Literature mentions that the 3-blade V-22 rotor hub is attached to the rotor
shaft by a means of gimbal or universal joint. Gimbal and universal joints
do not transmit a constant velocity when the hub and shaft axes are not
aligned.

Does anyone know if the V-22 uses a gimbal joint or if it actually uses a
Constant Velocity Joint?

Thanks.

Dave J.

It could be two universals close together?
But then it would need a supporting bearing/structure at the rotor end
aswell. ?
Hmmm...
A CV makes more sence.

Cam


"Dave Jackson" > wrote in message
news:aW6xc.702485$Ig.509981@pd7tw2no...
> Literature mentions that the 3-blade V-22 rotor hub is attached to the
rotor
> shaft by a means of gimbal or universal joint. Gimbal and universal
joints
> do not transmit a constant velocity when the hub and shaft axes are not
> aligned.
>
> Does anyone know if the V-22 uses a gimbal joint or if it actually uses a
> Constant Velocity Joint?
>
> Thanks.
>
> Dave J.
>
>

Cam

Two universals will only provide a constant velocity on the output shaft if
the axes of the input and output shafts are parallel. For instance, when
these two shafts are parallel but not aligned, the first universal will put
a varying velocity into the connecting 'shaft' and the second universal will
remove this varying velocity.

I think that the hub and shaft axes on the V-22 are not always aligned and
therefore a double universal joint will not provide constant velocity.

Dave J


"Cam" > wrote in message
...
> It could be two universals close together?
> But then it would need a supporting bearing/structure at the rotor end
> aswell. ?
> Hmmm...
> A CV makes more sence.
>
> Cam
>
>
> "Dave Jackson" > wrote in message
> news:aW6xc.702485$Ig.509981@pd7tw2no...
> > Literature mentions that the 3-blade V-22 rotor hub is attached to the
> rotor
> > shaft by a means of gimbal or universal joint. Gimbal and universal
> joints
> > do not transmit a constant velocity when the hub and shaft axes are not
> > aligned.
> >
> > Does anyone know if the V-22 uses a gimbal joint or if it actually uses
a
> > Constant Velocity Joint?
> >
> > Thanks.
> >
> > Dave J.
> >
> >
>
>

True, I had forgoten about that (parallel in/out shafts)

But does that mean a tractor or four wheel drive suffer from alternating
velocities on the front wheels when cornering?

Cam

"Dave Jackson" > wrote in message
news:Cynxc.674680$Pk3.470737@pd7tw1no...
> Cam
>
> Two universals will only provide a constant velocity on the output shaft
if
> the axes of the input and output shafts are parallel. For instance, when
> these two shafts are parallel but not aligned, the first universal will
put
> a varying velocity into the connecting 'shaft' and the second universal
will
> remove this varying velocity.
>
> I think that the hub and shaft axes on the V-22 are not always aligned and
> therefore a double universal joint will not provide constant velocity.
>
> Dave J

Are you folks sure the V22 is using a universal joint like what we find on
an automotive drive shaft? I would thing that that would be a very arcaic
way to transfer power. Modern front wheel drive cars us a CV (constant
velocity) joint in place of the old standard universal joint. I'm not
saying that a CV joint fully eliminate the problems you're talking about
with universal joints but they do work significantly smoother at higher
angles.

Some general links with pictures of what I'm talking about are:

http://volksweb.relitech.com/tech/cvjoints/cvparts.jpg
http://volksweb.relitech.com/tech/cvjoints/cvfrnt.jpg

Just a thought!
Fly Safe,
Steve R.


"Cam" > wrote in message
...
> It could be two universals close together?
> But then it would need a supporting bearing/structure at the rotor end
> aswell. ?
> Hmmm...
> A CV makes more sence.
>
> Cam
>
>
> "Dave Jackson" > wrote in message
> news:aW6xc.702485$Ig.509981@pd7tw2no...
> > Literature mentions that the 3-blade V-22 rotor hub is attached to the
> rotor
> > shaft by a means of gimbal or universal joint. Gimbal and universal
> joints
> > do not transmit a constant velocity when the hub and shaft axes are not
> > aligned.
> >
> > Does anyone know if the V-22 uses a gimbal joint or if it actually uses
a
> > Constant Velocity Joint?
> >
> > Thanks.
> >
> > Dave J.
> >
> >
>
>

Cam opined

>True, I had forgoten about that (parallel in/out shafts)

>But does that mean a tractor or four wheel drive suffer from alternating
>velocities on the front wheels when cornering?

Yes, and for sharp turns, it is quite noticeable.

