This etch contains sideframes, brake shoes, brake pull rods and coupling rods to produce a basic
chassis of the correct scale dimensions and appearance which can be used as a substitute for a
kit or RTR chassis.
We recommend the Mashima MHK1015 motor with either gearbox GB4/15 (single stage) or
GB5/15 (two stage) for this model, and can supply the gearboxes together with Markits driving
wheels if required. A separate fret of 00 spacers is included, which can be exchanged for EM
(LS10) or P4 (LS60) by returning them to us in a stamped, self-addressed envelope.
As supplied the frames are suitable for the Bachmann model.
Please note that all bends should be made with the half-etch to the inside and reinforced with a
fillet of solder.
Assembly Instructions
1.
The frames may be assembled rigid, or with sprung axles using our hornblocks and springs code
LS55. If you wish to spring the chassis cut through the spring hangers using a piercing saw and
remove them together with the centre portion of etch within the hornway. The sides of the hornways
are etched at approximately 5.85mm wide to ensure that any slight variations in the width of the
machined grooves in the hornblocks do not result in any one of them having a loose fit within the
hornway. Each hornway must be carefully dressed with a file to achieve a good sliding fit to each
hornblock, which should then be marked up or placed into a labelled bag to ensure it is assembled
only into the hornway to which it has been precisely matched. Take time and care over this stage,
removing material slowly and from each face equally. The hornblock must drop in freely under gravity
but must not show any fore and aft play which might cause the coupling rods to bind. This might
sound daunting, but the patient builder will be rewarded with a chassis having superior ride, track
holding and traction compared to an unsprung chassis.
2
For rigid axle assembly, carefully open out the axle bearing holes in the frames until the bearings are
a close fit, ensuring the bearing flanges fit snugly against the frames. This is best done using a five
sided broach. If you are using our chassis jigs (see below), DO NOT solder the bearings in place at
this stage. Open out the holes for the brake cross-shafts to 0.75mm.
3.
Select the appropriate frame spacers - their size and position will depend on the siting of the body
fixings and your preferred motor/gearbox and pick-up arrangements. A suitable layout of spacers is
shown (sketch 1) when using a Mashima MHK1015 motor with either GB4 or GB5.
4.
If you are springing the chassis drill out the holes at each side of the hornways and those in the
separate spring etches to 0.5mm as shown in sketch 2. The frame spacers fold to right angles on the
half-etched line. Solder your chosen ones to one of the frames, then assemble by clamping the other
sideframe to the first using the wheelsets to check alignment before soldering the second sideframe.
This crucial stage of the assembly can be achieved more easily and with greater accuracy by using
our frame assembly jigs (code LS16 for 00, LS17 for EM and LS61 for P4). Full instructions are
provided with them. If you are springing the chassis using our hornblocks please note that you will
need a set of four turnings code LS59 which are intended to locate in the hornway during this stage
of assembly.
5.
For a sprung chassis insert the spring and hornblock, ensuring that they are placed into their correct
hornways only. Note that the grooves in the hornblock are not on the centre line. This allows you to
choose a greater or lesser amount of sideplay on each axle. Use 0.45mm wire to locate the spring
detail and solder in place using a minimum of flux. This captures the hornblock and the protruding
centre shackle should ensure that the bottom of the hornblock is slightly above the bottom edge of
the chassis giving approximately 1.0mm of movement only. Do not be tempted to file too much
material from the top of the centre shackle. Greater travel should not be necessary and there is then
a risk that the spring could become dislodged if there is too much downward travel.
6
With the frames assembled, solder lengths of 0.7mm wire through the brake hanger holes, then
thread on and solder the brake shoes in place. Alignment is made easier if something of suitable
thickness is used to space out the brake shoe from the frame, with a wheelset fitted to ensure correct
spacing relative to the wheel treads.
7.
Lengths of 0.7mm wire are next threaded through the bottom brake hanger holes on one side of the
chassis, through both sets of pull rods (ensuring they are the correct way round) and then through
the second set of brake hangers. Solder the wire to the brake hangers, then slide the pull rods
outwards to line up with the inner edges of the frames and solder them to the wire. Finally, solder on
fixing nuts for the pick-ups.
8
The coupling rods can be articulated if desired by cutting the full length backing rod as shown before
soldering on the overlays. Whether you articulate the rods or not, this operation is simplified if the
crankpin holes are first drilled (1.2mm for Markits crankpins), and the backing rod tinned along its
length. Both the backing rod and the overlay can now be threaded onto the drill which will keep one
end in alignment whilst the other is squared up and the rods soldered together (sketch 3). If using
Markits wheels you will need to use a paper washer between the coupling rod and the crankpin
washer to prevent the rods being soldered to the crankpins.
9
If fitting the chassis to a Bachmann body, secure two blocks of plasticard to the sides of the body as
shown in sketch 4. These should be fixed so that their lower surfaces are at least 7mm above the
bottom of the buffer beam. Cut a piece of 2mm thick plasticard (or two 40thou pieces) to fit across
the body as a cab floor. Drill a 4mm hole on the centreline and secure an 8BA nut in it with epoxy
resin, making sure the nut does not project below the plasticard. Drill a 2.5mm hole in two layers of
20thou plasticard and glue these to either side of the fixing plate to prevent the nut being pulled out
when tightening the fixing screw. Fix the fixing plate to the blocks, and adjust the ride height of the
loco by inserting packing between the false floor and the chassis spacer.
The chassis can now be washed to remove any flux residues, but before painting we suggest
that you fit the wheels and check the fit of the body. You may find some slight filing is required to
obtain a perfect fit.
Our preference is for wiper pick-ups made from 26swg phosphor bronze wire as per sketch 4.
The wire is soldered to PCB strip which is bolted to a frame spacer. We recommend that, if
possible, you arrange the pick-up to be “bolt on” since this allows for easy removal and
adjustment of the wire wipers. Pack LS23 provides all the parts.
Components recommended to construct a
complete chassis:
6 off Markits 16mm wheels (WH200), 3 axles
6 crankpins and washers (RM2)
Mashima MHK1015 motor and gearbox GB4/15
(single stage) or GB5/15 (two stage)
LCP33
Chassis pack for
LNER Worsdell
J72 0-6-0T
Comet Models is part of Wizard Models Limited, PO Box 70, Barton upon Humber DN18 5XY
Tel 01652 635885, web www.wizardmodels.ltd, e-mail andrew@modelsignals.com
© Wizard Models Limited 2020
