LBSC 3 1/2 Britannia

It's been around a long while, and I've heard of some issue with the LBSC design, but not much mention of drawing errors. Problems I'm aware of:

1. Boiler Throatplate causes issues during soldering
2. Valve-gear design is not optimal.

Is anyone aware of any issues within the drawings themselves that should be noted? I did have a google and couldn't find any mention of any, but didn't know if thats because they have been corrected over the years. The drawings came from GLR Kennions.

Many thanks,

Jon.

I shall take this as a good sign!

Still probably worth having a word with your inspector as he will have the final say.

Brian

An excellent point, I shall ask his advice at our next meet. Thank you.

Doesn't answer your question and you've probably checked this out already:-
**LINK**

There is (used to be active & extensive) an "errors on drawings" section on the 'site but I couldn't find anything specific on LBSC;s Brit. It was a only cursory check though !

Still very useful all the same, many thanks.

Hello Jon,

While I have no direct knowledge of the following, a recent post on the Traction Talk forum mentioned that the as-designed Britannia water gauge dimensions or positioning were incorrect and cause the bottom of the glass to be below the top of the firebox crown. Chances are that's been corrected on the Kennion drawings if so, but it would be wise to check the dimensions regardless and just in case.

Best regards

Steve

Another good one. I'll amend the first post.

Or I wont! This forum doesn't allow it apparently.

Hi John,

I seem to remember something about the expansion links being difficult to assemble in the expansion link trunnions if built as per the drawings and 'words and music'.

Cheers,

Julian

More grist for the mill!

I don't usually like to resurrect old threads but this is a very pertinent addition!

**LINK**

I've been populating this page with any faults I'm aware of, feel free to add your own to help out other model engineers, or browse yourselves for a heads up on things you might not be aware of.

I apologise moderators if this isn't allowed, I offer this purely to assist.

Don't bank on it - there are numerous examples of errors that are still in the drawings you buy - in fact correcting an error by changing a drawing might be seen as a breech of copyright - it was not how the original guy designed it etc etc.

More practically it might be dangerous for a supplier to change drawings on the word of a constructor without checking that it wasn't they that had made the errors.

My favourite error is a solid boiler stay that is threaded backwards into the backhead and at the same time forwards into the smokebox tubeplate. 1/4" diameter rod with 1/4 by 40 threads. Go install that!!

Edited By Nick Clarke 3 on 07/02/2019 21:25:25

I'll raise this on the basis you're unlikely to be constructing the boiler just yet, but as you note the firebox tubeplate is pig to make with a combustion chamber and four (from memory) siphons. And a leak in any part of this is an even bigger pig to put right.

I have done quite a lot of work on model boiler thermal design, see:

https://www.model-engineer.co.uk/forums/postings.asp?th=136027

and I am convinced that the combustion chamber and siphons are a waste of time and money. Omit the combustion chamber, cram a few more tubes in (and another supherheater flue if you can) and it will be simpler and perform just as well.

Martin

Thats a great bit of advice, thanks. I'll include that on the page in a "recommended improvements" section.

I'd already come to the same conclusion about the siphon tubes with my friendly boiler inspector, I also plan to use a screw type regulator rather than the poppet or disc type, which will obviously mean a bit of redesign. I'm a bit vague on what you mean by the combustion chamber, does the firebox protrude forwards slightly? Or is it just a section directly above the grate? Sorry about my ignorance, still very much a novice.

I have just checked the info. I have. The combustion chamber projects 4.5 inches forward of the firebox, and has 6 corss tube thermic siphons in it. I had rather assumed you already had the LBSC drawings.

I have been in correspondence with another gentleman on Brit. boilers, If I can dig out his contact details, I will suggest he contacts you via. this forum.

Martin

Hello John.

It may help you to make contact with people who have built LBSC's Brit, I've seen examples from medal winners to those that appeared to have been built with a knife and fork. If yu suspect the valve gear then run it through one of the simulations availabe on the net, remember the design is now approaching seventy years old and many were built before the advent of computer simulation. built to the original LBSC words and music and all seem to perform excellently; again, with the boiler design reference should be made with your club boiler test team as there are several items needing up dating to moden good practice and they will advise accordingly. The boiler is relativly straight forward, but if you've never built one take the advice of your test team at each stage of construction.

Have a look at Youtube for the locomotive that won the Curly Bowl, that's how to do it!

Personally I think the locomotive is a little cracker and if I wasn't so long in the tooth I wouldn't mind having a go mysef.

Regards.

Bob

LBSC/Martin Evans' 3 1/2" Gauge 9F Evening Star has the same combustion chamber arrangement.

I DO have the drawings, I just don't know much about boiler terminology. At what point does the gap above the grate start to become the combustion chamber? I am a complete novice, and although I'm picking it up as fast as I can there are still big gaps in my knowledge.

Basically the area of the tube nest of the inner throat-plate is moved into the boiler barrel thus shortening the tubes and increasing the firebox volume. In the case of the Brit and the 9F the extended firebox crown is stayed by means of a number of vertical water tubes passing through the combustion chamber. IYKWIM