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My first steam boiler project

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Amber

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Discussion starter · #1 ·
This is the first time I've attempted to make a live steam boiler so this should be interesting. After all the reading I've been doing, I decided to try to build it using some of the methods that I've read about. This will be a vertical boiler using a piece of 2 inch type L copper pipe for the boiler shell and flue sheets. I cut the boiler shell piece off the pipe at about 8-1/2 inches and then cut another piece off the pipe about 2-1/4 inches long. I cut the short piece onso that I could roll it out flat and then annealed it with the propane torch using Mapp gas. It's much easier to bend after that. :)
I found that you can cut pretty thick copper sheet with heavy duty tin snips to rough in the outer corners of the circles for the tube sheets. I cut the circles away from the sheet with a coping saw, trimmed them as best I could with the tin snips, and then filed them to fit inside the pipe, with a slip fit.

http://www.flickr.com/photos/amber_darlene/6804821456/
 
Discussion starter · #2 ·
Last night I marked up and drilled the end pieces for the flue tubes, they're 1/4 inch copper tubing. I drilled 7 holes in the end pieces, I drilled them both at the same time so the holes would match. The holes aren't spaced as well as I would like them to be, but I was doing it just with a small ruler and a scratch awl. I probably should have drilled small pilot holes before drilling the 1/4 inch holes, I might have gotten a little better alignment that way. Next time...
I cut 7 flue tubes that are 7-3/8ths inches long, so that I'll get at least 7 inches of water and steam space inside the boiler.

http://flic.kr/p/bnjuto
 
Discussion starter · #3 ·
Here's the flue tubes test fit in the flue sheets.

http://flic.kr/p/bnjuBS

This is probably going to be a long project. I still have to buy the boiler fittings and bushings, and I need to go to the welding supply place and buy some silver braizing rod. I'm going to get the 15 percent rod, it melts at above 1100 degrees, so it should work. The main thing I'm wondering about at this point is should I put in more flues? I have room on the flue sheets for 6 more flues if I space them out between the holes that are already there. I don't know if I'll need any more than 7. I'm thinking about firing this with sterno until I come up with something else.
 
#6 ·
The flue placement also looks like it might be high and the top one may become exposed early in the run.

Disregard - as it's a vertical boiler - DUH!
 
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#7 ·
Amber,
As I have already suggested, I do wish that with all this work that you would follow a known boiler design so that you are assured success.
I know, you said that it is just a test of your ability in soldering and metalwork and that it doesn't matter!
Anyway, and this is for boilers for locomotives (horizontal) so may have no bearing on the matter, but JVR recommended that the flue tubes 'should' have an internal diameter of approximately 1/20 of their length, but the range of 1/15 to 1/30 can be accommodated by modifying the draughting.
So, 7.375" divided by 30 = .245", really only barely acceptable, depending on the vertical draughting.
Anyway, you seem to be enjoying the process, so we will see what happens.
All the best,
David Leech, Delta, Canada
 
#8 ·
My first vertical has 12 flues, 3/8" diameter, 5" long with a 2.5" diameter firebox. It drafts OK, but needs a little blower help. I could have packed 19 flues in, that would have helped a lot.
 
Discussion starter · #9 ·
Well, I have room for 6 more flues without much problem, maybe I should use 5/16 tubing for those? I was wondering if the 1/4 inch ones were big enough. I suppose I could cut another pair of flue sheets and use 5/16ths flues instead of 1/4 inch ones. My concern is that the more flue put in the boiler, the less water capacity the boiler has. I suppose there's a balance there somewhere.
Maybe I'll save the flue sheets and 1/4 inch flues for a shorter boiler, see if that works.
I plan on using pipe fittings for the fire box and the top where the stack goes. A straight coupling should work for the fire box, this one will be dry, no "water legs". I should be able to find a 2 inch to smaller reducer fitting to use as the smokebox. I'm not sure how much to reduce it for the stack, I don't want to restrict the air flow for the flues.
 
#10 ·
Amber,
the problem is that you can't scale nature. Steam is in relation more viscous in a model boiler compared to a 1:1 one. This means the tube diameters have to be larger than scale. Also at a given pressure difference the flow rate is roughly proportional to R^4, so a tube with twice the diameter carries 16 times (!) the flow of the smaller tube. This is also one of the reasons, all tubes should have the same diameter, otherwise the smaller ones get starved. A few large ones are better than many small ones (at least for our models). You are right, there is a tradeoff between heating surface and water capacity.
Regards
 
#11 ·
I have built a couple of vertical boilers, and think your width to height proportion seems incorrect, your boiler design is too high for the width.

If you look at the popular midwest boiler it is a bit wider that 2" and not much taller than 3 " not including the firebox. The midwest is a simple center flue design and works well. The Mark IV kit has the modeler solder the boiler together.
PMR Research also makes a nice vertical boiler kit, which has multiple fire tubes. If you silver solder both of these boilers they will be robust and good steamers.

One of my scratch built boilers is a proportially enlarged version of the Midwest boiler with a single center flue, I used 4.5 inch copper pipe for the main tube, it steams well and powers my large steam boat.

Steve
 
#13 ·
Enlarge the holes you already have and put in at least 3/8" flues, I would say. Are you going to use sterno for fuel? You will have to experiment with how much air to let in the bottom of the fire box. It looks like you have plenty of water and steam space to me.
 
Discussion starter · #16 ·
I think buying a Challenger would be quite financially challenging for me. :)
I think plan "B" is in order. using the 1 in 20 rule for flue diameter, a 5 inch flue would be about max for 1/4 inch tubes, so I think I'll shorten the boiler water/steam space to 5 inches. The proportions will look better anyway, for a vertical boiler. I don't think there's enough space between the flue holes in the end plates to make them bigger without them being too close together. I'll save making another set of flue plates for the next boiler. I know where I can get my hands on some 3 inch copper pipe, so that may be the next project.
Another thing I've been thinking about is making a boiler from 2 pieces of the 2 inch pipe cut open long ways to make the 2 halves of a larger diameter boiler. I could rivet the 2 halves together with copper rivets and then solder the seams with plumbing solder to seal them. The outer boiler temp shouldn't get hot enough to affect the solder as long as I keep the steam pressure at a reasonable amount.
My problem is that I have more ideas than time to do them. :)
 
#17 ·
Amber, if you are considering cutting up two pieces of pipe to make a larger dimension you may want to go through Erics thread on his coal fired ruby project. I believe he just made his boiler from a sheet of brass that he formed over a wooden rod the correct diameter. I'm not sure, but it seems simpler than cutting up two pipes and making them fit since you'll still need to form the ends to meet at the diameter you want. But that's my inexperience take on it.
 
Discussion starter · #19 ·
I think Eric made his boiler from a piece of pipe that he cut lengthwise to make the diameter smaller to make it closer to scale, but I could be wrong on that. Semper, from the reading that I've been doing, the rivet and solder method was what the old timers used to do regularly when making boilers. The rivets hold the boiler together, and the solder just seals the seam against leaks. Of course, I'd use silver bearing plumbing solder for that, it melts at 420-450 degrees, a lot higher than normal solder. Certainly not high temp enough for a firebox, but that's a different thing.
 
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