Britannia boiler Winson

[gargamel140]

Dear all, I became the owner of a Winson Britannia kit and I'm in the process of enhancing it and getting the boiler approved by the Dutch boiler inspector. I have the Winson pressure certificate dated 2001 but that's it. I do not have a more recent boiler certificate because the loco was never steamed due to all the known issues. My Inspector has a lot of trust in kit boilers but since Winson is not there any more it is bit difficult to check out some details like the double plate inside the boiler to compensate for the smaller firebox without combustion chamber. I know there are boiler inspectors on this forum and can one of them give his opinion about this specific boiler.

Regards, Michel

[Deleted]

Hi Michel,

I can't answer your question but I'd like to know what you mean by 'smaller firebox without combustion chamber'. One of my contacts who is also building the current Modelworks Britannia said that his club boiler testers had commented on the lack of a combustion chamber, leading to a relatively large unstayed area at the top front of the firebox wrapper, although they were happy to pass the boiler. The interior of the firebox looks pretty big to me - the lower front face slopes forward, parallel to the outer front face, until it reaches the level of the bottom of the barrel, and then goes up vertically around the tubes. What exactly is a combustion chamber?

Regards,

John

[baggo]

Hi John,

To answer your question - a combustion chamber is basically an extension of the front of the firebox inside the boiler barrel (see photo of my A1 firebox below)

This increases the heating surface of the firebox and also gives the gases produced by the fire more time to burn properly before entering the tubes. Combustion chambers are often fitted to boilers having very long barrels which would otherwise have very long tubes. Fitting the chamber reduces the length of the tubes and improves the ratio of tube diameter to tube length. The chambers often have vertical water tubes fitted which as well as improving heating and circulation also stay the chamber itself A lot of builders shy away from combustion chambers because of the increased work involved and the chance of difficult to get at leaks when assembled.

Hope that helps,
John

[Deleted]

John,

Thanks, that's very interesting, and an impressive piece of work.

I see that the full-size Britannias have the firebox extending a little way forward, as shown in this photo of 70013:



This allows the firebox roof stays to go right up to the front of the outer wrapper.

Michel, is the double plate that you mention reinforcing this part of the firebox wrapper?

Regards,

John

[gargamel140]

John, Yes that's what meant. When I read the Dutch regulations the copper plate is to thin to have this unsupported length (max ten times plate thickness). My inspector noticed that the front three stays go up in an angle to solve that in some way for the top of the outer firebox. When I looked into the boiler via one of the holes I noticed the double plate which creates a 6mm cover which allows a for a larger unsupported area at the LH and RH outside . Bottom line it looks good but safety first:)

Baggo, very nice and good pictures.

[paultomlinson]

It may be worth an email to Doug Hewson, I seem to recall that he had to replace a boiler on a Winson loco to meet the requirements of an overseas boiler inspector.

Paul

[Shawki Shlemon]

Everything has been explained ,the only thing I want to say is if combustion chamber is not fitted and longer tubes are required they must be larger in dia . Also the tube plate must be supported and this is controlled by thickness of the plate and the number of tubes and stays . this is where the double plate comes in .Boiler codes will give you these information in the country /region you are in . I built a boiler for NSW C 38 which similar to your biller even in size without combustion chamber following the above guide lines .For the model the boiler will perform satisfactorily . The time is not important as the boiler inspector will test the boiler and issue new certificate if he is happy about the above issues .

[gargamel140]

Hi Paul, Doug Hewson says the Winson boilers are ok but that the Australian rules require longer solder flanges. They are actually just ok reading the Dutch rules so I can imagine. Doug once had a Winson boiler with a non soldered stay and leaking so pressure testing was not always done, but what's new:)

[simonwass]

Sounds to me like an appallingly designed boiler.
If I 'see' it correctly, are you saying the tubes dont fill the tubeplate area leaving a gap at the top? Why didnt they space them out to give more water space, or shove an extra tube in?
I'd put a photo of my modified 2 1/2 Scotsman boiler up but my soldering isnt as good as Johns! I used silverflo24 so it all got a bit hot. Not I've got oxg gear I might sweat the joins with easyflo, theres less chance of it melting now I've got oxy gear.