Small "Mill Engine Plant" (Display)

[DeereGuy]

Awh, your write ups are always such a great read Peter.  I will be looking for the silver solder paste locally next week.  It certainly works well for you and your parts came out great.  Can't wait to see this project ready to go.

[klank]

Thanks Bob,
If you are thinking of taking the plunge to have a go at a boiler - silver solder paste is (obviously) not the right medium for its construction.
Paste is ok for small delicate joints/fittings and having a "quick go with" - using a fine jet on your propane torch.
For major boiler joints, look (also) for silver solder rod (1.5mm/3mm dia) and "wire" - 0.75MM dia.
Over here its branded as "EasyFlo" No.2 - melting point about 610 dgrees C. (There are higher melting point solders available in a range).
With this you will also need bigger torch jets, the appropriate flux (powder or paste), and some type of dilute acid solution for "pickling" the work afterwards (to remove all the flux residue) - citric acid, old diluted battery acid etc. - should be lots of references to this elsewhere.
In most types of silver soldering - you are heating up the metal around the joint to be made so that the solder melts by the heat in the metal and flows into the joint, not playing the flame on the joint directly. More metal to heat (bigger heat sink) = bigger flame. Even on my small boiler, it took quite a big flame for quite a long time to get the boiler barrel/end plate joints up to flying speed if you see what I mean.
All a bit obvious, but hope this helps.
I am sure the MM collective brains/experience here can provide lots more tips on Silver soldering if necessary.

Peter

[Stilldrillin]

Hi David
I sourced my paste from CupAlloys :- http://www.cupalloys.co.uk/ (usual disclaimer).

Thanks Peter......

They`re just t`other side of town to me! 

David D

[DeereGuy]

Noted Peter and thanks. 

[bogstandard]

Lads, you have to be very careful when buying silver solder paste, it has a very short shelf life, sometimes as little as 6 months, depending on the grade, and there is no rescue procedure, once the time is up, the whole lot becomes no good.

It is very good if you have a use for it all in the short term, but if you are only going to use a little bit every now and again, it can get very expensive. If you do buy some, check the dates very carefully, and make sure you only buy very fresh stock.

I used to nearly cry, when in industry, when we found our 1000 squid a tub had gone out of date, and it was only good enough to throw in the bin. I even brought some home to try out, and a couple of months out of date and it was useless.

Bogs

[Stilldrillin]

Lads, you have to be very careful when buying silver solder paste, it has a very short shelf life, sometimes as little as 6 months, depending on the grade, and there is no rescue procedure, once the time is up, the whole lot becomes no good.

It is very good if you have a use for it all in the short term, but if you are only going to use a little bit every now and again, it can get very expensive. If you do buy some, check the dates very carefully, and make sure you only buy very fresh stock.

I used to nearly cry, when in industry, when we found our 1000 squid a tub had gone out of date, and it was only good enough to throw in the bin. I even brought some home to try out, and a couple of months out of date and it was useless.

Bogs

Thanks John,

Not much good for me then........ 

David D

[klank]

Thanks for the warning Bogs - you got me worried with that timely warning.
As there was no "use-by" date on the goop I bought, I telephoned the manufacturer (Cup Alloys) to find out what the shelf life of it might be. I have bought a small syringe of the stuff, containing 10g of 842 paste, which (I quote!!) "is a mixture of powdered 42% silver, cadmium bearing alloy, with EF flux and held together in suspension by an organic binder." !!! Cost £8. (It looks like brown sticky toffee pudding!)
The syringe has a metal  push-in plug-cap in its nozzle.
I was told by Cup Alloys that provided the plug-cap was kept in the nozzle (to keep the air out of contact with the goo), the syringe contents should last for a long time. They have a demo syringe they take to exhibitions, which has been capped but used at all of them - lasted 18months so far and still going strong. Keep the cap in and you should be ok for at least that time was their advice.
If you have it in a tub though (like your example Bogs), then its lifespan may only be 6 months before it dries out, as air is always in contact with it.
I think my litttle syringe of the stuff should be ok for a while, and at £8 - provided I keep the cap in the end - shouldn't owe me too much when it finally goes off, possibly in a couple of years or so. Despite the cost, I think its still worth having at this small 10g amount (ready fluxed), as it does do really neat small silver solder jobs. A metre of 0.7mm silver solder wire (from them) costs the same, and I'm pretty sure I would use that up in the same time span, and probably waste a bit of it.
I hope this helps.

