PGK's 1" Minnie

Hi Bri,

If you mean is it ok to put strips of Silverflo 24 on the joints otherside of the flame plus flux, that is perfectly ok and means the silver solder only melts when the copper has got to the required heat. In fact this is the method I use for Silverflo 24. Otherwise the heat is so intense it is very difficult to apply the silver solder otherwise without it melting in the flame.

For Silverflo 55 this isnt necessary.

Thank you or reminding me of this. (Though in the above pic the Silverflo 24 was added otherwise for the rivet heads on the throatplate inside and out).

I hope my ramblings might be of some help to pgk pgk. Although I dont want to have a boot full of leaks in my car I would be more than welcome to visit and try and help, with a propane bottle and seivert set in my boot instead on the way up to lovely mid-wales.

Cheers,

Julian

Edited By julian atkins on 18/04/2016 21:22:15

This is a pic of my heart..obviously can be shaped for the job:

Even this open I've had the torch flame out in use from what I'm sure is O2 starvation.

Tonight's practice went a lot better. I used the thicker mix and allowed it to dry properly in the joints before use.. stops the issue I had with the water boiling out and spitting the flux. I also raised some copper in the flat plate joint by making some angled punch marks on the inside of one plate rather than sprinkling a few bits of copper dust in there. Lastly I was more efficient at dipping the rod in flux powder and getting the job to bright orange before bothering to try and apply.

It does look like I got thorough silvered joints this time. I'll only really know with the flat plate when machined square on the edges. The practice rivetted angle flowed well from the bend throughout the join though i'm still not calm enough/complacent enough to have remembered to apply solder to the rivet itself. It had flowed out around the head though (underneath)

Julian, That's a wonderfully friendly offer to come help.. and you'ld be welcome to come see this part of wales anytime (beers on me) and springtime my bit of valley is very beautiful. rationally I suppose if it comes to it i should do the driving and bring my sievert torch and cannister and copper bits etc. Doesn't stop you coming up without any brazing intent..and for loco lovers we have llynclys station on the Cambrian heritage track only 15 mins away and Bala lake railway about 30/40 mins the other side. Daffs are finishing, primroses at their best and bluebells starting and next month I hope my patch of wild early purple orchids flowers again in far field.

I may well end up begging for help when I bog-up on the first attempt and remake all the stage one parts (if not so disheartened I abandon the minnie) but feel the whole point of the hobby is to try and learn.

Overall a more positive evening.

Back to it.

Of the three attempts/practices at silver soldering the first pump pad had a tiny void at one corner when squared up. The second go with thinner flux had a big void and the third attempt came out perfectly (I needed practice anyway)

To cut the radius I set it up in the mill with the boring head. Set at the edge of the vice i used an adjustable parallel at the other end of the vice and a square to get the part vertical with finger feel and a feeler gauge.

It had to be slightly proud of the vice since the setup of this pad isn't central on the boiler tube but 1/32" low of centre. The face of the plate was found and the boring head set boiler-tube radius away and with the face marker pen blacked it was adjusted so the head just touched.

The radius is then cut, ideally until the far edge is just affected. I'll admit that I hadn't set it far enough out of the vice so about 1.5-2mm shy of radiusing the far edge but not important.. the tiny void should get filled by solder anyway. And some of that is lost in smoothing off with a file.

the the rivet hole is drilled and temporarily located with a screw.

It would look better if it was tightened down with a nut.

The practice sessions have made inroads into my solder supply so i need some more for safety..will order after the w/e and then plan to 'have a go'

Hi pgk pgk,

As a rule of thumb the silver solder will be just over the cost of the copper. I am far too generous with the silver solder, but I think that is a better fault than being too mean with the silver solder.

I buy silver solder every now and when so I have enough in stock in advance to do a boiler without having to splash out on a large very expensive purchase.

Do get some Silverflo 55. I buy this from Joe at Mac Models as I do most of my copper for the last 2 boilers, usual disclaimer.

Cheers,

Julian

Julian,

I have all three temp ranges from cupalloys but the practice pieces were all with the 424 hence i need a bit more stock in case I run out midway.

Failure!

