The main drive wheels will require a lot of attention. First job is
to get rid of any fluff, dirt and oil. The running surfaces and the
back of the wheels need to be spotlessley clean. Use matchsticks,
cocktail sticks or finger nails to clean off the compacted crud that
gets onto the surface. A lint free cloth with methylated spirit can
be used to help remove greasy deposits. Wipe with a dry section
afterwards - don't just leave it to evaporate. Get a hand lens. The
axle on the left looked clean to the naked eye and when viewed with a
reading style magnifying glass. Only with the hand lens and the
camera set in macro mode does the hair/fluff and grease show up.
Tweezers, pins, scalpels help to get get stuff like this out.
Oil and grease. Only recommended oils should be used. The axle runs
in a brass bush and brass is self lubricating. However, a tiny spot
of oil applied at the end of the brass sleeve will provide a very
thin coating between the two surfaces. I use a very thin oil, pour a
little into a plastic tray and dip a pin into it. The tiny drop that
forms on the end of the pin is about the right amount.
Now check the quartering.
This is a pretty accurate visual check. Given the amount of play that
is built into the design of the holes/slots on the drive wheel
coupling rod, this should be good enough. See picture to see how much
freedom the coupling rod provides on the centre pin. The same amount
exists for all 3 pins.
There are 20 spokes in each wheel, and the screw hole nestles between
two spokes. Take a piece of cork or balsa and draw a straight line.
Take a track pin or sewing needle and insert it from the inside
between the spokes near the screw hole on the side of the axle
without the cog. Count round 10 spoke gaps and insert another pin
from the inside. Turn the wheel over, and place the point of both
pins onto the line. Push them into the cork so that the wheel is held
in place. Do the same for all 3 wheels.
Having done this, you know that the underside holes are all facing in
the same direction. They are positioned on the line. Take a look at
the holes on the top. They too should be in the same position
relative to each other. Forget the term 'quartering'. A real engine
will have one side rotated 90 degrees from the other side to ensure
that when one piston is at top dead centre (and can't provide any
power to the wheels), the other piston is able to turn the wheels at
the most effective part of the cycle. For the model, how one side
relates to the other is irrelevant from an operational point of view.
(Purists would argue) - as long as the position of the holes relate
to the wheels on the same side of the engine. There is a parallax
effect in the photo above, but the position of these holes is good.
It is possible that the gear has rotated relative to the position of
the crankpin hole. (Or more likely, the wheel has turned). A quick
check can be made by looking at the teeth of the gear through the gap
in the spokes nearest to the crankpin hole. In practice, the slot in
the coupling rod will easily compensate for a gear that is half a
tooth out of alignment. If you can't turn the wheels on their axles
easily by hand, then dont try - they will turn, but forcing the issue
will result in a wheel that is more likely to slip in the future.
Check the Gauge.
The gauge is 9mm, but what is important is that the wheels go round
the track and over points smoothly. Place the wheels on a track. You
should feel that the wheels are able to move from side to side
between the tracks, rather than being tight against each side.
The wheels also need to go over points. There are two checks here.
The first is demonstrated in the photo opposite. The left hand wheel
(looking into the photo) is placed tight against the guide rail. Look
at the right hand wheel. It is about to hit the apex of the plastic
junction where the two rails meet. Not good. The wheels need to be
slightly closer together on the axle. Take an axle out of a newish
carriage or wagon to confirm the required gap. This axle would be
fine most of the time, but occasionally it will derail going over
points. Which is exactly what it used to do. I spent ages sorting out
issues with points !!!
The other test to carry out is the opposite of the above. Push the
wheel axle over to the left hand rail. Make sure that the right hand
wheel doesn't foul the inner guide rail.
You may have elected not to desolder the blue wire from the main
drive wheel pickups. However, you should be able to lift them from
the engine, clean them up and straighten the two arms. Clean the
point where the arm touches the wheel - use very fine wet and dry
emery paper. Then make sure that the arms are bent outwards so that
they press against the wheel rather than just touch it. I don't have
a picture of this component, but you can see the arms in this shot of
the underside of the chassis.
The front bogie has a shaped copper contact strip which acts as a
spring which keeps the wheels lightly planted on the track. However,
it also acts as a means of ensuring that the left wheel provides an
extra negative pickup for the chassis. This is important because only
one of the driving wheels has a permanent negative contact - the
other two have rubber tyres.
