# Coal-Fired Boiler Project



## Steve Shyvers (Jan 2, 2008)

Here's a few photos of a coal-fired boiler project for a Roundhouse Billy. It's taken me a long while to get started on this, but I've got high hopes that it'll get done. One cause of delay had been understanding how to configure properly a blast pipe. A recent parallel project to convert a Roundhouse Billy to alcohol firing provided the insight and confidence to go ahead with this one.

The first photo shows the setup to silver braze the flue tubes and firebox shell to the firebox tube plate. Those are firebricks. NEVER use regular bricks for silver brazing because of the high temperatures involved. Regular bricks can explode at these high temperatures.

The firebricks are stacked up to support the assembly and to shroud it to reduce heat loss. Firebricks will reflect heat, and they will glow red hot when the torch flame plays on them.

The ends of the flue tubes rest on a piece of ceramic insulating material, which keeps them from dropping out of the tube sheet as the copper heats up. The ceramic sheet also blocks the lower ends of the tubes to keep cool air from flowing up the tubes and cooling the area that's being brazed.

I use two torches. A propane torch (pointed right at the workpiece in the photo) heats the whole assembly, and a hand-held MAPP torch (the yellow gas bottle) provides heat right at the spot to be brazed. The "Contadina" tomato can keeps the MAPP bottle upright and in one place. The can is attached with screws to a board that's clamped to the workstand. The propane bottle is hose-clamped to a stand made from an old floor lamp with a heavy weighted base. With two torches going i don't want either one of them to come adrift.










The next photo shows the assembly after pickling.










The last photo is the throat plate that was formed out of 22-gauge copper sheet. This was my first attempt at riveting, and I've got a lot more to learn. I had to silver braze this in about five different sessions, with pickle and rinse between each, before I felt that the joint would be leak tight.










Next step is to fit the firebox outer shell, rivet it to the boiler shell and throat plate side flanges, and silver braze the riveted joint.

Steve


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## xo18thfa (Jan 2, 2008)

Steve: very nice work, especially flanging that throat plate. Boilermaking is a lot of fun, isn't it?

Looking forward to more, Bob


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## rbednarik (Jan 2, 2008)

Steve, 

You're off to a great start on your boiler. I like the hearth...couldn't do that outside over here now....too cold! If I can make it out to the NSS this year, I'd certainly like to have a look at it.


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## afinegan (Jan 2, 2008)

Steve, 
what reference material are you using to show you how to properly do all this. Or the gurus at a club/website are helping u out (I will be building something similar in the near future). 
I know people suggested a few books, just curious on what your using.


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## rkapuaala (Jan 3, 2008)

This is going to be a very interesting thread. I can not wait to read your next installment!


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## Guest (Nov 28, 2008)

For your boiler-building notebooks: 

100% of the joint/seam strength in a silver soldered copper model boiler is derived from the silver solder. The only mechanical fasteners (rivets, screws, etc) necessary are those which are needed to hold the boiler components together while assembling or silver soldering. 

A properly prepared and executed silver solder joint is stronger than the copper parent metal.


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## Steve Shyvers (Jan 2, 2008)

Andrew, 

Get a copy of K. N. Harris' "Model Boilers and Boiler Making". It has very complete design and construction info for copper boilers of this size. There's a LOT of design data and calculations but work through them to really understand what the constraints and requirements are for a safe and successful boiler. Harris has a lot of practical advice about the design and placement of the various boiler fittings as well. Several months ago Chris Scott posted in this forum the link to Henry Greenly's 1903 book "The Model Locomotive, Its Design and Construction", and it contains the same boiler design calculations as Harris. I wonder how long the same rules had been around before Greenly published them 105 years ago? 

Read every resource you can find and do some "google" research on the internet, especially for the smaller ride-on scales. Kozo Hiraoka's books and articles in Live Steam magazine are gold mines of tips and techniques. This forum has also had boiler fabrication postings with good photos that show how others have done things. Coal-firing has its own requirements (and problems) but all successful boilers for any fuel will share common features. 

