Boilers

[steamboatmodel]

Hi PDs,
Eddy was asking John about Boilers and John replied
"Hi Eddy,
With regards to making a boiler, I have built a few in my time, even gas fired ones using the same technology as they use nowadays, but to cut a long story short I don't fancy starting to make boilers again when there are perfectly good boilers to be had at very reasonable prices from the professionals. Besides the fact I have seen some boilers that people have tried to make in their garden sheds using small gas plumbers blowlamps, I am not saying that it can't be done, and again I have seen some great ones, but the thought of me giving free reign to someone to attempt to make a boiler to my specifications, I'm very sorry but NO, I just couldn't bear the thought if someone was injured. Leave it to the professionals. I saw a chap once pressure testing the thing he called a boiler, he had it weighted down with a brick in a bucket of water and it was directly connected to his compressor, he was standing over it to see if there were any bubbles, you couldn't see my a*** for dust. "

I agree with John I would be very hesitant about giving out designs, but if you wish to try Boilermaking you should start with a simple design. There are a number of Books I would recommend, Model Boilers & Boilermaking by K. N. Harris is number one, others are Simple Model Steam Engines Books 1 & 2 by Tubal Cain, Model Marine Steam By Stan Bray and Scale Model Ship Propulsion by Tom Gorman. There were a number of articles in Model Boats on Steam Engines and Boilers, two regulars were Peter Arnot and Basil Harley.
Regards,
Gerald  

[bogstandard]

Hi Gerald,
When I went on about boiler making to my design, it wasn't about trade secrets or anything like that. I was concerned about the safety aspect of it all.
The main problem with making boilers yourself is getting the silver solder to penetrate correctly, and all the way thru the joint.
You can get the solder to look great on the bit you see because you are putting heat into a localised area, it is what you can't see that is the problem.
Unless you can get a lot of heat into the boiler you just can't get the solder penetration that is required to make a perfect joint, and that was my main worry on the safety side. Looks like a good job on the outside but an accident waiting to happen from where you can't see it.
When I used to make boilers I would get the wife to do all the preheating for me with a big propane burner, and when it was up to the correct heat I would come in with a smaller localised  blowtorch and carry out the dastardly deeds with the silver solder. She would moan like hell about her arms aching, but a bit of a cuddle afterwards put her right, those days are long gone now, but I did get some nice boilers made.
Maybe we can get some input about this from a professional.

John

[BC Electric]

I seem to always be lurking here, so much good info on this site. This part about boilers is a problem for many live steam people. The real key to making safe boilers is two items, silver soldering and testing. I use Silver Solder that requires 1100 to 1300 F to melt, which means the boiler tube has got to be pre heated. This is done having it sit on fire bricks and pre heated in a oven to 600 degrees, then soldered using oxygen-propane torch. Having a degree in engineering does only one thing, taught me to be careful, the pre heating and welding is done at the University where I work, but do think a regular home oven could pre heat that high. Hydro test is done to 200 lbs, far above the normal 40 lbs they run at plus having safety valves set at 50 and then 60. Yes I use two safety valves set 10 lbs apart, just me, would prefer to much to not enough. The thing about safety valves is they have to be able to release more pressure than the boiler can build if the fire is full on. The second test done is with boiler complete, filled with water and heated to increase pressure to 120 lbs (without safety valves), this again is done in the pre heat oven so if something should give out, its contained.

I have to agree that unless you fully understand about getting proper penetration when welding, DON'T BUILD A BOILER. On the other hand, proper care, good understanding of welding and proper safe testing most people who build steam engines should be able to.

Now really I have seen pictures of some of Sandy's boilers, making one that is safe and works is one thing, making one that has that and looks like a work of art is something he has mastered.  I would love to have Sandy build one for me, just don't think the wife would allow me to second mortgage the house.

Now will go back to lurking, and thanks to the puddleducks for such a fine collection of info as this forum gives.