Front End Rebuild

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Glenn Brooks
Posts: 2930
Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Front End Rebuild

Post by Glenn Brooks »

This winter I decided to try to improve my steaming capacity on my Ottaway, an old 1950 4-4-0 amusement park 12” gauge coal, 12” diameter boiler, coal fired locomotive. I finished my initial restoration two winters ago, and have been planing on upgrading the 63 year old plumbing in two stages, this winter and next.

Now I only have a small backyard track of 430’. After 2 seasons firing and operating the loco, finally decided the loco doesn’t generate sufficient steam around my small pike. So I decided this would be a good time to rebuild the front end and improve operating capacity.

Here’s what the smoke box design looks like:
C10F3D6E-EBC8-4E61-9575-E1F1E45CDC48.jpeg
The locomotive was rebuilt by an experienced NY area live steamer in 1957, and I suspect this present configuration was installed at that time. I believe he added the internal petticoat and twin exhaust nozzles, as these are not original to the Ottaway. The original Ottaway front end was a very crude affair and reported to be an indifferent steamer. So this existing design seems to be a significant improvement - given what was known about front end efficiency in 1957. The loco does fire up nicely, and does have generally good exhaust. However, it still lacks proper evaporation to maintain reasonably constant 140 PSI operating conditions on my small track: slow speed, moderate passenger loads, two sections requiring reduced throttle and drafting with each loop of the track. So I’ve finally concluded I need to further optimize the locomotive for these light duty conditions...which means improving front end design.

An inspection of the existing front end build shows a couple of design issues:

- twin exhaust blast nozzles are positioned high up into the petticoat- approx 2” from the top of the smokebox. Likely creating insufficient vacuum and draught of intake air across the grates and thru the flues.

- exhaust nozzles are positioned at the extreme rear of smoke stack- far out of line with centerline of the stack, causing further problems with draft.

- the stack exhibits noticeable negative draft around the starboard third of the stack exit- continually sucking air into the smoke box on each exhaust stroke.

- all plumbing is still serviceable black iron, but at end of life, as one can observe heavy surface pitting and 1/4 to 1/2 diameter corroded away in some places.

So, more good reasons to redesign and rebuild both intake and exhaust apparatus.

I’ve chosen Engineer Porta’s Lempor Evacuator System as the replacement. Here’s an example of a friends 4 port Lempor Nozzle assembly- on loan for design and discovery purposes. I plan to build my nozzle assembly in a similar fashion.

The first photo shows the complete nozzle assembly. The actual nozzle has four orifaces each having 78% surface area of a traditional single stack blast pipe. Combined oriface diameter of the four small jets in the Lempor nozzle is around 148% larger than the traditional single stack blast pipe found in the 1895 Master Mechanics front end design. The Lempor nozzle creates lower back pressure on the cylinders, resulting in increased horsepower, lower fuel consumption and importantly, significantly increased airflow across the grates, creating a consistently hotter flame and higher evaporation rate in the boiler. Basically, more steam and greater operating capacity. Which is Exactly what I hope to accomplish! :)
D0379060-54CE-4B7A-BB78-EFDCE4856894.jpeg
This second phot shows the plenum, with nozzle removed. The nozzle headed is threaded for easy removal and replacement.
F920DBA2-EEE1-4366-88E3-F06899FACA96.jpeg

Glenn
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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
Glenn Brooks
Posts: 2930
Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Re: Front End Rebuild

Post by Glenn Brooks »

Next up is to strip all the old plumbing out and rebuild with copper and bronze.
2C612714-BD5B-487B-915E-82EFDB2BC7D9.jpeg
Iam going to try to use flare fittings and copper tubing to plumb the throttle intake lines. Looks like bronze pipe and street elbows might align the blast nozzle with the stack. This will simplify and declutter the smoke box a lot.
0F408A7F-9A5A-4E37-B604-602B75092C4B.jpeg
Also had to cut the end off the throttle line leading out of the boiler, due to corrosion and reduction of the pipe OD. So it will be tricky to cut new threads with a die inside the smoke box shell. Can’t imagine why the boiler maker welded the throttle pipe to the front sheet of the boiler.
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
Mike Walsh
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Location: St. Louis, MO

Re: Front End Rebuild

Post by Mike Walsh »

Glenn Brooks wrote: Sat Dec 21, 2019 10:46 pm Can’t imagine why the boiler maker welded the throttle pipe to the front sheet of the boiler.
Cause folks don't think about the next person owning/working on the engine.

"Well, I can weld a nipple in place, just gotta drill it and lay a bead..."

vs

"I could weld in a female pipe coupling so i don't have to worry about trying to re-thread these.... But a pipe nipple is $1 and the coupling is $10.... guess I'll save $9!"

