The 4mm Dingham Autocoupler
Assembly and Fitting Instructions
The instructions for the Dingham Autocoupler are included here to give
prospective purchasers the best possible idea of the coupler, its mechanism and
exactly what is involved in assembling and fitting it.
The instructions below are not an exact replication of the printed
instructions. In particular, the quality of the illustrations is inferior to the
printed version, which is available by post to UK enquirers in exchange for 2
First Class stamps.
The
coupler is intended for single-ended use. This means vehicles must always face
the same way
on the layout. Each vehicle has a hook with loop at one end and a
hook with latch at the other. Coupling takes place automatically as vehicles are
pushed together. The loop slides up the hook on the next vehicle, passes under
the tip of the latch and drops into the slot in the hook. Uncoupling can take
place when vehicles are buffered-up by means of magnetic action on a dropper
suspended from the tail of the loop under the buffer beam. The magnet pulls the
dropper down and the loop is lifted, flipping the latch upwards, then dropping
back on top of the latch and preventing re-coupling. Properly adjusted couplers
on 4-wheel wagons will couple and uncouple readily on curves of 3ft radius
or less.
Two
types of latch are provided on the fret. Try both and see which you prefer. Type
1 is less obtrusive and its operation is slightly more reliable, but type 2 is
probably easier to assemble and fit.
IMPORTANT:
For dependable working, the coupler relies on the correct relationship between
the positions of the hooks and the buffer faces of vehicles. If the hook is set
too far back, it may be difficult to couple vehicles on curves. If the hook is
set too far forward, the coupler loop will be pushed against the back of the
slot in the opposing hook when propelling, and the friction between loop and
hook will prevent uncoupling. Non-scale buffers are common on proprietary 4mm
scale rolling stock. If the buffer length is less than 6mm (scale 1ft 6in),
the couplers cannot be made to work properly and the buffers should be replaced
with scale-length items. Parts are included to allow the couplers to be fitted
to all vehicles with buffer length greater than 6mm and the couplers are
self-jigging for the two most common scale buffer lengths of 1ft 6in (6mm)
and 1ft 8½in (7mm).
NOTE:
THE COUPLERS SHOULD BE CHEMICALLY BLACKENED ON COMPLETION. THEY WILL NOT WORK IF
PAINTED.
Carr’s metal black for nickel silver is suggested. Some users of the 7mm
version of the couplers have successfully used spirit-based felt-tipped pen for
blackening. In either case, it is important to clean and degrease the couplers
before blackening. (Shake them in hot detergent solution in a small jar.) This
not only helps with the blackening, it also removes flux and other residues
which may impair easy working.
Hook
with Loop (diagram
below)
(a)
Prepare the hook. Solder
a short piece of 0.5mm brass wire into the pivot hole in the hook. (Make a
simple jig by drilling a 0.5mm hole about 2mm deep in a piece of wood). Trim so
that the total length of the pivot wire is about 3mm, with equal lengths
protruding at either side of the hook. Remove the upper half-etched latch stop. If fitting to a vehicle
with 6mm buffer projection, remove the lugs on the shank. Retain the lugs for
buffers of 7mm or longer.
 (b)
Prepare the loop. Bend the
pivot lugs upwards through 90deg (half-etched lines inside). The correct
technique (see diagram) must be used here otherwise the loop will be distorted.
Grasp the pivot lug in flat nosed pliers with the ends of the pliers level with
the nearside of the half-etched fold line. Then take a flat file, place against
the body of the loop and the ends of the pliers and rotate the file to bend the
body of the loop 90deg upwards. Repeat for the other pivot lug. Bend the front
of the loop upwards at about 45deg. Bend the tail of the loop downwards through
90deg making the bend as close to the body of the loop as possible. Bend the
last 3mm of the tail back to the horizontal. With a cutting broach or 0.6mm
drill, open up the holes in the pivot lugs to give a sloppy fit on the 0.5mm
pivot wire.
(c)
Fit loop to hook. Holding
the loop vertical in relation to the hook, place one pivot hole then the other
over the pivot wire. If necessary, part the pivot lugs slightly to do this and
squeeze them gently back into position after fitting. Swing the loop into its
normal position as shown in the diagram and bend the half-etched stop sideways
towards the tail of the loop.
(d)
Fit a magnetic dropper. Make
a magnetic dropper from the 0.35mm soft iron wire supplied. Trim its total length
to 10mm. It should clear the railhead by 1mm.
 Hook
with Type 1 Latch (diagram
right)
(a)
Prepare the hook. Remove
the lower half-etched loop/latch stop. Depending on buffer length, remove or
retain the lugs on the shank (see above).
