Heljan Class 35 Subframe

This section describes the construction of one of the two bogie subframes. In practice you would probably build the two subframes together.

Subframe etch The subframe etches (12) have already been removed from the fret to test-fit the bearings in the axle slots.

Take the main subframe etch (12) and ensure that the etched vertical slots, in the centre and ends of each side, are clear to take the material thickness.

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

Completed subframe folds Check that the folds are made accurately to 90°, and that the whole subframe is true and square.

Subframe stretchers Remove one each of the outer stretchers (13) and inner stretchers (11) from the fret.

Folding lower flange of outer stretcher Taking the outer stretcher, fold over the lower flange…

Folding side ears of outer stretcher …then the side ears.

First fold on inner stretcher Taking the inner stretcher, fold over the lower flange, together with the small tags within the apertures in the flange, noting that the fold lines on the flange are on the opposite face of the brass to those of the tags.

Completing fold of spring standoff on inner stretcher Using a small screwdriver, continue to fold the two small spring standoff tags through 180°…

Standoff tag fold completed …until they are flush against the vertical face of the stretcher.

Spring retaining ear folded Fold up the spring retaining ears from the lower flange, and fold back the side ears.

Completed stretchers The stretchers with all folds completed.

Stretchers in position Fit the stretchers to the subframe. They slot into the halving joints at the the ends of the subframes; it doesn't matter which ends you put them, the subframes are reversible. Support the stretchers in place and solder them in well, applying flux and solder to the inside corners and allowing the solder to flow in to other parts of the joints…

Inner stretcher soldered in place …this should keep the holes for the suspension wires clear, but do clean away any solder that strays into them.

Reinforced main subframe fold Check the subframe sides for verticality and consistent width overall, making any adjustments as required. Reinforce the main subframe folds with solder, taking care to keep solder clear of the region 0.5mm or so around the bearing slots.

Bolster fitted to subframe Take the bolster for this subframe (NB the triangular identification marks) and test fit the lower, curved, parts of the bolster between the subframe sides either side of the central vertical slots (the photo shows how the bolster fits into the finished subframe). A sliding fit (i.e. with slight resistance) is ideal.

If the fit is tight, you can file gently the outer edges of the bolster flanges, maintaining the curved shape as far as possible.

If the fit is loose, the legs of the bolster may be firmly, but carefully, bent slightly outwards.

Subframe ears Remove two of the Ears (9) from the fret, one of each hand.

Fitting ear to bolster channel Fit the curved parts of the ears to be a free sliding fit (i.e. with no resistance) into the channels at either side of the bolster, one either side.

The fit is to the outer part of the channel, away from the soldered joints at its base.

Gently file the curves as required, maintaining the curved shapes and taking equal amounts off each side of the ear, as far as possible. If they are significantly different, you might need to mark which side of the bolster fits which ear.

Folding primary seat Fold out the primary spring seat of each ear.

Primary seat folded Primary spring seat folded to 90°.

Making the 180° fold Make the 180° fold across the centre of the ear, with the half-etched slots on the outside of the fold.

Ear fully folded and secured Apply flux through the two access holes, clamp the fold closed, apply a small amount of solder to the outer edge of the fold and allow it to flash through the component.

Ear clamped to subframe Fix the ears to the sides of the subframe: insert the primary spring seat through the slot in the frame from the inside, with the folded-over section on the same side of the slot as the holes in the subframe. Apply flux, clamp the ear to the inside face of the subframe side and ensure that its lower edge is parallel with the edge of the subframe side…

Ear soldered in place …and solder up by applying a lightly loaded iron to the top edge of the subframe. This should avoid getting any solder on the inside faces of the subframe either side of the ear, or around or in the 0.5mm hole in the primary spring seat.

Sideframe brackets Remove four of the Sideframe Brackets (14) from the fret, two of each hand. Make the two 90° folds in each bracket.

Sideframe brackets in place Locate the Sideframe Brackets into the slots in the top edges of the subframe side, selecting the bracket of the correct hand in each case so that the sloping edge of the bracket bases are oriented towards the ends of the bogie. Ensure that they are pressed fully home, that the vertical edges of their bases are correctly aligned, and solder them in place.

Shaping of guard irons Remove two of the guard irons (10) from the fret and fold them to shape according to the template printed on the kit's card insert.

If you lose one of the guard iron etches, a piece of the main fret, from between the pivot frames, can be used as a replacement. How do we know this…?

Guard irons fitted Solder the guard irons to the outer corners of the outer stretchers.

That concludes the bogie subframe assembly. This is a convenient point at which to chemically blacken the subframes and bolsters, should you wish.