Brit Progress: Boiler Cladding

[freddo1]

Err, you can hardly accuse the goodly Dr. of NOT showing how to make a toy loco in conditions far worse than most will encounter??

Obviously you've not looked at his own website in the "Simplex" area.

Good point about a giant sized battery though.

[Deleted]

Dec 3, 2010 10:13:50 GMT freddo1 said:

Good point about a giant sized battery though.

Yes, but Club members have been using this cladding for some years without problems, and if I adopt DJ's suggestion, I probably won't get any corrosion when it's in a glass case!
JB

[drjohn]

Dec 3, 2010 10:35:07 GMT simplyloco said:

Yes, but Club members have been using this cladding for some years without problems...

How old did you say you were ....? And you still believe in fairies?

Smacks of the mating cry in S.E.Asia "We've done it this way for 100 years therefore it must be correct!" Progress???

DJ

[Deleted]

Keep the pictures coming JB, I for one appreciate them.....:-)

Pete

[dickdastardly40]

Dec 3, 2010 9:10:33 GMT drjohn said:

Incidentally, with the aluminium cladding of your insulation against stainless steel and copper, when a bit of moisture gets in between, there will be a battery effect with resultant corrosion.

The galvanic series is fairly well accounted for in the presense of an electrolyte such as seawater:

www.corrosion-doctors.org/Definitions/galvanic-series.htm

As can be seen Aluminium is more anodic than stainless which in turn is more anodic than brass. The more anodic will tend to corrode quicker than it otherwise would on it's own.

On a ship we have anodes such as zincs which are even more anodic than aluminium and mounted purely to be sacrificial or we can use an impressed current cathodic protection system.

Where aluminium is mounted to steel outside where it isn't submerged but prone to salt spray, a gasket is or tef-gel is used to act as a barrier to prevent making a galvanic couple.

If you were are worried about dissimilar corrosion you could make a zinc sacrificial or use thin NAF to insulate between layers.

All the above is only theory as boiler water is usually slightly alkaline if not neutral therefore not as good an electrolyte as seawater.

I'd be interested to know if anybody else has ever taken measures to prevent galvanic corrosion or even experienced it in a model.

[Jim]

G'day Dickdastardly,
I have a steel Briggs boiler with copper tubes in my Burrell SCC Traction Engine and have no problems at all and I might add I don't expect to for the reasons you give.
As you say it's a different matter though on a boat especially operating in salt water and with the added problem of often badly earthed electrical circuits. Our son owned a Ship Chandlery and sacrificial annodes were a steadily moving item much to his delight.

Jim

[drjohn]

Dec 3, 2010 18:41:15 GMT dickdastardly40 said:

Dec 3, 2010 9:10:33 GMT drjohn said:

Incidentally, with the aluminium cladding of your insulation against stainless steel and copper, when a bit of moisture gets in between, there will be a battery effect with resultant corrosion.

The galvanic series is fairly well accounted for in the presense of an electrolyte such as seawater:

www.corrosion-doctors.org/Definitions/galvanic-series.htm

As can be seen Aluminium is more anodic than stainless which in turn is more anodic than brass. The more anodic will tend to corrode quicker than it otherwise would on it's own.

On a ship we have anodes such as zincs which are even more anodic than aluminium and mounted purely to be sacrificial or we can use an impressed current cathodic protection system.

Where aluminium is mounted to steel outside where it isn't submerged but prone to salt spray, a gasket is or tef-gel is used to act as a barrier to prevent making a galvanic couple.

If you were are worried about dissimilar corrosion you could make a zinc sacrificial or use thin NAF to insulate between layers.

All the above is only theory as boiler water is usually slightly alkaline if not neutral therefore not as good an electrolyte as seawater.

I'd be interested to know if anybody else has ever taken measures to prevent galvanic corrosion or even experienced it in a model.

Not sure where you get the idea that boiler water is alkaline, Dick - with the agricultural policies in the west, rainwater is actually quite acidic.

However, this is academic --- unless global warming increases the sea level to engulf Hamble and JB's glass case, I don't see it as a problem in his case - but I certainly wouldn't have aluminium cladding on my insulator for a regularly used steamer.

DJ

[digger]

The best cleading material in my opinion is hard rolled brass, thickening pads can be soldered on the inside for mounting handrail stanchions etc (tapping directly into the thickening pads) washout plugs can easily be soldered in place too.
I know the difficulty with brass, is paint adehsion, but using the correct etch primer, it will take a durable paint finish and should never corrode.
But then I am a traditionalist, all fastenings either ME threads or B.A sizes.

Digger

[Shawki Shlemon]

Steel cladding is OK , brass is better but not as good for painting , I have been using bronze sheet 0.6 mm thick for the last ten years , it is hard to roll and shape but it is better than brass for painting and certainly durable on all accounts . I know its expensive but I am not taking my money with me when I go to Heaven . ;D

[dickdastardly40]

Dec 4, 2010 10:32:57 GMT drjohn said:

Not sure where you get the idea that boiler water is alkaline, Dick - with the agricultural policies in the west, rainwater is actually quite acidic.

My bad, I was referring to boiler water control of larger boilers where daily samples were taken, the salinity not allowed to rise above 70ppm which was controlled by blowing down and the alkanity controlled carefully by addition of boiler compound to keep a ph of about 10.

[Smifffy]

Not sure where you get the idea that boiler water is alkaline, Dick - with the agricultural policies in the west, rainwater is actually quite acidic.

