Tender Outer Tank
The photo above shows the MRSR91 tender. Note that there is a layer of boards between the tank and the frame. The boards were skipped and the outer tank was attached directly to the frame. The steel outer tank is open at the bottom and sets over the inner tank made of PVC.
Drawing above shows how the tender tank sets on the fame. The tank extends about halfway across the front and rear sills. The rivet pattern is similar but not identical to the prototype; minor changes were made to ease fabrication. The tank is held to the frame with six 6-32 studs, three on each side. The bead at the top is 3/32" X 3/16" half-round brass.
The back and front panels are identical. The overall width is 15.25" which matches the frame width between the sills. A width of 15.5" matching the cab width would have been preferred. However, the tender frame was already constructed.
The top was cut from11 gauge steel --- extra heavy to support the seat and engineer. The top was cut slightly oversize and filed/ground to fit the assembled sides. The top is tack welded to the sides on the inside. Four holes are required for the seat swivel and one large hole is required for the fill tube. These holes were positioned and drilled after the tank was assembled.
The two sides are identical. The rivets are #0 drive screws. The holes for the drive screws are 0.067" (#51 drill). A fixture was used to locate the rivet holes. The fixture was held in position with #0 screws. Holes where the screws were used were enlarged with a #50 drill so that the screws would pass through. The two sides were stacked and the holes drilled through both at the same time. Additional holes are required along the top edge to attach the half round bead. The bead was drilled first and then used as a template to drill the sides. The bends on the dotted lines at each end were made after the rivet holes were drilled.
The tank ends are shown above. The hole pattern is similar to the sides. Both ends were drilled at the same time
The photo above shows the drilling of the rivet holes in the ends. The holes in lower corners were drilled first and screws through the holes held the two sides in position. The clamps held the tops together. The drilling fixture with10 holes is a piece of 1/2" X 3/16" CFS. The holes in the fixture were spotted using the mill table indexing and digital readout. The fixture is shown positioned for drilling the holes in the sides. The fixture is held in place by the corner screw on the bottom. Once positioned properly and clamped in place, a hole is drilled at the other end and a screw inserted to hold the fixture for drilling the remaining holes. Once a string of holes has been drilled, the last hole drilled is used to position one end of the fixture for the setup of the next set of holes. The holes along the top and bottom were drilled from each side and the last holes in the middle adjusted as necessary to compensate for the slight deviation. The most important thing with rivet detail is to keep the rivets in a straight line and next most important is to make the spacing as accurate as possible.
The sides were reinforced with 1/2" X 1/8" HRS strips. The strips are held in place by the drive screw rivets --- 3/16" length when driven into the strips. The drive screws are 1/8" length where there is nothing behind the side. The studs are 1" long alloy SHCS with each side of the head ground flat. The studs are tack welded to the strips. The joints between the vertical and horizontal strips are also tacked welded. The welds were ground flat.
The tank ends were reinforced much like the sides.
The photo above shows fitting the tank to the tender frame--- the tank was used to locate the holes for the studs. The wood strip at the top was used to hold the sides apart.
The photo above shows riveting the ends to the sides. The end of a locomotive stand makes a nice workbench for this operation. The ends were first positioned correctly, clamped in place and the holes drilled though for the top and bottom rivets. Screws and nuts (#0) in these holes were then used to hold everything in position while the remaining holes were drilled. The rivets are 3/16" long #0 drive screws.
This shows the completed sides and ends. The dark spots are where the inside is welded. The next step was to fit the top. The sides were clamped tight against the top and the joint between the the reinforcing strips and the top tack welded. The corners were also tack welded. The welds are on the inside and not visible. A little flux-in-wire welder was used.
This photo shows the inside of the tank after it was painted --- forgot to take a photo before the painting. Three of the four holes that hold the seat swivel are visible.
The sill dimensions are shown in drawing above. A 5' length of oak planed to the 2" X 1.375" dimensions was obtained from a local cabinet shop. The three 16" long sills (two on tender and the third on the front of the locomotive) were cut at home..
The rear view of the tender with seat. The water fill is behind the seat. That fill port and the hole through the top of the outer tanks is described in the page on constructing the water tank. The finish is satin black from a spray can. After the locomotive is complete it'll probably be repainted.
The front of the tender. I always dread making these tanks but afterward have been very pleased with the results.