The 7mm Dingham Autocoupler
Assembly and Fitting Instructions
The instructions for the 7mm 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 4ft 6in 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 properly adjusted buffers on vehicles. If buffers are too
long, it may be difficult to couple vehicles on curves. If buffers are too
short, 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 the loop lifting and uncoupling. For the same reason, uncoupling may be
unreliable if buffer springs are soft enough to compress during normal shunting.
The short hooks and loops, intended for some industrial locos (8.5mm buffer
length), are a compromise, because 8.5mm is insufficient space to accommodate
the
Dingham geometry. The short loop will couple and uncouple with standard
hooks, but the short hook will suffer loop-hook contact. This problem will be
lessened if the type 1 latch is used with the short hooks.
NOTE:
THE COUPLERS SHOULD BE CHEMICALLY BLACKENED ON COMPLETION. THEY WILL NOT WORK IF
PAINTED. Carr’s metal black for nickel silver is suggested. Clean and degrease the
couplers before blackening.
Hook
with Loop
(diagram
below)
(a)
Prepare the hook. Solder
a short piece of 0.8mm brass wire into the pivot hole in the hook. (Make a
simple jig by drilling a 0.8mm hole about 2mm deep in a piece of wood).  Trim so
that about 1.5mm of wire protrudes each side of the hook and remove burrs. (A
jig made by drilling a 0.8mm hole through a piece of 1/16in brass strip is
useful here). Remove the upper half-etched latch stop. If fitting to a vehicle
with 10.5mm buffer projection, remove the lugs on the shank. Retain the lugs for
12.5mm buffers.
(b)
Prepare the loop. Bend the
pivot lugs upwards through 90deg (half-etched lines inside). 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 5mm of the tail back to the horizontal and (optionally) put a 90deg twist
in it to bring the eye at the end vertical. With a cutting broach or 0.9mm
drill, open up the holes in the pivot lugs to give a sloppy fit on the 0.8mm
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 0.7mm soft iron wire supplied. Trim its total length
to 17mm. 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 lines inside) to
ensure the correct distance between the legs. Pass a length of 0.8mm 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. Take a 3mm length of the 0.8mm-wide
strip, insert into the latch as shown and solder. Alternatively, fill the end of
the latch with solder. Remove any projections carefully. They may impair the
working of the coupler. With a cutting broach or 0.9mm drill, open up the pivot
holes to give a sloppy fit on the 0.8mm wire.
(c)
Fit latch to hook. Flatten about 0.5mm of one
end of a piece of 0.8mm 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 0.9mm drill to give a sloppy fit on the 0.8mm 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 – sprung buffers should be
adjusted to either 10.5 or 12.5mm projection. For all buffer lengths, the
couplers must be fitted so that the hook projects the same distance from the
beam as the buffers, or up to 0.5mm less (see diagram below). THE CENTRE HEIGHT
OF THE COUPLER POCKET SHOULD BE 24.5MM ABOVE THE RAILHEAD. If it  differs much
(more than about 1mm) from this height, remove the existing pocket, drill a
2.5mm hole at the correct height, and use one of the etched pockets provided.
The
couplers are fitted in the same way as the usual 3-link or screw couplings –
through the coupler pockets in the buffer beam. They should be secured by
soldering or by adhesive (cyanoacrylate or epoxy). Holes are provided in the
shank for fixing by spring and split-pin or by the spring-wire method used in
Peco kits. However, rigid fixing is much 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 2.5mm hole through the beam centred at 24.5mm above rail height.
Cover it with one of the pockets provided on the etch, and fit the coupler
through the slot in the etched pocket.
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 as shown in the diagram left. 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 over a 3mm length of 0.8mm-wide strip and
solder in place. 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 3 – 4mm 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.
©
Copyright DINGHAM 1999.
All Rights Reserved.
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