Modelling the Kerr-Stuart Brazil Class 0-4-2ST locomotive in 16mm scale. - Keith Bucklitch
Dome and Water Tank.
1. The loco is shown with twin valve stems on top of the dome. These will be cosmetic only, the real safety valve being beneath the dome. Make the dome first by placing a piece of brass bar in the lathe, face the end and turning down the outside to 21 mm diameter for a length of 20 mm. Centre drill, and bore out to 18 mm internal diameter for a depth of 16 mm. Drill the a 2.5 mm diameter hole in the centre for a further 2.5 mm. Part off at a length of 18 mm. Reverse in the chuck and mark a circle at a radius of 6 mm. Touch the tool tip on the work piece and traverse across the face to scribe a shallow line across the diameter. Make two cross marks on this line at 5 mm radius. Rotate the chuck 90 degrees and make two cross lines on the 6 mm radius circle. Turn the chuck approximately 45 degrees and make two more cross lines. Repeat this once more at 90 degrees in the other direction. Remove from the chuck and centre-pop at the intersection of the marks. Drill 6 off 1 mm holes on the 6 mm radius circle. Drill two 1.3 mm holes on the 5 mm radius. File a radius on the base until it fits closely on the boiler. Check the fit on the safety valve. If necessary, open out the central hole until it fits closely over the safety valve body.
2. Cut two 10 mm lengths of 1.5 mm silver steel. Turn down the end for 1.5 mm until it is a push fit in the 1.3 mm holes. Silver solder the steel into these holes. Make the arc piece from some 3 mm steel and drill two 1.5 mm holes at a distance of 10 mm apart. These holes should be 1 mm deep. Check that the silver steel will fit into these holes. Cut two lengths of spring (the car valve springs are ideal) to 9 mm long. Slip over the silver steel rods and soft solder the arc on top.
3. Water Tank.
If you wish, the water tank may be purely cosmetic, in which case, all you will need to model is the tank ends, top/sides and filler cap. It is not even necessary to make the latter open. However, if you feel that you might wish to fit a water pump to the model (possibly at a later date) then the tank needs to be able to hold water. The tank body is cut from 26-28 gauge material, brass or nickel silver. The endplates can either be flanged from thin copper sheet. (If you are using flanged plates, make a former as you did for the boiler plates.) or cut from 3 -4 mm thick brass. They are then soldered onto the body sheeting. I find it easier to cut the body sheeting in two pieces, one for the bottom and a second sheet for the tank top. These are curved and folded as carefully as possible to shape and the edges tinned with soft solder, along with the edges of the endplates.
This can be made by soldering a piece of 4.5 mm thick brass approximately 50mm by 15 mm to a sacrificial piece of brass about 1.5 mm thick. Mount this on the faceplate, adjusting the distance from the centre until you are able to scribe two concentric arcs on the brass 4 mm apart. Balance the faceplate to reduce vibration and turn an angle flange (NB, the flange is on the inner radius) with sides of 1 mm thickness. Heat to separate from the sacrificial piece of brass, cut to length and clean up. Mark and drill holes for 10 BA screws. Solder to the front of the water tank, place on the smokebox and spot through for the fixing screws. Drill and tap the smokebox.
The filler lid is turned from brass bar. Turn the step first and part off. Reverse in the chuck and turn/file the curve and knob. The rim is also turned from brass, bored out to fit the lid and soldered to the tank. The hinge components are filed from scrap pieces of brass and soldered to the rim and the lid. Use a piece of rod for the hinge pin.
If you have any questions, or comments or find any errors in these notes please contact me by email. Email Keith Bucklitch.
Copyright © 1998, Keith Bucklitch
Last Edited - November 1998