Prerotator vs partially powered rotor

[MikeBoyette]

Not sure of the magic number but Dick has always told me if I’m not mistaken he runs his blades to 110%.

 

[Jean Claude]

Even more nose-up and launched with more power (Rrpm), the rotor thrust will brake the forward acceleration more, while the anti-rotational flow (like a helicopter) will persist longer in slowing down Rrpm. This extra power is therefore wasted, and does nothing to reduce take-off distance.

To benefit from a pre-launch > 70%, A.o.A disc must be reduced (<20 degrees) during the run.

 

[Stanislavz]

the rotor thrust will brake the forward acceleration more,

Or lift ? Is it just two powered vectors which sum equals weight of autogyro. Plus for unpowered one - we need forward motion to provide air flow around rotor. Or zero for 100% powered rotor.

 

[Georgi]

Even more nose-up and launched with more power (Rrpm), the rotor thrust will brake the forward acceleration more, while the anti-rotational flow (like a helicopter) will persist longer in slowing down Rrpm. This extra power is therefore wasted, and does nothing to reduce take-off distance.

To benefit from a pre-launch > 70%, A.o.A disc must be reduced (<20 degrees) during the run.

Jean, not to divert you from the topic, but what are your thoughts about coax (counter rotating) props on heavier, more powerful ( where additional weight of coax unit is not so critical) gyros? Thank you.

 

[Jean Claude]

Or lift ? Is it just two powered vectors which sum equals weight of autogyro. Plus for unpowered one - we need forward motion to provide air flow around rotor. Or zero for 100% powered rotor.

The rotor thrust creates a drag that is detrimental to forward acceleration, and a pure waste as long as the rotor rrpm not fast enough to take off .

 

[Jazzenjohn]

Do you believe that RRPM limitation to be the same when taking off balanced on the mains as when rocked back to a tail wheel on the gyros equipped with one JC? or are you talking about an earlier part of the takeoff sequence?

 

[Jean Claude]

This value of 70% is the useful pre-launch limit for shortening the run of a standard take-off with the usual rotor angle of 18-20 degrees.

As you know, the last feets of the standard run make balanced on the main wheels to avoid the risk of a "behind the curve" take-off

 

[Gyro jeff]

Hello.

Ben here, looking for some Far103 gyros. Yes you can make them or buy - but it will be 503 or 447 powered ones without any extra.

No electric starter or prerotator. Unless hack with big cordless drill. And mostly limited to light pilots.

But ! After reading a lot of Gyrhino and other variants of partially powered rotor. Which saves same power transfered directly to the rotor.

Like if we transfer 10% of motor to rotor directly, we would have same affect as having 110% of motor power in total.

And now the question. If we take, underpowered gyro with 447 engine (40 hp), and add to it goped motor prerotator (5hp) to partially power the rotor in flight - would this transform this gyro to same level of performance as 50hp gyro ?

lot of engineering