PGK’s 1″ Minnie

[pgk pgkParticipant @pgkpgk17461]

Brian,

So far I've been dropping the hot boiler in my sulphuric acid bath.. but that's getting a bit nastier to do now that it's become a bigger chunk of hot copper, That along cleans it pretty well.. then rinse in clean water. If necessary scrub residues off and rinse again or back in acid again. It's been very effective at shifting flux residues. Of course i also have flux on standby to apply more during the initial cookup

AndyA,

Thanks for your order list.. the first part is as in the book I'm following and the rest much as I originally planned although the book suggested doing the whole foundation ring in one go and then the stays last. I figured that if I'm going to cook the ring hot enough for that then hopefully there'll be enough heat to get stays with solder wire wrappings done as a by-product…. or at least worth a shot.

I was also wondering about starting with some heat from the smoke box end before re-insulating it to get a warming start without flaming at the flux directly…..

[julian atkinsParticipant @julianatkins58923]

Hi pgk pgk,

I read your previous posts but didnt see any any reference to front foundation ring silver soldering. If I have missed this please do quote me what you had previously posted.

In context this is quite a small plain round topped boiler and ought not to beyond the whit of most model engineers. Traction engine boilers are relatively straight forward. They do not have the complications of most miniature loco boilers, which are also larger andif of tapered barrel and belpaire firebox considerably more complicated to make and to silver solder.

I reckon I could do this boiler in 3 weekends of time off. My second to last boiler was done in 6 weeks (a medium sized 5" g loco boiler) but I was working variable shifts on the fullsize railways at the time.

Cheers,

Julian

[pgk pgkParticipant @pgkpgk17461]

Julian,

I think we're at cross purposes here. Mr Mason's book has the foundation ring cooked up in total at this stage of boiler build and then the stay holes drilled and stays soldered. My point was that drilling the stays like that in soft copper distorts the wrappers.

I guess your thnking in terms of Andy's order of progression.. which makes sense.. but as a novice I was faithfully following the build book until that point. You're quite right that soldering what i fluxed last would be a mistake. something I recognised and didn't do. Instead i chose to make wood supports for the side stay drilling. With the stays in but unsoldered I'll then fit the foundation ring.

I don't question your competence and speed at doing these things. I'm slow and every stage causes me much thought and my nature is to worry at stuff. Put me in my comfort zone and you'ld see a scalpel fly.

[julian atkinsParticipant @julianatkins58923]

The principle problem is that the Minnie boiler was described in the early 1970s when considerably more ductile grades of silver solder were available such as C4 allowing easy step silver soldering. It is an old design and the boiler was not described for silver soldered stays.

In the last 40 or so years things have changed quite a bit. The boiler regs have been tightened up, and test procedures are much more demanding in clubs. Inspections also are required by the club boiler inspector at each stage of silver soldering.

I always do the front foundation ring to the throatplate with high melting point stuff such as 24 silverflo or sifbronze. It is the first joint I silver solder. That is of little help to you now.

I did my first miniature loco boiler throughout with the old Easyflo 2. That was in 1985. The boiler has passed successfully every test since completion, and is still in ticket and the loco running around, despite having been sold some 15 years ago.

There is no reason why your boiler should not be completed with silverflo 55, but it will I suggest require threaded and nutted comsoled firebox stays.

Cheers,

Julian

[pgk pgkParticipant @pgkpgk17461]

An update. I did finish the boiler but had a small foundation ring leak… fixed that but created a leak by one firebox stay.. fixed that and got 2 leaks on the wrapper seams.. fixed those and created a leak by the firehole. Fixed that and 2 new leaks by the foundation ring (repeat that sort of thing 2-3 times more)…. So I accept this is a combination of a lack of accuracy and hvaing gone about things the wrong way. Delays due to my very aged mum finally passing and all the estate stuff to sort and now coming up to planting season.

For the moment I'm off boiler making .. but do intend to start again.. differently and with way more formers and probably a few more rivets than the book description. I don't regret any of this (apart from hating spending money).. it's been a learning curve and i did start by admitting I was up for three boilers before giving up. For the moment I intend to have a play at making minnie gears via making my own cutters.. also a new challenge for me.

[Henry RuiterParticipant @henryruiter35703]

I made water/oil contaner from 3mm copper sheet I first soft solder that didn’t work so I silver soldered and I think I got good pen with it for my first try I was using LPG from a 9 KG gas bottle

[Ian S CParticipant @iansc]

I hope you got ALL of the soft solder off the job before you silver soldered, the joints may look ok now, but if contaminated there is a good chance of failure in the future.

