Page 42Is a Clutch Necessary?

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In a car, yes.
A special starting gear, 1st gear, is needed to overcome static friction
and clutch/accelerator skills are needed.

But with a Stirling – and connected to a propeller?

I argue “No – not necessary”

I have been using a 3 cylinder simple beta, atmospheric, for some years.
It is directly linked to the propeller. No gear box – no clutch.

Built by Norris Bomford around 1999, it has been starting nicely ever since (20 years)
See this video for a description of the starting procedure.

Yes, to start a Stirling engine when it is already connected to a load, it does require more energy from the engine.
But with a propeller, the load is proportional to the revs.
When the engine first starts to run the revs will want to climb, and the load will rise to match.

The load is variable and the engine coupled to the propeller is self regulating.

A recently built 100cc swept volume pressurised single beta is quite difficult to manage
when it starts on the bench. It roars into life and in the first few seconds is headed for
a thousand rpm and self destruction. Being attached to a propeller, in water, could be
very welcome news.

But yes, extra power is needed to start an engine under load.
My argument is that all that is needed is to wait a little longer for sufficient heat to build up.

Engines don’t start at 10 rpm. Usually under 100 rpm. So there is the need for the engine
to not just start and overcome its own friction, but to overcome the load of say 75 rpm.

Wait for the heat to build.