Crewe Tractor
You will need superglue (I find the cheap stuff from pound stores works well with plastic parts printed with PLA). I have not had much success with other glues. If you choose to print with other plastics you will need to use an appropriate glue or solvent.
The various holes for axles and screws are nominally printed
to the correct size but experience shows they vary. It is useful to have a 2mm
drill to clean up the axle holes in wheels and 2.1mm for the axle holes in
frame and motor mount/gear locating bracket. If you have a 1.4mm drill it would
be worth using it to check the clearance holes for the screws that hold the
frame together.
The motor, battery box and switches will need to be wired up using a small soldering iron.
The railway chassis frame is held together with 12BA hex screws and nuts. Most screws are ¼” long; longer 5/16” screws secure the rear frame cross member. If you do not have a 12BA hex socket, there is a 3D files to print one which is almost as easy to use.
12 tooth sprocket (2). I suggest purchasing commercial
sprockets (these are a very tight fit on the axles. It may be helpful to use a
vice to press these onto the axles). If you choose to use the 3D printed
sprockets you may need to spend some time cleaning them up to get the chain run
smoothly. Axles are 2mm rod. Press a sprocket onto each axle leaving 12.5mm of
the axle projecting from the longer spigot side
Wheels (4) - Slide one wheel onto each axle, hard
against the sprocket. For the front axle slide on the second
wheel and set back to back to 28.5mm. You will probably find you need a
drop of superglue to retain the wheels.
Motor
mount/gear locating bracket– use a 2.1mm drill to clean out the axle holes
and clean up so the 16 tooth pinion can fit freely into place. Slide the second
(rear) axle with sprocket in place into the motor bracket followed by the
pinion. Continue pushing the axle
through the motor bracket to be 15.5mm from the axle end. Slide on the wheels and set
back to back as for the front axle.
Left hand side and right hand side frames
These are deeper at the rear end. Insert
four 12BA nuts in the slots on the inner surface. You may find it helpful to
stop the nuts falling out by applying tiny spot of glue or filler after the
nuts are in place (I have used Milliput or UHU or a
sliver of Blutak)..
Front and rear end cross members The front cross member has flanges
to fit on top of the side frames. The rear sits inside the side frames and
needs two more 12BA nuts. The front cross member is secured to the side frames
by 2x1/4” 12BA hex headed screws. The rear cross member with 2x5/16” 12 BA
screws.
Suggested
approach is to first assemble the left hand frame side and the front and rear
cross members. Next drop the prepared axle and wheel sets in place (ideally
with the chain in place around the sprockets). The chain sprockets should be on
the left hand side of the vehicle. Lastly fix the right hand frame side.
Centre frame cross member – Fix to frames with 2x1/4” 12BA
screws. On the original a cross-member here would have been the mounting for
the turning jack.
The motor mount can now be secured to the
frames with 2x1/4” 12BA screws.
Assembly
gets easier after this!
Buffer coupling (2) - Glue into recesses on the front and rear frame
cross members.
Chain covers - These fit between the footboard steps
moulded on each side frame and over the bracket at the rear of the side frame.
Glue these in place so the locating strip at the front is below the footboard
and the back support lines up with the bottom of the frame.
Rear car axle clips - these retain the rear car axle. They form part of the side fames – the car
assembly can be removed by undoing the front axle securing screws and then
slipping the car chassis forwards.
Foot brake lever – secure this to right hand frame
just ahead of the frame cross member. Do this after mounting the car assembly
so the pedal is in a position for the driver’s right foot.
These parts
glue together. Superglue sticks this plastic (PLA) well. Neither ordinary
Polystyrene cement nor Acetone really worked for me though other people tell me
they are ok.
Front spring and axle - in two halves. This part has two
holes whic need to clear 2x1/4” 12BA securing screws passing downwards
into nuts held in the railway chassis side frames.
Rear spring and axle - in two halves. The axle sits on the railway chassis
retained by the two clips mentioned earlier.
Car chassis frame - glue to pads above front and rear springs.
The flat side is uppermost and the shorter arms go to the front.
Radiator front – This is best printed with support.
Support material at the back does not need to be removed. Line the radiator
front up with the front of the car chassis.
Dashboard – glue to back of bonnet
Bonnet - glue to back of radiator and the car
chassis frame.
Bonnet handles are a “U” of copper wire fitting in the holes at the bottom
edges.
Truck load bed – This part again should be printed
with support. There will be a lot of support material to remove on this part –
once cleaned up the car chassis frame should press into place between the truck
frames. The truck bed front should line up with the moulded notch on the sides
of the car chassis frame.
Rear cross beam - This fixes to the bottom of the
truck bed 5mm from the rear end. The circular studs on the bottom should line
up with the similar studs on the railway chassis.
Seat - this lines up with the front edge of
the third plank on the flat part of the Truck bed.
Seat back
Seat back support (2) – rather flimsy – I suggest
printing a few spares. Glue to seat and seat back.
Fuel tank - goes beneath seat.
Hand brake lever - fix to truck bed frame alongside
seat on right hand side.
Pedals – These can be added should you
desire. You will find 3 holes in the floor for dummy pedals. I used track
spikes for these. You could use small pins.
Steering wheel – Another part best printed with
support. It is rather fragile so take care removing the support material. Glue
to steering column which can be made from a cotton bud stem. Then glue into
angled hole in dashboard. The steering wheel should be about 35mm from the
dash.
Dummy coil springs – eind these
from 1mm soft iron wire round a suitable rod ( try an
M4 screw). These can be glued over the cylindrical studs at the rear of the
railway chassis. The top of the springs should just clear the bottom of the
truck body. These are about 13mm long around 5mm diameter
Starting handle – make from wire and fit in hole
below radiator.
Serv-o-link Delrin chain and 12mm sprockets (2mm
bore) – These can be
sourced from Motionco) 57 links should be a snug fit
on the 12mm sprockets.
Size A 1.5 – 3 volt motor (from Technobots)
Worm .5 MOD (from Technobots)
16 tooth .5 MOD pinion
gear (from Technobots)
Axle 2mm diameter (2) 52mm long
DPDT reversing switch. Latching push button on/off switch. (from China via ebay) – mounted in a dummy ammunition box.
AAA battery holder – Another dummy ammunition box or
boxes with battery contacts secures and hides the battery. Battery contacts can
be sourced through eBay.
12BA x ¼” and 5/16” hex screws and
nuts
Wire to connect up – will need to be soldered in place.
You will need to decide where you wish to put the reversing switch. In my first
model the reversing
was by an on/off/on toggle switch fitted from below through the
truck bed. This was tricky as there is limited clearance alongside the
motor. The battery holder went in at an
angle under the bonnet. This made changing the battery a daunting task as I had
to remove the whole car body from the chassis frame to get at it.
In follow up
models I have made a battery box out of a printed plastic box intended to look
something like an ammunition box or boxes of the period. I put the reversing
switch and on/off switch in another box.
The wiring is threaded through the truck bed to reach the motor with a
couple of inches of slack. I suggest using a plug and socket so car body and
railway chassis can be separated if required for maintenance or painting (again
these can be sourced through eBay).
The pictures show how I have wired up the most recently
built models.
A few fuel
cans – can be
printed and glued to the truck bed.
Paint – Tamiya
paints work well. I used TS-5 (olive drab) spray paint with XF-58 (olive green)
acrylic brush paint to touch up. XF-51 (khaki drab) and XF-49 (khaki) were
useful for the dummy ammunition boxes.
©Dave Watkins 2020