For a long time before cutting any metal I pestered the experts about design details and design formulae. Shamelessly at steamups with flashlight and ruler I would measure fireboxes, grate areas, and flue tubes (diameter, length, and number of), and then head back to Harris' book to see if the numbers corresponded to his calculations. I must have "finalized" my own design about six different ways in the past few years. For excellent advice about silver brazing techniques I will credit a couple of generous experts in our hobby and the writings of Kozo Hiraoka. 

I'm no expert but will try to help as best I can. 

Steve


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## Steve Shyvers (Jan 2, 2008)

Curmudge, 

I concur with you about the rivets. The fit between the throatplate and boiler shell was not perfect, so I used 6 rivets to try to pull the mating surfaces together. Otherwise 2 or 3 rivets would have been sufficient to hold the throat plate in position. Next time I will spend another hour to make sure the fit is better. Then fewer rivets would be needed and the silver brazing operation should go a lot quicker too.


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## afinegan (Jan 2, 2008)

Thanks, I am doing the same on here, I think I asked the boiler making question about 6 times now . I belong to the tradewinds and atlantic railroad club (http://www.livesteamers.org), 7.5" and I am pulling info from the 7.5 gauge scale too. Eventually I will start to poke at it and finally build my first working version.


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## Guest (Nov 28, 2008)

Well we use the rivets and fasteners we think we need to get the job done. Many years ago my first boiler had a couple of hundred fasteners which I know now was for most part a complete waste of perfectly good rivets. 

Andrew, be careful what you try to adopt or are told to adapt from large scale practice. The "language" and techniques of live steam vary from gauge to gauge and what might be considered good or required practice in large scale might not suit the limitations and requirements of Ga1.


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## Steve Shyvers (Jan 2, 2008)

Progress update with two more photos: riveted and silver-brazed the firebox outer shell to the boiler shell and throatplate today. A couple of the rivets just didn't peen over and cinch up as expected, so it took a lot longer than planned. One of the rivets sort of skewed sideways and made the hole larger. Then even a new rivet wasn't held captive so it wouldn't peen over properly either. Finally I filed a tapered pin from a length of #10 copper wire and gently drove it into the hole. Peened it over just a little after silver brazing and left it at that. While wrestling with the rivets of course I kept mashing the throatplate out of shape. Fortunately the copper was annealed from the brazing heat, and I could reform the copper back into place. If I had taken time to set up a proper bucking iron and support for the boiler it probably would have gone better.
The good news is that the brazing was done in only three passes. Once for the external side of the joint, with the boiler vertical, and twice for the internal side of the joint - twice because the boiler was lying first on one side and then the other. Here are the photos: 


















I should mention that one "tool" that's been indispensible is a length of ABS pipe that fits snugly inside the boiler shell. I slip it inside the boiler shell whenever I have to cut, file, or drill. The copper is very soft after it's annealed by high brazing temperatures, and the plastic pipe keeps the copper shell from collapsing while it's being grasped or held down on a work surface. Without the plastic pipe "tool" I'd be working with an unevenly egg-shaped boiler at best. Needless to say I discovered the ABS pipe trick AFTER I had done some cutting and filing on the annealed boiler shell, followed by, "Son of a gun...what happened to the boiler?..."

That's it for now. Before I install the front tube sheet and fit the flue tubes and firebox I need to do some measuring and checking for the various fittings. I thnk I'd better drill all the holes before installing the the flues and firebox while I can still use that ABS pipe to support the boiler shell.

Steve


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## Guest (Dec 1, 2008)

Something that I find very handy for accident (and heartbreak)-free hole drilling in copper . . . a Unibit. I don't know how I got along without one. Since your copper appears to be a bit on the thinnish side, and the Unibit takes some extra pressure to start, I would spot bushing holes through with a conventional 1/8" drill bit first, then follow with the Unibit.