Peter

[bogstandard]

Peter,

I wasn't trying to put people off at all, but just to be aware that it does have a limited lifespan.

You will find that certain retailers do give a warning about it's limited life.

I fact we didn't throw our tubs in the bin, but had the silver recycled from it by the people who recycled the gold off our scrap circuit boards, so all was not wasted, just about 80% of the cost.

Bogs

[klank]

Thanks John - you are right about the warning notice (or lack of!!) Certainly on this syringe there was no warning at all - not even "keep the cap on".
Those scrap - cost figures look dreadful - what a waste of resource!

Peter

[CrewCab]

Can I refer you gentlemen to "This" suggestion

I have a lot of respect for the guy who posted it & it sounds quite feasible but, .............  is there any real advantage over using a small piece of Silver Solder wire 

CC

[DeereGuy]

Thank's CC I do remember reading that now but forgot it....like I do most things now-adays..

[CrewCab]

I forgot it....like I do most things now-adays.. 

Don't worry Bob, we all seem to be wearing that "Tee Shirt" more and more these days as well 

CC

[bogstandard]

Dave,

I don't think it is a matter of advantage, but what suits the person using it.

If you are experienced in using flux and rod/wire, then no problems other than that of convenience.

But a few people do really suffer when it comes to silver soldering, I don't know why, because most of us don't, but for the few who do, then paste seems to be an ideal solution. I honestly think their major problem is taking advice about old wives tales about flux. Like the chap in your article who says he still uses plain borax, but then refers to Sif Bronze, which is a brazing flux not a silver soldering flux. Basic fluxes still contain borax, but a lot of differing additives nowadays make it a lot more potent and heat resistant.
So when it is mixed into a ready to use paste, it makes sure that the correct quantity and quality of flux in relation to the amount of silver solder is all there for the job to be done.

Paste really comes into it's own for automated processes. I used to service a machine that made around 1,500 perfect tiny silver soldered joints a day, and the two components when joined together only came out to about 12mm (1/2") long. To do that by hand, you would be very lucky to get 20% of that figure, and you would expect a fairly high failure rate as well.

Peter,

The recovery of the silver did give a reasonably good return for a recycled product. When you consider the paste only contained around 10% silver, the rest of the weight being made up of mixer metals and a carrier/flux.


John

[CrewCab]

Thanks for that John, 

I'd agree that in this day and age there have been advances in everything, including flux, so I'll be ordering some shortly, even for soft soldering, which I do a lot, I use a modern flux and failure is rare.

Cheers all 

CC

[klank]

Phew - I didn't realise silver soldering can be such an interesting and emotive topic!
I wonder, when TC, Stan Bray, Harold Hall, Elmer, and all the others wrote their so instructive books on engineering methods and practices for the beginner/modeller, if this (modern) type of solder paste were then freely and cheaply available to use, it may have become another recognised method of Silver soldering for the model engineer, next to tried and tested  silver rod/wire/flux. As Bogs said -used in the appropriate circumstances?
For small, delicate joints with no real gap filling, I like it. Quick to set the joint up, do not burn my fingers holding thin silver wire too close to red hot items, don't stick the end of it in my flesh when trying to bend the stuff into a little circle to fit round a joint - which always slides sideways when the flame blast gets close, don't get runs or waste too much of it, don't have to flux, and only pay £8 for the stuff - even if it lasts only 2 years in its syringe.

To continue with the project, I have completed the final component fabrication - a simple "Globe" valve (stop-cock) to go on the steam off take from the dome of the boiler. Silver soldering was necessary - see later!
I shall be using 4.7mm copper brake line for the main steam supply pipe (remarkably cheap to buy a coil on flea bay - it comes ready annealed!), so all internal holes are 3mm dia - as large as I can get without looking "over scale" - and trying to minimise internal back pressure in the steam passage from boiler to engine. The valve will be sited next to the dome, control handle sideways/outboard, inlet on the other side/inboard to dome off-take and outlet straight down (at right angles to the main body axis).

