Woes of the hard soldering.

[julian atkinsParticipant @julianatkins58923]

Hi Michael,

For silver soldering you need a minimum 2 thou gap and maximum 4 thou gap for the silver solder to penetrate. 'Push fits' indicate a complete mis-understanding of the basic requirements of silver soldering principles.

Apologies for being so blunt.

Cheers,

Julian

[MWParticipant @mw27036]

It's okay, i'm used to engineers

I'm afraid i must've missed that book.

Michael W

[JasonBModerator @jasonb]

Michael, have a read of Cup Alloys site about good practice.

As I said earlier, the end caps can be flanged and THEN TURNED TO FIT which should suit you and give control of the joint gap so that they sit correctly inside the tube.

Also have a search around the net for TC's Polly there have been loads made so you should be able to pic up some photos etc of how it should be done such as this . Also worth noting that the original design is quite old, things have moved on from rivited & caulked joints so the likes of SMEE who run courses on making this engine now use tube and silver soldered joints.

[Neil WyattModerator @neilwyatt]

Look on the bright side, plug the bottom and you have a nice Art Deco pen holder

It will remind you to take more care – like the pretzel-shaped flywheel on the back fop my workshop door.

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 28/06/2016 08:51:38:

Look on the bright side, plug the bottom and you have a nice Art Deco pen holder

.

Art Deco Baroque

… Or did you mean a nice holder for Art Deco pens

… or maybe 'a holder for a nice Art Deco pen'

etc. ad nauseam

MichaelG.

Edited By Michael Gilligan on 28/06/2016 10:39:57

[JasonBModerator @jasonb]

I think it's more Steampunk or Ratrod than Deco

[Neil WyattModerator @neilwyatt]

I didn't want to upset him further by saying 'Shabby Chic'.

Neil

[MWParticipant @mw27036]

If you really wanted to upset me you could say it's modern art. It's a metaphor for british politics.

Michael W – M.A fine art practitioner.

[roy entwistleParticipant @royentwistle24699]

If I can add a comment without upsetting you I would suggest that you need some practice ( or tuition ) in the art of silver soldering Soldering, silver soldering, and brazing seem to becoming a lost art these days It was something my dad taught me at an early age

Roy

[JasonBModerator @jasonb]

Michael, while waiting for your solder to arrive you could pass the time watching this series of four videos by Myfordboy where he shows the construction of a very similar boiler to the Polly.

You can see the endcaps being turned to final light push fit that I mentioned and also how the solder is drawn into the joint when the gap is right as per Julian's comments.

He does not say but you should be using a clean faced hammer not a dirty thing that also gets used for DIY

[MWParticipant @mw27036]

Thanks jason, some very interesting things i noticed, the first is that by the sound and look of the flame it looks like a propane burner? the flame from a butane/propane torch seems alot less aggressive (although the copper heated at about the same rate)

He annealed several times forming the copper and radius-ing the end cap, something i didn't take into account on my attempt. 2 bits of wood to keep the material clean, probably better than using steel shims.

Not a major thing but i noticed his lathe had what looked like a spindle clutch on the handle he keeps pulling to the right of the camera shot?

I did actually know about leaving a gap and soldering the joint, but he jumped onto my wording and implied i was therefore a poorly read serf. Theres something to be said for assuming and arrogance but i'm sure his sovereign grace has the finest engines, i should expect no less of his countenance.

Michael W

[JasonBModerator @jasonb]

Yes looks to be just Propane, its not so much the gas that matters but the size of the burner as the larger thay are the more kW they put out. (he has a big one)

The more you need to bend the more often you need to anneal, its not worth keeping beating away at a hard bit of copper as not only is it hard work you risk creases or cracks.

Sandwiching sheet material between two bits of wood stops it flexing about and makes cutting a lot easier as well a sprotecting teh surface.

Yes looks like a clutch, not sure I would want to keep reaching over the spinning chuck/work though.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 28/06/2016 20:08:01:

Yes looks like a clutch, not sure I would want to keep reaching over the spinning chuck/work though.

.

I believe Myford intended it to be a motor belt tensioner

Nicely illustrated on lathes.co.uk **LINK**

… But a clutch is still a clutch, by any other name.

MichaelG.

[MWParticipant @mw27036]

Hi,

I'm sorry it's been a while since i lasted updated this thread, progress had been slow getting the materials and some production work took precident for the past few days, more money to spend on my foolery that way!

I got a piece of 54mm plumbing pipe and cut and filed it to size, as machining a piece of tube to an accurate length seems nearly impossible without tearing or crushing the wall. I got on the lathe and machined the flange to size from 60mm, you may notice that i drafted away from the face so that theres less metal for the boiler to heat, I got a nice push fit on the flange, but i dont dare push it the whole way yet or i may never get it off again! I plan to silver solder the end caps after riveting them into place with small copper rivets. It was nice for the fixed steady to get some use.

So there you have it, thankyou for the encouragement to try again, i'm much more pleased with the result so far.

Michael W

[Jeff DaymanParticipant @jeffdayman43397]

Is that endcap brass or bronze?

If the fit is too snug from endcap to tube you will again have trouble silver soldering it. There has to be clearance for the silver solder to penetrate. Suggest you a)re-read the CuP Alloys guide b) follow a published boiler design c) use only bronze and copper in small boilers.

Don't become a statistic. JD

[Steven VineParticipant @stevenvine79904]

Posted by Jeff Dayman on 13/07/2016 18:49:48:

Is that endcap brass or bronze?

c) use only bronze and copper in small boilers.

