PGK’s 1″ Minnie

[pgk pgkParticipant @pgkpgk17461]

For other novices that may be reading along:

I had another go at the high temp solder.. with some success. To be sure I cleaned up the failed attempt pieces and then dunked them in dituted sulphuric acid.. rinsed, then scrubbed with wire wool. I made up a larger batch of HT5 flux and soemwhat thicker than before.. coated both surfeaces, sprinkled a few fragments of fine copper 'dust' to space them, left a step between the parts as somewhere to apply the solder rod.. and fired up an 8KW torch.

It still took longer than i expected to really heat up and I had it all well confined on vermicultie bricks. It got to orange/yellow before the solder would flow.. and having been excessively generous with the fux it was buubling and spilling onto the hearth. Next time I'll wear welding gloves.. It was probably reflection at night ( outside my shed with an eves security light) but it looked like the vermiculite was glowing.. and with just that torch some serious heat affecting my torch hand.. defo need gloves for the 25KW goes in future.

When the rod flowed it flowed well. I could assess and prove the concept of solder flowing towards the heat source (now directed at one end)

I suspect that my copper dust had flowed out with the flux.. the solder line between plates is almost invisible after milling the edges but hammering a screwdriver into the gap doesn't penetrate.

I reckon it's a lot easier to handle on fillets and curved edges.. will have a go at samples like that next and try to asses an optimum on flux which washed onto the bricks and under the part so I had unnecessary solder attached under there too – but I was determined to use too much rather than too little.

At worst i have a feeling for the colour temp needed for 800C and repetition should get away from the anxious newbie instincts of rushing with the solder and splashing it about.

[pgk pgkParticipant @pgkpgk17461]

Yesterdays preactive attempts were disasters (to learn by?).

I made a thinner flux mixture to solder two small 1" plates to each other.. a total failure. It still takes 2-3 minutes to heat up those little plates with an 8KW torch and the flux was exhausted in that time. Second attempt was with an angle piece riveted to a flat piece but spaced with two tiny bits of silver foil but the same flux thickness.. again exhausted before temperaturereached and one could see the solder just ball and sit there.

The I made up a thicker mixture again.. on two plates with a slightly larger 3 chips of copper as spacers. That way the flux persists but it does run everywhere.. a messy visual result and the sp[ace must have been too wide for good capillary flow..didn't flow the full width.

Next I plan to try letting the flux dry a lot more before cooking up in case it's the water boiling some of it away.

I'm having to consider downgrading my plans of using 3 temp ranges of solder. The original book used just c4 and easy flow.. so 2 temp ranges although he does soft solder too.

More practice needed.

[Martin KyteParticipant @martinkyte99762]

Can I ask about the set up. Are you just plonking your boiler on a flat surface and getting on with it. You should realise that copper being such a good conductor will act like a radiator and disperse much of the heat you are putting into it with your torch. If you surround as much of the copper with insulating materials leaving only the joint exposed you will do better. You will find that you need to get pretty much the whole job hot before getting on with the joint. In order to not exhaust the flux heat the boiler away from the joint first then once every thing is nice and hot you will be able to raise the temperature of the joint area reasonably quickly. Many people have said before its not the heat you use it's the heat you lose that makes the difference.

Keep going, you will get there.

regards Martin

[Neil WyattModerator @neilwyatt]

What flux are you using?

Easyflo flux will be exhausted by the time you get the far side of 800C, try using Tenacity flux (for alloys up to 880C) instead.

http://www.jm-metaljoining.com/pdfs-products/Tenacity%20No.5%20Flux%20Powder.pdf

Easyflo for melting up to 750C.

http://www.jm-metaljoining.com/pdfs-products/Easy-flo%20Flux%20Powder.pdf

Neil

[pgk pgkParticipant @pgkpgk17461]

Flux is HT5 and at the moment this is practice on small pieces rather than plonking the boiler down,

Hearth setup is a plank across 2 trestles outside my shed.. a layer of low density breeze blocks on the timber and a wind break built around the job from the same .. then vermiculite bricks surrounding the actual soldering job.