The results of my first effort of valve making went on the water tank stop valve - clunky looking plain hex stock body, with a naff control wheel - but its mine and may serve to show a youngster (assuming I get to display this affaire) that not everything you make has to be perfect and shiny when you are learning - fun comes first! (well its my excuse anyway).
A "Globe" valve body does look so much nicer and "fits the scene" well.
This time, I had previously come across a recipe to make a globe form tool (see earlier post and pic on this thread) and a (French I think) design for a simple right angle globe valve with easy to follow dimensions. I altered these a bit to suit the stocks of material I have to hand. The important item was the stainless steel rod for the spindle. All I have at present is some 5/32 rod - which is fine, but the only die I have for that size is a 5/32 X 40 (ME thread) - leaving aside metric variations. Since this is really an "on - off" valve, it shouldn't have such a fine thread - takes more turns to open it. However I have used it since I didn't fancy spending time turning small section stainless rod to a different diameter and then die thread the result.

I have taken too many pics. (probably) but it is my hope this may help any newbies reading this to see how simple the job really is.
My camera work using the "Macro" setting is b****y awful in parts - apologies - I was focusing too low - but hope the results give sufficient info.

The body is 1/2" hex bar. This is used 'cos its easy then to mark and drill the hole for where the soldered fitting will eventually go. The bar was drilled and tapped as appropriate, and the cross hole drilled.



The corners of the hex around te length to be "Globed" were then knocked off using my home made tipped tool - which will take the punishment of an interrupted cut.



I then used my globe form tool made from a bit of Austin A40 rear leaf spring - described earlier - in anger for the first time. I am dead chuffed with the result.
Here, the tool has just been withdrawn after forming the shape on the hex bar.



Then just clean up and chamfer the corners using an HSS form tool.



Then part off to overall length, reverse in the chuck (I had made a threaded brass fixture to hold the internally threaded end in the chuck), turn down and thread the other end, leaving a small hex next to the globe. The externally threaded end was deeply coned with a (Slocumb - lovely word) centre drill, ready to take the nipple when piping up later.



The threaded insert for the spindle was made from brass hex, drilled and internally screw threaded 5/32 X 40, turned and externally threaded to suit the body. The spindle had a 90 degree end machined on it by setting over the top slide to 45 degrees and gently using a very sharp fine tool. 90 degrees should give a fast opening action, albeit compromised somewhat by the "fine" thread - but needs must I suppose!
The shank then die threaded 5/32 X 40.



A gland nut was drilled, internally tapped and parted off from hex.

The side fitting (to be silver soldered in) was similarly made from brass hex, drilled, coned, externally threaded and left with a small thickness of hex to add symetry to the affaire when finished. A short length of brass (4mm dia) was left proud of the hex, as a locating peg in the hole in the body.
Here are the two parts. I had just "kissed" the side of the globe around the hole with an end mill, so as to give a "flat" face for the hex to sit on and more surface area for the solder paste to take to.


 
Here's the paste in its syringe next to the body sitting atop the side fixture.



I then simply anointed the mating surfaces and locating peg with the goo. Since the paste contains only 42% solder, and I am not certain as to its gap filling properties, I used quite a lot of the stuff. It's quick and easy to apply from the syringe, but I used a modellers micro spatula to compress it where it was needed (the mix contains Cadmium - nasty stuff to get in your system - don't get it on your fingers!)



Now if I had been using 0.7mm silver solder wire, the joint would be difficult to get at, fluxing needed, and I would have inevitably had "runs" trying to get into the joint with the wire tip when heating - notwithstanding using Tip-Ex fluid (or some such) as a barrier.
Here's how I set the thing up for just plain heating the paste.



Apply the torch flame around the joint (using a fine nozzle) for about 30 seconds, and job done with a nice silver collar around the inner joint - and absolutely no runs. Neato!! It took about two minutes to do start to finish. (My only caveat may be to see if the joint has properly "taken" when I steam it - but I am optimistic it shouldn't leak).
Here's the result immediately after taking the torch away.