To overcome the dezincification of the brass I have often wondered if 'wetting' the entire inside surface of the brass end plate, with a coat of silver solder, would afford sufficient protection from the chemicals in the boiling water. What does the team think about this idea?

I've read you can get tablets to slow down the dezincification process (for the boiler I mean).

Steve

[Brian JohnParticipant @brianjohn93961]

Michael : you can usually buy copper ends caps of the correct size to fit the copper tube. It leaves a nice edge where you can silver solder when pushed onto the tube. That is how I make my boilers.

[John OlsenParticipant @johnolsen79199]

Since Mamod have been known to make entire boilers of this general size and class from brass, I don't think it is going to be of great concern if the end caps for this one happen to be brass. It only needs to work at low pressures, so the temperatures are low and any dezincification will only occur very slowly.

There is a tendency for people to get over zealous with trying to apply rules that are appropriate in larger sizes to these small boilers. But the pressures and therefore the temperatures are much lower, and the volume of water is also much lower. The energy stored is very much dependent on both the volume of water and the pressure/temperature, the latter two of course being interdependent.

As far as the actual strength is concerned, if you use a small boiler like this with the usual style of methylated spirits burner, they are actually inherently safe, in that even if you plugged both the safety valve hole and the delivery pipe to the engine, there is no way that the burner could build up enough pressure to cause any sort of failure. Even with a propane burner, provided it is sized to suit, the boiler would not suffer any harm even if allowed to go dry. A reasonable size burner would not be able to put enough heat in to soften the joints or the material. This is quite different to the situation with larger boilers, where the heat of a normal fire is sufficient to soften crown sheet or furnace tube to the point of failure, should the water level drop too far.

John

[PeroParticipant @pero]

I hope I am not taking the thread too far off course here but can someone advise on how to get the required gap for silver brazing of boiler end plates?

I can readily measure the recommended 2 – 4 thou gap when cold (room temperature) but how do I translate this into a gap at brazing temperature? In the case of fitting a boiler end plate, will this become tighter or looser when heated and is there any empirical formula that I can apply?

I could do a test run or two but with the cost of copper I am hoping to avoid one potential source of error.

I haven't been able to find anything on this in my reading on brazing so am hoping someone can assist.

Thanks in advance

Pero

[Keith HaleParticipant @keithhale68713]

Hello Pero

Relax! The coefficients of copper and most common brasses are sufficiently similar as to ignore it. Set your gap up at 4 thou and you ill have no difficulties.

The differential only becomes significant with leaded free-machining brasses which expand 20% more than copper. You probably are not using these as the lead can make it a pig to braze.

As a direct result of your thread the Best Practice page on our website **LINK** is being amended to deal with this aspect. We thank you for the nudge!

As in all cases of difficulties when brazing, pick up the phone and call us. 01909 547248. Talk to us at exhibitions. There are over 100 years of brazing experience at your disposal, going back to 1969.

Understand and stick to the basic principles of the process, have confidence and you WILL be successful.

Regards

Keith

[MWParticipant @mw27036]

The reason i chose brass was because copper isn't typically supplied bigger than 2" in bar form, i could've gone with bronze, i'll admit to that but even bronzes have been known to corrode. The flange is fairly thick and i've already made a nice fillet all around the join and it feels very strong. Certainly more rigid than any sheet metal end, which this is made with.

Tubal Cain must've been totally oblivious to dezincification because he says if you don't have enough copper you can make the entire boiler from brass and the chimney is brass per the standard "polly" specifications. However, i still hold him in high regard when it comes to this and was certainly a great teacher, lived on in his books. I've even seen a 10" gauge steam engine with a brass boiler, whether i'd want to do that is another question.

Michael W

 

 

 

Edited By Michael Walters on 14/07/2016 10:58:04

[Ian S CParticipant @iansc]

I now make little boilers by flanging the ends so that thet fit inside the copper tube rather than the outside, I don't know if it's better or worse than fitting it over the outside of the tube, it just looks neater. The two far away boilers were made at a school night class, the far one by me, the middle one by one of the other class members, it didn't work, solder in the steam tube at the cylinder end, but no problem there, the boiler leaked like a sieve.

Ian S C

[JasonBModerator @jasonb]

Michael, take note of keiths comment about free cutting brass expanding I expect your sis a free cutting one like CZ121 and if it's tight already then will be even tighter when hot so no gap for the solder. Also watch that those riovits don't close up any gap once you have the fit right

Brass bar also contains more zinc than the softer brass sheet & tube so the effects of dezincification will be higher

[MWParticipant @mw27036]

Hi Ian,

I think it's really a matter of taste whether you want to join it in or out, presumably it takes a little more skill to solder it flush to the ends and clean it up.

The boilers all look quite nice regardless of the condition. Do you have to pay to get these night classes? i'd imagine the material cost isn't free. Certainly got alot more going on in Oz then they do in my town, local college probably has a nail art one i could do

Michael W

[MWParticipant @mw27036]

Jason,

It's probably the standard grade, i keep thinking of C101 but thats copper i think? the other end of the copper tube has warped slightly due to the tight fit i'm certainly happy with the soldering it's flowed well, despite being only 40% silver.

I decided against riveting it due to the tight fit it already had, was more of a backup plan if it was too loose.

What i'm really puzzled with is the end plate for the base, T.C says i need to tap 4 holes in the bottom of the cylinder, is this kosher considering it will be a breach? Ps. The chimney on the drawing goes all the way to the bottom, is this to isolate the water slightly from the steam that condenses on the chinmey or just a formality? 

Michael W

Edited By Michael Walters on 14/07/2016 11:56:32

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