ASSEMBLY GUIDE – STAGE 49
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components that will suffer a certain amount
of wear and tear in an RC car.
To make the glow plug coil heat up initially, it
must be supplied with electricity from a glow
starter, but once the engine is running, the coil
will stay hot and the heater current will no
longer be needed. The temperature of the
element depends essentially on its thickness
and length, so glow plugs can be made to suit
the different operating requirements of
various designs of engine.
The shims
The cylinder in your Huracán’s engine
contains an inner lining, in which the piston is
housed. In order to compress the fuel-air
mixture in the combustion chamber formed by
the piston liner and the cylinder head, the
piston must fit within the cylinder as perfectly
as possible. As the engine runs, the piston and
cylinder work together in such a way that
when the piston moves up, it forms a
hermetical seal with the cylinder liner and
head at top dead centre, and when the
piston is at the bottom of the cylinder,
the extra space above it allows lubricant
into the cylinder to keep the parts
working smoothly. To make the most of
the energy released during combustion,
the distance between the top of the piston
and the cylinder head must be correct: too
much space, and there is a loss of power,
resulting in poor performance, while too
little space can impair the internal workings
of the engine and reduce its efficiency. By
using shims, you can adjust the size of this
space and optimise the engine’s efficiency.
The use of shims is linked to the type of fuel
mixture that you want to use. One of the most
widely used techniques for getting the
maximum performance from an engine is to
increase the proportion of nitromethane in the
fuel. The higher the percentage of
nitromethane, the greater the pressure
generated by the combustion of the fuel in the
cylinder. Experienced RC modellers
recommend using a 0.1 mm-thick shim for
approximately every 10 per cent of
nitromethane. So, with a 16 per cent mixture
(the most common in 1:10-scale models), you
should use one of the two 0.14mm shims
supplied with this stage.
Above: An RC car being
prepped for use. You can
see the glow starter
(arrowed) projecting from
the top of the engine.
Below: The cylinder and
liner (on the left) and
cylinder head (on the
right) with the glow plug’s
filament visible (arrowed).
Above: A shim positioned
on the cylinder head. Your
use of shims will depend
on the fuel mixture you
want to use.
Left: Here you can see
the glow plug (circled),
screwed into a hole in the
cylinder head, directly
above the cylinder itself.