All- Copper Boiler Build

[sunworksco]

I'm building a boiler from David Phillip's drawings.
I'm building it with 12" OD x .405 Wall copper tubing and 3/8" thick copper plate for the top/bottom.
Can I hard solder the joints with Sil-Phos solder?
Thanks,
Giovanni

 

[Jasonb]

Its not allowed under the Australian boiler codes and not used here in the UK so best not to.

Jason

 

[sunworksco]

What can I get here in the USA?
Thanks,
Giovanni

 

[GWRdriver]

Giovanni,
The phos-coppers (Silphos, Phoson, etc) are intended for cold water joining of copper and have deficiencies such as embrittlement when used at elevated temperatures and are especially susceptible to decomposition in sulphurous atmospheres, such as coal smoke. For this reason they are either strongly not advised, or prohibited, for model copper boilers. The stuff to use is any 45% silver content silver-solder, whether cadmium bearing or non-cadmium bearing. I personally use only non-cadmium bearing (Harris Safety-Silv 45) but all US manufacturers make a 45% general purpose silver solder any one of which will do the job.

45% silver solder is carried in wire form (usually 1/16") by many welding supply houses and there are also on-line welding supply sorces which will have it. However, I STRONGLY recommend that you buy the solder for your boiler in rod (or stick) form for this job. I recommend 1/8" or thereabouts. The reason is the joints of a boiler of this size are going to drink up solder at a fairly high rate. For sound joints you need to be able to feed the joints all the solder they will drink while they are hot. You do not want to have to stop in mid-heat to search for more solder or to unroll a coil because you've run out of wire.

 

[sunworksco]

Are there any disadvantages to using copper to build my boiler?
Thanks,
Giovanni

 

[GWRdriver]

Giovanni,
If we assume for the moment that it will be built to a structurally sound and therefore safe design, there might be two. The first would be material cost. Copper of the size and weight you quote is incredibly expensive so in the size you quote steel would be the material chosen by most people on account of cost alone. However, if you somehow got the copper very cheaply or at no cost then that's not so much a factor. Also, if copper of far less thickness than you have or propose is used then one could add strength as a factor to be considered.

The second consideration would be your individual circumstances, your resources, abilities, and equipment. What you have and are capable of can tip the balance one way or another. For instance I am an abysmal welder but a very good silver-solderer so I build almost exclusively in copper in spite of rising material costs. Some people are very good welders, or have access to reasonably priced welding services, so it makes more sense for them to use steel. It takes a great deal of heat to solder the boiler you propose, so much so that it will be uncomfortable standing too near the boiler while it is up to full soldering heat, and most amatuers don't have the heating gear needed to do the job. The cost of acquiring such gear, and the likelihood of using it again, needs to be factored in the balance sheet.

 

[sunworksco]

Thanks Harry,
I am a pipe-fitter by trade, now for over 32 years.
I have assembled very large copper water lines and
have used a lot of hard solder and can fabricate the boiler.
I usually use two oxy/acetylene torches and four hands for anything over 6" diameter.
I have a metal spinner that does spinning for my business. He can spin a very decorative flue.
I want to use copper rivets, too.
I want to learn as much info as possible before I step up to the bench.
Thanks,
Giovanni

 

[Kmot]

I was considering using Sil-Phos also for a boiler I am going to make. Are there some documents online where I could read about it not being suitable for hot water and steam, and the scientific reasons why?

I have used Sil-Phos to hard solder exhaust systems for four stroke model aircraft engines and the exhaust gets rather hot and I have not noticed any failures in the joints.

Thanks.

 

[Kmot]

I did a little Google searching and came up with some information from a maker of Sil-Phos brazing rod and yes, it does mention that working in steam can accelerate the corrosion process.

 

[sunworksco]

The reason is that coal and wood create acid when burned and dissolves the Silphos solder.
I would think that it would be OK using propane/butane.
The corrosion happened on The Little Engines fireboxes due to a supposedly poor casting that was porous and may have put the burden of doubt on the Silphos.
Regards,
Giovanni

 

[sunworksco]

What is wrong using all copper for the boiler?
Regards,
Giovanni

 

[Jasonb]

Nothing wrong for your use, its really just a cost factor as said above. For something like a traction engine where the boiler is infact the chassis and stressed then steel is the better option in the larger sizes.

Copper also has the advantages of better heat conduction so more efficient use of fuel and is far longer lived as it will not waste like steel. As said above and also by me elsewhere steel with copper tubes is a good compromise.

Is your boiler design based on coal or gas firing, you do not get the radiant heat from gas that you would from coal in the firebox, it all comes from the tubes which may need re specing to get the most efficient heating. Also have you thought about the gas usage and the problems of pressure drop as the container cools trying to supply a substantial burner, you won't get a pair of 47kg propane bottles on your bike.

Jason

 

[sunworksco]

I am using propane.
Here is an image of a Polaris water boiler.
I am going to build the steam-bike boiler like this with an exhaust fan and the flue outlet on the bottom of the boiler.
Regards,
Giovanni

 

[Jasonb]

Thats going to be a big boiler to fit on a bike, if the boiler is 12" then it must be 15" over the insulation on clading which would gove a length of 36-42" ??? What amount of steam is it supposed to produce?

Jason

 

[sunworksco]

Take a look at the bike. It has a 16" OD x 12" height boiler.
Regards,
Giovanni

 

[GWRdriver]

I can't provide reference but in the last 30 years there has been a steam bicycle written up in either The Model Engineer or Live Steam magazines. The bike itself appeared to be a standard heavyweight contemporary one with the power unit built to straddle the rear wheel, the boiler hung off one side (left) and the engine and auxilliaries hung off the right side. The boiler is in vertical orientation and looks to be somewhere around 6" diam x 18" high. Unfortunately that's all the detail I can recall except that apparently it was succesfull and was ridden regularly.

 

[Kmot]

Quite an ambitious project, but it sure would be neat to have it!

 

[Dan Rowe]

Giovanni,

I had considered this at one point and for me speed was what I was looking for because I rode a Harely at the time. Highway type of speeds need good brakes so my plan was to start with a Harley frame so the brakes are standard parts.

The range of one of these could be extended by towing a 2 wheel tender for fuel and water.
So it would be a 1-1-0.

Dan

 

[itowbig]

Giovanni,

You have to be careful riding those steam bikes.
You don't want to be like that holiday tune "Chestnuts roasting on an open fire..........".

Pat J

HAHAHAHAHAHA THATS FUNNY HAHAHAHA i needed a laugh today and this is it thanks

 

[sunworksco]

You sooo funny, Pat!LOL!!!
I might have to buy some asbestos nickers!
I think that the boiler that I am planning will be more efficient with a blower and and bottom flue exhaust.
Thanks for the links!
Giovanni