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## David BaileyK27 (Jan 2, 2008)

* Re holes in boiler shells, I always mark out and machine the holes with the copper in its "as drawn" state, it is much harder and easier to drill, for large holes I use " Q-max" cutters, * When riveting I anneal the rivets first, makes them easier to form.
David Bailey www.djbenginering.co.uk


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## Guest (Dec 1, 2008)

Re holes in boiler shells, . . . "Q-max" cutters

David, 
Over on this side of the pond those are known as "Greenlee" chassis punches. Very nice to have, hard to find used, very costly new. 
C


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## Shay Gear Head (Jan 3, 2008)

A quick search on the net turned up Newark electronics as carrying these hole punches.


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## Steve Shyvers (Jan 2, 2008)

Time for an update. Today I silver-brazed the front tube plate and flues in the boiler shell. Actual brazing step took about 10 minutes, but it took several hours of prep work to get to that step. 

Last weekend I started preparing by trimming the parts here and there and making things square. Then the various bushing locations had to be figured out and double-checked. Then I discovered that a couple of dimensions came out different than planned, so I had to rethink how the firebox would mount to the loco frame. By this time I knew that the brazing step would need to be postponed to this weekend.

"Thank you" to Curmudge for recommending the Unibit. I bought one last week, and used it today to bore the holes for the bushings. Worked like a charm. I've always dreaded boring large holes in thin copper with a standard twist drill. Never seems like it's under control and probably isn't, because the holes never seem to come out in the right places. With the Unibit I have seen the light.

Here's a couple of photos of today's work. As you can see the firebox will be deep. The top of the grate will fit against the lower edge of the firebox inner shell. A thin-gauge stainless extension will enclose the grate and lower part of the firebox, and the ashpan will attach to it. The lower edges of the firebox outer shell are planned to be level with the top of the Billy loco frame.

Next tasks are to fabricate the bushings, drill for the firebox and crownsheet stays, and fabricate a blower line to fit from the backhead through the boiler to the smokebox.



















Steve


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## Semper Vaporo (Jan 2, 2008)

Mighty fine looking boiler!







Good work and workmanship. 


(Please don't heat it with a propane torch like those fellas at Halley Base in Antartica!







)


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## Guest (Dec 14, 2008)

With the bushing holes drilled first you can turn the bushing spiggots to a press or tap fit in the holes and the bushings will be self-jiggiing while silver soldering. For anyone who is unfamiliar with the term "jigging", a jig is a construction tool, usually a machining or assembly aid or guide which holds parts or assemblies in place while another operation is taking place. In model engineering it is not uncommon to have to make jigs, and every once in a long while one needs to make a tool, to make a jig, to make the final part. ( . . . no one said it was going to be easy!)


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## Agra (Jan 15, 2008)

Steve, 
cool (and hopefully hot!) project. I'm currently collecting bits and pieces of copper for a boiler project for next year, somewhat along the lines of what you are building. It will be nice to see your finished boiler, and find out what you learned along the way. 

Thanks, 
André, 
Norway


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## xo18thfa (Jan 2, 2008)

Steve: Coming along great. Looks like the hard work is almost done. What silver solder are you using?

Bob


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## Steve Shyvers (Jan 2, 2008)

Bob, 

I think you are correct that the hard part is about done. With my increased confidence in what I'm doing, the remaining assembly steps don't appear to be that tough. The front tube sheet was a big hurdle because I felt that I had only one chance to get it right, because it would be a mess to try to rework. The hardest part, of course, was just getting started on the boiler in the first place. 

The brazing alloy is Silvaloy 45, which has cadmium in it. (45% silver, melting temperature 1125 degrees F, flow temperature 1145 degrees F) Diameter of material is 1/32 inch, which seems to deposit about the right amount of material in the seams. I am putting snippets of the material in almost continuous lines along each joint and a ring of material around each rivet head and flue tube end before heating up. That amount of material is filling the joint and leaving a nice fillet. Silvaloy 45 is recommended to be used for "close joint clearances" of 0.000 to 0.003 inches. 