If and when I think I have the hang of doing this stuff then i also have loose vermiculite gravel for packing into spaces

[Martin KyteParticipant @martinkyte99762]

Well done, you sound like you are already thinking about heat loss. Keep at it.

Martin

[Ian S CParticipant @iansc]

You could also think of a thermal blanket to wrap around the outside of the boiler.

Ian S C

[julian atkinsParticipant @julianatkins58923]

I dont see anything wrong with pgk pgk's containment of heat method using Silverflo 24.

With Silverflo 24, if you have too much heat containment you get substantial heat throwback which makes it very difficult to apply the silver solder when the job is up to heat. Pgk pgk has already alluded to this with his burnt hand the other day.

Neil, there is quite a world of difference between using Easyflo 2 silver solder at 608 degrees C, and Silverflo 24 at 740 degrees C and above. In theory the extra 132 (plus) degrees ought not to make much difference, but believe me it does! I actually think using Silverflo 24 is pretty similar to using Sifbronze brazing rod. Those who have done Sifbronzed joints with propane will know what I mean. I dont think Silverflo starts to flow properly till well above 740 degrees C

Cheers,

Julian

Edited By julian atkins on 18/04/2016 19:34:28

[nigel jones 5Participant @nigeljones5]

Here's me being negative again, but I only ever use sf24 if I absolutely have to. As Julian says, it is not easy to work with and I only ever use it with oxy and a big propane torch, and then its all I can do to get it to temperature. When at temperature it doesnt flow as well as the lower temp does, and the Tenicity flux doent seem to promote good flow either. Im a bit perplexed re the flux bubbling and spitting – never had that occur. Dont forget that if you get the copper too hot it will burn, and you will never recover from that.

[Boiler BriParticipant @boilerbri]

Julian. Is it acceptable to put strip joint covers on the outside, I have always put them inside which does take up waters space between the wrapper and the fire box on small boilers.

Bri

[julian atkinsParticipant @julianatkins58923]

I totally agree with Fizzy re Silverflo 24 being 'difficult'. John Baguley (Baggo) described using same on his 'Helen Long' boiler in 2.5"g and even John admitted it wasnt easy to use.

I would not personally advise a beginner to use Silverfo 24. My first boiler (5"g Don Young No.1 Railmotor boiler started when 16, and started at 18 on the boiler) was done throughout in Easyflo No.2, but the stays were caulked with comsol.

For flux running when heated up, please do let it dry out before lighting up.

I have never had a problem with Thessco F which is what I use (JM Tenacity 4A, and Cupalloys HT5 being the same) with Silverflo 24.

(as an aside to Neil's previous post re ordinary Easyflo flux it is totally unsuitable for miniature loco boiler work using Silverflo 55 630 degrees C or even the old Easyflo No.2. Anyway that is what Alec Farmer of Reeves fame told me in 1984!)

In the over all scheme of things the cost of silver solder isnt that bad, and there are only 2 grades recommended by JM for silver soldered copper boilers since the Cadmium ban (unless you still have old stocks of Easyflo or Easyflo No.2).

Cheers,

Julian

[julian atkinsParticipant @julianatkins58923]

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

[pgk pgkParticipant @pgkpgk17461]

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.

[pgk pgkParticipant @pgkpgk17461]

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'

[julian atkinsParticipant @julianatkins58923]

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

[pgk pgkParticipant @pgkpgk17461]

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.

[pgk pgkParticipant @pgkpgk17461]

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.

[julian atkinsParticipant @julianatkins58923]

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

[pgk pgkParticipant @pgkpgk17461]

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

[pgk pgkParticipant @pgkpgk17461]

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….

[pgk pgkParticipant @pgkpgk17461]

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.

[pgk pgkParticipant @pgkpgk17461]

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.

[Raymond GriffinParticipant @raymondgriffin40985]

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

[JasonBModerator @jasonb]

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

[pgk pgkParticipant @pgkpgk17461]

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…

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