Bachmann Class 66: Bolster

This section describes the assembly of the Bogie Bolsters.

Bolster parts

Bolster Centre folds Remove the Bolster Centre etch (B1) from the fret. Make the two folds as shown.

Bolster Stffeners Remove two of the Upper Stiffener etches (B4) from the fret and fit them into the slots in the Bolster Centre.

Fitting pivot screw Clean up the faces of one of the 2mm brass nuts to remove any machine oil and grease and prepare for soldering. Take one of the 2mm screws. Apply some grease to the the top few threads and lower face of the screw head. From the outside, insert the screw through the hole in the top of the Bolster Centre and thread on the nut.

Pivot nut soldered in Tighten up the screw, with the nut sliding between the Upper Stiffeners. Check that the nut is central between the stiffeners and flat to the face of the bolster top. Run generous fillets of solder around the nut and the Upper Stiffeners.

Check that the screw can be removed from the nut (the grease should have prevented it from being soldered in place). It is as well to tighten it again and leave it in place while the rest of the bolster is soldered up.

Bolster side Remove two of the Bolster Side etches (B3), one of each hand, from the fret.

Check that the vertical slots are clear to take the etch thickness.

The production etches do not have the lower slot in each traction ear.

First bolster side fold Make the longitudinal fold (in two sections) closest to the main body of each Bolster Side. Check that each part of the fold is to 90°.

Making the second side fold Now make the second longitudinal fold on each Bolster Side, which also is in two sections, one at the top of each traction ear, to form a 'Z' bend with the first fold.

A thin, competent, straight edge can be used to drive this second fold. A nice, beefy steel rule works well.

Check Z bend Again check that these folds are at 90° and that the lower parts of the traction ears are parallel with the upper part of the Bolster Side.

Folded bolster side Adjust all folds as required.

Bolster frame folds Remove two of the Bolster Frame etches (B2), one of each hand, from the fret.

Check that the round part of the slot in each secondary suspension seat will pass a 0.5mm drill.

Make the longitudinal fold (in two sections) to fold out the two brackets from the lower edge of each frame.

Fold down the secondary spring seat at the outer end of each bracket.

Fitting of frame and side Check that each of the Bolster Sides sits snugly against the faces of the Bolster Frame of the same hand, with the tabs at the ends of the secondary spring seats engaging in the slots at the top of the traction ears. Adjust as required.

Soldering outer parts of frame and side Solder up the outer parts of the Bolster Sides and Frames, aligning the slots, perhaps with a piece of scrap etch as shown. Leave the central parts free of solder.

Fitting first side to centre Assemble one of the Bolster Sides and its Bolster Frame. Fit the Bolster Centre to the slots in the middle of the assembly, and support/clamp the three components together, ensuring that they are square and that the tabs are fully home in their slots.

Solder up the Bolster Centre, Side and Frame, reinforcing all the main folds with fillets of solder.

Bolster second side fitted Repeat for the Side and Frame on the other side of the Bolster.

Bolster and Subframe united Pair up the bolster with its subframe, as designated by the presence or absence of the etched triangular marks on the Bolster Centre and the Subframe Mainframe.

Orientate the Bolster correctly with the Subframe: the sloping ends of the Bolster are towards the outer (coupling) end of the Subframe (that's the 'two-dot' axle end).

Check the bolster for dimensions and squareness:

A tight fit can be addressed in the first instance by light filing on the circular edges of the traction ears or lateral restraints: half-etched guides are provided to help preserve the correct shape. Other adjustments may be made by gentle tweaking of either the bolster assembly or the longitudinal restraints. If you do need to tweak the bolster, try to end up with the faces of the traction ears vertical.