The model is both a
nostalgic reconstruction as well as a complex exercise in CAD. Many years ago,
my brother Christopher and I spent hours glued to the TV watching California
Highway Patrol (CHiPs) episodes. In 1982 I received a plastic 1000cc Kawasaki
CHiPs motorcycle model kit produced by Revell, which was quickly glued together
willy-nilly. It eventually was stood on, becoming distorted and mangled (as many
kids toys eventually become). In about 1987 (and after accumulating quite a bit
of Meccano), my brother and I decided to build a Meccano version, based on the
remaining mangled parts of the plastic kit (Of which I still have the remains
today!) At that stage, some Meccano components in the engine were held together
literally by string due to lack of parts/technique! It did however receive
favorable comments when we presented it at the first Meccano club meeting we
attended at the Johannesburg Meccano hobbyists in Johannesburg.
A Union Plastic Model
The remaining Revell
Chips Motorcycle Kit parts
Since then, the model
underwent a rebuild in 1994 for the Rand Easter show. Then, in early 2000, I
started experimenting with drawing parts using a package called Pro Desktop. I
did'nt have far to look for a subject! Amongst the first parts drawn were those
on the motorcycle and it wasn't long before I had made some headway with the
front suspension. The project was then shelved due to other distractions,
although I knew I would eventually get around to drawing it completely. By 2002
I had completed various Meccano CAD projects, but the motorcycle always remained
incomplete. Until now.
The TV series made the
Kawasaki police bike famous around the world. An unintentional marketing stunt
par excellance. The model represents a much sought-after 1981 version. The
police motorcycles differed from civilian ones by the presence of the obvious
rear mounted radio, the lights, siren, colour, etc. Unseen modifications relate
to engine modifications: from larger ports and pistons to polished intakes (some
say they were opened up to 1200cc, but this is more likely urban legend). At the
time they were really performance pocket-rockets. Many of these cycles are still
in use to day and are highly prized collectibles. There are still various clubs
who dress up as cops and go riding around the countryside. (No, at this point
you can't start singing YMCA....)
An MO Mk II (or III) powers
the rear wheel via chain. All-round suspension, complete with functional front
and rear disk brakes add a degree of realism, but are more of a token effort
than of any real stopping power. The flat windshield is different to the more
familiar molded/windswept ones found on later police cycles. Triangular clear
plates would have come in useful here! I have added some of the newer French
parts and a few narrow fishplates from Exacto for improved detailing. Another
feature is the multiple component construction.
You might argue that lots
of the model features compromise on the "real thing". For example, the chassis
is marginally higher than it needs to be, due to the chassis strip construction.
The angle of tilt of the engine is slightly too large and brake calipers are not
floating, like on the real thing, etc.. What you must remember is that the model
was built when we were only 12 and 14 years of age, when a true sense of scale
and engineering principles still required some refinement! If I were building it
from scratch today, many things would be done differently. That is not to say
that its a bad model! There is still large scope for experimentation and
improvement by modelers:
The original model had a
(somewhat fiddly) 2 speed gearbox, actuated by a gear lever in appropriate
position (not present in this model plan). The hand accelerator was attached to
a potentiometer, which allowed the motor to rev as the grip was rotated. At the
same time via cable, the rev counter (a piece of wire trapped behind the head of
a screw) would also climb the revs proportionally. Also fiddly, and not included
in the imodel plan. I suppose if you were really dedicated, it might be possible
to build the entire frame from formed 4mm wire, which would be far more
proportional since parts would sit INSIDE the frame rather than on top and
below. (I might do a CAD version of this). It is also possible to outfit the
model with the appropriate sound effects from one of the IR kits remote control.
Failing that, a recording of the real thing might do nicely. I will present a
compact DIY circuit for 30 second solid-state sound recording and playback in a
future article. Suitable LEDs can be attached inside the modern plastic parts to
act as the main lights of the cycle. Batteries can be housed inside the saddle
bags and radio. For exhibition purposes, a base was originally constructed to
allow both wheels to rotate.
