Minnie Boiler under construction part 2

[Lindo]

Thought I would keep you posted with photo's of progress so far.

The holding fixture is doing a good job for me in part assembly and marking out.
The height vernier was made from an old digital vernier,cut off the jaws and fitted a new knife edge.
I decided to rough assemble the various pieces for fit check and secure with 10 BA screws and nuts.
Had to use a pair of forceps scrounged from my local vet to hold the nuts
when locating to the screws.
See photo of trimming the wrapper to final height,never enough clamps I find when machining copper and climb milling is preferable to me.

Now a question to the forum,and the experienced boiler builders. Is it feasible during final assembly of the pieces and fluxing for brazing to use 8 BA brass countersunk screws to replace the temporary 10 BA nuts and bolts and no riveting.
As the use rivets in this case according to the book are just a loose fit,I am thinking of drilling and tapping the temporary holes 8 BA, slightly countersink the wrapper for under the screw head,flux, assemble and braze.Afterwards file the heads flush to the boiler profile.
There should be no load to snap the screw heads off during brazing,
but also run a dab of braze around the screw heads for good measure.
This would help avoid some serious hard to get at riveting and the making of special snaps.
It's just a thought.
John

 

[Lindo]

For some reason my name Lindo gets translated to Cute automatically
by the computer,but not all the time.
Lindo in Spanish means just that.not sure if the moderators can fix this
problem.
Linda of course is the feminine alternate.
Sorry for that,but being born in England,and now an American citizen,I guess I have brought my family name back to it's origins.
John
Spain.

 

[Lindo]

Would you believe the original posting has now reverted back to Lindo.
How strange is that ?

John

 

[Jasonb]

You should be OK to use screws if soldered both sides and not pulled up too tight as you need a tiny gap for the solder to flow into the joint.
But DO NOT use brass, make some from bronze as you are unlikely to be able to buy them.

You don't actually need any special snaps for teh boiler, none of the heads on the inside are seen so you can just back up the rivit with a bit of bar as the dolly and all the outside heads are filed flush so can just be peined over with a hammer.

 

[GWRdriver]

Hello John,
I concur with Jason, do not use brass fasteners anywhere in a boiler. Much has been written about dezincification of brass when used in boilers so I won't go into it here. Bronze is the ticket, when screws are called for, but bronze screws have become difficult to find in sizes smaller than #8/US. For some years now (in addition to rivets) I have used short snippets of annealed copper wire to make headless "rivets" which serve as both rivets and locator or retaining pins for final assembly. The wire can be squashed with pliers (or tapped with a hammer) to expand them slightly. This dodge has worked very well for me over time.

 

[Lindo]

Jason/Harry

Many thanks for the information,you are correct in what you say.
Brass does have a tendency to de-zinc (gas off) and weaken in these circumstances.
Did not think of that.
I will go the rivet route, without to many problems.

Do you use distilled water with an additive to reduce calcium build up when
running your boilers?and drain out all the water left when the boiler has cooled down after use?
Thanks
John

 

[GWRdriver]

John,
I run both very small (Gauge1) and large-scale boilers and generally speaking everyone in Ga1 uses distilled water which in the very small volumes needed is easily captured or bought. The water in my area has a high lime and iron content so owners of larger scale boilers typically use tap water, or rain barrel water, and also use a boiler water treatment to inhibit the formation of lime scale.

 

[Lindo]

Well I am almost ready to start the brazing operation.
Thank you all for the advice on the use of brass by the way.
I have made the 2 inner pads for the motion plate and cylinder
(copper) and the pump / water gauge boss in bronze.
The copper plates of a thickness 2 x 13 gauge were initially hard soldered together,(the book mentions sweated together) and then roughly formed over a bar with a hammer.and then finally finished the profile on a lathe,sticking the pieces initially onto a bar with double sided tape and wrapping the outer 1/2 the width at a time with duct tape and then turning the radius to suit the inner barrel dia. Duct taping the finished half and removing the original tape
to expose the half to be machined.
The bronze pieces were stuck to a piece of MDF (the gorilla snot glue)
and with a boring head created the radii to suit the outer radius
of the barrel and wrapper plate.
Hope the pictures are of some use.
Hopefully this will be my last question in reference to boiler building.
The inner copper plates will be temporarily held in place by rivets after
fluxing,during the brazing I am sure the hard solder will melt before
the braze wants to "run".
It should not be a problem,I think with slippage of the parts as the rivets should hold the pieces in place,OK the question?
If the braze "Silver solder hits the hard plumbers solder will there be a problem of 2 dissimilar metals not forming a union together,or should I un sweat the
parts and silver solder them.
Hope this makes sense.
Thanks guys.
John

 

[Jasonb]

Not sure where you got the idea to soft (plumbers) solder two layers together.

