Springs, Bogie Assembly and Rolling Test

Spring wire sizes are listed on the card inserts that come with the kits.

Cut four lengths of the primary spring wire, each 56.5mm long. Make a 90° bend at one end of each wire, leaving a straight long length of 54mm, ±0.5mm.

Cut four lengths of the secondary spring wire, each 30mm long. Make a 90° bend in each wire, 7mm from one end.

Take one of the bogie subframes and slot its two wheelsets into place.

Route of Primary Spring Wire Route of Spring Wire through Carrier Take one of the primary spring wires, and thread it into place as shown in the diagrams here. It passes through first the inner stretcher, then the carrier for the inner axle, then the traction ear, then the carrier for the outer axle, then the outer stretcher, and should stop just short of the outer stretcher cosmetic detail. It need only project about 0.5mm beyond the outer stretcher; trim it to length if necessary.

If the wire will not pass freely through the carrier, use a 0.5mm drill to clear any excess solder from between the bearing and the carrier etch.

Similarly fit the primary spring on the other side of the bogie. Hold each spring in place with a small blob of Blu-tak on the inner stretcher.

Primary Springs fitted Similarly fit wheelsets and primary springs to the second bogie. You now have two rolling bogies with fully functioning equalized primary suspension.

Do a hand-powered rolling test to check for any tight bearings, wobbly wheels etc. It is easiest to correct such things at this stage.

Bolster in place Now take the bolster assemblies, pair them up with their respective bogie subframes and orientate them correctly to each subframe; the face of the bolster tower which is set back from the bolster base faces towards the outer end of the bogie.

Put one of the bolsters in place, over the traction ears of its subframe, and pass the long leg of one of the secondary springs through the left hand hole in one of the bolster sides. Thread the wire through the holes in the two secondary spring seats (mounted on the undertray of the subframe) and then through the corresponding hole in the opposite bolster side. Clip the short leg of the spring into place in the small hook at the base of the bolster side. Take care as the hook is quite fragile. A small flat bladed watchmakers' screwdriver is possibly the best tool for this.

Secondary springs in place Similarly fit the second secondary spring from the other side of the bolster.

Bolster and sideframes fitted Similarly fit the bolster to the other bogie. This view, with cosmetic sideframes in place, shows the secondary springs passing through their seats on the undertray of the bogie.

Class 25 Ride Height settings You can now fit the bogies into the chassis block of the loco and do static and rolling (pushed or pulled) tests to check ride height, body clearances, track-holding and suspension behaviour.

The alignment of the spring seats has been set up assuming 0.5mm diameter holes, 0.4mm (0.016″) diameter spring wire, and 0.5mm static deflection under the weight of the loco, to give nominal buffer height of 13.8mm. Variations in manufacturing and materials may affect the exact values by a few tenths of millimetres, as will the fit of the loco body to its chassis. As shown in the diagram here, a couple of ready alignment checks are built in to the design: