PGK’s 1″ Minnie

[julian atkinsParticipant @julianatkins58923]

HI pgk pgk,

I use a 'Thor' hammer using the copper end and a fair 'whack'.

I do all my boiler work indoors, and silver soldering with the patio doors the end of my workshop open.

I am also in Wales albeit the South Wales Valleys.

Cheers,

Julian

[pgk pgkParticipant @pgkpgk17461]

I looked up thor hammers.. look good.

I've got double doors and 4 windows..so plenty of ventilation. But back pain means i have to work at standing or sitting heights ( as in weeding veggies means crawling).. so any indoor hearth is going to be closer to ceiling and ceiling strip light fittings??

What i have in mind is two trestles with a board across, line with light thermalite blocks (and windbreak) then line that with vermiculite blocks. Can be dismantled and stored quite quickly.

I'm guessing copper rivets need annealing first?

[JasonBModerator @jasonb]

I've not found the need to anneal rivits, they are soft enough as they come.

[julian atkinsParticipant @julianatkins58923]

Hi pgk pgk,

I agree with Jason absolutely no need to anneal copper rivets. Dont close them up too much as you ought to have silver solder penetrate around them, plus both heads covered with silver solder. They are a pain to silver solder whilst doing the relevant joint so try and use as few rivets as possible.

It is not unknown for me to remove the ceiling light fitting in my workshop when doing the last set up and silver soldering for the backhead and last bit of the foundation ring etc.

Cheers,

Julian

[pgk pgkParticipant @pgkpgk17461]

Thanks for that, guys.

My supply order included some silver foil to stack snippets between rivet layers to avod them being too tight. I note that Mason's instructions for throatplate and wrapper state one rivet midline top warpper and tube and one each in wrapper/tube/throatplate ears. However i don't see how that can keep the throatplate perpendicular to the boiler tube..effectively a hinge..and ought to need an additional rivet somewhere between throatplate and wrapper to prevent movement? I guess i'll find out on preliminary bolting up….

[Raymond GriffinParticipant @raymondgriffin40985]

Hi, it looks as though there are a number of us making the 1” Minnie. I seem to be a little ahead of pgk pgk, in that my boiler is completed, and I have pressure tested it to my satisfaction. I have a similar problem of boiler inspection. I live in the South of France, so access to a boiler inspector is out of the question. I belong to my local Model Club, but am the only constructor in steam. I find boiler making irksome, and can fully understand anyone buying one. I wonder what percentage of these models are made just for the pleasure of construction, and in fact never envisaged for fires and steaming. I have just fitted the horn, spectacle, and back plates, and was pleased to be able to purchase them as laser cuts from Blackgates. Laser cut material is a great saving in precious workshop time. Shafts placed in the pre-cut bearing holes are parallel, so no fear of misalignment. My only worry is that the centres may not be perfect for the gears. Mr Mason emphasises clock making methods to ensure correct meshing of the gears. I will cross that bridge when I get there. Three photos of work so far.

Happy constructing, to pgk, and other Minnie builders.

[pgk pgkParticipant @pgkpgk17461]

Raymond,

Looks nice so far. At my rate of build you're weeks ahead. Was this your first boiler? Any little tips, tricks you discovered along the way?

As you say, many will hardly ever be steamed. For me it's really about whether i can make one rather than wanting one.

[Brian AbbottParticipant @brianabbott67793]

Well this makes 3 of us making a Minnie, anyone else ?

[Tony SimonsParticipant @tonysimons69671]

Yes! Boiler completed 35 years ago – just started progress again, front axle done, all gears cut, winding drum finished wheel rims turned. Will take pics soon.

[julian atkinsParticipant @julianatkins58923]

Hi Raymond,

You are to be congratulated on an excellent boiler.

Small boilers are not easy to make. Plus in the case of traction engine boilers they require a higher degree of precision than miniature loco boilers, plus lots of awkward add ons, so I am always in awe of those who make their own boilers for traction engines.

Pgk pgk is to be congratulated on his own achievements so far and starting this thread. I personally think it would make an excellent series in ME magazine, and would help recoup the cost of the copper and silver solder!

Cheers,

Julian

[Raymond GriffinParticipant @raymondgriffin40985]

So good to see the work of other Minnie builders.

Pgk, I have made other boilers over the years, but none as complex as this one. My previous efforts have been in water tube boilers for model boats and stationary engines. I followed the guidelines in the book by Mr Mason for much of the construction of this boiler; with a few strategically placed copper rivets to hold assemblies together. My silver soldering is based on much of the existing literature. There is a helpful series written by Keith Hale of CUP alloys called “Overcoming difficulties in silver soldering” in the “Model Engineering in Miniature” magazines of November, December 2015 and January 2016.