(b)
Prepare the latch. Fold the
latch around the edge of a piece of fret material (half-etched dots inside) to
ensure the correct distance between the legs. Pass a length of 0.5mm wire
through the two holes in the latch. If the wire and latch are not at 90deg, push
the latch gently sideways until they are. Fill the end of the latch with solder
as shown. File the latch flat, top and bottom. Any unevenness may impair the
working of the coupler. With a cutting broach or 0.6mm drill, open up the pivot
holes to give a sloppy fit on the 0.5mm wire.
(c) Fit latch to hook. Flatten about 0.5mm of one
end of a piece of 0.5mm brass wire by squeezing in pliers. Position the latch
over the hook and pass the wire through the pivot holes in latch and hook. Cut
off the wire 0.5 – 1mm from
the opposite side of the hook and flatten this end
also
in the pliers. Fold the upper latch stop sideways.
 Hook with Type 2 Latch (diagram
right)
(a)
Prepare the hook. Prepare the hook by
soldering in a pivot wire in exactly the same way as for the hook with loop.
(b) Prepare the
latch. Bend the
pivot lugs upwards through 90deg (half-etched lines inside). Bend the tail of
the loop downwards through approx 45deg. Open up the holes in the pivot lugs
with a broach or 0.6mm drill to give a sloppy fit on the 0.5mm wire.
(c) Fit latch to hook.
Use the same method as
described for fitting the loop. Bend the half-etched stop sideways, towards the
latch tail then adjust the angle of the tail until the latch is almost vertical
when the tail meets the stop.
Fitting Couplers to Vehicle
 IMPORTANT: check
the lengths of the buffers on your stock – IF POSSIBLE, sprung buffers should
be adjusted to either 6 or 7MM projection. For all buffer lengths, the
couplers must be fitted so that the hook projects the same distance from the
beam as the buffers (see diagram right for method). THE CENTRE HEIGHT OF THE
COUPLER SLOT SHOULD BE 14MM ABOVE THE RAILHEAD. If it differs much (more than
about 0.5mm) from this height, remove the existing drawgear endplate from the
buffer beam, drill a 2mm hole at the correct height, and use one of the etched
drawgear endplates provided.
The
couplers are fitted in the same way as the usual 3-link or screw couplings –
through the coupler slots in the buffer beam. They should be secured by adhesive
(cyanoacrylate or epoxy). Holes are provided in the shank for fixing by spring
and split-pin. However, rigid fixing is to be preferred, because it gives
positive positioning and more reliable operation.
If no
coupler slot or pocket is provided, or if it will not fit the shank on the hook,
drill a 2mm hole through the beam centred at 14mm above rail height. Cover it
with one of the drawgear endplates provided on the etch, and fit the coupler
through the slot.
Double-Ended Operation
On
many layouts, rolling stock is never turned, so single-ended couplers are no
problem. However, to allow locos to be turned, it may be possible to fit
double-ended couplers. A loop and a type 1 latch (but not a type 2 latch) can be
fitted at both ends of the loco. In assembling
double-ended couplers, first solder the pivot wire into the hook. Then bend the
type 1 latch until the eyes on the ends are about 3mm apart and place over the
pivot wire. Squeeze the latch together adjacent to the pivot wire and fill the
end of the latch with solder. Finally add the loop in the usual way. It is emphasised that
the couplers will almost certainly not work as well in this set-up as in
single-ended mode.
Operating with Dingham
Autocouplers
Electromagnets
are recommended for actuating Dingham Autocouplers. Suitable magnets are
available from several suppliers, or may be home-made. Permanent magnets, with a
lifting and lowering mechanism (lift the magnet to actuate the couplers), may
also be used. If using permanent magnets, make sure that a pole of the magnet is
facing upwards. (The magnetic field is strongest near the poles).
Examples
of operation are given below.
Example
1: A passenger train enters a station where the service terminates and the
loco runs round. The train is stopped with the coupling between loco and train
over a suitably placed magnet. The loco now eases back on the train (a movement
of about 2 – 3mm and quite prototypical, because the buffers have to be
compressed to allow the screw coupling to be unhooked). If the magnet is now
briefly energised, latched uncoupling will take place, and the loco can move
away from the train at any time.
Example
2: For shunting a yard, magnets can be placed at the entrance to a fan of
sidings. Only one electromagnet may be required, though it is often advantageous
if several are provided. As a train is propelled into the yard, any coupler may
be uncoupled by energising the magnet as that coupler passes over it. The
vehicles will remain uncoupled so long as they are propelled steadily.
Example
3: The diagram below shows the arrangement of magnets on the layout for
which the Dingham Autocoupler was developed.
A
more detailed account of positioning magnets for realistic operation is included
in the instructions for the Dingham electromagnets which can be accessed on the Dingham website or is available from
Dingham
in return for an SAE.
©
Copyright DINGHAM 2002.
All Rights Reserved.
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