Chloe Boiler Suggestions

[Fender]

I don't have a Chiloe drawing, but if the boiler is less than 17" between tube sheets, then .250 ID tubes fit into the ratio.

0.250 ID tubes? I believe this is a typo.

[milwiron]

Fender asked what fuel I was planning on using. This is only my second loco build. The first engine I built was a CP173 and burned coal in it exclusively. That's all I'm familiar with for firing.
For the Chloe I'm torn between coal or propane, at this point I'm leaning towards propane but I wouldn't bet the house on it.
To answer James Powell the distance between tube sheets is 24 inches. The drawings show 3/8 i.d. x 1/2 o.d. K-copper tubes.
Thanks all,
Denny

[gwrdriver]

FWIW, the formula (for L = 24") gives an ID range of .565" to .660".

[James Powell]

Dan, if you use the formulas, then you come up with
length/diameter
17/.250=68
That is right at the very "efficient" end of the boiler scale- and why I wouldn't be using them in a horizontal firetube coal fired boiler. But, it is inside the numbers of what the calculations provide. If you were going to gas fire, alcohol fire, or oil fire, then it is possible to use tubes of that sort of size. It will require more draft (difference) to get the flow rates up to appropriate for the fire, than, say, a single 3" flue (yes, seen it...), but it will likely result in a much cooler smokebox flue gas temperature, meaning a more efficient boiler. That does not translate to a more efficient engine- in that even smaller tubes could be used, but then the fire won't ever burn, and the engine will have 100% n

I'd go with 5/8" if the boiler is 24" between tubesheets. The one downstairs is 17" between sheets, and is .520 ID/.625 OD, and I think, looks right. (L/D=32). I think it would have been OK with 1/2 OD/7/16" ID (LD=38), and would steam like a badly behaved dog if you went much smaller even though the calculated # would be acceptable. (3/8 ID= 45, 1/4" ID = 68)

Some of this is based on experience- the previous version of the steam roller boiler had 3/8" OD tubes on about 11" between tube plates, and it suffered from excessive fouling. It was runnable for about 3 hours at a time on coal, before requiring flues being cleaned. The older 2" traction engine was 1/2" tubes and suffered far less than the roller did, as did the Hudson. (though the flue we jammed the "superheater" down probably didn't carry much, as the S/H was a single piece of 1/4" OD ss tube...in a vain attempt to keep a then 11 year old James from flying off the corners...)

There are some things which scale well, and some which don't, and I suspect that fluid flow of a multi phase fluid through a tube is one of the things that doesn't scale well. We are left with some rules of thumb, from experimental engineering, to guide us.

Options that I can see likely to work:
1/2" OD K copper (.065 wall, 1600 PSI burst @ 72f), LD= 64 (probably smaller than desired for coal)
14mm K copper (1mm wall, 1800 PSI @ 72) LD= 50
5/8 OD K copper (.065 wall, 1200 PSI burst @ 72f) LD=48
16mm K Copper (1mm wall, 1400 PSI burst) =LD 43-----this is probably my happy spot, or the next one smaller
3/4 OD K copper (.065, 1000 PSI Burst @ 72F) LD= 38
7/8 OD K Copper (.065, 800 PSI burst @ 72F) LD=32, and I strongly suspect would result in a very hot smokebox if the engine is worked hard. Also, I would want to do strength calculations before accepting that out of hand.

[Fender]

James, 0.250” is the diameter squared, not the diameter (0.50” X 0.50” = 0.250 in sq). The question was about the diameter.
Another poster stated that it was ok to use tubes smaller than 0.5” diameter because that was what he used on a 1/2” scale (2.5” gauge) pacific. This is a meaningless comparison to make to a 7.5” gauge Chloe boiler with much longer fire tubes. I agree that the formula is a good starting point, but this is one of those things that does not scale perfectly for all sizes, at least not from my experience. Nor does it work the same for all fuels or vertical vs. horizontal fire tubes.
I would follow Pontiacguy’s advice, because he has the same engine and boiler you plan to build.