Ah, well.. so it goes.
FKreider
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Location: Massachusetts

Re: Front End Rebuild

Post by FKreider »

Nice work!
-Frank K.
Pontiacguy1
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Re: Front End Rebuild

Post by Pontiacguy1 »

Do yourself a favor and plumb up those lines and flare fittings using stainless steel tubing, especially if you are burning coal in it. It's a lot harder to bend and get in there correctly, but once it's in, I don't believe you'll ever have to replace it. You can buy 303 type stainless tubing from suppliers on the internet, and it is made in the same dimensions as the same size in copper.
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NP317
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Re: Front End Rebuild

Post by NP317 »

Glenn:
Source: onlinemetals.com in Seattle, just at the SE corner of the Ballard Bridge.
RussN
Glenn Brooks
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Location: Woodinville, Washington

Re: Front End Rebuild

Post by Glenn Brooks »

Thanks guys, I’ll go look for SS fittings on Monday.

This last week, installed a simple vacuum gauge system to measure possible improvements in draft in the front end.

The key to making this work was to turn down a bit of brass and thread the OD (1/2” x 20 fine thread OD) to screw the brass thru the outside of the smoke box shell. Then drill the brass thru and thru and thread both ends of the ID to accommodate a 1/8” NPT angled flare fitting, as shown in the third photo. The flare fitting is threaded into the ID of the brass and pointed towards the bottom of the smoke box to minimize soot intake. Also using a flare allows me to install a vacuum pick up tube extension to measure changes in the stack vacuum or position the intake at other possible locations inside the smoke box, if desired.

Turning and threading some 3/4” brass round stock into a smoke box fitting.
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The ID was then threaded to accept 1/8” NPT fittings on both ends,
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Commercial flare fitting attached to inside of the smoke box fitting
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Finally attached a small shut off valve and ran 1/8” copper tubing back to a low pressure vacuum gauge mounted in the cab.
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Previously I was able to measure 3/8” (water column) vacuum with a mamometer. So hoping to detect significant improvement in vacuum - and hopefully, greater draft- once the new exhaust system is installed and operational.

I plan on using this little vacuum system as a test bed for blast nozzle refinement to finalize oriface diameter, and latter when I convert the loco to propane. Also to get some sense about vacuum rates in general for small boilers under different operating conditions. There doesn’t seem to be much information generally available about front end performance in the smaller size locomotives. Iam hoping this will fill the gap a little bit.
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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
RET
Posts: 960
Joined: Wed Jun 07, 2006 8:36 am
Location: Toronto, Canada

Re: Front End Rebuild

Post by RET »

Hi Glenn,

The smoke box vacuum is going to be very low. To measure it, you probably need a vacuum gauge that measures 1" of water at full scale. The other thing you need to remember is that the smokebox vacuum won't be steady, but it will pulse with the exhaust.

When I went through this process with the Boston and Albany, I found it to be much more useful to think of the system in terms of momentum transfer at the different stages where you are trying to mix the high velocity exhaust from the blast nozzle with the contents of the smoke box at two different levels (that's where the secondary petticoat comes in). This is why having four separate nozzles helps because you can use that geometry to entrain the gas flow between the 4 separate nozzles and get more effective mixing of the blast with the smokebox contents with very little loss.

Make sure that everything is aligned on the same axis. As you found out, this was one of the problems you had with the old set up.

I also found that it helped if at several stages in this process, I went off in a corner and thought about what I was trying to do to make sure I wasn't missing anything. This step is very important. The end result with the Boston and Albany is a docile locomotive that anyone can run easily. A real "pussycat." You should be able to get the same result as I did.

Richard Trounce.
Glenn Brooks
Posts: 2930
Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Re: Front End Rebuild

Post by Glenn Brooks »

Hi Richard,

So far haven’t been able to find a pressure gauge that reads from 0-1”, or even 0-3” for that matter. I did order one that reads 1-15”. Below that they seem to be not common, or are very high end (expensive) for precision testing or laboratory work.

Did you use a VLP gauge on on our loco? I’d so, any leads where you acquired it?

Thanks
Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
RET
Posts: 960
Joined: Wed Jun 07, 2006 8:36 am
Location: Toronto, Canada

Re: Front End Rebuild

Post by RET »

Hi Glenn,

I didn't even try to measure the smokebox pressure because I didn't think it was going to help me do what I wanted and I was pretty sure it would take an inclined manometer to do the job anyway. In full size I'm sure the smokebox vacuum is higher, but not in the models we work with. As I said before, I approached it as an exercise in momentum transfer and looked at the most efficient way of accomplishing that. Pulling at more than one level in the smokebox is much more effective in clearing out the smoke and ash. It also evens out the draw on the tubes so the flow is more even from top to bottom.