>"Dave Jackson" > wrote in message
>news:Cynxc.674680$Pk3.470737@pd7tw1no...
>> Cam
>>
>> Two universals will only provide a constant velocity on the output shaft
>if
>> the axes of the input and output shafts are parallel. For instance, when
>> these two shafts are parallel but not aligned, the first universal will
>put
>> a varying velocity into the connecting 'shaft' and the second universal
>will
>> remove this varying velocity.
>>
>> I think that the hub and shaft axes on the V-22 are not always aligned and
>> therefore a double universal joint will not provide constant velocity.
>>
>> Dave J





-ash
Cthulhu for President!
Why vote for a lesser evil?

Cam wrote
> But does that mean a tractor or four wheel drive suffer from alternating
> velocities on the front wheels when cornering?

Steve's post covers the front wheel drive.
To elaborate a little, The FWD has 2 CV joints; usually a Tripod joint at
the 'differential' and a Rzeppa joint at the wheel.

Dave J

"Steve R." > wrote
> Are you folks sure the V22 is using a universal joint like what we find on
> an automotive drive shaft? I would thing that that would be a very arcaic
> way to transfer power. Modern front wheel drive cars us a CV (constant
> velocity) joint in place of the old standard universal joint. I'm not
> saying that a CV joint fully eliminate the problems you're talking about
> with universal joints but they do work significantly smoother at higher
> angles.
>
> Some general links with pictures of what I'm talking about are:
>
> http://volksweb.relitech.com/tech/cvjoints/cvparts.jpg
> http://volksweb.relitech.com/tech/cvjoints/cvfrnt.jpg
> "Cam" > wrote
> > It could be two universals close together?
> > But then it would need a supporting bearing/structure at the rotor end
> > aswell. ?
> > Hmmm...
> > A CV makes more sence.
> > "Dave Jackson" > wrote
> > > Literature mentions that the 3-blade V-22 rotor hub is attached to the
> rotor
> > > shaft by a means of gimbal or universal joint. Gimbal and universal
> joints
> > > do not transmit a constant velocity when the hub and shaft axes are not
> > > aligned.
> > >
> > > Does anyone know if the V-22 uses a gimbal joint or if it actually uses
> a
> > > Constant Velocity Joint?

There are all FAR to mathematical for me but there are a few
pictures that I liked too:) The unicopter link in particular
has a lot of diagrams.

google [v-22 gimbal] returns:

http://rotorcraft.arc.nasa.gov/publications/files/Acree_AHSF02.pdf
Which says:
"The V-22 hub comprises three composite arms, or yokes,
connected to the shaft by a constant-velocity joint."

There is no detail of the CV joint in this document but tehre seem
to be other documents on the same site.
e.g.
rotorcraft.arc.nasa.gov/publications/files/Acree_AHS01.pdf

Note that the google results contain an incorrect space
where in the URL displayed after the summary text.


Google [v-22 "constant velocity joint"]
http://rotorcraft.arc.nasa.gov/research/tramdetails.html
"Gimbaled hub with constant velocity joint (spherical bearing
and elastomeric torque links)"


http://www.unicopter.com/1301.html
Much *detail* and many ##-DIAGRAMS-##
"(Somewhat similar to the V-22 tilt-rotor)"


http://www.aero.polimi.it/~quaranta/Papers/ERF-2000-60.pdf
"Significantly,
it considers the gimbal joint, that links the hub to
the mast in order to allow the fapping motion of
the overall hub, and thus implementing a constant
velocity joint, and the swashplate, with all the re-
lated components that are required to transmit the
pitch controls to the rotor blades."


http://pcwww.liv.ac.uk/eweb/fst/publications/AHSSLA_feb11.pdf
"In contrast, the homo-kinetic, constant velocity joint,
featured on the V-22, requires that the drive
component be connected after the gimbal springs
eliminating cyclic variation of the rotor angular velocity."

Thanks for the web sites.

The actual operation of the V-22 CV joint and whether it transmit a true
constant velocity still remains a mystery. Both Bell and Sikorsky have
patents on differing ideas for CV joints but I don't know if they have
implemented them.

The implication of a true CVJ in a rotor-head is interesting, because it
should eliminate the Corollas effect and thereby eliminate a primary source
of lead/lag.