Just a question of quick pickle, scrub down in washing up liquid/suds and gently polishing with a soft emery flexi pad and an ink-rubber disc in my mini drill.
I haven't yet decided on what type of control wheel - so many ideas - quite a few on MM. I don't think, though, I shall be filing a square end to the spindle shank. I'll probably turn it down and thread it.
Just the piping up to do now, and making a few threaded fixtures and coned nipples.
The display board will be painted/textured after a trial steam - when I expect every joint and gland nut and gasket on the engine to leak - such fun to look forward to, but thats what its about.
Be a while before I can give the results but I'll be back when I've fired it up for the first time.
In the meantime - best wishes to all who have taken the trouble to read this waffle and reply - much appreciated.

Peter

[rleete]

Nice writeup.  Thanks for taking the time and the pics.

[klank]

Thanks rleete, you are most welcome.

[Stilldrillin]

Peter,
Very nicely done, and shown...... 

David D

[bogstandard]

Klank,

You will find that 5/32" (4mm) and 1/8" (3.2mm) is available for use as brake lines, and is used more over here for steam lines than the 3/16" (4.7mm). The Americans tend to go for large pipework for some reason.

Unless the engine is rather large, say over 1.25" bore, then 5/32" is ideal, then for say 1/2" and below, 1/8" would become the normal piping to use.

It isn't just for show either, it has a lot to do with keeping the steam hot enough, as when you use too large a bore, the steam is expanding into it, and so losing heat and pressure, and then of course, efficiency. Seeing how steam engines are very inefficient anyway, it needs all the help it can get.

Bogs

[klank]

Thanksfor that Bogs - all new to me, but most useful and filed away - I clearly did not do enough research before doing the piping! As I said, I went for the bigger pipe to try and eliminate back pressure in the bends I shall have to make.
Anyway - I've bought the pipe now and will carry on with it (budget is very tight). I shall be running the steam line around the heated part of the boiler cabinet/burner to try and minimise heat loss and give its contents some form of drying (not really a superheater), so maybe that will help a bit.

Peter

[DeereGuy]

Peter very nice job once again on the write up.  You do a great job of explaining everything very clearly.  I have bookmarked this page for future reference.  You should be writing articles for a magazine....

[klank]

Thanks Bob - I am not sure how to respond to your very kind remarks without sounding callow.
 
I spent the last 35 years writing reports as an insurance company surveyor - from that experience I have found that there are times when you have to make the thing "interestingly readable" rather than just a load of mind numbingly boring stark facts.
In recent years, I once got ticked off by the underwriters for describing a building as "repellent in its ugliness" - better, I thought, than saying it was a "pile of badly assembled building materials in a random design"!
Prior to this was the time before the "Disclosure of Information" legislation came along. You could then couch the truth in all honesty - like "The policyholder appears to be as crooked as a dog's hind leg. Divest ourselves of this risk urgently". Technically that used to come under the heading of "Moral Hazard"!
Nowadays, this is not allowed.

I would love to write for Mad Magazine.

Peter

[Stilldrillin]

Peter,
Some people have developed a good way with words. 

Others have spent a working lifetime muttering at machinery........ 

David D

[klank]

Ha Ha .
If in doubt, club it to shape, then debur and remove all sharp edges.

[klank]

On the home stretch.

The piping and associated fittings were made from the copper brake - line and brass hex. Economic circumstances dictated that I had to go with what raw materials I have - even though it might be better to follow Bogs advice on smaller size pipe diameter. Anyway - I thought it might be interesting to see how the boiler steamed and the engine ran by using this larger pipe, with a modest steam dryer (not a superheater) to help improve some possible lost efficiency.
The dryer is simply a question of running the steam outlet from the globe valve back into the boiler cabinet via one of the portholes and directing it three times (in a sort of loop) up and down the length of the hottest part of the interior (between the water tubes) and over the burner and then down and out of the bottom of the cabinet by the burner, and back up to the engine/lubricator on the steam chest.
After some further thought, I felt that using the copper brake line (all I really had in stock) would be a good choice, if, for no other reason, that it is of much thicker gauge than the pipe Bogs suggested - it shouldn't come to much harm when sitting over the burner when lit.
It took an awful lot of continual re-annealing to get the pipe properly bent to where I wanted it - quite thick material!

Here is the dryer sitting amongst the entrails of the boiler and above the burner, inside the cabinet.



