>>In the discussion of large multibank/cylinder engines, the term 2
speed
>>supercharger or turbocharger comes up. How did they do this? It would
seem
>>shifting a turbo or supercharger while it was running (I assume) would
be
>>'interesting' considering the load or RPMs
>
>In the drive train of the mechanical supercharger there was a small
>two speed gearbox. The pilot had a little switch for 1st or 2nd gear
>of the supercharger.
>
>So they could get good charging pessure at low engine revs in the
>first gear and use the second gear to avoid too high revs of the
>supercharger when the engine reved high.
>
>The BMW engine of the Focke-Wulf FW 190 had a mechanical governor,
>called the "Kommandogeraet" which did all this for the pilot, like
>a modern electronic motor management.
The Spitfire too in later marks but without the "command system"; the
pilot made the _up-shift_ at around 10,000 ft to increase blower speed
and maintain manifold pressure in the thinner air, an epicyclic box as I
recall. Failing to make the down-shift when bounced by one of Andreas'
FW 190's and loosing altitude in the heat of the moment could, of
course, have exciting consequences with bits of hot and oily Merlin
escaping into the sky at a most inopportune moment.
Richard
(Southampton UK)
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