In Section 2 the bogie assembly is completed. This is a beautifully executed
model of the full size loco providing axle-box, bogie stretcher and side control
springing. When assembling the axle-boxes make sure that they slide well in the
horns without rocking. Sometimes the paint in both horns and suspension holes
makes them a little tight and this must be gently relieved using a fine file.
Smooth operation in all planes is essential for good performance.
The buffer beam needs no comment but next come the expansion links which require
precision in your work. Many of the parts are laser cut and all bearing surfaces
need smoothing. Polish the surfaces of both the links and the trunnions so that
a fine finish is achieved without removing too much metal. The trunnions must
slide in the links without rattle and remember to polish the slotted ends of the
When assembling the eccentric straps note the joggle in the Pts 2-4 & 2-13 which
are handed. The joggle aligns the bearing in each end with its expansion link.
After assembling the expansion links to the 2-1 and 2-3 ‘bridging’ plates ensure
that the links all rotate freely in their bearing hangers and that the trunnions
are free to move over their full range. Any off set or out of alignment built in
will result in stiff operation and will be detrimental to valve performance.
Last in this section is the fitting of the balance weights to the main driving
wheels. No problems here but remember that the bolt heads are on the inside of
Section 3 starts assembly of the frame and frame spacers which should be
completed on a flat sheet of glass to ensure everything is true. The section
then installs the inside cylinders between the frames together with the valve
gear sub-assembly to which the front drivers are then attached. The right-hand
crank pin leads the left when looking from back to front in the frames. PTFE
strips are wrapped around the eccentric prior to fitting the straps and I smear
silicone grease over them during fitting. These bearing surfaces have proved
both hard-wearing and easy to fit in all recent products and in the future
renewal will be a breeze.
The inside connecting rods are next assembled on their crank pins after first
fitting the PTFE bushes. The technique for fitting these bushes is not difficult
if the correct procedure is applied though it seems quite brutal at first sight!
The bush is made with a split in it into which a screwdriver blade is inserted
to ease the bush open. It is then stretched further open until it can be pushed
over the crank pin. The bush has a memory and will return to its original shape
aided by its enclosure within the connecting rod big end straps.
The wheels are retained in the horns by horn keeps also acting as dummy springs
under the axle boxes. The suspension is provided by coil springs located on
spigots in the top of the horn guides and in a small recess in the top of the
axle box. The tuning of the chassis to get correct weight distribution and a
level footplate is achieved by adjusting the length and hence preload of these
springs on each axle.
The weight shaft and levers connecting to the radius rod are next assembled.
Operation of the assembly must enable full range of movement of the trunnions
equally either side of the centre pivot of the expansion link. You will now be
able to judge how well you have prepared the bearing surfaces in the valve gear!
Section 4 tasks include fitting the remaining driving wheels and keeps, at which
point the final adjustment of the springs should be made. Then fit the outside
cylinders and slide bar supports, frame spacer-mounted axle pump and the
associated bypass valve, cylinder lubrication tank and a frame spacer with
additional weights to improve weight distribution over the axles. Aster returns
to a pressurised cylinder lubrication system with this loco, as was used on the
Duchess. I have been much impressed by this system and modified my King to this
design some years ago.
The axle pump eccentric is also fitted with a PTFE strip bearing surface and the
performance of the pump can be further enhanced by the fitting of 1/8” dia.
nitrile balls replacing the 3 mm stainless steel balls provided. The assembly of
the pump is straightforward but take care to keep the silicone sealant to the
merest smear over the banjos faces to avoid ingress to the ports.
Next, having fitted the outside cylinders, the slide bar supports should be
carefully adjusted so that the crossheads will slide over their full range of
movement without resistance. The bolts left loose earlier may then be finally
Lastly, when assembling the bypass and oil control needle valves, smear grease
over the threads to avoid damaging the O rings. Chamfer the mouth of the
threaded holes using a Slocomb centre drill twisted between the fingers. This
will guide the O rings and help to avoid ring damage.
Section 5 completes the motion and outside rods and great care should be taken
in fitting the reverser gear and weight shaft assembly. Set up precisely in mid
gear as the next section depends on your accuracy here.
This section also includes the fitting of the bogie stretcher and bearing pads
and finishes with attaching the bogie itself. Personally, I leave the bogie off
until much later but a trial fit now is recommended to check clearances.