Automatic Drain Cocks

[baggo]

Having completed the valve gear on my Helen Longish I've had the chassis running successfully on compressed air ;D . Of course, I could not wait to try it out on steam so I cobbled up a suitable steam supply and gave it ago. The 'boiler' could only supply enough steam to run the chassis for a few seconds at a time but that was enough to prove everything seemed ok. ;D ;D

At the time I had not made the draincocks so the holes in the bottom of the cylinders were just plugged with suitable screws. Hence the only escape for any condensate was through the exhaust. After liberally spraying everything in sight (including myself!) with oily water I decided to make and fit the draincocks before any further steamings!

Most 2½" gauge locos are not fitted with draincocks but I had already decided to fit them to Helen. To avoid fitting operating gear I went for the automatic type which seem to work quite well on the locos I've seen fitted with them. The 'standard' ones are a pretty basic shape and tend to look a bit massive on a 2½" loco so I chose to make a smaller version which looks like the manual/automatic type fitted to some locos such as the Horwich Crabs. The bodies were built up from brass bar and use a 3/32" stainless ball. The end cap is a press fit and secured with a touch of soft solder after assembly. I made up a prototype before making all six and tested that as I wasn't sure how successful the design would be. Fortunately it worked perfectly, draining all the condensate before shutting off completely with no leaks. It would be a simple matter to add manual control as well by just drilling the outlet end and fitting a small operating pin to hold the ball of it's seat. For larger gauges the design can be scaled up using a 1/8" dia. ball and larger diameter chamber.







The two cocks on the middle cylinder are shorter to clear the front bogie underneath.

John

[John Lee]

So why didn't you do the outside cylinders with the same as the inside?

They look huge for scale, a very nice neat job though

[baggo]

Hi John,

The tapered bit on the bottom is just really for appearance sake and in the full size version contains the spring loaded relief valve. The threads need shortening a bit actually so that they screw in a bit further. They are quite big things on the full size Crabs, much bigger than the ordinary type drain cocks fitted to the Black Fives etc. I've got the Don Young drawings for his 5" Horwich Crab and just more or less halved the dimensions.

John

[Shawki Shlemon]

This design was published in AME sometime ago and I used this type of drain cocks on my Garratt and the Stirling Single successfully and I will be using it on my Dukedog .