Does anyone know the whereabouts of the double Belpaire boiler model that used to be at the Museum of Transport in St. Louis? I saw it there in the late 1970's but nobody I have asked so far knows its fate.

It just so happens this was recently mentioned:



viewtopic.php?f=1&t=32900&p=171643

Yea, we were thinking it'd be just the right size for a Cagney-scale 4-8-6. :-)

Here's a photo of it from the earlier thread:

I believe I remember seeing the model boiler sitting next to the Daylight 4-8-4 on a trip to the Museum in 1971, maybe painted silver.

Many years later I went back to St. Louis in the company of a PE who had been quietly retained by an industrialist to design a modern steam locomotive. Unlike the ACE 3000 proposal of around the same time, my friend concluded that the hot setup would be a Diesel-electric's running gear with the generator turned by a Unaflow engine. His calculations told him that within the loading gauge the double-Belpaire design couldn't be improved upon as a steam generator, so at least that part of the locomotive would be traditional. We wanted to see the model, but no one could show it to us at the time. (That is all I know about that project.)

Do I remember correctly that the model was intended to be fired or pressurized as some kind of test?

Aarne Frobom
Return Bend, Michigan

I'm not really getting the advantage of a Belpaire combustion chamber. I can see on a firebox having the flat top eliminates the oddball angles for the radial stays connecting a curving wrapper with a relatively flat crownsheet. But for a combustion chamber, a cylinder within a cylinder would seem to be more elegant engineering-wise with nice straight stays. Is it just a larger interior volume? Please enlighten.

Steve

Aarne- That visitor must have been associated with T.W. Blasingame's project(s). I haven't heard from Mr. Blasingame in some time, but he has sent me quite a bit of info on his projects in the past. The Unaflow engine had been replaced with a patented rotary expander (from France?) on the latest revision to his planned locomotives.

According to the account in Hirsimaki's book on Lima, the model double Belpaire boiler was indeed hydrostatically tested and it was found that the firebox underwent significantly less deflection than a conventional boiler under similar conditions. I don't know if they ever fired it or not.

Steve- one of the main advantages claimed for the double Belpaire was that it allowed more gas-flow area for a given size boiler. This provides more heating surface but it also requires less pumping work for the exhaust system to draw combustion gases through the boiler tube bundle. This was accomplished because the double Belpaire combustion chamber allowed the rear tube sheet to be bigger than the inside diameter of the boiler barrel. With a conventional combustion chamber, a significant gap has to be left between the combustion chamber and the boiler barrel for water circulation. The squared off double Belpaire outer boiler section around the combustion chamber provided more room for the combustion chamber, allowed a rear tube sheet which was larger than the barrel inside diameter, and allowed a few more tubes to be "squeezed" into the boiler barrel at the bottom.

I saw the Lima scale boiler at NMOT in 2000 when working on the Frisco 1522. It was stored in a truck trailer on site. Quite rusty. Had not been displayed for a long time and was no longer mounted on the display stand seen in the photo. An effort was made to arrange a loan to the Allen County Museum in Lima for display but achieved no positive results. Whodom's response is well detailed - but . . . . the rear flue sheet is not bigger than the inside diameter of the barrell. The entire third course IS the combustion chamber and the flue sheet is set just to the rear of the steam dome at the rear of the second course. The squared off design did not allow " a few more tubes to be sqeezed into the belly of the boiler". Rather, the squared off design allowed more superheater units to be included in those corners -thus raising the total available square footage of heating area.

Gary- Since I've never seen the actual boiler, I'll have to defer to you on the details, but I think we're pretty much saying the same thing.

Here's an excerpt from the Lima advertisement showing the inside of the combustion chamber, a graph illustrating the effect of the increased gas flow area, and a few lines describing the improvement:



At any rate, the configuration does allow more tubes and/or flues to be installed in a given size boiler barrel.

Here's a highlighted closeup of the combustion chamber photo above. The red areas are what I believe comprise the additional flue sheet area mentioned in Lima's advertisement. These areas would not be present in a conventional radially stayed combustion chamber; hence a few more tubes or flues can be fit inside the boiler barrel in these areas.