I fluxed the components thoroughly.. using a good tapioca mix of HT5 on both surfaces and having it almost dry before rivetting (partly due to my slow plod at doing that). I figured more flux better than less and the thick coating acting to prevent the rivettng beng too tight.

The everything allowed to dry.

I hit te same issues Brian had.. failure to get the first stage boiler bits hot enough quick enough. I had it poitioned siting on the flat firebox end, enclosed on three sides with vermiculite blocks but necessary with space to access the pump plate and the tube end open to acess the inner pads.

I directed the 25KW burner first at the outer surround of thermalite blocks to warm them up, then generally over the whole assembly until it was blackening and then concentrated the heat up from the firebox end with the flame shooting up the tube. The wrapper heated up to dull red and bright orange quite quickly with the flux liquifying but getting it to the yellowish tint I now recognise as necessary for high temp solder proved impossible. Stupidly I still tried to solder. The HT5 exhausted very fast..perhaps helped by the heat air-flow. I did manage to get one seam soldered by dipping a rod in flux powder and laying along the seam but even blowng sraight at the tube from outside of one of the inner pads doesn;t get the inner pad hot/bright enough to solder.

I could see that if I'd laid solder rod along the outer parts' seams I maight have succeeded but accessing the inner pads in the same session that way would prove hard to impossible. There was enough heat blowback that even with my cheap welding gloves my hands were getting hot and I coudn't get closer than 1/3 a rod.

I should have abandoned the session but foolshly plugged away thus destroying any sane chance to reuse any of the bits.

What i did learn: I had always assumed that copper conductivity would get all of it more evenly hot but at one pont I had one end almost at yellow heat but the other end still black - suggesting one could sub-divide this part of the soldering further allowing more insuation of sections.

It also makes me wonder how th author managed with presumably a parrafin blowtorch..unless they actually burn hotter than propane.

Brian Abbot listed his failure even with a larger torch and i can see how that could easily fail by just exhausting the flux quicker.

Even success at this stage doesn't bode well for success at the further stageswith more lump to cook.

Hi pgk pgk,

I dont know whether this is the answer, but in the set up you tried, I would always put a thermalite block over the smokebox end otherwise the barrel if left open and upright merely acts like a chimney and much heat is wasted.

As i have previously stated Silverflo 24 is not easy to use especially for a beginner.

Put the Silverflo 24 to one side, and do all the joints with Silverflo 55, and the backhead and foundation ring last piece with Easyflo 2 if you have any.

There is no point making things more difficult for yourself than need be by using Silverflo 24.

Just my personal opinion of course.

Cheers,

Julian

I don't have any easyflow2. I do have both 38% as well as 55% so while still needing significant heat to 650-720 thats better than trying to get 750+ and could allow the 55% for final stages??

I don't think the part is salvageable but I'll mull it over for a day or two..it might well be worth cooking it up a few times in different configurations/insulations just to see what works best for the next go...better to make errors ona dud part than more copper sets.

You're right about the heat goign up the chimney...I'd hoped (in my novice state) that allowing it would heat up the pad areas ready for a direct blow.

I also need to experience and learn the necessary colours for the other solder grades..albeit by wasting some.

Just my personal opinion of course.

..and valuable experience/knowledge.. Ta.

pgk

I'd hoped to have more regular progress reports than I've managed of late but it was time to redecorate the sunroom and living room (kitchen next) and there's been rain every free evening so no chance to do test cook-ups. 25L paint later i need a break from that..

Once again i failed to read the book properly.Mason himself talks about using the c4 for the firebox end but easy-flow for the tube pads. doh! Eventually I'll learn.

(wife was planting some Rosemary the other day and telling me it's good for memory. I replied that I don;t care what it's called so long as it has nice legs and can take short-hand)

I've wondered about trying to salvage my work so far but abandoning that idea..I don;t think i could asses how well the solder penetrated after such a disaster and it' be worse to find impossible leaks later. I need another length of tube ordering.

I do have the following pics of the parts pre-solder.. washed in acid, cleaned up and fluxed.

Hopefully some dry days coming.

Meantime I'll press ahead with the firebox components on tonight's session....