Ian S C

[Henry RuiterParticipant @henryruiter35703]

I’m pretty sure I got it all off before I silver soldered it and wasn’t stuck very so just scraped off with I craft knife.It was quite strong afterwards.

Thanks Henry

[Henry RuiterParticipant @henryruiter35703]

You can see it in my first photo in my gallery.

Thanks Henry

[Jon CameronParticipant @joncameron26580]

I have just read this thread through from start to finish, (works been quiet today).

My thanks to PKG for posting all his failed attempts as well as his triumphs, I believe there's much more to be learned from those mistakes. As for his posting earlier as to someone else been able to learn something, you have certainly succeeded on that count.

Having got the book (quite cheap compared to some copies I've seen), ive been reading through the pages and searching websites on builds. This is by far the most helpful I've read, thanks also to those that have offered advice along the way. I will post progress of my build when it begins.

[pgk pgkParticipant @pgkpgk17461]

Wow – 3 years…

That boiler still sits on my shed table mocking me with it's leaks and the weight of silver solder rattling inside it and my constant 'must get around to having another go'…

..and then something else crops up…

pgk

[henrybParticipant @henryb]

I have used this thread as a reference a lot as well in the last year.

[Jon CameronParticipant @joncameron26580]

Julian, id like some clarification on a post on the previous page you say that you solder the foundation ring to the thoat plate first. I assume that this is before soldering the throat plate to the main barrel, or at the same time as soldering the barrel and throat plate? I guess it would serve a couple of useful points in that you will have a spacer to clamp to when you come to solder the inner Firebox, to the barrel and wrapper assembly. Also while soldering the barrel and throat plate first, the front part of the foundation ring would get pre warmed, meaning that a blast of the flame should see this heat through and the solder melt and flow.

So order of assembly would be (HT=High temp solder, LT=lower temp solder) numbered steps are cook ups, possibly could reduce these but where?

1.barrel and front throat plate, then onto the foundation ring front part. (HT)

2. Then outer firebox wrapper to barrel. (HT)

3. Inner Firebox wrapper to front firebox tubeplate (HT)

4 crown stays to firebox (HT)

5, tubes to front firebox tubeplate, rings of solder, use smokebox tubeplate to align tubes. (LT)

6. Inner assembly and outer riveted together clamping to front foundation ring, (foundation ring drilled and tapped for copper/bronze slot head screws?) and riveting the crown stays to The wrapper. (LT)

7. Front tube plate, and around tubes (LT)

8. Inner Firebox firedoor ring (HT)

9. Inner Firebox to rear Firebox wrapper (LT)

10. Foundation ring sides (LT)

11. Backhead bushes (LT)

12. Backhead, and rear foundation ring. (LT)

Just realised I missed the steam take off block from that assembly should be same time as step 2, screwed from below and then drilled though after cook up.

[julian atkinsParticipant @julianatkins58923]

Hello Jon,

As you have taken the considerable trouble to quote me plus provide a detailed post, you deserve a detailed response…

Your:-

1. I do the front foundation ring to the throatplate first. I don't make the front and rear foundation ring out of square section copper but out of a slab of copper, which gets profiled further back and forward respectively around the inner and outer firebox wrappers with a step on the ends.

3. I tried this once with J-M silverflo 24 but the tubeplate got far too hot for my liking, and was stopped partly silver soldered, so the answer to your 3. is LT not HT.

4. LT J-M silverflo 55, not HT J-M silverflo 24.

6. No need for any fixings between front foundation ring and firebox tubeplate. Your 7. done at same time.

8. I do special phos bronze stays for the inner firebox doorplate to backhead at the same time in HT.

Between your 8. and 9. I silver solder up the firebox side stays, and do the foundation ring sides (your 10.) all LT. The throatplate stays have been silver soldered at your stage 6.

11. Backhead bushes are HT done before the backhead is silver soldered to the outer firebox etc as the final stage, the previous stage which was silver soldering the front smokebox tubeplate to the boiler, which would also have it's bushes done beforehand with HT.

I silver solder in the longitudinal stays. Dome bush is done early on in the the last 2 cases with HT. Safety valve bushes done the same time as silver soldering the crownstays to the outer firebox wrapper, LT.

I hope this makes sense. I did a detailed 'build log' of my last boiler on modeleng.proboards.com, and a lot of the pics of same are in some of my albums on here.

