Modelling the Kerr-Stuart Brazil Class 0-4-2ST locomotive in 16mm scale. - Keith Bucklitch
Building the Frames
Building the Frames.
Open a better drawing of the frames.
Plan view of frames.
Open an enlarged plan view of the frames.
You will need some 1.5 mm steel for the frames and buffer beams. This is available from model engineers suppliers in widths of 38 mm (1 1/2"). Cut two pieces about 255 mm long. Coat one side of one piece with marking blue, and mark out the positions of the end holes for the fixing screws. Clamp the two pieces together, (a suggestion is to glue them together with Superglue) drill the holes and rivet the two pieces together (or fix with 10 BA screws). File the top edges to ensure that they are level and straight. Mark out the lower edge 35 mm parallel to the top edge and saw and file to the line. Take some time and care to get this parallel with the top edge. Mark out the ends to length and cut/file square to the edges. Mark out the various hole positions, drill all these 1 mm initially, opening out as appropriate subsequently. Cut the slots for the axle bushes to allow the wheels to be dropped from the frames, taking care to get these parallel. Separate the two sides and place to one side for the moment. (If glued together, use gentle heat to break the bond.)
2. Buffer Beams
Cut the buffer beams from the same material as the frames. Mark one piece for the rivet holes, clamp both together and drill and rivet the two pieces together. Mark out the shape and cut/file to the lines. Separate the two pieces. Make a slight countersink in the rivet holes. Mark one beam for the front and one for the rear. On the inside surface of the beams, mark two parallel lines 62 mm apart and square to the top edge. Cut four lengths of brass angle (6 mm or 1/4") to 35 mm long. Clamp a piece of angle carefully to the marked line, (Take care to get these square to the top edge of the buffer beams.) drill through from the beam and rivet in place with 1.5 mm rivets. These should have their heads on the inside, and be hammered flush into the countersunk holes on the outer surface. Clean up and smooth the rivets with a file and/or emery paper.
3. Temporarily clamp the frames to the brass angle on the buffer beams. Place the frame assembly on a flat surface plate (a piece of plate glass will do nicely) to ensure it is not twisted. Spot through the frame holes, open out and thread 8 BA. Temporarily fasten with 8BA hex head screws. Cut the lower spacer from a piece of brass to 62 mm length. Clamp in place and spot through the frames. Drill and tap 8BA. Open out the frame holes to clearance size (2.25 mm).
4. Frame Spacers/stretchers.
The front stretcher is made from 6 mm (1/4") brass angle. Cut the rear upper stretcher from 6 mm square (1/4") brass. The rear stretcher needs to support the boiler. Make the support from 1.5 mm brass or steel, riveted to the stretcher. Clamp in place, drill and tap 8 BA. Recheck to ensure that the frames are not twisted.
There are two other spacers/stretchers. Both made from 3 mm thick brass. (Steel will do equally well if to hand.) The position of these is shown on the drawing. The lower spacer has a pivot hole in it for the pony truck A-frame. The Pony Truck Bearer has a curved slot cut in it to retain and guide the pony truck as it swings.
Disassemble the frames. Fasten the cylinder block in place with the front fastening screw. Adjust the angle so the centre line of the bore is in line with the rear axle hole. Spot through from the frame and drill and tap 6 BA.
There is a valance along the top of the frames, presumably to stiffen them. This is rivetted in place. Cut the valance from thin 5 mm brass angle. (A thin brass angle is available from the 'Metal Centres' in the model shops.) Clamp level with the top edge of the frame, drill through from the frame holes and secure with 1 mm round head rivets - heads on the outside. Re-assemble the frames/buffer beams/stretchers with 8BA hex head screws. Before tightening the screws, check the frame assembly is square and flat. You will also need to rivet some 6 mm x 6 mm x 1.5 mm brass angle along the inside of the frames to secure the front and rear footplates. These should be level with the top edge of the frames. Later the footplates can be secured to these with countersunk 10 BA screws.
6. Motion Brackets (See previous page for drawing)
The motion brackets to support the end of the slide bars can be cut to the shape shown in the drawing at this point if not already done so. Fold up as shown and clamp in position on the frame and slide bar. Spot through the frames and rivet or hold in place with a 10 BA screw. Spot through into the slide bar, drill and tap for a 10 BA hexagon head steel screw.
7. Axle Bushes.
The axle bushes are turned from bronze or gunmetal bar. Turn these to a close fit in the frames. File a small flat on one flange of the bush, to prevent rotation when the keeper plate is fitted.
8. Keeper Plate.
Cut keeper plates from some spare frame material, remove the axle bushes from the frames, align the keeper with the lower edge of the frames, spot through from the frames, drill and tap 10 BA. Refit the axle bushes, apply the keeper plate, and carefully file away any excess until it can be screwed in place whilst holding the bushes securely in the slots without any shake.
9. Reassemble the frames ensuring that they are square and flat. Take a reamer the size of the axle and push through the axle bush on one side and across the frames through the bush on the other side. Check the squareness of the frames once more by placing some axle steel through both sets of bushes and sighting along to see they are parallel.
If the cylinders are not secured to the frames, they should now be so placed. Now is the time to make the steam and exhaust tees and check they can be assembled into position between the frames and screwed into the cylinders If you do not intend to disassemble the loco for painting, then secure the steam pipes with some nut locking adhesive. This will prevent them working loose, and seal off any steam leaks that may occur.
Copyright © 1998, Keith Bucklitch
Last Edited - October 1998