[Bill Shields]

Nah..have no trouble with clogging of 7/16 od tubes with coal...3/8 yes.

Would look carefully about tube arrangement of larger tubes in a small boiler....hence total flue area may be a concern with 3/4 or 5/8 tubes.

[LVRR2095]

James, 0.250” is the diameter squared, not the diameter (0.50” X 0.50” = 0.250 in sq). The question was about the diameter.
Another poster stated that it was ok to use tubes smaller than 0.5” diameter because that was what he used on a 1/2” scale (2.5” gauge) pacific. This is a meaningless comparison to make to a 7.5” gauge Chloe boiler with much longer fire tubes.

Well....if you don’t think the 1/2” scale Pacific is a good example, I have another locomotive to compare. It is a 3 - 1/2” gauge 7/8” =1’ scale model of a Lehigh Valley RR Pacific built by Lewis Bullock. It has a 5 - 1/2” diameter boiler with a 19” long barrel. I would think this compares with a Chloe boiler. The Bullock Pacific has 3/8” fire tubes and 3/4” superheater flues. I have run the engine all day long and never had to brush the tubes until the end of the day when I was shutting down. I burn good quality coal and I sift out the dust.

Keith

[Johnny O]

Good morning folks
I must say I find this thread very interesting as I am currently building my A3boiler in 1.5 scale. I was a bit confused over some terminology on the L/d formula. I used “d squared“ in my calculations. It helps to use O.D. , I.D. or Nom. When ref. sizes too. I used 1/2” Nom. Type K with .625 O.D. X .527 I.D. & .049 wall. I looked high and low to gather the info I now have to aide in designing a boiler. Internet, magazines and the Australian safe model boiler code. I’d like to know where the guideline like grate to tube ratio and such come from. I know I read these on the internet somewhere, so They must be true. Not being one to color within the or stick to conformity, I opened up my frame and widened the firebox. After some due diligence though. My L/dsq. = 65 (18/.277). Grate/Tube area ratio = 16.5%. Grate area 20 sq. In. Tube area 3.33 sq. In. 15 tubes total. I went with 3/16 ligaments in a 3/8” back and 1/2” front tube sheet. Grate/Fire box area ratio is 15.4. I also went with the foundation ring around firebox. I already have a couple of tube rollers for the 1/2” Nom. Tubes and a bunch of tubes left over from a job so that had some influence. Been fun learning all this stuff for sure.

[Andy R]

If you change one thing it affects something else.
Try reading through this string:

https://www.chaski.org/homemachinist/vi ... 82#p155016

(initially about the stack and nozzle designs but it's interrelated with the tube designs as well.)
Regards,
Andy

[Pontiacguy1]

To the original poster: Go with what has been PROVEN to work... and on the same locomotive that you are building! I will see if I can get a picture of my front tube sheet, so you can see. The boiler is off right now so it should be a good pic to see what it should look like. If it were me, I would not use anything smaller than the 1/2" type K (5/8" OD) copper flues if you are going to burn coal. I have seen some with smaller tubes, but if you burn anything other than a really high grade of coal, they would plug up and have to be cleaned out frequently. I have run my chloe locomotive for many, MANY miles, often using dirty and smokey coal, and it was always a great steamer and good puller for it's small size. It always made more steam that it could use. All this academic stuff is great, but proven results are worth a whole lot. I know of at least 3 Chloe-based locomotives that have been built this way with the 6" boiler and 1/2" copper flues, exactly in this configuration, and they all performed great.

[milwiron]

Thank you Pontiacguy1, I look forward to and appreciate any pics you can offer.
Denny

[Pontiacguy1]

Here are a couple of shots of the front tube sheet of my Chloe boiler. One with a tape measure across for reference. BTW, it's 6 5/8" OD, not 6 1/2" as I previously stated.

The center tube in the middle row can be left out if you want to. It really doesn't do anything since you can't get to it to brush it out, because the blast nozzle is in the way and wide enough that you can't work around it. With the tank mounted on the back, you really don't have a good way to clean it from the back end either.

Hope this helps you.

Scott