NSW 'B' class mogul

[uuu]

We may still have a misunderstanding. It is abrasion of the nose of a non-radiant superheater within the flue that's the problem - although there will be scouring of the flue tubes as well. You're right though - getting a more complete combustion will reduce the unburned coal content - but eventually all the rubbish that ends up in the smokebox still have to race down the tubes.

Of course, a radiant superheater would have its nose within the firebox, so it may not get abraded to the same extent.

Wilf

[David]

I took a grinder to the shields yesterday and they fit in the flues now. I had to thin the tops and bottoms and narrow them a bit but they should still provide protection for the sloped parts and the point at the end.

It makes me wonder how the firebox ends of the tubes and their soldered joints fare. But they don't seem to suffer as much as the superheater elements.

Next is to sand down the JB-Weld filler on the front of the firebox cladding. It's had about 5 days to set so should be as hard as it's going to get.

An arch would be interesting but certainly isn't common practice down here. Not sure how I'd fit one to this loco. My first thought for an 'arch' would be to have it welded to the grate but this grate has to tip back over the rear axle and slide out the small space available back there so that wouldn't work.

Not too worried about that because everyone I know gets along without one.

[springcrocus]

Sept 30, 2019 10:02:50 GMT David said:

I took a grinder to the shields yesterday and they fit in the flues now. I had to thin the tops and bottoms and narrow them a bit but they should still provide protection for the sloped parts and the point at the end.

It makes me wonder how the firebox ends of the tubes and their soldered joints fare. But they don't seem to suffer as much as the superheater elements.

They can't get much hotter than 160 degrees C as they in contact with the water. The superheater elements are in free space.

Regards, Steve

[David]

Hi Steve, I was wondering more about the abrasion of particles flying from the fire into the tubes and why doesn't it wear the ends out? It could be the flow of gas is already parallel to the tube so it would still hit the ends of the superheater elements head-on but not the end of the tube so much. The tubes are pretty thin copper - much thinner than the superheater elements.

Here is how they look now. The top one has a gap between the shield and the element at the 'bottom' of the point in the photo that could be filled with solder - I'm tempted and am wondering if that will be the first place to fail. I just don't want to remelt it all and have the shields move or something.



I cleaned up the JB-Weld this morning, it took a couple of hours. There's a few bubbles and divots but I think it looks better than it did before.





The superheater header parts are in the acid getting clean now so I can solder it all together. They're filthy after the drilling - I can't remember if I used some sort of oil but there is black gunge in them.

[David]

One last photo for the day, starting to fit up the superheater header. The good news is everything so far fits. It's a little twisted but not enough to be a problem.

[jma1009]

Hello David,

Had you orientated the fixings for the superheater wet header by 45 degrees, you could have had 2 take offs from the wet header to feed each superheater element and avioded the use of that horizontal feeder tube on the wet side, and considerably simplified things.

Wilf (uuu) has not provided a proper analysis IMHO... copper superheater elements [Not extending into the firebox] fail typically just after the brazed return bend. With a block of copper or hard drawn phos bronze as the return bend this still happens, and the firebox ends of the elements are wafer thin. I have replaced more copper superheater elements than I care to remember, and all of the 'LBSC' type show these features upon failure.

A copper superheater element must never extend into the inner firebox. When the fire is very hot and by the blower the return bend will get red hot. Copper superheater elements need to 'return'/end some 1" if not more inside the superheater flues from where they meet the firebox tubeplate.

Anything closer or extending into the firebox has to be of welded stainless elements.

Cheers,

Julian

[David]

The wet side has been soldered together and in for a test fit before being put into the pickle. I did it in two stages because I couldn't see a way of keeping the boiler takeoff and the elements in position in one heat.



Thanks Julian. Re setting the return bends back from the end of the flue Barry told me the same thing last week and I think someone mentioned it on this thread earlier so I've done my best to get them at about that point. This is a tiny boiler so the elements have ended up quite short. I'll measure them when I take them out next. That has just given me an idea of how I could have measured the flues to get the elements the correct length - a simple builder's roll-up tape measure with a hook on the end of the tape would be just the thing. I tried mine after writing that last sentence and it's too wide to fit in the flues.

