If you want to drive a car,
there’s quite a lot that has to be taught and learned.
take lessons from a driving instructor, have to take a written
examination and a practical
driving test on the road. That’s
the law in the UK.
An important part of this “learning
curve” is about the engine and the car – and how to
Pulling away from a standing start has to be learned.
Changing gear with a manual gearbox.
Knowledge about stopping
distances being the square of your speed.
there are “things you need to know” about the use of a
Because Stirlings have little in common with
our everyday experience of petrol engines.
start with the lawnmower and its pull cord. (A pretty abysmal
situation – but a
worldwide “that’s how it is” pretty
bigger the “pull” that you can achieve – the
better. Sudden, fast and strong.
The reason is this four
stroke business. The spark plug will only spark every fourth
Every other revolution
of the engine. If you can spin the engine twice – there is
chance that the plug will spark and start the
If you can get it to spin for four revolutions, then
there are two chances that it might start.
have to provide the effort to
compress the gas to get the engine through that fourth stroke –
the compression stroke.
Stirlings are very different.
There is no spark plug. Or four strokes to the cycle.
the hot end of the engine is hot enough – it wants
As soon as
it is running, there is no compression stroke. But for the first
turn – there is
compression. It is necessary to lever,
or pull the engine past the first contraction stroke.
cold air inside the engine has not been cooled/contracted below
Once that cold gas has been shifted to
the hot end and heated - then the expansion stroke
– and then the rest follows. Cooling causes a partial vacuum
and the contraction
stroke keeps the piston moving.
absolutely no need for a huge spin to get revs – and energy
– into the flywheel.
To start a Stirling you
must WAIT for it to get hot enough.
like making a piece of toast.
It takes time for the heat to
get to the piece of bread and do the job.
When it is
hot enough, the engine will
run. Just wait.
Cranking away at a Stirling when it is
not hot enough is counter productive.
When a Stirling
is running, heat is taken from the hot end and turned into
energy. The temperature of the hot end is
when the hot cap is not hot enough, and you crank the engine, you
are actually making the hot end even less hot – and less
able to run.
NOT to do
a Stirling is running, it is essential to keep an eye on the state
of the cooling water system.
It’s obvious that the hot
end of the engine must be kept hot.
The burner must be
alight – to keep the engine running.
heat must be removed from the cold end by the cooling system.
cold end must be kept cold.
If the cooling system
fails, then the engine power will fade. The cold end of the
just gets hotter and hotter. Too hot. The engine will
slow and stop.
The problem is that once heat has got
into the cold end. It takes quite a long time to
get the heat
out. The cooling system will have to run for quite a while to
the coldness of the cold end.
essential to keep the water in the cooling system and flowing