Scratchbuilding Wagon Bogies
by Stephen Harris
|Photograph by Mark Fielder|
This photograph illustrates the basic form of most of the bogies which I have built. On the left is a brass sideframe, which as been shaped to be hidden behind a dummy cosmetic casting (not shown), and with holes for axle bearing cups.
On the right is the stretcher/pivot unit. This consists of two layers of 3mm wide by 1mm thick brass bar. The lower layer has been filed to the exact length required between the sideframes, whilst the top layer has been made about half a millimetre shorter at each end. The two layers are held together by the two 14BA countersunk screws which are clearly visible, and the pivot hole passes through both layers. The two layers have then been soldered together at one end only, the end furthest from the screws, The bottom layer has been cut right through, adjacent to the pivot hole, on the side furthest from the screws.
The next stage in the assembly would be to glue or solder (low-melt) the sideframes to the ends of the lower layer of the stretcher unit whilst all are held upside-down on a flat surface against a clamped Tufnol block or similar. For this reason, the top of the sideframes and stretcher must be flush. Drills through the axle cup holes are used as a check on squareness and twist, and when all is satisfactorily assembled, axle bearing cups are added.
Thus by undoing the two screws, the bogie can be split, allowing easy fitting and removal of the axles. Some minor bending of the brass sideframes is usually necessary at this stage to achieve the minimum amount of 'slop' of pinpoints in bearings (whilst the bogie is fully assembled) consistent with good free running of the wheels. After this, the dummy side frames are glued on.
In the centre of the photograph is a completed bogie after spray painting, viewed from above. A 10BA screw and some packing washers will hold the bogie onto a 10BA nut glued or soldered to the underside of the wagon; the screw must be of such a length that when it is gently tightened into the nut on the wagon body, the bogie is free to rotate and to rock a little in all directions.