Dave J


"AnyBody43" > wrote in message
m...
> "Steve R." > wrote
> > Are you folks sure the V22 is using a universal joint like what we find
on
> > an automotive drive shaft? I would thing that that would be a very
arcaic
> > way to transfer power. Modern front wheel drive cars us a CV (constant
> > velocity) joint in place of the old standard universal joint. I'm not
> > saying that a CV joint fully eliminate the problems you're talking about
> > with universal joints but they do work significantly smoother at higher
> > angles.
> >
> > Some general links with pictures of what I'm talking about are:
> >
> > http://volksweb.relitech.com/tech/cvjoints/cvparts.jpg
> > http://volksweb.relitech.com/tech/cvjoints/cvfrnt.jpg
> > "Cam" > wrote
> > > It could be two universals close together?
> > > But then it would need a supporting bearing/structure at the rotor end
> > > aswell. ?
> > > Hmmm...
> > > A CV makes more sence.
> > > "Dave Jackson" > wrote
> > > > Literature mentions that the 3-blade V-22 rotor hub is attached to
the
> > rotor
> > > > shaft by a means of gimbal or universal joint. Gimbal and universal
> > joints
> > > > do not transmit a constant velocity when the hub and shaft axes are
not
> > > > aligned.
> > > >
> > > > Does anyone know if the V-22 uses a gimbal joint or if it actually
uses
> > a
> > > > Constant Velocity Joint?
>
> There are all FAR to mathematical for me but there are a few
> pictures that I liked too:) The unicopter link in particular
> has a lot of diagrams.
>
> google [v-22 gimbal] returns:
>
> http://rotorcraft.arc.nasa.gov/publications/files/Acree_AHSF02.pdf
> Which says:
> "The V-22 hub comprises three composite arms, or yokes,
> connected to the shaft by a constant-velocity joint."
>
> There is no detail of the CV joint in this document but tehre seem
> to be other documents on the same site.
> e.g.
> rotorcraft.arc.nasa.gov/publications/files/Acree_AHS01.pdf
>
> Note that the google results contain an incorrect space
> where in the URL displayed after the summary text.
>
>
> Google [v-22 "constant velocity joint"]
> http://rotorcraft.arc.nasa.gov/research/tramdetails.html
> "Gimbaled hub with constant velocity joint (spherical bearing
> and elastomeric torque links)"
>
>
> http://www.unicopter.com/1301.html
> Much *detail* and many ##-DIAGRAMS-##
> "(Somewhat similar to the V-22 tilt-rotor)"
>
>
> http://www.aero.polimi.it/~quaranta/Papers/ERF-2000-60.pdf
> "Significantly,
> it considers the gimbal joint, that links the hub to
> the mast in order to allow the fapping motion of
> the overall hub, and thus implementing a constant
> velocity joint, and the swashplate, with all the re-
> lated components that are required to transmit the
> pitch controls to the rotor blades."
>
>
> http://pcwww.liv.ac.uk/eweb/fst/publications/AHSSLA_feb11.pdf
> "In contrast, the homo-kinetic, constant velocity joint,
> featured on the V-22, requires that the drive
> component be connected after the gimbal springs
> eliminating cyclic variation of the rotor angular velocity."

Coriolis effect has to do with dissimetry of lift (advancing blade vs.
retreating blade) not blade velocity. On an articulated rotor head, lead/lag
will remain, so CV joints are moot in that regard.

Bob

sorry...dis SYMMETRY that is...aduhhh

Bob

Definition of Coriolis Effect ~ Rotor blades will accelerate when its CG
moves closer to the center of rotation and will decelerate when it moves
farther. Rotor blades accelerate and decelerate accompanied with the rotor
blades flapping.
__________________________

Bob you are correct when discussing a conventional teetering rotor or a
flapping rotor. The above definition supports your statement, but, the
"center of rotation" it is referring to is that of the mast. On a gimballed
rotor, the teetering does not causes the blades to move closer or further
from the "center of rotation" (tilted axis) of the teetered rotorhub.

It must be noted that the rotor blades of a teetering rotor are connected to
the mast via a Hooke's (Universal) joint. In this arraignment, the mast
will turn at a constant velocity but the rotor will accelerate and
decelerate. This effect can be equally well explained by the cyclical
Coriolis effect or by the Hooke's joint effect.

By replacing the Hooke's joint with a Constant Velocity joint the rotation
of the teetered rotor hub will now be constant. In other words, the blades
will no longer lead/lag in respect to the axis of the rotorhub AND will no
longer lead/lag in respect to the axis of the mast.

Dave J


"Bob" > wrote in message
...
> Coriolis effect has to do with dissimetry of lift (advancing blade vs.
> retreating blade) not blade velocity. On an articulated rotor head,
lead/lag
> will remain, so CV joints are moot in that regard.
>
> Bob
>
>

I believe I stated that the "moot" application is and articulated rotor head
and should have said a Fully articulated rotor head.

Agreed. The subject is rotor with three or more blades. I used the
teetering rotor as the example because it is easier to understand, and the
out-of-plane flapping and teetering hinges are functionally very similar.

Researchers have been looking into the possibility of a soft-in-plane rotor
for the tilt-rotor, to reduce the strength and weight of the current rotor.
This implies, of course, that there is lead/lag activity in the V-22 rotor
and the question is one of what activities are causing this lead/lag.