Cheers,

Julian

Edited By julian atkins on 12/11/2019 23:40:19

Edited By julian atkins on 12/11/2019 23:41:18

[Jon CameronParticipant @joncameron26580]

Julian,

Many thanks for your response, it wasn't planned as been detailed or to quote you, so appolagies if I've caused annoyance or offence. I simply wanted to try make a bullet point list for assembly of soldering.

After acquiring a scrap boiler for nothing that even after my inexperienced view is shoddy and dangerous, it's been lopped apart with an angle grinder and the front tubeplate cut off, and the barrel at the throat plate cut, which has left me with a nice section of 13SWG copper that is quite possibly going to get hammered soon. It's also left me with dozen 3/8" tubes, at around 7" length. So after a clean up an flattening, (flattering…dammit autocorrect, as if you could flatter a peice of copper that causes you so much frustration haha), I'll have a tube plate, and backhead that's 13SWG, and tubes which makes the cost of the boiler quite small by comparison.

After your response I have clear in my head which steps to take going forward, hopefully as does PKG should he attempt a third try at the boiler, or at least try to chase the leaks to satisfaction.

I do testament to another thread and this one where light weight insulation blocks from builders merchant, reflect heat a a fraction of the cost of commercial thermalite blocks. I soldered a thin gauge brass boiler (of mamod proportions) with plumbers flux and solder, using a small hand held torch filled with lighter gas. The solder ran beautifully after the tube was well packed around with offcuts of the blocks something that I thought would be impossible.

Again thanks for your contributions hopefully I may make a boiler in 1 attempt but then again pigs might fly.

[pgk pgkParticipant @pgkpgk17461]

Justin,

I'd appreciate your further comments, please

To shape the front foundation ring I guess you have to have the inner firebox assembled at least temporarily (or solder its wrappers first). Indeed it was the fiddly corners when my original leaks happened unless one manages a good fillet to smooth it out. Is there any benefit to adjusting the inner firebox to have it's wrapper inside the ends?

You suggest using a wider piece of copper to shape that front foundation ring (which makes sense). If curving that around the side of the inner firebox do you cut a step so the side foundation rings can also be stepped and sit on top?

pgk

[julian atkinsParticipant @julianatkins58923]

Hi pgk,

Quite the contrary.

The front (and latter rear foundation) ring bits are milled and filed to fit the inner plates namely the inner firebox tubeplate, and inner firebox doorplate up to where the inner firebox wrapper starts and later ends. You dont have to have the inner firebox made up to do this for the front piece of the foundation ring, but you would have to hand the already flanged plates for the inner firebox to hand.

Obviously, to do this you need wider section copper first than the simple width of the water space.

Many boiler makers have problems doing the foundation ring sections, and to my mind anything that makes this easier and less fraught ought to be adopted.

I hope this makes sense. A simple sketch would probably make this a lot clearer.

Cheers,

Julian

[julian atkinsParticipant @julianatkins58923]

Hi pgk,

Quite the contrary.

The front (and latter rear foundation) ring bits are milled and filed to fit the inner plates namely the inner firebox tubeplate, and inner firebox doorplate up to where the inner firebox wrapper starts and later ends. You dont have to have the inner firebox made up to do this for the front piece of the foundation ring, but you would have to hand the already flanged plates for the inner firebox to hand.

Obviously, to do this you need wider section copper first than the simple width of the water space.

Many boiler makers have problems doing the foundation ring sections, and to my mind anything that makes this easier and less fraught ought to be adopted.

I hope this makes sense. A simple sketch would probably make this a lot clearer.

Cheers,

Julian

[pgk pgkParticipant @pgkpgk17461]

Julian,

First I must apologise for the brain fart in calling you Justin! Sorry.

So you fit to the curve of the inner firebox tube plate and then later file the flats for the firebox wrapper once that is ready for fitting? Any benefit in my suggestion of curving it further round then having a step for the side piece of the foundation ring to sit on?

pgk

[julian atkinsParticipant @julianatkins58923]

Hi pgk,

The front foundation ring section is milled and filled to be a jolly good fit between throatplate and inner firebox tubeplate, also as you note fitting the side curves of the inner firebox tubeplate, having determined where the inner firebox wrapper will be, to which it will end up abutting. The step on the ends is milled. It isn't a big step, but enough to intersect with a step on the foundation ring sides and avoid that problematic butt joint plus avoid the foundation ring sides moving latter on.

I make the flange depth quite generous.

Cheers,

Julian

[pgk pgkParticipant @pgkpgk17461]

Julian,

 

Excellent. Understood. Thanks

pgk

Edited By pgk pgk on 15/11/2019 00:18:21

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