These instructions deal with fitting of the brake gear components supplied on fret F011. We recommend fitting the brake details at this stage, because the details are fixed to the subframe's traction outriggers and there is, therefore, some interaction between adjustments made to the outriggers, to fit the bolster, and the relationship of the brake shoes to the wheelsets.
The fret has been designed to assist in drilling and folding operations. We advise that you do not remove components from the fret until indicated in these instructions. In many cases, small components are folded 180° on to larger ones on tags which assist with alignment. With the fret supported on a firm, flat surface, you can make these folds with two small, flat-bladed screwdrivers, or similar implements, one pressed on to the tag to define the position of the fold and one acting on the smaller component to drive the fold over.
With a 0.35mm drill in a hand pin-vice, check that the drill will pass through all the fully etched round holes
in each component, drilling them through gently if required.
To help prevent distortion,
hold the parts against a hard, flat surface while drilling.
There is fine detail in the etch which can easily become obscured by solder. It is perhaps as well to tin all components with a thin film of solder now, to avoid bringing excess solder on the iron to the components when assembling. Run through the holes with the drill again after tinning.
Taking the central brake details (items 5, 6, 7, 8 on the Component Map), fold over (180°) the shoe
detail laminations. Pass a short length of 0.31mm wire through the hole in the shoes for the centre
wheelset, and solder the laminations together. Trim the wire flush with the back of the shoe detail,
but leave a short stub protruding from the front to represent the end of the cross rod.
A useful jig is a piece of tufnol with a 0.35mm hole drilled close to one edge. The component can be rested on the edge of the tufnol, with the face of the brake shoe over the edge, and the wire passed through in to the hole. Solder may then be applied to the face of the shoe and allowed to flash through the joint, at the same time infilling the laminations at the front face of the shoe, whose surface may then be finished with a half-round file.
This image shows the terminology we have used below to identify the brake gear parts, and which lower boss
shapes go where when you come to fit the central details. Note that the bogie
subframe is inverted in the image. See also the Component Map included in the F011 pack.
Taking each central brake detail etch in turn, fold up (180°) the bosses at the lower ends of each
brake hanger (hold the fret against your hard, flat surface with the flush face of the half-etched
fold tags facing outwards).
Align the bosses with the blind end of a 0.35mm drill, and remove the component from the fret. Solder a short
length of 0.31mm wire into the bosses of the hangers facing the outer and inner axles (i.e. those whose shoes
do not have the wire cross rod end detail) and trim it to protrude about
1mm or so from either side of the detail. The tufnol jig is useful again for this. Secure the other bosses
with a touch of solder;
there is no need to
fit 0.31mm wire to them (although we did do so in the photo here), unless you intend to fit the centre axle's
pull rods (see following note).
There are 20 pull rods on the etch, enough to fit inside and outside rods around the inner and outer wheelsets of each bogie, and to fit outside rods to the centre wheelset. To allow sideplay, on a working model, we suggest that the centre pull rods be omitted altogether, as they are virtually invisible in service. There is a fold-over boss spacer at the end of each rod, to provide ample clearance between rods and wheels on the inner and outer axles of a working model. For a finer appearance, you might wish to experiment with omitting the spacers.
Check, with a piece of scrap etch, that the slot, at the back of the shoe facing the inner or outer axles, which forms a halving joint with the subframe outrigger, is clear to the material thickness. If required, open it up with a 0.4mm or 0.45mm drill, used as a file.
Remove and clean up the half-etched fold tags at the bottom of each brake shoe. It's probably as well to leave the upper tags in place, as they're invisible when fitted and help prevent the detail from coming apart during subsequent soldering. They might, later on, need a little nip with a file to avoid interference with vertical movement of the wheels.
Make the outer folds in the central brake detail. Apply flux carefully to this fold only, and touch
the iron against
an outside corner of the fold to allow solder to flash into the fold and reinforce it, without filling
the half-etched lines for the adjacent folds.