This one got me thinking, so I did a bit of research (i.e. typed a few keywords into Google - that apparently is research nowadays) and got the following from the July 2009 Drinking Water Insectorate Report for Thames Water (my local water co. and ex employer):

"pH (Hydrogen ion)

pH is a measure of the acidity of the water. Where water is supplied from upland areas the water naturally picks up iron and humic acids from the peaty soils, resulting in slightly acidic water with a low pH, which is commonly described as ‘soft water’. Such water has an increased potential to corrode iron pipes and leach material from cement-lined mains. Acidity can also be affected when water is artificially softened by a treatment device in a consumer’s property.

In the Thames region, out of a total of 11,323 tests, the specification was exceeded on three occasions in 2008. Thames Water reported pH out of specification in samples collected from consumers’ taps in April, June and August from different water quality zones. In each case the company investigation found that a reverse osmosis or water softening treatment device had been connected to the incoming mains water supply inside the premises. The householders were given advice about the need to retain a tap connected directly to the mains for drinking and cooking.

Specification:
pH (Hydrogen ion) 6.5 – 9.5"

So, if anything, going by the spec, drinking water is more inclined to be Alkali.

And apologies to John, for totally hijacking his thread.

Smifffy

[drjohn]

Dec 5, 2010 16:26:19 GMT Smifffy said:

So, if anything, going by the spec, drinking water is more inclined to be Alkali.

Only in the south of englandshire - in Scotland, (as you explained) the water is soft and acidic.

DJ

[Smifffy]

...and it carries across into the locals' humour :-)

[Deleted]

I was looking for rivet nuts on the net for attaching the wrappers to the firebox end plates, and 3mm appears to be the smallest available. However, I was looking for 10BA, so my own version was made and soldered into the back of the copper test piece shown on the left of the picture. I find making test pieces extremely useful. It seems to be quite strong enough and permits easy disassembly.

I also needed a couple of jigs for the smokebox rivetting and these were made out of 3/8" gauge plate: one for the double row at the back and one for the single front row. Wherever possible I make jigs that fit in the vice: freehand ones, especially for rivetting, often require the use of three hands....

The slot on the LH jig is bigger than its counterpart because I managed to knacker the 1mm slitting saw by running it in the Proxxon at its minimum speed of 600rpm, so had to finish it with a bigger one.

[Deleted]

Forgive me, but I don't know what these are for.... Stay heads? Washouts? ??


Some of us use the term 'To Productionise' and it is appropriate in this case, as some 20 are needed: six on each of the firebox sides, six on the backplate, and two spares!

Taking on DJ's comments about newbies, here is the production sequence for facing, drilling, boring, tapping, OD (two diameters) and parting off which gets the time down to about 75 seconds each using a lever action tailstock. If I had a power collet chuck and an automatic bar feed they would take a lot less!
This is not difficult: have a go!
JB

General setup using a purpose made parting/turning/facing tool. It is less than 1.5 mm wide, and is the only lathe tool used here. The recess is done with a D bit.
You can see the home made 4-way bed stop down on the left of the saddle which controls the relative positions of the tool.


Stop to pos 1. Turn OD to 6.75mm for 2mm
Stop to pos 2 to give the .5mm wide outer rim. Plunge and turn to 6.35mm - to fit the slightly out of round hole in the wrapper!



Drill for 10BA to take the dummy SQ nut. This will be put in when the wrapper has been painted.


Recess to take the dummy nut. D-Bit 5.8mm ID 1.3mm deep.



Tap 10BA - note the locknuts!



Piece parted off. It provides the machined face for the next one. The stop is turned to pos 4, the lightly held bar is pulled out against the tool edge, and the saddle moved to the left to put the bar in the right place. (A video would be useful here, and don't forget to tighten the chuck!)

[Deleted]

Nice work JB and great sequence photos... Loving it...

Pete

[Deleted]

Hi DJ

Well personally I don't see admiring work done by another model engineering enthusiast as polishing his or her ego. JB has put some interesting stuff on the forum which I for one find very informative as I'm sure others do to. I'm new here so do not know the guys who post here very well yet ,something I hope to change as time goes on. You say Shawki has built 14 loco's, I say that's fantastic and a sign of a very competent and experienced model engineer and I'd love to see his work.
One of the great things about forums like this is you get to meet people from all parts of life from across the world and you can learn from them, wether they have just started in this hobby or have been doing it for many years all contribute equally in my eyes, after all you can never be to old to learn.
I'm sorry to hear of your friend DJ , his Britania is truly beautiful and his personal problems in building such a wonderful locomotive just shows how determined and skilled an engineer that he truly was and I'm sure he had a great passion for his hobby too.
But you see that's what joins all of us here on this forum "passion" including you DJ I admire your work just as much as anyone else.
I noticed your comment on " leaving this boring forum" I hope you stay DJ as you have so much to offer and teach those who have less experience in this hobby, including me, hey I'm a newb here and will need all the help that I can get when I get further into my own build.
Now I think I've hijacked JB's thread long enough , I just felt I had to answer your comment DJ since it was directed at me, I say let JB continue his great thread in peace, it's informative, creative and skilful and it helps to teach us all how to tackle various jobs. We all have our own ways of doing things but that doesn't mean that someone else doesn't have a better way that we can learn from, the more threads like this the more we can all learn from.

From one enthusiast to all other enthusiasts.....:-)

Pete

[drjohn]

Apologies for my rudeness to all including JB and I have removed my last rudenesses. SOrry Pete - it makes your post a bit out on it's own.

[Deleted]

Dec 8, 2010 9:52:22 GMT drjohn said:

Apologies for my rudeness to all including JB

The good Doctor wasn't rude to anyone else, so no apology was needed in that regard.
JB
BTW, I'd still like to know what those side bits wot I just made are for!

[kwil]

Must be it is the heat out there, I would not like to be there, making a boiler by locally applying a gas torch of some sort.