Kozo K-27 Boiler

Part B



This disk of about 2" diameter will be used to form the firedoor ring. Two slices will then be made in it to create the two semicircles that will form the top and bottom of the firedoor opening. I'm waiting on the copper strip that will form the firedoor ring. September 2, 2023.


Here we see the throat sheet mounted on a fixture that was bolted to a rotary table to true up the cradle that the boiler shell will rest in. The sides and bottom have also been trued up on the mill. The three large holes in the copper will be used for  the 1/4" staybolts. The two smaller holes at far left will be used to secure the mudring while it is being soldered in place. This step also required the machining of an #2 MT plug with 1/8" locating pin so that the wood fixture could be accurately centered on the rotary table. The throat sheet is now ready for final assembly and soldering. September 4, 2023.


The firedoor ring was formed out of a copper strip approximately 3/4" x 6" long bent into a ring of about 2" diameter. The flats were cut from the bronze ring a couple photos up and then soldered to the ring. September 9, 2023.


Today was spent making a wooden backing plate for the front tube sheet and laying out the tube locations in the two tube sheets. These will be bolted together on a faceplate so that the tube holes can be bored simultaneously in both sheets. The tubes will be 3/4" copper pipe with 10 tubes running through the boiler. September 10, 2023.


My grandfather's old South Bend lathe didn't come with a slotted faceplate so I had to pick one up on epay. This one isn't in to bad of shape and was fairly reasonable. September 10, 2023.


Boring on the lathe with the faceplate didn't work out since the swing of the lathe needed to be about an inch larger. Instead I am using a boring head on the mill. Here we see the first two tube holes opened up to accept the 3/4" tubes in both the front tube sheet and the firebox tube sheet.. The third hole has been drilled about as large as I want to go and will be bored to the final size. Drilling alone isn't an option since the holes are so close together and large drill bits might deform the hole next to the one being drilled. Just seven and a half more to go! September 17, 2023.


Half of the tube holes are now bored to fit the 3/4" tubes. Only five more to go. October 1, 2023.


The ten tube holes have been bored in the front tube sheet and the firebox tube sheet. October 8, 2023.


The front tube sheet has been left on the table since six more holes need to be drilled and we don't want to lose our reference location. October 8, 2023.


The front tube sheet after some deburring of the holes. The outside edges of the sheet will need to be machined before any soldering of the firebox. October 8, 2022.


Additional holes have been added to the front tube sheet. The outer four holes will have studs added to secure the smokebox to the boiler. The four small diameter holes will be used to attach some support ribs to the backside of the sheet. The other two holes will be for the fittings for the blower outlet and the steam outlet. October 15, 2023.


The front tube sheet was chucked up on the lathe and the outer diameter machined to the dimension of the boiler tube. This will make for a nice machined surface to solder the tube to. I'm waiting on some 1/4" x 1" copper strip to construct the ribs that will go on the backside above the tube holes. October 21, 2023.


On the mill one of the firebox sheets is getting a hole bored for the firebox door. Next will be drilling of all the staybolt holes. October 22, 2023.


The firebox back sheet and the backhead have been match drilled for ten staybolts and the hole for the firedoor ring. The firebox back sheet has also had all of the outer edges machined and the staybolt holes have threads. The backhead has additional holes for the throttle base, blower bushing, water gauge bushing and a support rib. The small holes in the bottom of each sheet will be for the mud ring.  October 28, 2023.


The ten staybolts and the firedoor ring have been silver soldered together to complete this piece until final assembly. October 29 , 2023.


The outer edges of this sheet have been machined and the three staybolt holes are threaded. November 1, 2023.


The outer edges of the backhead have been machined to provide a smooth surface for the outer shell to attach. November 4, 2023.


A 1/4" thick support rib has been added to the top of the backhead to provide support since there are no staybolts this high. November 5, 2023.


The staybolts have been soldered in place for the firebox tube sheet. November 5, 2023.


One of the ribs for the front tube sheet has been made. A second rib will need to be made for the very top but I ran out of 1/4" stock. November 5, 2023.


The two 1/4" ribs have been soldered to the back side of the front tube sheet along with the four smokebox mounting stubs. The next step will be to fabricate the boiler shell sections. November 11, 2023.


The front boiler shell is made from 0.080" thick copper and has been trimmed to about 18" x 10.250". Layout work to locate the various appertunances is shown above. Next will be the rolling of this shell. November 18, 2023.



The front boiler shell has been annealed and rolled to the required diameter of about 5.75 ".  This section is approximately 10.25" long. November 25, 2023.


The middle boiler shell has been formed and is approximately 6.5" in length. November 26, 2023.


The outside firebox sheet is a semicircle that is about 6.75" in length. November 26, 2023.


The front shell with the seam riveted together in preparation for silver soldering of the seam. November 26, 2023.


The front boiler shell with all holes bored for the various fittings. From front to back we have the water fill bushing on top, water inlet and running board mount down low, handrail bosses up high and finally the steam dome base. The shell is shown in about the approximate location on the frame. All of these fitting will need to be silver soldered to the shell. December 10, 2023.


All of the fittings have been silver soldered to the shell. December 26, 2023.


A ring has been added to the rear of the shell which will be used to connect the middle shell. December 29, 2023.


The middle shell has been temporarily joined to the front shell to provide a visual of how this might look on the frame. Further work on the middle shell will be next on the list. December 29, 2023.


The outer firebox shell with the manifold bushing, generator base and studs for mounting the outer jacket, December 30, 2023.


The middle boiler shell with bell base, handrail mounts, air compressor mount and running board mounts. This will need to be cleaned up in an acid bath. December 31, 2023.


All of the completed boiler sub-assemblies for this segment of the project. The next segment will be the completion of the boiler. January 1, 2024.