It's interesting you have mentioned the same point of failure Barry did - not at the pointed end but just beyond it where I guess the copper is thinner than the point but has maximum exposure to the ash in the airstream.

I see your point about the takeoffs from the wet header but it would still require some 90deg corners made up. Not having to drill 3/8" holes in a small pipe would be a bonus though. One feature of the current setup is that the pipe from the snifter valve goes into that horizontal feeder tube. I guess it could also have gone into the wet header somehow with your scheme. Helpfully this has also made me realize I have to double-check which side the snifter is on before soldering this up.

I was going to purchase stainless elements but figured I'd have a go at making them and see how I went. I was quite worried about the stainless to copper soldering.

I'm looking forward to seeing if it makes a difference. The red loco has about the same sized boiler (saturated) but you have to work hard because it uses a lot of steam compared to other locos I've driven. I'm hoping the superheater makes this one easier to drive. Perhaps a relatively clean boiler will also help!

[David]

I've been chipping away at the superheater bits. Yesterday I machined the flange and nut that clamp it to the steam chest inlet pipe and today it got soldered together. It's not pretty but I'm favouring 'done' over 'good' these days. A couple of near misses with the flange - I nearly soldered it on without putting the bore into it, without putting the captured nut on, etc! But I got there in the end.

Sketchy setup for soldering the flange into an almost completely cut away elbow. I used 15% solder for this one because there were big gaps to fill between the machined part and elbow.



Putting the rest of it together to be soldered in-place. 55% for these parts. It looked like the joint nearest the elements hadn't go the solder flowing around it but after I saw it out of the acid it looked fine.



Out of the acid. It looks like the solder got everywhere it needs to be.



A test fit before putting the smokebox on:



And it even fits with the smokebox in place!



So the snifter valve pipe and blower pipe should see the smokebox plumbing done. Pretty pleased with this progress.

[mugbuilder]

See David, It wasn't so dificult after all. looks just like mine does. A good lob well done.
Barry

[David]

A couple of 'simple' jobs today - the blower and snifter valve pipes.

The blower pipe was easy enough, although I did ruin the first ferrule by having the solder too close and too much flux - the solder all went over the brass rather than under it :-\ Here is it in place, along with the smokebox floor stood on some supports to about the correct height. I tried using the solder trick to get the pipe runs but it didn't help me much. The blower pipe would have been better about 5mm shorter but it fits which is the main thing.

I found the best way to solder these on was to have a ring of very thin solder just a bit back from the ferrule and use a plumbers MAPP torch to heat the pipe on the side away from the brass. The brass is so thin the copper seems to heat it sufficiently and the solder runs under the brass rather than all over it.



That photo shows how I had backed myself into a corner with the snifter valve pipe. The thread on the superheater is too long, and that end cap needed to be closer to the element. Put those together and I needed a very sharp bend in the pipe, which I couldn't do.

I decided to try a square bend by filing a wedge out of the pipe with a square file.



This meant I had to solder the corner with the nut in place because the nut can't go around such a sharp bend. I used a dummy fitting to screw the nut as far from the join as possible, with a coating of tippex on the ferrule. I think I got away with it, as long as the joint holds. Even if it doesn't, is a small leak into the smokebox going to cause much trouble?



It all fits.



Unsurprisingly, getting it in when the smokebox is on is a challenge. I have to put the superheater headers into the smokebox a little way, screw the snifter valve pipe to it while I can still get at the nut (it's a tricky start), then push all that home, squeezing the big outlet nut & flange though the door opening where they need a slight tweak to get through, do all that up, then the blower pipe can go on!



And that's without the door. I expect that will add to the fun.

[ettingtonliam]

Did you think about an elbow fitting rather than a straight one from the end of the dry header?
In answer to your question any small probably unsuspected leak in the smokebox is going to cause you all sorts of grief wondering why your loco isn't steaming as well as it should do after all your hard work.

[David]

I didn't think about a different fitting because I didn't realise how tight it would be - thinking ahead isn't my strong suit.

I've been able to built this whole tender and loco with no variation from the drawings so I just expect things will work out! Looking at a photo of Barry's version he has a very tight bend in this pipe too, but somehow got away with it where I couldn't make it fit.

