A few years ago I saw a photo spread of the rebuild of the CB&Q engine 4960.

I was wondering about the combustion chamber. If I remember correctly, there was a space created between the fire box throatsheet and the flue sheet.

I want to know what the reason was other than better fuel consumption.

Are there other examples in existance or is this special to this locomotive?

Thanks for your thoughs.

JD Johnson, Morhead and Northfork Railroad Historian

The combution chamber in a locomotive boiler is an extension of the firebox into the first cylindrical course of the barrel between the brick arch and the throat sheet. The Big Boys also had them as well as others that don't come to mind at the moment.

The idea was to give the unburned gasses one last chance to find some oxygen and ignite before entering the tubes / flues. Once the gasses enter the tubes, they give up heat not that far in to the point the temperature drops below that of the ignition. Once this temperature level is reached, you have smoke (unburned fuel - money) traveling the rest of the way to the smokebox and out to the sky.

Ray,

Thanks for answering this question. I want to pose another. Was this arrangement only for oil burning locomotives?

Thanks

JD Johnson, Morehead and Northfork Railroad Historian

No, lots of coal-burners had 'em too. Very common after about 1925-30 or so, particularly on "Super-Power" and the equivalent locos. If you look at a copy of a Locomotive Cyclopedia from the 1930 edition on (the 1930, 38, 41, 44, 47 and 50 editions) , you'll see the "Boilers" section illustrates combustion chambers quite nicely. Some roads even put syphons in the combustion chambers to extract even more BTUs from the fuel.

Jason, Definitely not just for oil burners. Most modern steamers had combustion chambers. The N&W used large chambers on all of the "Big 3". The combustion chamber on 1218 almost seems large enough to hold a small narrow guage loco!

Combustion chambers were used on quite a few engines. For the most part I believe they were used on coal burning engines but I'm guess some oil burning engines had them. Like you said, the Big Boys had them and all of them were coal burning engines. One was converted to oil with very poor results and I believe it was converted back to coal.
Many Northerns had combustion chambers, as well as Berks. The GTW 6325 has a pretty good sized combustion chamber, but no where near as big as the ones in the Big Boys. I think the ones in the Big Boys were bigger than the room I live in. A good way to tell if an engine has a combustion chamber is to look for Flexable staybolts extending into the first course of the boiler.
The 1522 had one, and if you get on the Friends of the 611 yahoo group you can see pictures of the inside of the 1218's boiler and a great shot of the combustion chamber in it. If I have some time, I have a great picture of the combustion chamber of the 6323 at IRM that I can upload to my website. When I get it up I will let you know.

Like you said, the Big Boys had them and all of them were coal burning engines. One was converted to oil with very poor results and I believe it was converted back to coal.
Big Boy 4005 was converted to oil for about a year & converted back. It was done during one of the many coal strikes because UP wanted to find out if it was feasible which of course it turned out not to be..............Wooly

Even the Pennsylvania Railroad's K4s, L1s and I1s designs of 1914 and 1916, respectively, included combustion chambers, though not as large as those applied on later designs.

Thanks everyone for your responses.

I appreciate the information.

JD Johnson, Morehead and North Fork Railroad Historian

Jason, John White's book, "American Locomotives", mentions the use of combustion chambers as early as 1832. It is an excellent reference on early locomotive development.

I looked up some P&R diagrams, and Milholland's anthracite burners of 1858 had combustion chambers, and most of Wootten's camelbacks had them.