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Posted: Mon Feb 16, 2015 10:56 pm
by Bill/Rubery
Nearly finished the 7/8" scale conversion of my Brunel. A question, I wonder why there is the 'Blow-down' valve fitted? I fill the boiler up with my sringe (spelt wrong?) and then withdraw 30 ml. for steam space. At the end of the run I turn the loco upside down and shake out the water out of the boiler Am I doing things in such a way to make the above valve redundant??
Posted: Tue Feb 17, 2015 6:22 am
by mikewakefielduk@btinterne
I too have wondered why Mamod fitted the blow down as it sticks out to the side and has a habit of catching things. I guess the best use for it is to open the valve immediately you've finished steaming for the day to ensure there's no danger of steam oil being sucked back into the boiler as everything cools down.
Posted: Tue Feb 17, 2015 6:06 pm
by Chris Cairns
Bill/Rubery wrote:I wonder why there is the 'Blow-down' valve fitted?
mikewakefielduk@btinterne wrote:I too have wondered why Mamod fitted the blow down
It is actually the sight glass drain valve and was one of the quoted sales improvements for the Mark 1 Version 2 model, along with the spare boiler insert.
Mamod had to find a new supplier for their sight glass fittings after the initial production of the prototypes & the Mark 1 Version 1 models, so ended up with this version fitted with the drain valve. As you will probably be aware sight glass's on many of our model locomotives are notoriously inaccurate so these drain valves are beneficial in trying to work out the correct boiler water level. The Regner water top up valve is fitted by a banjo bolt fitting into the top of their sight glass.
On larger models & the full size versions the sight glass would also have cut off valves fitted top & bottom primarily to safely cut off the escaping steam in the event of a sight glass tube failure.
Chris Cairns