5" gauge Britannia (a builder's diary)

[oldnorton]

Hi Steve

I will be stuck with an external blower pipe for my Britannia so I have yet to discover how much water will be sprayed onto bystanders! Perhaps a tiny steam blow all the time to keep it hot?

I really hesitate to add the following but I do so in case it helps with your planning. I was looking at a Perrier Britannia a few weeks back and it had the cross stay square heads showing through the firebox cleading. The problems are that the heads look rather large, are all orientated the same way, and for wash out plugs there should be six LHS and five RHS and staggered. Of course the stays can be cut back and small wash out dummies set into the cleading, and perhaps you were planning to do this anyway.

Norm

[Jim]

For what it's worth I fitted a small globe valve for the blower connected to the manifold and placed where the valve would be on the prototype. With the delivery pipe running across the top of the fire box and down to connect to the hollow stay it is fairly unobtrussive. The valve and pipe work are hidden under thw fixed forward section of the cab roof.

The photo shows the setup with the driver's side of the cab removed.

Jim

[springcrocus]

Richard:


Norm: Yes, I agree. The heads are way oversize, and I discovered on a higher-numbered drawing an alternative design. However, to cut the heads off the stays risks exposing the drilled hole for the internal threads and would mean even more soldering. Also, there is a clash of positions on the fireman's side. I'm just going to have to accept I've made a crap job of it and get on with the next bit. I never intended to make this model highly-detailed when I started, I've just embellished it a little along the way as my confidence has grown.

Jim: I'm assuming you joined to the blower stay in a similar fashion to my choice to keep within the 7/32" space available.

Regards, Steve

[delaplume]

Didcot tradgedy}----------https://www.heraldseries.co.uk/news/15846991.heralding-the-past-the-milton-train-crash-of-1955-left-11-people-dead/

[don9f]

Hi Steve, if its any help to you, one of my pals has built his 9F with an external blower pipe instead of the hollow stay type and he does actually regret this because of the "wetness" it causes at the chimney.

Cheers Don

[ettingtonliam]

I did manage to locate a copy of the official accident report. During engineering work near Reading one Sunday in 1955, up main line traffic was diverted onto the up goods loop, with a 10mph speed restriction at the cross over. An excursion train from South Wales had a Brittania from Cardiff onwards. The driver had read the weekly notices, and had complied with several other restrictions, but admitted that he had overlooked this one. The Brittania was left hand drive, but the Western Region signals were sited to suit right hand drive ex GWR locos It was fitted with GWR type ATC, which was tested by the driver before leaving the shed at Cardiff and known to be in working order.

The approach to the accident site was on a long right hand bend, and the signals were difficult to see from the left hand side of the cab. Tests later showed that it was only possible if the driver leaned well out of the window, and even then, visibility was limited by the smoke deflector, the handrail and (I think) the ejector on the left hand side. The fireman was too preoccupied with a malfunctioning injector to see the signals.
They ran past a Distant signal at caution without noticing it and claimed that the ATC siren didn't go off. Not expecting to be stopped they carried on at about 50mph, only spotting the Home signals and the points set for the cross over at the last minute, trying to take the cross over at 50mph instead of 10mph. The loco turned on its side, followed by 6 of the coaches with a death toll of 11 and multiple injuries. The driver and fireman both survived to give their evidence at the enquiry.
Apparently the ATC equipment on a Brittania was very near the firehole, and the siren was much more prone to getting blocked with coal dust, so the inspection regime was reduced to once in 14 days rather than once in 28 days for GWR type locos. It seemed to be accepted fact that Brittanias were noisy and dirty to drive, and this made it more likely for the siren to malfunction, and be difficult to hear. Early Brittanias, of which this was one, didn't have the ability to automatically bypass the large brake ejector if the ATC applied the brakes, and the ejector could seriously affect the brake application.

[springcrocus]

Bah! Norm is right, of course. Those over-large square stay ends are going to look bloody awful and if I don't do something now then I will forever kick myself for not fixing it at the right time.

