Britannia 70047 "Derek Stokes"

[barlowworks]

I totally agree with you regarding the loco cradle, a Britannia is a big lump, especially in 5 inch gauge.

Mike

[JonL]

Luckily mine is only 3.5 inch, I think is struggle with the bigger one!

[JonL]

I've made a somewhat contraversial decision today. After faffing around with a friends Heilan lassie I've realised what a godsend the split smokebox on my william is. As a result I think that will be a modification to the Britannia. This will be a heavily used locomotive, and anything that assists with maintenance and assembly is good with me. The splits should be largely hidden by the smoke deflectors.

[Deleted]

Aug 21, 2021 17:30:57 GMT JonL said:

I've made a somewhat contraversial decision today. After faffing around with a friends Heilan lassie I've realised what a godsend the split smokebox on my william is. As a result I think that will be a modification to the Britannia. This will be a heavily used locomotive, and anything that assists with maintenance and assembly is good with me. The splits should be largely hidden by the smoke deflectors.

IMHO that's a good move Jon, lots of extra work but worth it in the long run. Owning a Lassie with solid axle boxes and 4472 with split, the later will be much easier to work on when required in the future.

Pete

[darrene]

Agreed. Given the smoke deflectors, it seems like a particularly worthwhile modification

[JonL]

Today I've finished making a few of the components of the motion work; I've got over my inertia that was caused by making a fundamental error with the radius arm. Fitting the DRO has given me a bit of confidence in my measuring and the final result I'm quite pleased with. I did make one link slightly too thing at one point so silver soldered a bit of 0.6mm sheet on the side before machining it back down to size; it's improved the strength and cosmetics (even though it will be hidden round the back).

Progress like that really boosts my spirits. I'm still very much an amateur but moments like that make me feel like I'm learning and making progress.

[JonL]

Making the return crank today. I made the component exactly to the drawing. Probably my best bit of engineering to date.

Did I check that the crank pin had been made to the drawing? (remember this was a rolling chassis when purchased). No I did not. It's 5/16 rather than 1/4. The easiest solution is to remake the components rather than alter the pin (it's not a big drama and will probably have greater friction so I understand the reasoning) but what a pain...

I've chosen to laugh it off... Other than neglecting to check the dimension of the crank pin I really didn't do anything wrong for once.... start again tomorrow.

[JonL]

Making the reversing screw today. I enjoyed the process. I threaded the whole length with a single point HSS tool which I profiled to a whitworth thread form on the grinder, then reduced the ends to 1/8 of an inch. I then checked it using the test nut I made before hand, and the thread form was good. It's a left hand thread which I think is easier for me if anything (I've accidentally made lots when intending to cut right hand threads...). I was able to then cut off from the bar (I machined it with the bar stock through the chuck) and finish the end with a touch on the linisher.

I've no idea if these pictures will work, so bear with me....

[JonL]

One


Two

[JonL]

I've been a bit quiet on this but I've managed to get hold of an almost finished boiler. It appears to be very well made but needed a couple of things to finish it: the top feed clack bushes and blowdowns (as one of my previous posts sneakily hinted towards before I bought it....).

My boiler inspector has had a look with his boroscope and his big Sherlock Holmes magnifying glass and has given us the go ahead to finish it off. The boiler is stamped that it was originally made in 1982, making it two years younger than me.

We used Oxy-Propane to fit top feeds and blowdowns, with Propane providing background heat. Next up is the hollow stay. I've got the stay, I'm just awaiting a delivery of bronze to enable me to make the threaded sections.

[mbrown]

I knew boiler inspectors could be a bit mystical about their art - but I'd never heard of one consulting a horoscope before passing judgement...

Then I read your post properly!!

Well done- sounds as if it is coming on really well.

Nalcolm

[JonL]

I've currently got a positive covid result so my work have said I've got to stay clear. I'd love to say that means I've had lots of lovely workshop time but I've been too knackered to move for days; I got out of breath putting my trousers and false leg on a couple of days ago. Yesterday was the first day I've felt well enough to do anything so I had a tentative workshop session. Things that would usually be done in half an hour took all day. I made and installed the hollow stay but it took many short batches of effort interspersed with sitting for a long cup of tea.

That was the last obstacle before the pressure test...

[JonL]

Boiler pressure tested today; I bought a cheap central heating pressure tester just to do a sanity check before I take it to the club (£18 delivered for a tester, even though I had to modify it, it's cheaper than the round trip of petrol for a wasted journey). I made a new hose for it suitable for model engineering and a series of connectors to allow me to connect it to the safety valves of the different boilers I have.

I did a couple of smaller ramp-up tests to the required pressure, then took it to twice working pressure, which I thought was 2x 90psi. It turns out most Britannia boilers run at 80psi... anyway, it's been tested at 180psi now and holds pressure with no issues.

I spent a while trying to locate the reason it was slowly dropping pressure. Turns out it was the tester... locking off the pipe to the boiler resulted in a pressure that was still holding 180 psi after half an hour.


EDIT : I was suprised to note the boiler holds 4 litres of water when full. Bearing in mind my William is 1.8 Litres this came as a shock. I had to remeasure to confirm.

[dhamblin]

When we tested Grandad's one it held roughly 3.5 litres of water, but it does have a combustion chamber that reduces water space slightly. Plenty of capacity for sustained power output.

Hope the formal test is now an easy pass.

Regards,

Dan

[JonL]

This one also has a combustion chamber but no siphon tubes. Where I've managed to hide half a litre of water I don't know!

[andyhigham]

4 Litres
My little 3 1/2" gauge Baldwin holds 9 Litres

[JonL]

Apr 22, 2022 10:44:50 GMT andyhigham said:

4 Litres
My little 3 1/2" gauge Baldwin holds 9 Litres

No such thing as a little one! 

[JonL]

In the interest of easy maintenance I've made a small reservoir that fits under the boiler, from this comes pipes which feed the top of each axlebox and the two eccentrics. The theory being while steaming up I lift a flap (which keeps the dirt out) and add a few squirts rather than trying to do gymnastics to get to the hidden parts.

[flyingfox]

Jon, do you put wicks in the top of your pipes in the oil reservoir?
Regards
Brian B

[JonL]

Apr 26, 2022 6:33:14 GMT flyingfox said:

Jon, do you put wicks in the top of your pipes in the oil reservoir?
Regards
Brian B

I haven't, no. It's literally a central manifold which just feeds pipe to drop a little in the axleboxes. I don't see why it couldn't be done.