1. I try to get joints that are not too tight or too large. Too tight restricts capillary flow: too large, hard to fill with expensive silver solder

2. I clean all my copper pieces in acid before each heating cycle. I use nitric acid, diluted to about 5% from the 25% stock sold by our local hardware shop: adding acid to water, of course. Copper immersed in the dilute nitric acid will become clean in seconds. I learnt to use nitric acid for silver soldering in metalwork classes, at school in the 1950’s. However, all the safety precautions for using strong acids must be followed rigorously. I clean mine in the open air as obnoxious/toxic fumes can be evolved if care is not taken. Nitric acid will not normally be available in the UK, so dilute sulphuric acid or citric acid can also be used. I do wonder if the acid treatment is a bit over the top, as in reality only the areas to be soldered need to be bright copper. This can easily be done with wire wool. The flux should take care of any local oxidation from heating.

3. The size of torch used is important even in a small boiler such as this. I found that the Sievert 3491 (3.1Kw) burner normally used for heating smaller jobs could not provide sufficient heat quickly. So changed to a 2942 (26Kw) burner used with an extension tube, as it gets very hot. The larger burner did the trick for me; it brings the job up to temperature quickly and easily.

4. I used silver solder with two melting points as normally recommended for work of this nature. I used No. 438 (650°-720&deg and No.455 (630°-660&deg from the CuP alloys selection, following advice from their stand at the Midlands show.

5. I find some form of insulation around the work essential when heating. Coke is mentioned a lot in older literature; but I don’t know where you would get it. Anyway, the fumes from the hot coke could be a bit daunting. I have two insulation blankets from CuP alloys at £10.80 each they are cheap and for me, indispensable. One is kept whole and wrapped around the boiler; the other is torn into pieces and stuffed into large orifices to prevent the circulation of cooling air through the boiler.

Good luck with your soldering.

Brian, your gears look really nice. Do you have any tips on getting them to mesh nicely? I am just starting on the bearings for the shafts.

Bonne courage, to all

Ray

[Raymond GriffinParticipant @raymondgriffin40985]

Addendum to my recent post.

I made a real faux pas with my Minnie boiler. Once it was completed, but before the side stays were in place I did a hydraulic pressure test for leaks, as recommended by Mr Mason. He suggests 10lb/sq. in. Me, being clever, thought that a bit more pressure could be more revealing. So I took mine to about 15lb/sq.in: lo and behold, the internal and external side panels of the fire box puffed out, like trumpeters cheeks. It was a miserable job getting them back to parallel and straight using clamps. I think that this intermediate test could be left out, as there is a full pressure test when the stays are in place. Leaks can be rectified at this stage.

[pgk pgkParticipant @pgkpgk17461]

Ray,

Thanks for the extra comments. I bought some conc. sulphuric acid today (one shot drain cleaner) and along with vermiculiye bricks i had also bought some loose vermiculite.

I'm delayed on getting more done due to wife having to go away for a few days and that leaves me with all the animal feeding and domestic chores as well as my usual ones.

[Brian AbbottParticipant @brianabbott67793]

Hello Ray, hope all is well with you.

Regards the gears, I just used the method described in the book, made the small setting tool. Possibly a little tighter than I would have like but I think they will be ok, I fabricated all the parts for the boiler, but had to get help to solder as I failed miserably, so have a great deal of respect for anyone who can master it..

[pgk pgkParticipant @pgkpgk17461]

Ok so I've been getting a bit more done but very slowly..probably 'cos i'm on the edge of my comfort zone and spend too much time worrying about each step but wife tells me that I've stressed about every hobby I've ever had – so no change.

I cut annealed and bent up the inner support plates. To get them right i turned down my scrap block of ally to id minus 13g thickness as a former.. scribed a horizontal line and matched that to lines scribed on the plates to try and get the curve on the midline. Before bending I drilled 1/16th holes in the location required that i could later open to my rivet size – just easier to mark and get right while the plate is flat

I really had a hard time figuring how to drill up the rivet holes for the throatplate/wrapper/tube combo. re-reading the text I'd missed that Mason stated a 'couple of rivets each side' in the throatplate.. initially I'd read that as just a couple of rivets through ears/wrapper/tube and had wondered how that could possibly hold the throatplate straight.

The book simply states 'clip it together' for drilling. I do wonder how he did that.

The top hole is easy.. just scribed seperately on wrapper and tube and bound to match. Once bolted through I eyeballed and marked where wrapper holes should be relative to the throatplate ears.. spot drilled and drilled the wrapper then marker ink and align wrapper over the tube to mark through for first tube hole…lots of time with it set up in the mill vice and a magnifying lens to centre on that marked circle. (I tried a transfer punch but the wrapper is too thin for that to work). Once both top and one side hole bolted up I could do the other side hole the same way.. the the issue of drilling the throatplate ears.. wrapper off for access and clamped as you'll see. the backhaus towel forceps aren't rigid enough..they just twist compared to bone fragment forceps but the rochester-pean gave a half decent hold. Spotting and drilling were further supported by hand as well as various packings. then all those parts were bolted together, checked for alignment and perpendicularity before clamping up the end of the wrapper for the last holes. I should have done those in two stages too.. 'cos the last one did slip a tad. I managed to recover that by slotting the hole a little with a tiny slot drill and the rivet head holds it correctly.