Steve


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## Slipped Eccentric (Jan 2, 2008)

Looks good Steve, glad to see you got started on it.


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## rkapuaala (Jan 3, 2008)

Steve, 
Is this your first boiler? Because if it is, it is incredibly good.


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## Steve Shyvers (Jan 2, 2008)

Justin - Thanks. I have tried to apply some things I learned from your K-27 about flue tube positioning, but the small size of this boiler limits how much things can be moved around. As it is the firebox should be about 1.5 inches deep below the flues, so hopefully I can get a relatively deep fire without too much ash getting sucked into the flues. I squeezed in 7 flues in order to maximize the grate size. Still the grate size to flue area is higher than considered optimum (it's 8.6:1), but it's also close to that of a Barrett gauge-1 coal-fired Atlantic. We'll see what happens. 

Richard - This is my first attempt at a locomotive type boiler, and I'm learning as I'm going. Thank you for your nice comment. I've built a couple of soft-soldered Midwest boilers and done some silver-brazing of small things like burner wick tube assemblies, but this project is on a completely different scale. My hat is off to anyone who successfully completes building a gauge-1 locomotive-type boiler. Anyone who commits to and builds a run of identical boilers, such as for the Ruby and K-27 coal-firing conversions, is a genius, or saint, or just ornery. (I'm joking of course about the ornery part.) 

I'll post some more photos in a couple of days. The weather here has been too cold and wet to get much work done. (Garage is unheated and I do the brazing outside.) However I have fitted and brazed the firebox side stays, but not without a small scare. The chosen stay material is regular #10 bare copper electrical wire, which has about the same diameter as a #38 drill bit (0.1015 inches). However because the copper boiler is so soft from repeated heating, and because a hand-held drill will wobble a bit when going through thin metal, the first holes for stays came out about 0.010 inches larger in diameter than the wire. The #10 wire stays slid right through the holes. Fortunately I could rig up a way to brace the stays in place during brazing and also fortunately the silver brazing material filled the gap okay. Subsequent stay holes were drilled 3/32 inch (undersize), and then the #38 drill bit was chucked in a hand-held pin vise and used like a reamer to open the holes up to the correct size. Then the #10 wire stays fit just right. Next step is to fit and braze the crownsheet stays. 

You really have to take care when handling the annealed boiler. The copper is so soft that things can easily get bent and pushed out of alignment with just the normal bumps that happen when performing so many different operations on a workpiece. One thing I've got to do constantly is double-check all alignemts and fits before each brazing operation. Otherwise some subtle and overlooked handling damage could become permanent. I dread ever dropping the boiler on the floor. 

Steve


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## David BaileyK27 (Jan 2, 2008)

Steve, for your first boiler I think you are doing well, just a few tips, we only put 4 flues in our small boilers ( Billy, Lady Ann Edrig and Ruby) 3/8" OD and with a grate size of 2" long x 1.5" wide and a depth of fire 1.5" it works very well, we also use 3/32" copper rivets for the stays. 
A round top firebox will save you having to fit Crownstays, and I drill all the holes including the stay holes with before I assemble any parts, this makes it easier and simpler to de burr the holes, Keep it simple is my motto when boiler making. 
I shall be interested to see how it performs. 
You can see our Lady Ann and Billy conversions on our website at www.djbengineering.co.uk we shall be bringing out a simple 0.4.0 coal fired engine kit next year. 
David Bailey


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## Steve Shyvers (Jan 2, 2008)

David, 

Thank you for the info. If the 3/8 inch OD flues have an ID of 5/16 inch, then the flue area of my boiler's seven 1/4 inch ID tubes is only about 0.04 sq. inches more than the flue area of the four tubes in your small boilers. The grate area on my boiler is also about 3 sq inches, so the grate area to flue area ratios are very close too. This is very encouraging. 