The water inlet pipe to the clack valve was coupled up underneath the board - within the "well" formed by raising the base on its outside walls.
The blowdown pipe was bent to shape and fiddled into place, emerging from the front of the board. I found it easier to make up the pipe runs first by using copper wire as a sort of template, and cutting/bending the copper pipe to match.
The engine exhaust was a simple right angle bent length of copper tubing to the front wall of the board.
The drain cocks were coupled to a short length of 1/4" copper pipe (off cuts left over from the water tubes), and brake pipe soldered into those and ducted out through the front wall.
The outlets were angled downward slightly and cut off. A piece of aluminium right angle strip acting as a sort of shield. (The top edge is horizontal, somehow the re-sizing of the photo makes it look "skewed"!) This is only a temporary measure - the exhausts etc. being fired down towards a bucket positioned below the bench for the time being whilst the plant is tried out. I appreciate this is a bit crude, but when materials come to hand, a proper sump/container will be fabricated.



The steam pipes have been lagged with string and wound in PTFE (plumber's) tape.





(I did remove the hanging whisker of tape, stuck to the lower water gauge fitting, near the fire-hole door - I understand that flame and PTFE tape leads to a very nasty acidic vapour! )

And here is an overall view of the complete outfit.



The original Stuart engine was made according to the recipe with a brass piston, in which I had grooved a single piston ring - using wound PTFE tape. This seemed to worke well when I ran it originally on compressed air.
I dis-assembled the cylinder from the trunk guide to properly pack the piston rod gland with graphited yarn and felt that the piston/rod screwed connection was not all it could be (made when I was still very much learning how to use my first lathe) so i decided to make a new piston/rod before re-assembly. I happened to have blagged a length of gun-metal rod of just the right diameter from another source, and decided to make one from this, cut with three oil grooves instead of a PTFE or graphited string piston ring plus a new stainless steel rod.
That done, I re-assembled the engine, re-packed the valve rod gland, re-timed it and ran it in very slowly on the lathe for a while, with plenty of oil.

I was then running out of excuses not to fire her up and see what happened.

The cat's entrails looked good, and the moon was in the seventh house, so I half filled the boiler and water tank, charged the burner tank with lighter gas, filled the lubricator with steam oil, opened the steam cocks, shut the valves and lit up the burner to a very low blue flame with the ceramic starting to glow nicely. Rotating the flywheel a few times showed no sticking in the engine.
The water bobbed up and down in the gauge glass, and then several drips started appearing from a few unions, but nothing daunted I carried on. When the pressure gauge needle started to move off the bottom pin, I opened the globe valve to allow wet steam into the dryer. No signs of leakage around the lubricator union, and so with the safety valve starting to fizz at 25p.s.i. I cracked the engine/lubricator valve open. Immediately I did this, the flywheel jerked round with a violent hissing and spluttering from the drain cock outlets. I rotated the flywheel a few turns and shut the cocks, and she sprang into life. Opening the engine valve further caused the engine to rapidly pick up speed, but the steam pressure seemed to remain constant. Then things got a bit more exciting as leaks rapidly appeared in the valve chest cover plate, the cylinder front cover and the union between the pressure gauge and the syphon, plus several pipe fittings. None of the glands appeared to leak luckily. Watching all these leaks, running the hand pump to maintain boiler water level and reduce the burner flame whilst disregarding my wet trousers became a most interesting period.
Fortunately, by that stage, the burner had consumed most of the gas in the tank and the flame died down without me having to shut it off.
I lifted the safety valve stem to release most of the pressure and then blew the remaining boiler contents down into the bucket.

That was overall a great experience.

I am sure those of you who read this and operate steam, must have had a similar memorable time on your first (semi) successful run. It sure beats the hell out of running on compressed air, and you get the advantage of a luvverly smell (hot oil and steam).

If it is of further interest to anyone, I will try and get a short movie using my little camera of the plant running after I have fixed a few leaks.

Thanks to all who have encouraged and offered advice - I am sure I have made some mistakes here, the overall result is not all that blingy, and certain circumstances have not allowed me to do all I wanted. However, I have enjoyed the build and got the pleasure I really wanted from seeing the little engine run as a first build, under steam from a home made boiler.

For those who maybe think about steam running rather than just compressed air - do give it a go - its messy, but well worth it.

Peter