Make the inner folds. The outer folds should not distort as they have already been soldered. Reinforce
the inner folds in a similar manner.
Taking one of the bogie subframe assemblies, assign each of the four central brake detail etches to its correct position on the subframe (see above). Locate the detail etches in the slots in the top of each of the subframe's outriggers. Each slot makes a halving joint with the similar slot in each brake detail etch.
Support the detail etches in the correct alignment and solder up the joints,
taking care not to let excess solder flow into the detail. It is convenient
to invert the assembly and support the detail etches on two parallel blocks, as shown. Check that the etches
are parallel with the subframe both horizontally and vertically, reheating and realigning if necessary.
Test fit the wheelsets to check that there is sufficient clearance between the brake shoes and the wheels
over the operating range of the suspension (the design static position of the wheelsets is with the
tops of the bearing carrier ears level with the top of the subframe sides, with dynamic deflections of
±0.5mm service, ±0.75mm max, from there).
The brake gear is designed to give a minimum clearance between wheel (15mm diameter) and shoe of 0.5mm. With natural variation in assembly, clearances can be tight, especially with a full 15mm wheel. We suggest tweaking, if necessary, of the detail etches and subframe outriggers to get clearance for the shoes against the centre wheelset, then, if required, filing of the shoes facing the inner and outer wheelsets (they're invisible once the bogie is fully assembled).
Any adjustments to the outriggers will, in turn, affect the fit of the bolster
between them, so check that fit and either make any adjustments required to the bolster, or look again at your
initial tweak to the outriggers and/or brake detail. Also check that the brake
detail etches do not foul any parts of the bolster secondary spring detail over its normal range of movement
relative to the subframe.
If you have not already done so, make the two joggle bends in the brake shoe guides at the ends of the subframe stretchers
as shown. Try to avoid any 'stretcher outrigger droop', as exhibited to the left of the photo! Test fit the
wheelsets to ensure clearance between the inside faces of the shoe guides and the outside faces of the wheels.
Now we turn to the end brake shoes and their hangers, parts 1, 2, 3, 4 on the Component Map. Each shoe and hanger assembly is made up of an inside and outside lamination. Note that, for more efficient use of fret space, the inside laminations (1, 2) are etched adjacent to the outside laminations (3, 4) of the opposing pair.
Fold over the shoe detail (180°) of the outside laminations (3, 4). Align the folds using the blind
end of the 0.35mm drill through the holes in the shoe.
Cut through the tag holding the top bracket detail, as close to the detail as you can, and fold over
(180°) the bracket, aligning through the upper pivot holes with the 0.35mm drill.
Fold over the lower boss detail (180°), this time folding the larger part of the component over on to
the small boss, as far as you can with the component still on the fret. Then cut the remaining tag, as close
as you can to the boss, and complete the fold, again making the final alignment with the 0.35mm drill.
Similarly fold over the top brackets and lower bosses of the inside laminations (1, 2), ending with them removed from the fret.
Take a pair of inside and outside laminations (1, 3 or 2, 4) and apply flux to their shoe and lower boss
areas.
Thread the pair together on a length of 0.31mm
wire passed through the holes in their lower bosses.
Thread a second length of wire through the holes at
the other end of the hangers.
Insert the first wire into the hole in the Tufnol jig, with the inside lamination face
down against the jig. Press the laminations together and solder up the assembly.
While the solder is still molten, withdraw the second wire. You should find that, when it cools, the
solder forms a small dimple at the location of the hole, which can then be redrilled 0.35mm.
Trim the free end of the first wire to about 1mm.
A better alternative, which we haven't yet used successfully, might be to use a length of 0.3mm pencil lead rather than the second wire (a trick borrowed from Mike Clark). Check the exact diameter of the pencil leads before starting and drill holes accordingly before removing parts from the fret (our 0.3mm leads turned out to be 0.4mm diameter).