Steve


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## Steve Shyvers (Jan 2, 2008)

Got the four crownsheet stays brazed on Christmas Eve. Also brazed on the steam turret, water gauge top bushing, and safety bushing. Brazing the crownsheet stays inside the firebox went easier than for the side stays, probably because access was more open. In a small firebox the side stays closest to the tube sheet are enclosed on three sides, and I think that the enclosed area tends to snuff the torch flame so that full combustion, and full temperature, is not achieved. 


Today I ground down the ends of the stays. I had planned to use a Dremel, but the bit would skip off the stay and score the firebox wall whenever I applied anough pressure to remove some metal. I gave up on the Dremel and used a coarse file instead, which worked okay. I did not try to file the stay ends down flush with the firebox surface in order to avoid scoring the firebox surfaces with extraneous file cuts.


I also started cutting and fitting the backhead today, and then I need to fabricate the blower nozzle and blower steam line, which will lead through the boiler steam space. I would like to get the backhead brazed on by New Years Day, after which the mudring will be the last major piece of the boiler that will need to be fitted and installed. 
Here's a couple of photos to show how the stays are configured. The bushing on the firebox side is for the water gauge, which was brazed on when I installed the side stays. The steam turret for the regulator is from the original Roundhose boiler for the Billy.


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## rkapuaala (Jan 3, 2008)

Looking good Steve, keep the images coming


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## Steve Shyvers (Jan 2, 2008)

The backhead is on, but not without learning a few things. One of which is that the firebricks get HOT when doing silver brazing, and then they can then burn you. 

Anyway, the backhead got attached in three brazing operations on January 1. It required three sessions (pickle and rinse between each) because I heated the silver brazing material sooner than the copper parts, and then it melted and didn't stay where it was supposed to. Something else learned: make sure when heating that you heat the workpiece first. It's got to be at the brazing material melting temperature when the brazing material itself melts. When doing electrical soldering the rule is to heat the components to be joined and then let the hot components melt the solder. Same rule applies to silver brazing really, except it's not so obvious when your gas torch is pouring heat like mad all over the workpiece and the brazing material at the same time.

Another thing learned was that a "scratch rod" will break the surface tension of the molten brazing material which helps it to start it flowing along the joint. Kozo Hiraoka mentioned the scratch rod in one of his Livesteam articles about building his New Shay, The tool is a pointed steel rod that's bent 90 degrees a half inch to an inch from the tip. The tool is dipped in flux before being applied to the work. I made mine from a piece of coat hanger and it works fine.

January 2 was cold and wet here, so no brazing was done. I faired the backhead piece to the firebox outer shell and made the parts for the blower line. The 1/8" copper tubing blower line runs through the boiler steam space, passes through the backhead, and terminates with a brass coupling that is NOT part of the boiler proper. In the smokebox the 1/8" line passes through the front tube sheet and then couples to a 3/32" copper tube to the 27-mil dia. SS capillary blower nozzle. I had brazed the blower nozzle to the 3/32" line a few days back.

Today was clear and sunny, but COLD with a slight wind. Started with brazing the blower line coupling to the 1/8" copper tubing. Then the blower line was threaded through the backhead, steam space, and front tube sheet. The boiler was positioned vertically with the backhead up, and the blower line and pressure gauge siphon were brazed on.

After pickling and a wash the boiler was inverted with the smoke box end up, and the 3/32" section of blower line was attached to the 1/8" blower line protruding through the tube sheet. (the 3/32" tube was sleeved inside the 1/8" tube for about an 1/8".) I used this brazing operation to install two more boiler bushings (filler and clack) because they were nearby, and also to improve the brazing around one of the flue tubes and along a short length of the joint between the boiler shell and tube sheet. (I didn't like the look of the original brazing and didn't want the leak test to convince me.) I made sure to heat the boiler shell slowly from the outside near the tube sheet and bushings, and brazing went well. I did have to heat it a second time (after pickle and wash) to improve the brazing around the filler bushing, but that went okay too.