I could probably cut the existing end cap off and make a new one but I think I'll take a chance on what I have. I could caulk the corner with 965 solder to try and avoid leaks if necessary.

[mbrown]

One way of getting in a tighter bend might be to make the nipple shorter so that the bend begins nearer the union nut. You'd have to be careful with the soldering, but it should be no harder than what you have just done.

Maybe worth a try as the only cost is a length of pipe and another nipple.

Malcolm

[David]

Moving on to another job that was in the 'too scary' pile for a couple of years, the smokebox door. Step 1, a couple of years back, was to take the disk of 6mm steel that was cut out of the smokebox rear plate, so just under 5" dia, heat it red hot and bang it with a big hammer while it was sitting on the rim of a thick pipe. This was dish it a bit. And that was it until yesterday.

I had drawn this part in F360 a few weeks ago with the idea of making it using the Tormach RapidTurn. Then it all seemed a bit much hassle so I just followed the instructions, eventually.

So drill a hole in the centre of the door blank and turn a piece of bar so it's round with a small dia on the end to fit in that hole. That's not in the instructions but (a) I first attempted a M8 threaded mandrel and thread in the door and stripped the thread, (b) I didn't think I had any chance of silver soldering the mandrel to the door straight so wanted a positive locating device. This is the unpromising looking result. I couldn't get the solder to flow nicely - I think I had too much heat in the mandrel and not enough in the door, but it was good enough. It's been in the phosphoric acid for a few minutes and has taken on some of the copper from there.



That was last night. Today, turn the outer dia and clean up the inside.





Hacksaw off the mandrel.



Turn the outside. The dishing was very uneven because I didn't hit it in the middle all that time ago, so I was using the compound slide to turn it at various angles as a start, then just started doing it freehand with the cross slide and saddle handwheels. I don't know what profile it should have, and neither does anyone else I'm guessing. I just wanted to get all the dips and bumps out at this point.



Then a 120 grit flap wheel in the angle grinder while turning at about 200rpm in the lathe. I forgot to cover the ways of course, so there's a ton of grit to clean off! There is also a distinct hump about halfway in but I gave up trying to remove it. I can't use an angle grinder with any finesse, it usually ends in a scrapped part so I quit before that happened.Some sandpaper after that.



Next I have to make a boss to go in the middle and may have to face a little 19mm flat on the door for it to sit on.

It went better than I expected, but not as well as I'd have liked. The shape doesn't look right to me, but I'm sure I'll forgot all about it once it's on and has a few details around it.

[David]

Smokebox door hinges. Barry managed to bend these up from 1.6mm steel. I have no idea how - I tried it for a laugh with the expected result. So I fired up the CNC machine and it chewed them out of a piece of 40x15 free cutting steel in no time.



I used a slitting saw to cut them from the stock. I am hopeless with a slitting saw! I always forget how much of the arbor there is under the saw and once again had it grinding into the side of the vise. No idea how my leadscrew nut still has teeth. Then I broke a tooth off the saw... but got there in the end.



Finally a file cleaned off the ~0.5mm of stock from the bottom.



Now I have to figure out how to bend them to match the door.

[mugbuilder]

Just finished fitting up a smokebox door and hinges to another 'B' class. A ##*#**# of a job' .The door hinges and fittings took about 6 hours all up. If i knew how to download pictures I would send a photo.

Barry

[David]

I'd be pleased if I could do it in 6 days.

[don9f]

Oct 15, 2019 9:30:16 GMT David said:

Now I have to figure out how to bend them to match the door.

Yes it’s a bit of a 3 dimensional puzzle!.....just done the Jinty.

Cheers   Don

[Roger]

Oct 15, 2019 9:30:16 GMT David said:

Now I have to figure out how to bend them to match the door.

I guess you could have 3D modelled the shape and machined them out of solid ready to fit....

[David]

I would have done it that way if I had cut the door with the CNC. I did model the door and was going to do it on the RapidTurn, but decided against it. So now I have a door of unknown and inconsistent profile (it has a hump in it I'm not willing to try and remove) that I can't measure so that idea's out.

There's probably a hammer involved somewhere. I'm wondering if these hinges will be more difficult to bend than ones wrapped from sheet due to the internal structure of the steel from a thicker bar.