Details such as siren
(attached to the front bumper bar, right hand side) and stand (either pull-back
or tilt), spark plugs wiring, lighting, motor control, etc. are left up to the
imagination of the builder. As mentioned previously, one of the sound effects
tabs from the French IR kit can possibly be used for the public to press at
The list of improvements
could go on and on!
Drawing it in
The main challenge of
drawing the model was not drawing the curved strips, but surprisingly getting
them in the correct relative positions. In the realest sense of the word, the
model was "rebuilt" in CAD from photos, using parametric modeling constraints
and interactive components to ensure everything fits correctly and the frame
bends variably if required. For instance, the width of the chassis depended on
the width of the engine, which depended on the angle of the front spar of the
motorcycle. Instead of pulling out a calculator and working out all the
geometry, it is much easier to create the engine and the frame separately, then
deform the frame to match interactively. Granted, the curved strips are one-offs
and not modified flat strips, but who cares, the extra work of drawing them is
worth it, and the one offs are filed for future use (much like my permanent
collection of warped strips which sit in a separate box). Re this: Consider for
example the warped 3.5" strip on the petrol tank!
Presentation is a mix of
exploded drawings, assembley sequences, numbered parts and multiple views of
fully assembled modules. I did not stick to one particular style of
presentation, since it would have made things exponentially complex.
Pro Desktop parts (some 450
now) are still not posted on-line. Coming soon.
I tried extremely hard to
avoid what South Africans are fond of calling "jippos", "maak-n-plans" or just
plain shortcuts. All of the parts used in the model are standard in size and the
model can really be constructed as shown.
No real warnings are given
as to holes that must be left open during construction. Exact attention must be
paid to each stage to avoid frustration and undoing of bolts to get things to
Many of the collars in the
model can be substituted using plastic spacers.
This next statement sounds
so obvious, but there are important implications for saying it: the correct
spacing between the two halves of the frame is decided by the following points
only: The 1" double angle brackets at the rear, the rear wheel screwed rod (81),
the carburetor, the front steering column and the front engine mounting points.
All the others points must follow on from these.
You will no doubt complain
about the way that the frame is constructed! It is unfortunate in that it lacks
rigidity and relies on everything being tight. When constructing, try to keep
the upper 3.5" strips parallel with the bottom 2" strips. Hand tighten all
points on the frame. Once all the various modules are fitted, adjust and tighten
well. It will take some time to get this part right!
Note the system used for
the front suspension to hold it together: a 1mm wire is bent over at its end to
form a small ball. The free end of the wire is passed through the bottom of each
suspension damper, down the centre of the keyway rod. The small ball of wire is
trapped against a shoulder bolt screwed into the damper. The free end of the
wire is then attached to a screw on a collar on the steering column.
Disc brake performance may
be significantly improved by using a screw-actuated type of some kind. Note that
the front left disk free-wheels. You can either glue or solder the disk to the
front wheel. If a larger disk (or gear blank) is used which is more to scale,
then two of the radial holes can be used to bolt the disk to the front wheel,
with larger clearance for the pads.
Note that plastic rods have
been used in certain parts of the model to represent "bumper bars". These can be
gently heated and bent into shape. Alternatively, use large (4mm) chromed coat
hanger wire. The joins between bumper bar T-junctions are non-existant at
present, but the builder is left up to his/her preference to do something about
The exhaust currently uses
a plastic plate that is heated and rolled into shape. Alternatively, you may
consider a pair of rolled up plastic "wings" from the Crazy inventors bat set
for the two exhausts.
Original construction time
(real parts): 200 hours.
Computer construction time (excluding presentation):
100 hours on an AMD Duron 600Mhz PC, 200Mb RAM (no 3D-Gl card) spread over a
month (using existing parts).
CAD package: Pro/Desktop
Most screws, nuts, bolts and transverse bores are shown
Time taken to ray trace final model: 35 minutes.
Swap file size
during rendering (virtual memory used): 4.5Gb
Multiple layer format using window capturing to Paint shop Pro. Exported to
The various model files use
about 30Mb of hard drive space. If separate part files are included in the
tally, the size is approx 130Mb.
Total number of parts:
approx 2400, including the "invisible" ones required for threading.