New photos are now available from the Continental Fabricators factory floor in St. Louis showing Chicago & North Western 1385’s new boiler under construction. The new images mostly show the installation of the front flue sheet at the front of the boiler.
The front flue sheet (along with the rear flue sheet) support the flues which carry the smoke and hot gasses from the firebox – located at the rear of the locomotive – to the smokebox – located in the front of the locomotive – where they can then escape through the smokestack.
The front flue sheet also has multiple larger diameter holes for supporting the superheater flues. In a superheater-equipped locomotive such as the 1385, the superheater re-heats the steam generated by the boiler, increasing its thermal energy and decreasing the likelihood that it will condense inside the engine. Superheating the steam increases the thermal efficiency of the steam engine.
Lastly, the single largest hole in the front flue sheet supports the dry pipe. The dry pipe carries the saturated steam (i.e. non-superheated steam) from the steam dome to the superheater header before being directed to the superheater flues. Inside the superheater flues the saturated steam becomes superheated and is then directed to the cylinders, which in turn provide power to the driving wheels.
C&NW 1385 new front flue sheet. March 21, 2018. Photo courtesy Gary Bensman.
A Continental Fabricators welder installs C&NW 1385’s front flue sheet. Photo courtesy Gary Bensman.
C&NW 1385’s new front flue sheet is welded in place. Photo courtesy Gary Bensman.
The following two images show 1385’s old boiler to help give perspective of where the front flue sheet resides within the locomotive. You may notice the pattern of the smaller holes for the tubes is different between the new and old sheets.
One advantage of building a new boiler is that we can correct some compromises made when the Chicago & North Western modified the engine to add the superheaters. We can also incorporate an updated design for arch tubes in the firebox which will allow us to put tubes back into the area formerly blanked off in the old boiler. The old boiler has a patch in the belly of the barrel to repair cracking believed to be caused by uneven heating. Those thermal stresses were thought to be the end result of that bottom area of tubes being removed. Another advantage of populating that area with flues again is a gain in heating area so the new boiler should steam a slight bit better.
This image of 1385’s old boiler shows the location of the front flue sheet at the front end of the boiler where it connects to the smokebox. Note the steam dome visible on top of the boiler toward the rear. MCRM photo.
Detail of 1385’s old boiler showing the front flue sheet and smokebox.
The last image from St. Louis shows the hole cut into the top of 1385’s new boiler where the steam dome will be installed.
The large hole is where the 1385’s steam dome will sit. Photo courtesy Gary Bensman.
During the second week of March, SPEC Machine’s Steve Roudebush and Tyler Roudebush along with Brett Morley of Performance Engineering traveled to Tennessee Valley Railway Museum to meet with and assist Gary Bensman of Diversified Rail Services. Diversified Rail Services was contracted by Continental Fabricators to flange the four firebox sheets needed in building 1385’s new boiler.
The McCabe Flanger in a 1921 American Society of Mechanical Engineers Catalogue and Directory.
Flanging is a process to make a smooth bend in steel forms while the steel is cold. Flanging can also be done while the steel is hot but it adds more time, work and requires more people. The choice of whether to use hot or cold flanging is made largely on the shape being bent and where on the sheet of steel the bend needs to be made.
The machine seen in use here is a McCabe Flanger, a steam-era machine which uses pneumatic pressure for power. The bends are made a little at a time to prevent creating a wrinkle in the sheet.
The accompanying photos show the the aforementioned persons along with formation of the 1385’s rear tube sheet. The tube sheet forms the front of the firebox, meaning one side will be exposed to intense fire and combustion gases while the other side will hold back a wall of water. Before being installed, the rear tube sheet will have holes drilled for and support nearly 200 2-inch fire tubes and 24 superheater flues. The tubes and flues go through the water space of the boiler to conduct the combustion gases from the firebox to the smokebox at the front of the locomotive and allow the water and steam time to absorb more heat from those gases. The tubes and flues also serve to help support the tube sheet. Since the sheet is a large, flat surface, steam pressure is constantly pushing on it, trying to bow the sheet, but the tubes and flues mechanically tie together the front and rear tube sheets, providing strength and holding the sheets flat.
The metal sheet which will form the 1385’s rear tube sheet is carefully measured before any cutting or bending begins. Photo courtesy SPEC Machine.
Excess material is removed from the rear tube sheet using a torch track. The self-propelled cutting torch gives a better cut over a long distance than can be achieved by hand. Photo courtesy SPEC Machine.
Gary Bensman carefully marks the locations and degree of the bends to be made. Photo courtesy SPEC Machine.
The McCabe Flanger machine at Tennessee Valley Railway Museum’s shop. Photo courtesy SPEC Machine.
The rear tube sheet is marked up and ready for the flanger. Photo courtesy SPEC Machine.
Crew members move the sheet into position. Photo courtesy SPEC Machine.
Steam veterans Gary Bensman, operating the McCabe Flanger, and Al “Uncle Al” Phillips (left), are assisted by 1385 Team representatives Steve Roudebush and Brett Morley as the 1385’s rear tube sheet is positioned for flanging. Photo courtesy SPEC Machine.
A slight bend in the tube sheet is visible here after a turn through the McCabe Flanger. Photo courtesy SPEC Machine.
C&NW 1385’s new rear tube sheet takes shape. This is a view of a blend from a straight side to 12.5″ radius corner to 72″ radius crown sheet. Photo courtesy Gary Bensman. Mr. Bensman of Diversified Rail Services was contracted by Continental Fabricators to form the sheets for #1385’s firebox and tube sheets.
Today, Dave drilled the mudring holes in the rear tube sheet, side sheet patches and the rear corner patch. The 3/4” tack bolts were installed. The next step is to pull the sheets tight and check the sheets for gaps between the sheet and the mudring. If any unacceptable gaps existed, the sheets will need to be flattered into position. Jeff will be next week to start the welding on the rear tube sheet.
Bob worked on needle scaling the frame and cylinder casting. He still has a ways to go to complete this. The next step will be start checking the frames for cracks.