Why are gyrocopters so small?

Jack Cunniff wrote:
I thought it interesting that the other people responding to Kyler's
thread had apparently not heard of the "Rotodyne", and didn't check out
the Fairey Rotodyne (google for it!).

There IS a company working on a very cool -new- gyroplane - Groen
Brothers. See http://www.groenbros.com/product/hawk4.htm. Elsewhere on
their website, they propose converting existing fixed-wing airframes to
rotary wing.

"The same process would permit the quick and economical introduction of
VTOL GyroLiners in the 19, 35, 50, and 75 passenger sizes. These runway
independent airliners could provide safe and reliable, regional
point-to-point transport and alleviate the continued congesting of air
travel systems, a topic of major concern for the airline industry as
growth begins to return. "

Well, some of us did know about the Rotodyne but, considering its age
and spectacular lack of success, didn't consider it relevant. The
Rotodyne was developed out of the Jet Gyrodyne and - significantly, from
the point of view of this discussion - was a *failure*. It first
appeared in 1957, failed to garner much in the way of orders (though the
RAF briefly considered it) and was abandoned in 1962.

Also, the Rotodyne was *not* a true gyro in that its rotor blades were
driven by turbine compressor air. The same was true of its predecessor,
the Jet Gyrodyne, which in turn was derived from the Gyrodyne which, in
spite of its name, had rotors driven directly by the engine. It got its
name because it became a sort-of gyro in forward flight: the aircraft
had a forward-facing anti-torque prop on a starboard stub wing. That
prop also provided forward thrust and in cruise flight a gyro effect
provided the lift. None of these aircraft, however, could be said to be
a true gyro, and they suffered the fate of so many hybrid aircraft -
killed by their own compromises.

The Groen project is as yet unproven. This kind of thing comes and goes
all the time in aviation and I think their belief in gyroliners is
fanciful at best. We'll see, but don't hold your breath. So the fact
remains that gyros tend to be small aircraft because that's the only
market open to them.