You do not want plumbers solder anywhere near where you intend to silver solder. Also the pads only need to be one thickness of 13g plate. Also you don't want quite such a good fit of teh pads, the solder needs a thou or so to be able to flow, on large areas its quite common to add some punch marks to throw up a small burr which spaces the plates apart

Where Mason mentions soldering pieces together refers to the pump pad and the solder he specifies is "C4" which is a higher melting point silver solder than what will be used on the other parts of the boiler.

I'd make new cylinder and motion pads as by the time you have tried to file off all traces of the plumbers solder combined with having skimmed the top the plate will be getting a bit thick.

Can you post what solder/braze you are going to use on te boiler as I'm a bit worried about your use of the word Braze, don't want you using teh wrong stuff.

 

[Lindo]

Jason
Many thanks for stepping in and bailing me out.
I can put brakes and clutches on F1 cars (that was my job for many years)and even invented the carbon/carbon race clutch while I was working in the States,but boiler building as I have said in previous posts is alien to me.
I have Brazetec 5507 rods with flux and also a few lengths of rod pre-coated in flux which I have had for a few years and used for quite a few applications with success,including joining steel together.I cut up a standard carbide tipped lathe parting tool to make a 90 degree dog leg tool to machine the rear wheel flange recesses,it worked well,but I do not know the brand or part number.I just now it is strong with what it seems is
around 680 degrees C to liquefy the flux,then the rod just runs into the joint faces.Excellent for a part time solderer such as me.
In previous posts you know I get confused with sweat,solder,braze.

I will make up a couple more pieces of 13g copper for the internal pad problems,no sweat to save a (pun).
I could send all the boiler pieces out to be soldered? but that would be defeating the object.
Beginning to also realize,solder needs a gap to run into.I am making the parts possibly to exact,it's not as though Minnie will be at Silverstone and or Indianapolis 500.
Thanks again
John

 

[Jasonb]

Those rods should do fine google suggests they are to Ag155 standard

J

 

[Lindo]

Hello guys.
Just a few snaps of progress.
I gave up a BBQ pit for pre heating the shell for soldering and come up with a an idea of using the top plates off a gas cooker (stove) and it worked well.
Most Spanish homes out in the country have an outside kitchen,it's to hot to deal with preparing food most of the year.
The stove is quite well beaten up through age and usage.The photo's
were taken after the soldering and a good clean up was ordered from the wife,
it got quite messy.
Also I am using an old bathroom waste bin with internal bucket as my pickling
tub.
See photos of pieces waiting to be put together,I will ream
the holes for the tubes after soldering the firebox.
All seem's OK in the assembly and thanks for the advice now and the future.

John
Spain

 

[mikegw1961]

John and I have been discussing this week the positioning of the hornplate on the boiler. On the original drawings there is a dimension to show the position of the hornplate vertically but we cannot find the dimension horizontally. I had to use the models from the metric version to get the position but it must be on the original drawings somewhere.

 

[Jasonb]

The front edge of the hornplate should come level with the front edge of the wrapper. Boox explains the use of a template to make sure the holes in the hornplate match the stay positions.

If looking at the metric drawings don't fit the cylinder studs like he shows as you will never get the cylinder on.

J

 

[mikegw1961]

Jason

Thank you. I have read the book and studied the drawing. I am using the original drawings and the book for the build but the metric drawings are very useful as I have all the solid models and it can explain anything I am not sure about.. I am about to start on the boiler so John is much further along than me.

 

[Lindo]

Hi Jason and other forum members.
The boiler is almost done,stays not yet in place.
A quick pressure test at 10 PSI showed no leaks.Phew.
I had a Chinese foot pump with a pressure gauge that is +/- whatever.
I think i peaked to 15 PSI disconnected the tube of a car valve
adapted to fit the mud box outlet and it seemed to hold pressure over 1 hour,no bubbles under an immersion test.Again phew.
I did notice a slight swelling of the boiler plates inwards and wrapper plate outwards.The former plate (used for creating the back face) sorted out the boiler inside and a tap on the wrapper plate with a flat piece of wood sorted that bowing problem out.
Question,for you or others.
The throat and back plate for the fitting of the stays 6 per side not a problem,but would it be an overkill if the hornplate stays 9 each per side,the middle 3 stays be a continuous rod through the boiler space to prevent this bowing effect.
Still maintaining the brass and steel nuts as per the book page 31.
I read that a pump up in water be at 150 PSI.I understand the use of water for testing but PSI is PSI.
Thanks
John

 

[Lindo]

It's nice to have Mike W to communicate with as we are on the same
wavelength as regards the build and we share ideas frequently.
This is a excellent forum full of very knowledgeable people with the
been there and done that scenarios,and the faultless replies.
Many thanks to all and the past assistance.
John

 

[Jasonb]

The stays do go through the boiler (water) space and stop the wrapper bulging out by the equal force that is trying to bulge the sides of the firebox in towards the fire. No need to go from outside to outside right across the firebox if that is what you mean.

Pressure testing with water is far safer as if the boiler failed it will not expand (expload) much where as air at the same pressure being a gas will expand (expload) more violently.

 

[Lindo]

Jason
Thanks

John