I figured out after a few trials that it would be very difficult to do the job in one stage and then I remembered Joe Nelson's book "So you Want to Build a Live Steam Locomotive," where he talks about a secondary petticoat. While I was at it, I decided to incorporate the blower nozzles into the blast pipe assembly.
Blast nozzle installed with secondary petticoat lying on the front buffer
Blast nozzle installed with secondary petticoat lying on the front buffer
For the blower I found out that the best and simplest design was to use a triangular needle file to file four equally spaced grooves around the outside of the blast nozzle from the top and then apply the steam to these grooves with an annular sleeve so that the steam is blown out around the top of the blast pipe along the same axis as the pipe. By making the taper of the grooves so they are bigger at the top, it made a simple assembly that worked well with no leaks at the bottom of the sleeve.

I also put a step in the top of the blast pipe so that any cylinder oil in the exhaust couldn't migrate over and plug up the blower nozzles. If you look closely at the installed blast pipe in the picture, you will see what I am talking about. You can also see the secondary petticoat lying horizontally on the top of the front buffer. If you look closely, you can see that it will just slide over the annular sleeve on the top of the blast pipe.

Look closely and you will also see that the whole assembly is easily taken apart for cleaning when necessary and that all the piping is arranged to make the tubes easy to clean. A .303 caliber brass cleaning brush is just right to clean both the tubes and the flues and a toothbrush and vacuum cleaner does the rest.

Hope this gives you some ideas. I know it works very well for me.

Richard Trounce.
Glenn Brooks
Posts: 2930
Joined: Mon Nov 10, 2014 1:39 pm
Location: Woodinville, Washington

Re: Front End Rebuild

Post by Glenn Brooks »

Finally settled on a suitable design for the blast nozzles and throttle intake. This has turned out to be very difficult to reinstall. The original builder drilled the 1/2” exhaust ports in the saddle rearward and offset from the smoke stack centerline.

So nothing aligns properly - regardless of how I try to plumb the front end. I am insisting on using 45 degree elbows to make a clean exhaust run, and properly align the blast nozzles with the centerline I’d the stack. So the 1/2” pipe fittings either place the exhaust oriface to high in the smoke box for proper drafting, or require a twisty spaghetti like maze of 90* bends in the plumbing. Maddening.

Finally, today, (again) stripped out the unsuitable plumbing and decided to sketched out the existing geometry of the stack diameter, blast pipe centers, and the related radii. Where they intersect is where I need to connect the blast pipes to the exhaust nozzle. Then made up some one off pipe nipples to properly align the ‘S’ shaped blast pipes with the desired radii around the smoke stack. The red lines and numbers show the radii and offsets I need to move the port nozzle. Looks like it will work. :shock:

Here’s what the geometry looks like:
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In the photo below, the two center pipe assemblies are the lower part of the blast nozzles. I intend to mount a four jet blast nozzle on top of them - where the plumb bob presently hangs is the location of the blast nozzle assembly. The plumb bob also marks the center line of the stack. The custom, new length nipples will move the port side blast pipe center forward and to the right of the center line .- along the desired radius around the centerline of the stack.
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This photo shows my work table, with dead and dying last remains of innumerable, discarded iterations of pipe fittings.
As they say on TV: “Remember boys and girls, Do not try this at home!”
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And last photo, started turning a lovely bit of shiny brass.
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Once I chip away the unwanted bits, this will be the two piece blast nozzle: the lower part, amixing plenum that attaches on top of the aforementioned blast nozzles, and a removal upper blast cap, with four jets pointing up into the petticoat. In the Lempor evacuation system, four smaller jets entrain more exhaust gas than one large jet- improving draft, increasing evaporation, reducing back pressure on the cylinders, and cutting down on smoke and harmful climate emissions. (Each set of jets will be threaded to screw into the blast cap- each set drilled and reamed with a different size oriface. One set for testing coal, another set for propane operation latter on)
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
RET
Posts: 960
Joined: Wed Jun 07, 2006 8:36 am
Location: Toronto, Canada

Re: Front End Rebuild

Post by RET »

Hi Glenn,

Sorry to rain on your parade, but if I were doing it, I would take the smoke box off and join the two cylinder exhausts together below it, thus winding up with something like the set up in the Boston & Albany with a single blast pipe that is aligned with the stack. The two cylinder exhausts could be joined under the smoke box using two stainless steel sweep elbows that were cut and then silver soldered together so that each exhaust is curved up and discharges into the vertical blast nozzle. While not ideal, even a plain pipe tee would work OK. When the smoke box is reinstalled, you would have a much cleaner setup which would also allow for incorporating the B & A blower setup.

I would also try to put the steam chest feeds more to the sides away from the blast nozzle setup. This gives more room for any design changes or alterations you may want to make.

Think about it and try to draw it up, preferably in CAD before you cut any metal. When designing, I always make an accurate assembly drawing and that is where the design process actually takes place.

Hope this helps a bit.

Richard Trounce.
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