Drill the hole in the centre of the brake shoe detail 0.55mm, to allow the 0.5mm brass wire supplied in
the kit to be inserted freely.
Clamp the component in a vice, and gently finish the edges of the shoe and hanger with files to reduce the laminated appearance. Remove the folding tags from the top and bottom of the shoe. Keep the folding tags on the lower bosses and upper brackets, for now.
Repeat the above for the remaining seven pairs of laminations.
Returning to the fret F011, place the fret on a hard working surface such that the flush sides of the
half-etched folding tags of the pull rod bosses are facing upwards. Apply a light smear of paste flux
to the boss surfaces and fold the bosses (180°) over onto the rods, finally aligning the folds with
the blind end of the 0.35mm drill.
Cut through the tags to separate the pull rods from the fret.
Cut two lengths of 0.31mm wire, each long enough to span between the outer end of the subframe stretchers and
the vertical sides of the subframe. Take the end brake shoe/hanger for one side of the inner end of the bogie (the end without the guard
irons) and, on that side, thread one of the wires through the hole in the stretcher end, then the top hole of the
brake hanger, then the hole in the end of the vertical side of the subframe.
As you insert the wire from the outside, use small, flat-bladed screwdrivers to steer the wire through the holes.
Take one of the pull rods, orientate it with folding tags facing downwards and the end with the half-etched 'slot' detail towards the end of the bogie. Thread the pull rod on to the 0.31mm wires protruding from the lower bosses of the end brake hanger and of the central hanger facing the inner axle.
Align the end brake hanger with the slot etched in the upper flange of the subframe stretcher, and
use the wheelset to check for clearance. If fitting 3'7" (~14 - 14.3mm) wheels, you might consider
making a closer fit by opening up one of the half-etched holes in the pull rod, separating and repositioning the
fold-over spacer, and fitting that hole over the wire at the central hanger. When satisfied with the fit
(if a touch tight you can file away a little from the shoe, once fixed), solder the pull rod and end shoe
detail in place.
On the other side of the bogie, thread the brake shoe/hanger onto its wire as before.
Align the end brake hanger with the slot etched in the upper flange
of the subframe stretcher. Cut a piece of the 0.5mm wire exactly to length to span between the two brake
shoes, protruding just slightly from the detail on each side.
Use a vernier to capture the dimension then cut the wire against that.
Thread the 0.5mm cross rod into place through the end brake shoes. Fit a pull rod to the unfixed side, choosing the correct hand and orientating as above. Solder the cross rod into the shoe on the side already fixed. Back to the unfixed side, align the brake shoe/hanger with its slot in the subframe stretcher, then solder the hanger and pull rod in place.
Test clearances against the wheelset once more and, if necessary, file the shoe faces to fit.
Fit the inside pull rods over the inside-facing ends of the 0.31mm wires. Solder the outer ends only…
…then
cut the rods just short of the axle centreline. Remove and discard the inner ends. Bend the remaining part
of the rods to clear the inside faces of the wheelset.
Repeat the above for the end brake detail at the outer end of the bogie. Here you have the additional
factor that the 0.31mm wires, from which the end details hang, also must be threaded through the holes
in the guard iron ribs. This path rarely turns out to be straight, but the wire is flexible enough
to be guided/steered through and provides effective strengthening once soldered in.
To finish off, trim off the excess lengths of 0.31mm wire, leaving short stubs protruding to represent
the ends of the securing pins. Dress the components with a file to remove the fold tags and to
reduce their laminated appearance, though perhaps don't overdo it, as on the prototype the pull rods and hangers are
also assembled as a laminated sandwich of components. You can also now dress the guard irons to remove the
etching cusps from their edges and tidy them up.
That concludes the fitting of the brake gear details and, indeed, the assembly of the brass bogie components. If you wish to chemically blacken the bogies, this is a convenient stage to do so.