Decision made! I will saw the ends off and if the screws become exposed then they will get soldered on Friday when we fix the backhead in place. Shallow dummy washout plugs will be made and fixed into the cleading at the appropriate time. It would have been better to just use simple stays in the first place but hindsight etc...

I just hope I don't fall into the trap of chasing ever greater detail and then fail to finish the loco because I'm never satisfied. It started as a nice, simple project but could too easily turn into a monster if I'm not careful.

Regards, Steve

[simplyloco]

Nov 5, 2019 8:50:41 GMT springcrocus said:

SNIP

I just hope I don't fall into the trap of chasing ever greater detail and then fail to finish the loco because I'm never satisfied. It started as a nice, simple project but could too easily turn into a monster if I'm not careful.

Regards, Steve

Been there, dunnit! Desist!

[Cro]

Nov 5, 2019 8:50:41 GMT springcrocus said:

Bah! Norm is right, of course. Those over-large square stay ends are going to look bloody awful and if I don't do something now then I will forever kick myself for not fixing it at the right time.

Decision made! I will saw the ends off and if the screws become exposed then they will get soldered on Friday when we fix the backhead in place. Shallow dummy washout plugs will be made and fixed into the cleading at the appropriate time. It would have been better to just use simple stays in the first place but hindsight etc...

I just hope I don't fall into the trap of chasing ever greater detail and then fail to finish the loco because I'm never satisfied. It started as a nice, simple project but could too easily turn into a monster if I'm not careful.

Regards, Steve

When you first published it I wanted to say something but held back knowing you don't like to be told!!! Glad you have changed your mind though, worth it in the end. 

Detailing these things is a curse as like you say you can easily get sucked into it but you'll find a happy medium.

Look forward to seeing the boiler finished.

Adam

[oldnorton]

Sorry to cause grief Steve!! but I sort of guessed you might want to know now, when you can at least add more silver solder. You will need to make the stays stick out as little as possible (2-3mm) as the dummy wash our plugs in the cleading will end up touching some of them (that's what happened for me).

It was the Britannia shown by Station Road at the MME that made me realise what the earlier Perrier drawings were describing. It did spoil an otherwise reasonable engine. It is still on their website if anyone wants to look. I hear it had a sold sign on the Sunday of the show.

Norm

[springcrocus]

Done!



I'm often stubborn and obstinate, sometimes daft but (hopefully) not normally stupid! It needed to be done and I needed a kick up the rear for motivation.

Thanks chaps, Steve

[uuu]

Looks like you've not got any of the inner studs exposed, as you feared - that's a bonus.

Wilf

[ettingtonliam]

Might be worth flushing them over anyway when you are soldering again, just in case any of those inner studs are only just below the surface.

[springcrocus]

I have now finished all the prep work prior to soldering the backhead into place. One thing I didn't like about the earlier boiler stays was the size of the heads on the copper rivets. For the backhead, I have machined eighteen of them down to a much smaller size.



The holes have been marked out at 7/8" intervals, as noted on the drawing, piloted at 4.0mm and finish drilled at 4.7mm. I have dry-assembled them with the heads to the outside but I will change that prior to soldering.





I have also put the 1/4" x 40 thread on the longitudinal stays, then parted them off to finished length. They are quite a bit longer than my headstock so I used a piece of tube to extend the back like a barfeed tube. Without this, the bar would whip round to ninety degrees and destroy itself on the geartrain cover.



These will be difficult to assemble with the backhead in place so I have drilled a 3mm hole into the ends for a 1/2" length to allow a guide pin to be inserted. If I push them too far through the tubeplate then this will assist in bringing them back through.



I will now dismantle the assembly and put all the parts, incuding the screws and the rivets, into the pickle overnight. Tomorrow, everything will be rinsed off prior to assembing the backhead and the penultimate soldering session. It will be quite important to assemble everything in the correct order to make sure solder rings, for example, are where they should be. There will be quite resticted access around the firehole area.

Steve

[delaplume]

Hello Steve,

and congratulations on a job well-done so far..It's that old adage that if a thing looks right then it is right and your boiler is certainly looking the part so far.....

