or can be found at some suppliers at the ME Shows.

The photo above shows the 4 units piped to a common live steam union, ready to be fitted. The drawing shows the principles of the original 1993 design by Mr. J.Fecherolle published in ‘La Lettre de la Confrerie’. Dimensions can be easily adapted to suit the loco in mind.




STEAM
OPERATED
DRAIN COCKS
by
Peter
Squire