Excluding lesser activities such as drag, a Constant Velocity joint will
cause the rotor hub to tilt and have the same plane as the tip-path-plane.
This will mean that the hub and blade roots will rotate at a constant
velocity. There are patents for rotor head CV joints, but the original
question asks if a CV joint has actually been implemented.

The use of a CV joint in the V-22 should imply that it could also be
implemented in conventional rotorcraft and result in simpler smoother
rotors. http://www.SynchroLite.com/1301.html and its associated pages is
the reason for originally asking the question.

Dave J




"Bob" > wrote in message
...
> I believe I stated that the "moot" application is and articulated rotor
head
> and should have said a Fully articulated rotor head.
>
>

Dave,
I am following your idea of the tetering rotor hub i.e. the Bell 206, and I
must state clearly that the blades on such a hub never change the angular
relationship with respect to one another. The angular relationship from the
trailing edge of one blade to the leading edge of the other blade NEVER
changes. There is no mechanism in the rotor head that could possibly allow
that to happen. positions on the head are FIXED PERIOD.

The reason the head teters os to provide for equal lift on the advancing
blade side of the rotor disk and the retreating blade side of the rotor
disk. The higest point of the teter is over the nose and the lowest point
is over the tailboom.

Coriolis will ALWAYS accelerate a blade whose center of gravity moves toward
the axis of rotation. Lift being agreed now equal all around, and blade
angular relationships never changing, therefore velocity with respect to one
another never changing, where does coriolis effect enter into this
discussion at all??? Forgive me, but even after 20 years of strictly
helicopter maintenance of All shapes and sizes I am at a loss to see the
merit in your discussion.

On a V-22 the same physics apply. For coriolis to enter the picture, it
would necessarily be induced only by lead/lag of the blades and a hinge or
mechanism to allow that to happen. I'm certainly not a V-22 guru but on ALL
helicopters thae same things will happen for the same reasons. Now I'm
sitting here asking myself where this might be going.

Bob

Hi Bob,

The intent of the original post in this thread was for me to get a clear
understanding of exactly what is taking place in the V-22 rotor.
Specifically, to find out if it is only a gimbaled hub or it is in fact a CV
hub.

I believe we agree on what the Coriolis effect is.

We probably both agree that if a rotor mast is vertical and its TEETERING
rotor disk is tilted 10-degrees down at the front, then the two blades, in
unison, will be experiencing a two/rev. acceleration and deceleration, as
they move toward and away from the axis of rotation. This rotational
vibration is absorbed in the mast.

In addition, we probably both agree that if a rotor mast is vertical and its
FLAPPING rotor disk is tilted 10-degrees down at the front, then the blades
will be experiencing a two/rev. acceleration and deceleration, as they move
toward and away from the axis of rotation. This rotational vibration is
absorbed in the lead/lag hinges.

Now lets tilt the masts in both examples 10-degrees forward, so that the
masts are now normal to the disks. I think that we will agree that in both
examples the blades will no longer experience a two/rev acceleration and
deceleration. There is no Coriolis effect about this tilted mast.

This is where the CV joint differs from all existing rotor heads. The CV
joint takes the constant rotational velocity of the vertical mast and
delivers a constant rotational velocity to the axis of the tilted rotor
disk. The blades are now rotating about tilted axis of the rotor disk and
when viewed along this axis there is no Coriolis.

Hope this explains my original question.

Dave J.



"Bob" > wrote in message
...
> Dave,
> I am following your idea of the tetering rotor hub i.e. the Bell 206, and
I
> must state clearly that the blades on such a hub never change the angular
> relationship with respect to one another. The angular relationship from
the
> trailing edge of one blade to the leading edge of the other blade NEVER
> changes. There is no mechanism in the rotor head that could possibly
allow
> that to happen. positions on the head are FIXED PERIOD.
>
> The reason the head teters os to provide for equal lift on the advancing
> blade side of the rotor disk and the retreating blade side of the rotor
> disk. The higest point of the teter is over the nose and the lowest
point
> is over the tailboom.
>
> Coriolis will ALWAYS accelerate a blade whose center of gravity moves
toward
> the axis of rotation. Lift being agreed now equal all around, and blade
> angular relationships never changing, therefore velocity with respect to
one
> another never changing, where does coriolis effect enter into this
> discussion at all??? Forgive me, but even after 20 years of strictly
> helicopter maintenance of All shapes and sizes I am at a loss to see the
> merit in your discussion.
>
> On a V-22 the same physics apply. For coriolis to enter the picture, it
> would necessarily be induced only by lead/lag of the blades and a hinge or
> mechanism to allow that to happen. I'm certainly not a V-22 guru but on
ALL
> helicopters thae same things will happen for the same reasons. Now I'm
> sitting here asking myself where this might be going.
>
> Bob
>
>

Yes Dave. That does explain your original question.