Britannia 70047 "Derek Stokes"

[JonL]

I'll endeavour to take some tomorrow night. Off to the tank museum in the morning. Thank you for your support, it is appreciated.

[JonL]

I'm doing the last of the fittings now. I've carried out my own 1.5x test with all the fittings in place with success. I decided to take the rather daft decision to light a fire in her.

She has now raised boiler pressure using Steam Coal enough to lift the Safeties. It's been a long journey but she is nearly there....

[dhamblin]

Well done Jon! Hopefully the rest of the build progresses smoothly.

Regards,

Dan

[Jim]

Congratulations Jon!
Having your loco in steam for the very first time is a very special moment and one to be enjoyed.

I look forward to the hearing more on your Britannia's progress.

Jim

[JonL]

Finished the reversing gear today. Was off on a cruise for a week so was itching to get back to some engineering. I was originally going to use the protypical bevel geared version of the BR Class 7 but realised I prefer the type which sticks straight back at the driver, so engineered it to face out from the rear of the cab in an easier to access reverser stand. I hate fiddly locomotive controls! The only thing is I don't have any feedback as to the position of the reversing gear. Some form of indicator would be nice. I'll work on something.

[JonL]

Water axle pump tested, it pumps, it flows well on bypass, and fills the boiler pretty quickly. Pleased with that.

[JonL]

Well I've now done a proper steam test so I could see how the safeties, axle pump, lubricator etc all work together. Two things were discovered; I've got too much air getting around the grate, and my piston valves need better sealing. Otherwise I'm calling it a success. I was very pleased at how rapidly it was possible to fill the boiler using the axle pump. My William's axle pump has only ever been good enough, but not exactly overwhelming in its efficiency.

www.youtube.com/watch?v=0-3ldi3m4Mg

Excuse the state of my work bench! 

[mr swarf]

Great work, nearly there. Your bench looks just like mine😀

[JonL]

Bit of an annoying failure on the final boiler tests. She held pressure at 1.5x just perfectly, the ball valve regulator is excellent. However the Pressure gauge, which was purchased new from a specialist, overreads by 15 psi throughout the range. Also I had a pesky clack that held perfectly at 135 psi but let steam back to the hand pump at 90! As a result the hand pump felt like it was sprung. The safety valves worked very pleasingly though, I'm proud of those.

So a few things to rectify, and the axle spring preload needs a tweak, but this is all steps in the right direction.

[dhamblin]

Have you also got the drag beam mounted clack making two in line from pump to back head? Good progress again though.

Regards,

Dan

[JonL]

Jun 12, 2023 19:16:04 GMT dhamblin said:

Have you also got the drag beam mounted clack making two in line from pump to back head? Good progress again though.

Regards,

Dan

I wasn't aware of that one....

[dhamblin]

If you've got a copy of the build articles it is on page 153 in MEM issue 2724 from August 1953. PM me if you want a copy 🙂

Regards,

Dan

[JonL]

The extra clack in the hand pump feed was just the think. The handpump feels undersized for the amount of work you have to do to get water in but its good enough to be safe. Very pleased to say she now has a boiler certificate and pulled me round the track for a couple of laps before I retired not wishing to push my luck!

Lots of little things to put right before I finish the cosmetics:

My draincock mechanism is flawed. Relying on a spring to push the valves shut means the spring can buckle refusing to shut the drains. I either need to guide the compression spring better or switch to a tension spring.

Handpump could do with a larger piston.

Piston valves are not as good as they should be. Redesign needed. 


Good things:

The blower I was really proud of is super efficient and raises steam beautifully. I will be retrofitting one to William.

Five years of work and its actually come to something. I feel oddly numb....

[Jim]

That is really fantastic news to hear. It's quite made my day.

Jim

[dhamblin]

I'll second that and glad the extra clack worked too.

With you on the hand pump, does seem a bit small for the boiler size. Will know for certain on next test with the re-packed ram.

Regards,

Dan

[JonL]

I guess it wouldn't usually be a problem with an injector, but I've not installed one as yet. I've got the boss on the backhead and the spare union on the turret for when I bite that bullet.

[JonL]

Piston valve redesign seems to have worked on the bench, I've steamed it on rollers and it worked fine. much less blowby from the high pressure side of the piston valve (the centre) to the low pressure side (each end).

[nonort]

Just catching up with your progress. Fantastic news I think the hand pump problem will fade with time as you get more used to the engine. The statement of to much air getting to the grate is a bit of a red herring when you have sorted the piston valve leak once and for all you will be able to open up the ballast nozzle a sixty forth at a time until it all balances out. Over driving the fire causes clinker and you can always put a crack of blower on if you find yourself struggling with bit of dodgy coal. You will find that as your confidence grows so your driving style will become much more relaxed.
But all in all great news.

[JonL]

A good few laps with the Britannia last weekend, stripping down to improve it yesterday. Pleased to say it was fine on the whole, and I managed to track down the timing issue to a loose lifting arm on its shaft. It flopped around quite a bit as the taper bit had worked itself loose. Rectified now I believe.

[JonL]

Just sorting the running boards (more cruical than it might seem; I've used the Starboard one to hold the cable guides for the draincock mechanism) and then I need to start thinking about paint. I really like black locomotives (they still look realistic no matter what the scale) but I suppose being a Britannia I should go Green. Undecided at the moment. I'll do all the bits that will be black regardless then make a call.

Do not expect a Roger/Chris Vine style finish.