A dry evening at last. I already had the two firebox plates flanged and used the template to drill the 1/8" pilot holes in one. For the other I turned down the firebox ring to specs (allowing for the fact that my piece of tube was 1/8 less od but same gauge), filed out the hole for its seat and had another go at brazing with 24%.

Fluxing and prelaying a ring of solder around the joint and just letting it cook up and flow worked well..specially with vermiculite bricks overlaying the flat part..it easily got to bright orange/yellow.

..and a very nice solder ring both sides.

As an experiment I cooked up the dud/failed tube and wrapper from before to see how hot I could get it..you can see from the pics below...melted and burned copper..all down to better insulation! (OK so you guys all knew that). I got the base all the way to yellow colour and a pile of oxide slag.

I looked up the melting point of copper at 1085C. No question that propane gets hot enough.

JasonB, (if your still keeping an eye on me ).. You suggested way back that I make up some bronze spacers between firebox and outer wrapper for the hornplate fixings. I didn't twig back then that on this build the outer wrapper is placed before the firebox soldered unit is inserted. That would make placing your spacers problematic. Options that i see would be to just place rods with no spacing function or plaigerising the idea from metric minnie of making up rods and slipping them through s/s spacing sleeves????

For my next barrel/wrapper attempt (need to order more barrel) I'm thinking in terms of subdividing the cookups... do the pads before adding the throatplate and wrapper. I'm getting better success with the solder layed before heating and I think i can do the pads with mid-range solder (mason uses easyflow).

As an interesting aside. even though i cooked up the failed throatplate/wrapper to melting copper the 24% didn't reflow (but then again no flux used). I'd read that silver solder chages on cooking and then takes a higher heat.

Hello pgk pgk,

Agh the trials and tribulations of silver soldering; especially on a small complex boiler such as the 1” Minnie. I soldered the pads in place before moving on. The pads were held in position with copper rivets. It is easy to remove the protruding piece with a file when the job is cold; the head can be left inside. The advice from Julian about stopping the boiler acting as a chimney is very sound; as are the other first class suggestions from him and the others on this thread. I wish that I had read all of these suggestions before I stared on my Minnie boiler. I plugged holes with an insulation blanket from CuP alloys; torn into pieces and stuffed into large orifices to prevent the circulation of cooling air through the boiler. With regard to the boiler stays between firebox and outer wrapper, I followed the method in the book. It worked for me, though I am sure that JasonB offers a more modern approach. Take note of my comment earlier, about pressure testing the boiler (as advised by Mr Mason) before these stays are in place. As you say, the melting point of silver solder is considerably higher once it has been used. I know this to my own chagrin from the times that I have tried, unsuccessfully, to re-melt a silver soldered joint that has gone wrong.

Good luck

Ray

Yes still following along, just that I have not used the 24 solder so could not add any practical advice. Tend to just use easyflow even if the assembly needs several heats to add various bits

Plain rods slipped in will be OK and a couple of punch marks should stop then slipping out while soldering. You could also turn then to have a small lip on one end like a top hat to help retain them.

J

Jason,

Thanks again

Ray,

Despite all my pre-solder reading there is no substitute for experiencing it,, and I just have that habit of doing things the wrong way first. It makes it a longer learning curve but the info sticks better

..then again if I keep documenting all my cockups the next guy might have it easier.

When I cooked up the dud barrel/throatplate/wrapper to melting temps I simply surrounded the barrel on three sides with vermiculite bricks, popped one on the top of the barrel and another bridging the throatplate and directed the heat into the wrapper base, The comment was made earlier in this thread that it's less the heat you put in and more about the heat losses one avoids...

Hi pgk pgk,

I am sorry things went badly wrong with the throatplate to barrel and outer wrapper with Silverflo 24.

It is not the stuff for beginners. The C4 used in the old original description is of course no longer available.

If you had decided the barrel and throatplate were beyond hope, I wouldnt have been so destructive on valuable copper, that could be re-used!

Next time, when you have got over the shock on the bank balance, do all the bits in Silverflo 55.

Jason is lucky to have plenty of Easyflo left. I have a bit left for boiler fittings but not enough for another boiler.

