beginning in rotary wing

[david perry]

Thanks to all who offered help and advice. I had my first lesson today with
ATS. Superb fun on the Raptor. I think I'm hooked.

One question though...from a scientific point of view - how do the paddles
work? I gather they add stability to the rotor disk, i.e. they damp the
movement of the disc..but HOW? And why do I suddenly not need paddles if I
go for three or more rotor blades? And why does a jet ranger, or a Robinson
for that matter, which does have two blades, not need paddles? Yes I know
early Bells had balls on a fly bar...not paddles? How so?

Anyone know?

David

[Steve Simpson]

> One question though...from a scientific point of view - how do the paddles
> work? I gather they add stability to the rotor disk, i.e. they damp the
> movement of the disc..but HOW? And why do I suddenly not need paddles if I
> go for three or more rotor blades? And why does a jet ranger, or a Robinson
> for that matter, which does have two blades, not need paddles? Yes I know
> early Bells had balls on a fly bar...not paddles? How so?

The Bell system used the bar with ball weights to create a gyroscope which was connected to the
rotor cyclic along with the pilot's controls. If the heli decided to tilt, then the stabilizer
would resist and acted as a very effective counter force to keep the heli stable.

Naturally, you have to intentionally tilt the rotor to fly around and the stabilizer has to come
along for the ride, but it wants to remain horizontal. Therefore there must be some method by
which the stabilizer can be 'forced' to follow the heli inclination. On a real Bell, this is
done with dampers (connections) between the heli and the stabilizer.

Dampers are not practical on a model, so someone came up with the idea to borrow the servo
paddle principal from the Hiller system to perform the task of forcing the flybar to a specific
inclination.

Modern models use this Bell-Hiller hybrid system. I say modern because there were some very
early development models which actually used servo paddles to provide grunt for moving the main
rotor pitch, just as in the real Hiller. But those are long gone and today's heli's just use the
servo paddles to push the flybar. The servos act on the rotor cyclic directly through a shared
linkage. On many heli models, that linkage is adjustable so that the influence of the flybar vs
pilot input can be proportioned.

Because the flybar is connected to the main rotor and it is possible to 'overdrive' it to the
point where it is actually 'leading' the pilot input, some people have come to believe that it
is supposed to provide a 'power steering' of sorts.

[david perry]

Steve, a concise and readable reply. Many thanks indeed.

david
"Steve Simpson" <simpsons34@NIXcox.net> wrote in message
news:8Uhwa.25236$fm4.4618@fed1read06...
> > One question though...from a scientific point of view - how do the
paddles
> > work? I gather they add stability to the rotor disk, i.e. they damp the
> > movement of the disc..but HOW? And why do I suddenly not need paddles
if I
> > go for three or more rotor blades? And why does a jet ranger, or a
Robinson
> > for that matter, which does have two blades, not need paddles? Yes I
know
> > early Bells had balls on a fly bar...not paddles? How so?
>
> The Bell system used the bar with ball weights to create a gyroscope which
was connected to the
> rotor cyclic along with the pilot's controls. If the heli decided to tilt,
then the stabilizer
> would resist and acted as a very effective counter force to keep the heli
stable.
>
> Naturally, you have to intentionally tilt the rotor to fly around and the
stabilizer has to come
> along for the ride, but it wants to remain horizontal. Therefore there
must be some method by
> which the stabilizer can be 'forced' to follow the heli inclination. On a
real Bell, this is
> done with dampers (connections) between the heli and the stabilizer.
>
> Dampers are not practical on a model, so someone came up with the idea to
borrow the servo
> paddle principal from the Hiller system to perform the task of forcing the
flybar to a specific
> inclination.
>
> Modern models use this Bell-Hiller hybrid system. I say modern because
there were some very
> early development models which actually used servo paddles to provide
grunt for moving the main
> rotor pitch, just as in the real Hiller. But those are long gone and
today's heli's just use the
> servo paddles to push the flybar. The servos act on the rotor cyclic
directly through a shared
> linkage. On many heli models, that linkage is adjustable so that the
influence of the flybar vs
> pilot input can be proportioned.
>
> Because the flybar is connected to the main rotor and it is possible to
'overdrive' it to the
> point where it is actually 'leading' the pilot input, some people have
come to believe that it
> is supposed to provide a 'power steering' of sorts.
>
>
>
>

[david perry]