I thought I'd have a go at sweating the two pieces of pump plate together with high temp silver solder.. assembled my hearth and figured i could get away with a simple hand can blow torch for such small bits of copper. Total disaster. I got it bright luminescent orange hot -like a glowing satsuma but the solder stayed solid. I got my new big torch out only to find the vendor had forgotten the regulator adapter.. which he's since sent. So that's the next job. But it illustrates quite how much heat I'm going to have to get into this thing and I'm going to have to practice handling and access to the different parts and how to keep them insulated before i contemplate the first big cook-up. I'm going to have to practice on bits of scrap too.

I've also now marked the wrapper length to trim back..leaving a little for final tidying up later. i also bought a new hacksaw frame thats nice and rigid and I'll be free cutting these.

[JasonBModerator @jasonb]

That bright a red does sound a bit hot, solder should have run by then. did your flux melt and flow like water after the initial bubbling up? What flux did you buy?

[pgk pgkParticipant @pgkpgk17461]

HT5 and I thought a good layer between the 2 bits of copper but to be honest i never saw it bubble/melt as such. I did wonder if the flame was blowing it away at the edges. I need to practice more. I couldn't run the flame from underneath as intended 'cos with the gas cannister upside down the flame size surged but with a poor low temp burn (liquid phase)

[JasonBModerator @jasonb]

"I did wonder if the flame was blowing it away at the edges"

Did you apply it as a powder? should be mixed with water to a paste.

Also when soldering two flat items together put a few punch marks in one as the burr around the punch mark will leave a small gap between the two

[julian atkinsParticipant @julianatkins58923]

Hi pgk pgk,

Exactly what grade of silver solder were you using for the above joint?

Cheers,

Julian

[pgk pgkParticipant @pgkpgk17461]

Yes it was mixed with water and i also warmed the rod and dipped it in powder. High temp solder.. can't remember the exact grade number.. but was the somethingC to 800C stuff

Its supposed to be dry for a few days here so I'll play some more (between farm chores)

[julian atkinsParticipant @julianatkins58923]

Hi pgk pgk,

I presume you are trying J&M silverflo 24 or cupalloys equivalent, which is only one of 2 grades ductile enough and suitable for boiler work in the UK (the other is silverflo 55).

Silverflo 24 has a melting range of 740 to 800 degrees C. It is not easy to use, and takes a bit of getting used to.

It requires a considerable amount of heat, and the heat really needs to be whacked up to a considerable degree, and as quick as possible. Use lots of Tenacity 4A or Thessco F flux or cupalloy's HT5 mixed to the consistency of melted ice cream, and you can let it dry out a bit after applying before lighting up, so that the flux doesnt run off where it wanted when the job is heated up.

The copper needs to be glowing bright red in my experience for Silverflo 24. Higher than the temperature colour than for annealing copper.

Silverflo 55 (or Easyflo 2 if you have any) is considerably easier to use. In fact it is a doddle compared to using Silverflo 24. Since the cadmium ban I have built 2 new boilers using Silverflo 24 on step silver soldering.

Cheers,

Julian

[julian atkinsParticipant @julianatkins58923]

Your throatplate and barrel joint should look something like the above when done with Silverflo 24.

Cheers,

Julian

[pgk pgkParticipant @pgkpgk17461]

When i did the annealing with the same can blowlamp I went through the silver to the stage where one ould chase the oxide film around with the flame with an undr colour of plum and it anneled nicely after that first poor attempt. For this solder try it was way way hotter than that ..as said bright satsuma orange but it did take a while and I'm guessing the flux either was hck enough or got used up/blown away. So I need soem more practice to get used to the changes and with my new bigger torches.

If you would like to move close to midwales you can give ne lessons in xchange for a bootful of leeks

[julian atkinsParticipant @julianatkins58923]

There is a problem with flux exhaustion if the job is not heated up and the silver soldering completed within a certain timescale.

I aim to get the job up to heat in no more than 10 minutes with propane, and the actual silver soldering a few minutes more.

The temperature required for Silverflo 24 can be a bit frightening. Do not attempt the whole boiler with it, silverflo 55 can be used for later joints. Do not use Silverflo 24 for the tubeplates or tubes.

Cheers,

Julian

[pgk pgkParticipant @pgkpgk17461]

Indeed. I've got 3 temp ranges to get used to.

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