Might I now tentatively suggest that you leave those backhead rivets with their heads on the outside as shown ???..........Compared to chopped-off tails they appear neat and tidy with a nod towards the nuts that would be on the full-size loco.......

If however you are planning on having a cleading sheet fitted then of course it's better the way you propose.....

Alan  

[springcrocus]

Tough luck if I do, really, fait accompli and all that. And if I had wanted a professional boiler I, too, would have gone to Helen or Paul.

Steve

[delaplume]

Nov 7, 2019 17:35:15 GMT springcrocus said:

Tough luck if I do, really, fait accompli and all that. And if I had wanted a professional boiler I, too, would have gone to Helen or Paul.

Steve

Hello  Steve----I sense you feel offended ??.....Sorry, only trying to be helpful.

Yes,  I did go to a professional boiler builder ( John Ellis ) for the actual construction but that was only after spending just short of 3 years designing it myself....Like a lot of Model Engineers I too used to build a boiler using someone else's design... and learned a great deal down the years ....... These days I try to pass on some of the better lessons learnt if I can....

OK,  so I've now removed the photo and any associated wording....

I'll continue to follow this thread with quiet interest..

Alan 

[springcrocus]

Thank you. It's a great boiler and people can admire it in your own interesting thread. It's totally irrelevant here, though.

The first job was to load the five chamfered rivets that sit above the firehole, set from the inside of the firebox. These were indented to keep them in place and solder rings placed over top followed by lashings of flux. The backhead was then eased into position and the nine bronze screws fixed in place. We need to keep the boiler in this vertical position the whole time.



To indent the stays, I use a pair of very sharp cutters. These are Xuron track cutters which I use for OO gauge rails. A quick sqeeze of these and the deformation is enough to ensure the rivet can't fall back through the hole.



The next hour was spent just getting the stays into place with their solder rings, followed by the longitudinal stays and the blower stay. I also found some 5/32" dia copper tube so a tail to the blower stay was formed so that it could be soldered at the same time.



Solder was also laid all around the backhead perimeter and the firehole plus rings or loops over all of the screws and stay heads. Loads of flux, including any existing solder work in the general vicinity and a built-up hearth as we usually do. I used the cyclone burner, mostly inside the box but also into the water space, whilst my colleague used the normal burner around the outside. We had a good melt but it took quite a long time as there was a lot of solder to melt.



We are going to need some more solder around the firehole but it has probably sealed already because of the shoulder on the firehole ring. Everything else seems to have gone very well indeed.





And a shot of the boiler resting on the frames.



Foundation ring next, plus the front of the four longitudinal stays, then a hydraulic test. Let's just hope it isn't an expensive colander.

Steve

[springcrocus]

I have made a start on the ring that connects the boiler to the smokebox using another section from the bronze plate. I had previously prepared the rough blank using a jigsaw with a fine-tooth HSS blade. The blank was loaded to the independant 4-jaw chuck because this is the only chuck I have that is large enough. The O/D was turned first, then the centre trepanned out using a grooving tool mounted side-on.



For those who may be wondering, the clamp is there to help protect the toolpost. If the tool snagged, it is possible to break the pull-in clamp or the back of the toolholder. The bearing is there to extend the live centre. When trepanning, I prefer to take small pecks at two different diameters so the the groove is about thirty thou wider than the tool. This way, the swarf never jams up in the groove, which becomes more important the deeper the groove gets. Here, I'm nearly at breakthrough with a full witness showing on the back.



At this point I stopped and removed the part from the chuck, not wanting to machine my chuck jaws. A few smart blows with a hammer and the centre fell away and will be used for something else later.



The next picture is a close-up of the tool I used, a parting / grooving tool with 3mm carbide tip. I've ground away the bottom of the tool on the one side to ensure it doesn't rub on the work.



Then it was back into the chuck with the jaws reversed and holding on the inside. The ring was then turned to about twenty thou oversize and the front faced for a full clean-up. I shall now transfer to a faceplate or maybe some big soft jaws for the next stage because there is too much chance of distortion holding the ring like this with point-contact.



More on this later.

Steve

[Jock McFarlane]

I like the way that you make the ring but would I need to use the tailstock as you have done ?