Here's a photo showing the backhead:










And the boiler on the Billy chassis:








.

It pretty much fits as planned, and doesn't make Billy tail heavy at all. I feared that all the copper in the firebox would shift the balance point too far aft, but it seems okay even without the massive RH cylinders installed. Next step is to fabricate and install the mudring. Meanwhile I also need to start preparing the various plugs and fittings for the hydro test. 

Steve


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## Semper Vaporo (Jan 2, 2008)

NICE work!


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## Rob Meadows (Jan 6, 2008)

Steve, really enjoying your progress and can't waite to see the finished engine. I just have one wee question for you, where exactly do the Tea Bags go?
















Regards,

Rob


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## Steve Shyvers (Jan 2, 2008)

Rob, 

A design compromise forced me to eliminate the tea bag bushing. Have to make do with single-serving tea bags in the cup. Tetley's satisfactory? 

Steve


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## David BaileyK27 (Jan 2, 2008)

Steve, you are making a very good job on your boiler, you may be interested to know that we produce an Axle Pump for the Billy and Lady Ann chassis, a must for a coal fired engine, it is illustrated on our website. 
David Bailey www.djbengineering.co.uk


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## Steve Shyvers (Jan 2, 2008)

David,
Thank you for the advice about the axle pump. I saw the Billy and Lady Ann axle pump photos on your website, and wish I had known about them before. Figuring out how to make an axle pump was another long diversion before I could get down to the task of making the boiler. Definitely an axle pump is a requirement for a coal-fired boiler. Here's a photo of my "mark 1" axle pump mounted in the Billy frame. The scotch yoke rides against a "fence" on the eccentric to keep it vertical. The pump still needs to be plumbed up, of course, but tests showed that it did pump. The big constraint with my simple scotch-yoke design is the clearance between the bottom of the pump and the rails. Your pump design with its curved eccentric strap avoids this. 










Steve


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## Charles (Jan 2, 2008)

Steve
Really like your innovative way to make an axle pump, your build shows the progression that many live steam hobbyist venture through from RTR to build 'em


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## David BaileyK27 (Jan 2, 2008)

Steve, I also have a similar pump on one of my models, but the problem was getting enough throw and keeping it clear of the track, so I designed the pump as shown on our website, with this design you can keep the pump diameter down to 5/32" dia x 7/16" stroke, which reduces the amount of horsepower required to drive it, the larger the area of the pump ram the more energy it will consume to drive it. 
Our pump will cope well with the water requiements of our boiler design and can be left on for long peroids before it overcomes the boiler. 
David Bailey www.djbenginering.co.uk


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## Steve Shyvers (Jan 2, 2008)

The mud ring was installed yesterday. Won't say "done" until after the hydro test. I cut and fitted three pieces of 1/8" thick copper to make the mud ring. Each of the three pieces had to be shaped to fit around all the little corners and jogs that resulted from the imperfect fits of the firebox inner and outer shells, the throatplate, and the backhead. It took a lot longer than expected to fit these jigsaw puzzle pieces together. Even though I thought the fits were good and close, still the seams soaked up a lot of siilver brazing material before I thought the joints looked acceptable. Here's a photo.











I added two 0.100 inch stays for the throatplate, and used the mud ring brazing operation to braze those too. The smaller wires sticking out are to keep the mud ring pieces from falling out of position during brazing. I drilled 0.052 inch holes (#55 drill) through the throatplate and the firebox outer shell and into the mud ring pieces about 1/16 inch or so, and then inserted short pieces of 0.050 inch diameter pieces of copper wire. It seemed to work and avoided the complication of screws or rivets into the 1/8 inch thick mud ring pieces.

