Subframes

This section describes the construction of one of the two bogie subframes. You will probably find it convenient to build both subframes together.

Preparation

Spring seating locations Check that the suspension seating holes, located on the fret as indicated, will each allow a 0.5mm drill to pass, opening them out where necessary.

Main frames

Subframe main etch Take the main subframe etch and ensure that the etched slots (one in the centre of each side to take the traction ears, and one on each of the four outer ends to make halving joints with the end stretchers) are clear to take the material thickness.

Folding bogie main frame Make the two main longitudinal folds, each of which is in two parts carried over the transom sections under each axle slot.

Folding end plates Fold in the end plates. Pay attention to the fit; remove etching cusps on the edges of the end plates as necessary to avoid forcing the sides of the mainframes apart.

End stretchers

outer stretcher etch Remove one of the outer stretcher etches from the fret.

Folding first transom flange Fold over one of the transom flanges, firmly holding and supporting the web of the transom, and working against a hard block, as shown.

Folding second transom flange Firmly holding the other flange, and with the web supported against a hard block, start the fold for the other flange. Once started, the fold can be finished by finger pressure or pliers.

outer stretcher inner folds Make the two inner vertical folds and reinforce them with a small amount of solder, applied to the inside of the folds.

outer stretcher outer folds Make the two outer vertical folds. Care is needed to make the folds true to the direction of the half-etched lines, as they are quite short.

inner stretcher etch Remove one of the inner stretcher etches from the fret.

inner stretcher inner folds Make the two inner vertical folds and reinforce them with a small amount of solder, applied to the inside of the folds.

inner stretcher outer folds Make the two outer vertical folds.

inner stretcher in place Fit the inner stretcher in place. It slots into the halving joints at the inner ends of the subframes; the inner ends have the shallower of the two pairs of slots for the joints.

outer stretcher in place Fit the outer stretcher in place at the other end of the subframe.

Check that the top edges of the subframes run straight and parallel between the two stretchers. Solder the stretchers in place, applying flux and solder to the joints from the inside of the subframe. Support the joints from underneath as shown in the photos above; at the joints the lower edges of the stretchers should be at the same level as the lower edges of the subframe sides. Do not apply too much solder; the holes for the spring wires should then remain clear. If they do become blocked, clear them with a 0.5mm drill.

Stretchers and main folds aligned and secured Reinforce the main longitudinal folds, and secure the joints between the subframe sides and end plates, with a fillet of solder. Take care to ensure that the region immediately around the subframe bearing slots, for at least about 1mm around the edges of the slots, is kept free of solder.

outer stretcher detail Remove the outer stretcher detail etch from the fret and fold as shown. Take care to maintain the correct alignment of the folds. Fettle the etch to fit snugly in place in the channel of the outer stretcher.

Fixing stretcher detail Apply flux to the web of the outer stretcher and put the stretcher detail in place. Hold the assembly face down against a flat surface to align the outer edges of the flanges and apply solder through the slots on the outside of the stretcher folds. Solder should then flash around the web and make a tidy joint between the stretcher and its detail.

outer stretcher detail and outrigger flanges Carefully make the folds to form the top and bottom flanges of the outriggers of the outer and inner stretchers.

Traction Ears

Traction Ears Remove two of the traction ears from the fret. There is one of each hand for each bogie. Make the single fold on each ear.

Traction ears fitted From inside the subframes, fit each ear through the slots in the centre of the subframe sides. The base of the ear should come up flush to the inside face of the subframe side, handed so that it is on the same side of the slot as the hole in the subframe. Make sure you have them the right way up; the top of the base should align with the top of the subframe, and the hole in the ear should be towards the top. Solder each ear in place, applying flux to the base and solder to the large hole in the subframe, letting it flash round the joint. Ensure that the hole in the ear, for the primary spring beam, remains clear.

Undertray and Secondary Spring Seats

Undertray Remove the undertray plate from the fret. Make the folds at each end of the plate. Check the fit of the plate into the subframe, noting that the lugs on the sides of the plate engage in the recesses in the lower edges of the subframe, and that the fit is reversible end for end.

Secondary Spring Seat etch Remove the secondary spring seat etch from the fret and clean it up.

Spring seat and undertray Make the folds in the spring seat etch and fit its tabs into the slots in the top face of the undertray. Ensuring that the seats and undertray are correctly aligned, solder the two together.

Fitted spring seats and undertray Fit the undertray into the subframe and solder up.

Undertray bottom view That concludes the bogie subframe assembly.