Garden Railway Forum

TTHLRMatt wrote:Does anyone know the thread used on the regulator valve? I know its the same as the gas valve.

As far as we know Mamod have used 2 different types of regulator valves on the Brunel boiler, one being the standard gas valve at that time, the other having a larger diameter shaft (like mine).

Best to contact Mamod for the definitive answer. They do seem to be replying to E-mails at present (although they are related to the Thomas Telford development) otherwise give them a phone and ask for Peter Johnston, their designer. Contact details already discussed on Page 2 here - http://gardenrails.myfreeforum.org/ftop ... asc-15.php

Chris Cairns

I believe Mamod are now closed until the first full week of the New Year.

As for the thread, Mamod have used a variety of sizes, mainly imperial but with the odd Metric one thrown in for good measure (for example, the Telford regulator seems to be M3 x 0.35).

I'll take the regulator out of my Brunel tomorrow and see if I can match the thread to a thread gauge. Unfortunately I only have gauges for metric and BA threads, so if its something else I won't be able to help.

Mike

Both the regulator and the gas valve on my Brunel are threaded 6 BA. Of course, this doesn't mean that other Brunels are the same as Mamod have a policy of "constant improvement" which some might cynically rephrase as "what we have a surplus of".

Running my Brunel this afternoon to see if my condenser chimney works alright (it does)...made me wonder what that short bit is that pops up and down on top of the Mamod engine??? when the engine is running....

Its the end of the piston valve that controls the inlet and outlet of steam to and from the cylinder.

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??

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.

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