In order to drill the holes for the stays and mud ring wires so close to the boiler shell I had to make a special long pin vise that could be chucked in a hand drill. The hardware store provided a collet chuck made by Gyros Precision Tools, Inc. (part # 45-01819), that's sold as an accessory for Dremel type tools. The chuck has a 1/8 inch diameter shank and comes with two collets to handle #42 to #80 drill bits, although it held a #38 okay for me.

I made a handle from a steel hex-section standoff that had been liberated from an electronics chassis. The standoff had a 6-32 threaded hole on one end, and a short 6-32 threaded stud on the other end. I drilled the 6-32 hole out to 0.120 inch, turned the shank of the Gyros chuck down to about 0.121 inch, and press fit the two parts together. The resulting tool has a little bit of runout, but that doesn't really affect low speed or hand operations. The 6-32 stud provides a means of attaching another length of standoff if an extension is needed. In the next photo the 6-32 stud has been covered for protection by another short standoff that had been bored through and threaded 6-32.



















Today I took a break from silver brazing and started making fittings for all the boiler bushings for the hydro testing. Got four of them done and there's two to go. Then I need to convert a too-large axle pump that I bought several years ago to a hand pump. Need to do a decent job of that because it will undoubtedly become the tender hand pump. I'll post a photo of the fittings when I get them all made.

Steve


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## xo18thfa (Jan 2, 2008)

Steve: Very nice work, really first class. That is a lot of boiler, it will steam like crazy.

BTW, how is the Dunkirk doing?

Bob


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## Steve Shyvers (Jan 2, 2008)

Hi Bob, 

Thanks again for the kind words. The Dunkirk still runs well, although I'd like to reboiler it to get more steam capacity and longer duration. The Jane boiler that's on it is just not powerful enough. Got to keep a rein on my boiler building ambitions, though, and work on one at a time, because there's so much to be learned from each one. Maybe the Dunkirk will get shopped next winter, which will come soon enough. 

Steve


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## xo18thfa (Jan 2, 2008)

Hi Steve: A "T" boiler for the Dunkirk may be in order. Keep up the great work

Bob


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## Guest (Jan 19, 2009)

Bob,
You just made me reread the Dunkurk book and I did not find a mention of a T boiler version. Did I miss a refference somewhere?

Steve that looks good, I will be following your foot steps and building my first boiler soon.
Dan


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## Steve Shyvers (Jan 2, 2008)

Dan, 

I built a geared loco a while back that I called a Dunkirk/Climax because it was a hybrid and really not more one than the other. That said, any boiler would do, as long as it makes enough steam. Bob suggested a T-boiler. I've been thinking about an alcohol-fired boot boiler as something different. Won't be coal because the loco's whole structure is wood. 

Steve


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## Steve Shyvers (Jan 2, 2008)

Success! Hydro test passed at 120 psig! 
Took a while to get to it - had to make the fittings, assemble the hand pump, and - along the way - fix a few leaks! After silver brazing the mud ring back in January I made enough fittings to do a low pressure leak test with water and compressed air from a bicycle pump. This type of test at no more than 20 psi is recommended by Alec Farmer in his book "Model Locomotive Boilermaking" as a preliminary to a full hydro test. The boiler is partially filled with water and then pressurized with air. If there are leaks then they will be easy to see, and perhaps hear. 

Leaks I found. Three of them along about a 3/4 inch length of the joint between the backhead to the outer firebox shell. One was a pinhole that squirted a steady stream of water. The second was more of dribble, and the third was comparatively just seepage. I assumed that I missed seeing them during a visual inspection of the joint because after silver brazing the seam had been filed to fair the backhead to the firebox shell. The filing removed some silver solder, which might have opened up the holes, but the filing operation would then have jammed filings into the holes making them invisible. Pressurizing the boiler then blew the filings out of the holes.