If I could make a 5"g loco boiler when aged 18 in 1985 I reckon anyone ought to be able to. That loco with same unaltered boiler is still running, although I sold the loco many years ago.

Cheers,

Julian

Julian,

I hadn't actually intended to melt the copper..just to see if I could get things really hot.. and proved a point to myself.. a lesson well worth paying for and there's still recoverable wrapper. I couldn't see any practical way to reuse the barrel.. apart from cutting it up for other purposes.. can't unsolder the badly attached pads inside and boring it out would be more bother than it's worth and probably weaken it.

I've got a bunch more high and mid temp solder left and plan to use it for the firebox wrapper....your method of laying it on and heating worked nicely for the firehole..and it's all practice.

Not much achieved tonight.. just made a former for the firebox wrapper bends and cut the sheet out. i usually try to avoid hand-work but it's good for the soul now and again.

pgk

The former I made was just for the top of the wrapper..flat with two curved corners. With the benefit of hindsight either a longer bar one could grip in vice and have clearance to make the bends or a solid block of timber to form it round. I didn't want to 'waste' a good bar nor start laminating up timber to make the block. I ended up with some shenanigans to use this former:

Anneal the middle and working out where the bend starts and squaring it in the vice end.

And getting creative for support to make the start of the second bend

drilling for temp bolts was just a fiddle and faff and takes a long time while making sure everything stays square.

It's now ready for an acid wash and scrub and fluxing and rivetting..hopefully tomorrow

Today started full of promise.. cleaned and fluxed and rivetted and laid 24% around the seam with a second piece each corner which were my weak points.

You can see the hearth design for this... surrounded with vermiculite bricks and blasted the heat inside. It was my first daytime cookup and really couldn't see the flame or colour changes on the copper

But after 3+ mins i could see the rods melting in as they should and being sucked into the seam. While the immediate post pic looks messy it cleaned up nicely.

The process was repeated for the other end as a seperate cook.. and did not go well..the same setup but just didn't want to get hot enough and then flux exhaustion. I did try running a little 55% fluxed rod onto it but it was turning into a mare.

the pic shows unmelted rod bits stuck all wrong drifted from the corners and the seam rods unmelted as well.

I cleaned up and scrubbed the seams and went for a second cookup. This time I cut up a vermiculite brick to have a piece inside and another on top and the side bricks closer. Its till took a long time to get to heat and exhausted most of the flux but it did get hot enough to add fluxed rod.

I haven't got pics handy and it's in the acid bath. I can see solder penetrated to inside but I'll have to scrub up and file off the mess before assessing this..possibly with a lower temp solder additional cook if needed.

If i ever build another I may well avoid 24% but having started it's a case of being stubborn even if I have to start over. Once again the lesson to take home is insulate the outside as much as access allows

I managed to clean it up.. filing the proud 24% was a apin ..so I hit it with the belt sander and while not pretty on that second side I've go a pic showing good penetration through the seam.

The worry with the firebox is access to fix any leaks and no easy way to test at this stage.. so i am still considering running over the seams with 55% just to fill them in fully.....?

Hi pgk pgk,

I dont think I have seen anyone silver solder up an inner firebox like that before! It precludes fitting silver soldered firebox stays. However, the silver soldering on the inner firebox doorplate especially looks very good. Soak in a hot sodium hydroxide solution to remove all hardened flux deposits then scrub in hot soapy water then dunk in sulphuric acid then soak in hot soapy water again and scrub, then poke about at all the joints with a dental probe or scriber etc.

When you do other bits on the firebox you can run Silverflo 55 over all the joints and rivet heads - this will be a piece of cake compared to using Silverflo 24!

I am very sorry about the barrel etc., but at least you have got reasonable joints with Silverflo 24 on the inner firebox. The Silverflo 24 hasnt flowed quite how I would expect on the tubeplate joints to inner wrapper, hence running over with Silverflo 55 later on and when all the joints and cavities are as clean as possible.

I do hope this is not becoming just a dialogue - surely this must be of more general interest ? (Ray and Jason excepted!)

Cheers,

Julian