First serious steam engine build.

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NP317
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Re: First serious steam engine build.

Post by NP317 »

zimerkin said:
"Also, silver solder seems to be much cheaper now and available in store."

That makes no sense with rising silver prices.
And that store better be a welding supply store or the solder will not be at least 45% silver bearing, the minimum appropriate for bonding steam pressure fittings.
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

So your inspector said that since it is not on rails he is not interested?

Ever hear about what happened in Medina?

Was not on rails...was still a very nasty boiler explosion.

I see where you are headed now.

Ever see the boiler in a Stanley steamer?
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zimirken
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Re: First serious steam engine build.

Post by zimirken »

"And that store better be a welding supply store or the solder will not be at least 45% silver bearing, the minimum appropriate for bonding steam pressure fittings."
I was actually going to ask, my local Menards sells both stay-silv 15 and stay-silv 45 now. It looks like there's only a difference in temp of about 100 degrees or so, but I take it you would recommend the 45 over the 15 then? After double checking, I guess the low price was a temporary sale and the normal price is in line with what I bought it for last time.

"Ever see the boiler in a Stanley steamer?"
Yeah, I'd love to have a Stanley if they didn't cost more than my house, they're my favorite of the old steam cars. Those aren't code because the shell wall is thin but wrapped with steel cable for strength. That's actually why wheeled vehicles are exempt from boiler codes in most states, because otherwise all the Stanley owners would have had to get new much heavier boilers. There's never been a stanley boiler failure besides tube blowouts, so the whole cable wrapping thing certainly works, kind of like steel braided plastic hoses.
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

the concept of a flash boiler like the stanley (along with it's heating system), could be a good guide for you.

25% silver is a minimum i ever use for any boiler work....and you need to be VERY CAREFUL with the OXY-ACET torch as it is VERY EASY to OVERHEAT the flux and / or silver solder, thereby making a mess that will not seal.

I do 90% of my heating with multiple large Sievert air / propane heads, then use the OXY ACET to just 'kick it up' to melting point in the area where I am working.
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zimirken
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Re: First serious steam engine build.

Post by zimirken »

The stanleys used vertical firetube boilers. The whites and dobles used monotube boilers.

If I wanted to attach copper to steel or steel to steel, should I still stick with silver solder, or can I use regular bronze brazing rods. I'd love to get a tig welder some day.

I ordered some 1/4in steel tubing because the price is comparable to copper tubing but there's less risk of it blowing out if it runs dry. Also I've read that it's less prone to kinking when bent. I plan on using flare connections as well, a good flaring tool is worth its weight in gold.

So I sketched up a quick model of what I'm planning on. It's all 1/4in steel tubing. My circulation pump uses a double acting cylinder, so I'll have two circuits: the water wall and the pancake coil. The water wall calculates out to being like 80 feet long with 2.6 square feet of surface area, but it's not going to be that long because I have to route the coils around the firebox door. Since it's a water wall, the surface area is effectively halved unless I space out the coils for airflow which I might do, that would also reduce the amount of tubing. The pancake coil is just under 50 feet for a total of about 1.7 square feet of surface area. Together this should put me somewhere between 3 and 5 square feet of surface area, which is right on target.

I'll have a steel plate on the top that has holes for threaded rods that all the tubing will be bound to, so that they are held in place against sagging, and I can lift the entire coil assembly up out of the firebox for servicing.
1.PNG
The water wall won't look exactly like this, as I need to make room for the firebox door. Also, I think I'll be spacing the coils out a bit to use more of the outer surface area. It will be held in shape by 6 sets of rods.
2.PNG
You can see how the pancake coil is arranged inside the top.
3.PNG
The yellow part is the top frame plate, with rods screwed or welded into it. The green part is a separate piece that is bolted to the plate. I'll make that out of a piece of 2.5in exhaust pipe, with welded rods to hold the pancake coil in place vertically. The rods coming off the top plate will hold the pancake coils in place horizontally.
4.PNG
Here you can see the two frame pieces by themselves.
5.PNG
This should give plenty of space for fire, and allow easy accessibility for repairs and modifications. It also won't cost an arm and a leg, as I can get 25 feet of 1/4in steel tubing for ~$15. Plus, since it's steel, I won't have to worry as much about it running dry if something happens to the circulation pump.
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

Do not do a boiler with brass rods.

You will not have to worry about running it dry if pump problems? Really?
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zimirken
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Re: First serious steam engine build.

Post by zimirken »

Nobody ever said anything about brass rods? Perhaps you mistook the yellow paint color for brass? Those are going to be steel rods, I just colored them yellow in the model to differential between the various parts of the framework.

Steel tubing has a lower risk of bursting than copper does with insufficient flow, yes. There are plenty of pictures and videos of solid fueled copper monotubes going pop, whereas steel ones are a bit more resilient.
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

I was referring to your comment about bronze brazing rods...which is a nono for boiler service.

As for boilers going pop...well...plenty of pictures of steel boilers exploding also because of <fill in the blanks>.

Best to keep head on straight and keep water in the boiler rather than designing for disaster.
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zimirken
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Re: First serious steam engine build.

Post by zimirken »

I managed to find 100 feet of 1/4in stainless steel tubing for $45, so that settled my debate between 1/4 and 3/8 for the water wall. Hopefully it arrives quickly, as I'm excited to start putting things together.

To pass the time, I made this sight glass that I'll put on the outlet of my circulation coils. It should give me a good look at what's happening inside the tubes. There's not much you can make for a boiler on a CNC. Turns out the glass I have fits perfectly in 3/8 sch 40 pipe, and three silicone o rings fit perfectly inside the cavity between the two threaded end parts of these particular couplers. After some teflon taping it holds pressure just fine. I even managed to cut the glass perfectly the first time. The secret was to use a well dressed grinding (not cutoff) wheel, and roll the glass against the corner of it.
20220706_073033.jpg
I had an idea for the steam drum. I think I might try and get a nice piece of 4-8 inch diameter pipe, and machine end caps held on with tie rods. I've seen a few boilers made this way in my research. It's easy enough to use the CNC to carve a circular slot for the pipe to go inside of, and then seal it with silicone. I can put all the NPT threaded holes I want in the caps wherever I want. If you take a compression fitting and drill the center out so the tubing can go through it, you can route the tubing so that it opens up where ever you want inside the boiler. I did this with good success in my current boiler, as there wasn't any other way to have a steam takeoff at the very top of the tank. I would really like to have it horizontal for aesthetic reasons, but if it has to be vertical that's ok. This method also makes boiler cleaning a breeze, which is good because my water at home has enough iron in it to forge a sword from an evaporated kiddie pool. It's super easy to calculate the tie rods and stresses too.
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

So...you need additional steam generating capacity...and you are going to use stainless steel tube?
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Andrew Pugh
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Re: First serious steam engine build.

Post by Andrew Pugh »

At some point increasing surface area will compensate for the lower thermal conductivity of the stainless; I wouldn’t hazard a guess as to how much more area would be required though. Would be an interesting CFD experiment…
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Bill Shields
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Re: First serious steam engine build.

Post by Bill Shields »

Since the difference in thermal conductivity is ~ 30...gonna take a lot of tubing to break even.
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