To do a repair I first cut carefully along the section of seam with a 40 tooth/inch Zona saw to see if the seam would break through completely, which would have indicated a really porous joint. No additional holes or porosity were detected. Next I liberally fluxed the area, reheated, and applied more silver solder to the joint. I wasn't really happy with the results, but it was after dark on a Sunday evening by this time, so I chose to postpone additional work until the following weekend.

The next weekend I reheated the boiler to reflow the solder after applying flux to the area. Then fluxed and reheated it again after pickle, rinse, and another inspection with an eye loupe. A repeat of the low pressure test showed the leaks to be repaired, and, just as important, no new leaks had been created. Sorry there are no photos of these operations to show you, but my concentration through all this was on avoiding making matters worse. I was not eager to document a disaster of my own making!

Here's a photo of the hydro test setup. The hand pump, which uses a large axle pump bought a few years back, was submerged in a bread pan full of water for the test. It's really easy to build up pressure to 120 psig quickly, but I found that the check valve in the pump did not seal well at this pressure. As a consequence constant slow pumping was necessary to maintain 120 psi on the gauge, but if I did not watch the gauge as I pumped the pressure could build up to 160 psig within a couple of pump strokes.

The various plugs and fittings in the boiler bushings all weeped under pressure to varying degrees. This caused water to dribble on the outside of the boiler around the fittings so I was careful to mop up the water and to double check visually the brazed joints in those areas. The whole firebox and smokebox tube plate remained dry. (hooray!) Please note in the photo that special plugs had to be made for the steam pressure gauge siphon, regulator attachment stud, water gauge bushing, and (on other side of boiler) clack bushing. Two standard Roundhouse 5/16-32 threaded plugs with knurled caps were used for the top of the steam turret and the upper water gauge bushing, but these have o-ring seals which leaked at 120 psig. A lot of teflon tape was used to make them seal better. Next time I'll make some high-pressure plugs using gaskets.










After the 120 psig hydro test, I attached another pressure gauge to one of the boiler bushings to compare to the gauge shown in the photo. The second gauge is older and from a different manufacturer. I wanted to see how well the two gauges matched, because I had no way of calibrating either of them to a reference standard. They were within 2 lbs of each other from 20 through 120 psig.

Then I attached the steam gauge to its siphon, raised the pressure in increments to full scale on the steam gauge - 80 psi. Here's a comparison between the miniature steam gauge readings and the large gauge in the photo. Note that the miniature gauge starts reading significantly higher than actual above 60 psig, and reads low below 40.

Miniature gauge Large gauge
10 13
20 23
30 32
40 40
50 49
60 60
70 66
80 72

Steve


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## Semper Vaporo (Jan 2, 2008)

and a







!!!


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## xo18thfa (Jan 2, 2008)

Good show Steve. 2 thumbs up.

Bob


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## FH&PB (Jan 2, 2008)

Sweet! I love seeing what you're doing.


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## Steve Shyvers (Jan 2, 2008)

Charles, Bob, Vance, 

Many thanks for all the encouragement. This boiler fabrication thread is finished now. Next to be tackled on this project are all the boiler fittings, smokebox (blast pipe, petticoat, etc.), firebox (door, grate, ashpan, etc.), and of course finishing off the Roundhouse chassis running gear. I also need to work out the feed pump piping and bypass valve, so there's a bunch more head-scratching ahead of me. I plan to start new topics as I get these things far enough along to post photos and provide useful info. 

Regards, 
Steve


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## Old Boy (Feb 9, 2009)

Steve, 
Yes, very good work all around. I wish more US Ga1'ers were more interested in doing the job as well as this. The large, over-range, test gauge is also just as it should be. For general information, on my hydro test rig I made the boiler connection fitting with an integral relief valve which allows me to bleed away any air remaining in the top of the boiler or the pump lines, although practically speaking the bleeder can be anywhere on the boiler. I don't think 100% elimination of air is an absolute, and not always possible as bubbles here and there will often elude us, but I agree with the conventional wisdom which says it's best to get out all air possible.


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