My Mallard is a Hornby Minitrix Model. My Flying Scotsman is a later
Minitrix (not Hornby) model. Essentially they are identical - except
in a few small details. When I was investigating what appeared to be
an electrical fault in the Scotsman, I discovered that the contact
point for the copper spring for the front bogie, had been painted
over with the rest of the chassis. (Arrowed in the photo linked to
the bottom thumbnail, after I had used emery paper to remove paint.)
It occurred to me that this may be true of all later (non hornby) models.
The pictures on the left are all from the Flying Scotsman.
I checked the rear bogie too. The axle sits in a half round slot and
is secured by the plastic cover, which is held in place with a
plastic pin and a single screw. Remove the screw, lift off the cover
and remove the axle. Note that one wheel is insulated where the axle
joins the wheel. The axle should be connected to the left (negative)
side of the loco, so the insulation should be on the right side.
Remember that the loco is upside down when you follow these
instructions. In the photo, left (negative) is the wheel towards the
top of the picture.
The half round slot was also painted, so there was no electrical
connection here either. A small area of wet & dry emery paper
wrapped around a watchmakers screwdriver soon made a nice shiny
smooth contact. No brass here, so a tiny dab of oil was applied
before fastening it up again. Check the continuity between the left
wheel and the chassis.
Now check the half round slots for the 3 main drive wheels. Clean
them in a similar manner. Blow away any debris.
I checked out my second-hand Britannia model, which had been running
erratically. The Britannia uses the same chassis and drive wheels as
the Mallard, but the bogie and tender connections are different. Only
the live wire runs to the tender. Negative pickup is transmitted
through the coupling to the main chassis. However, the Britannia also
had all points of electrical contact painted over. These were between
the chassis and axles and between the chassis and front and rear
bogies. I removed the paint in the key areas and re-assembled, and
the engine no longer stalls over points and round some bends as it
There is a brass plate fitted to the underside of the motor which
sits on top of the chassis. One tab of the plate is soldered to the
contact strip of the motor, and is there to provide the electrical
connection between the motor and the chassis. It is worth cleaning up
the underside of this strip and the area of the chassis with which it
makes contact. I dont have a specific photo for this, but you can see
the strip under the left hand end of the motor, and the large blob of
solder where the strip is folded up and attached to the lower contact
strip of the motor.
Loco / Tender connection. Unlike some locos, there is no need for a
spring connection under the draw bar between the loco and the tender.
Electrical connection for the chassis is provided through the black wire.
The plastic slider should slide smoothly. If the metal has acquired a
light coat of grime, this may not happen. Wet and dry paper and a
wipe of tissue with oil on the slide bars should make the motion nice
and smooth again. The photo shows the rear view of the right hand
side valve gear, with the slider half off the fixed bar. (Note that
as it is now, the slider needs to be positioned to the other side of
the pivot arm. Springing the horizontal arm slightly may help to get
the linkage rivets to move past each other.
The motor is a standard piece of equipment and can be easily obtained
on the internet from German Model Railway shops. The same applies to
the brushes. The brushes have part number 40015400 and the motor is
41207610. Google this number with the word 'Trix'. The german for
brushes is Kohlebürsten.
Peer in and see if the brushes have plenty of carbon remaining. Look
at quality of the commutator - they may be covered in carbon and need
a clean. Dont use anything that will leave minute strands of
material. Meths or alcohol may help if it is used to slightly dampen
the lint free material you are using to clean.
A tiny drop of oil can be applied to the bearing at each end if it
looks as though they need it. Don't oil anywhere else and dont apply
more than a tiny drop. It will end up all over the place and possibly
ruin the motor. Give the motor a run - the contacts can be pressed
against the 9mm track. Check it runs fast and then slow it down.
Check the tyres. If they have been on a while, then replace them.
Even if they are still intact and not moving, the rubber will harden
over time and the wheels will slip as a result. The one on the left
has seen better days. Not got any ? The part number is 72087800. The
german name is 'Haftreifen'. Put Trix 72087800 into Google. You
should be able to get a pack of 10 (10 Stück) for less than a
£5 plus p&p. And its not as if they are about to go out of
stock. Many current models use the same tyre. I find the German
suppliers are fast and efficient, and have more stock than the
This is a comparison - on the left, tyres removed from a late 1980
MiniTrix Flying Scotsman. (Same chassis and wheels as Mallard),
compared to a brand new set. The Scotsman was slipping considerably
at starts and on gradients. The removed tyres are slightly larger
than the wheels, and the rubber has hardened. It turned out that the
wheel was spinning inside the tyre. The new tyres look odd - the
'flat' seems to be on the side rather than across the width - but
this is how they are, and they stretch into shape around the wheel.