"Steve Simpson" <simpsons34@NIXcox.net> wrote in message
news:8Uhwa.25236$fm4.4618@fed1read06...
> > One question though...from a scientific point of view - how do the
paddles
> > work? I gather they add stability to the rotor disk, i.e. they damp the
> > movement of the disc..but HOW? And why do I suddenly not need paddles
if I
> > go for three or more rotor blades? And why does a jet ranger, or a
Robinson
> > for that matter, which does have two blades, not need paddles? Yes I
know
> > early Bells had balls on a fly bar...not paddles? How so?
>
> The Bell system used the bar with ball weights to create a gyroscope which
was connected to the
> rotor cyclic along with the pilot's controls. If the heli decided to tilt,
then the stabilizer
> would resist and acted as a very effective counter force to keep the heli
stable.
>
> Naturally, you have to intentionally tilt the rotor to fly around and the
stabilizer has to come
> along for the ride, but it wants to remain horizontal. Therefore there
must be some method by
> which the stabilizer can be 'forced' to follow the heli inclination. On a
real Bell, this is
> done with dampers (connections) between the heli and the stabilizer.
>
> Dampers are not practical on a model, so someone came up with the idea to
borrow the servo
> paddle principal from the Hiller system to perform the task of forcing the
flybar to a specific
> inclination.
>
> Modern models use this Bell-Hiller hybrid system. I say modern because
there were some very
> early development models which actually used servo paddles to provide
grunt for moving the main
> rotor pitch, just as in the real Hiller. But those are long gone and
today's heli's just use the
> servo paddles to push the flybar. The servos act on the rotor cyclic
directly through a shared
> linkage. On many heli models, that linkage is adjustable so that the
influence of the flybar vs
> pilot input can be proportioned.
>
> Because the flybar is connected to the main rotor and it is possible to
'overdrive' it to the
> point where it is actually 'leading' the pilot input, some people have
come to believe that it
> is supposed to provide a 'power steering' of sorts.
>
>
>
Steve, I have been pondering this through the day. Essentially then there
are two components - the mass of the flybar / weights (paddles) and the
aerodynamics of the paddles. One, the mass , adds stbility and prevents
movement, the other, the paddles, provides movement to over come gyroscopy
of the mass component.

So, why do the blades NOT have suficient mass themselves to provid
stability? It seems that something lie 1.2m of carbon blade whiring round
will have more energy than the flybar whirring at the same speed. Well, it
WILL have more energy and more gyroscopy, so why are the blades needed at
all? What happens if one flies with NO flybar / paddles?

David

[david perry]

"Steve Simpson" <simpsons34@NIXcox.net> wrote in message
news:8Uhwa.25236$fm4.4618@fed1read06...
> > One question though...from a scientific point of view - how do the
paddles
> > work? I gather they add stability to the rotor disk, i.e. they damp the
> > movement of the disc..but HOW? And why do I suddenly not need paddles
if I
> > go for three or more rotor blades? And why does a jet ranger, or a
Robinson
> > for that matter, which does have two blades, not need paddles? Yes I
know
> > early Bells had balls on a fly bar...not paddles? How so?
>
> The Bell system used the bar with ball weights to create a gyroscope which
was connected to the
> rotor cyclic along with the pilot's controls. If the heli decided to tilt,
then the stabilizer
> would resist and acted as a very effective counter force to keep the heli
stable.
>
> Naturally, you have to intentionally tilt the rotor to fly around and the
stabilizer has to come
> along for the ride, but it wants to remain horizontal. Therefore there
must be some method by
> which the stabilizer can be 'forced' to follow the heli inclination. On a
real Bell, this is
> done with dampers (connections) between the heli and the stabilizer.
>
> Dampers are not practical on a model, so someone came up with the idea to
borrow the servo
> paddle principal from the Hiller system to perform the task of forcing the
flybar to a specific
> inclination.
>
> Modern models use this Bell-Hiller hybrid system. I say modern because
there were some very
> early development models which actually used servo paddles to provide
grunt for moving the main
> rotor pitch, just as in the real Hiller. But those are long gone and
today's heli's just use the
> servo paddles to push the flybar. The servos act on the rotor cyclic
directly through a shared
> linkage. On many heli models, that linkage is adjustable so that the
influence of the flybar vs
> pilot input can be proportioned.
>
> Because the flybar is connected to the main rotor and it is possible to
'overdrive' it to the
> point where it is actually 'leading' the pilot input, some people have
come to believe that it
> is supposed to provide a 'power steering' of sorts.
>
>
>
> Steve, I hve been pondering this through the day. Essentially then there
are two components - the mass of the flybar / weights (paddles) and the
aerodynamics of the paddles. One, the mass , adds stbility and prevents
movement, the other, the paddles, provides movement to over come gyroscopy
of the mass component.

So, why do the blades NOT have suficient mass themselves to provid
stability? It seems that something lie 1.2m of carbon blade whiring round
will have more energy than the flybar whirring at the same speed. Well, it
WILL have more energy and more gyroscopy, so why are the blades needed at
all? What happens if one flies with NO flybar / paddles?

David

[Steve Simpson]

>
> So, why do the blades NOT have suficient mass themselves to provid
> stability? It seems that something lie 1.2m of carbon blade whiring round
> will have more energy than the flybar whirring at the same speed.

The main rotor does have gyroscopic effect, but it also has cyclic control which quickly
overcomes that.

> Well, it WILL have more energy and more gyroscopy, so why are the blades needed at
> all? What happens if one flies with NO flybar / paddles?

You can fly fine without a flybar. You just loose the stabilizing (or destabilizing) effect.
More than once, people have taken off with a flybar lock in place. Because the linkage is
arranged to rely on input from the flybar, the heli will usually just act sluggish.

Gyros on the cyclic axis do a better job that a mechanical (aerodynamic) stabilizer, and there
are now many excellent gyros available but so far, that hasn't been a priority with model helis.
I set up my CCPM gasser to take a gyro on the elevator axis, but I got busy with other projects
and the heli is just gathering dust at the moment.