New Magni M24

Greg, have you seen a Magni rotor opened up all the way?

My guess is that there is a concentrated weight at some point along its span; probably at 80% to 100% of radius.
 
Greg, have you seen a Magni rotor opened up all the way?

My guess is that there is a concentrated weight at some point along its span; probably at 80% to 100% of radius.

I've seen a split open set of rotor blades - from an accident. I did not see anything different along the length. I've also watched them lay up rotors - through a window to their clean room - and the spar was just many long lengths of resin impregnated unidirectional fiberglass bands from the root to the tip - special length strips rolled up for installation from tip to root and back to tip. The trailing (about 75%) was blue foam in long strips - did not notice anything different from the tip to the root and I don't think they would want to add any weight on the aft 75% foam filled section of the chord. The only metal in the blade I saw is the leading edge rod and the root connection - they specially avoid metal in the blade to avoid distortions in the heat curing process. I did not see if the leading edge weight had any heavier sections in the bar, but I know there are no separate special weights any where along the length of this leading edge rod.

The blade tip is maybe 3 inches of solid fiberglass - no metal. There is an M6 threaded hole in each tip, to add trimming weights (lead wire or lead BBs) and a set screw to hold it in the hole. - so the tip probably is a little higher weight than the other sections of the blade. As far as I know, they take special care to be sure the weight and airfoil shape is uniform along the whole length of the blade - that's how they avoid needing tracking or string adjustments - track and lateral string are fixed and not adjustable and cannot change due to the horizontal bolting arrangement - see previous pic.

They match the span and chord balance point of each blade with a mate. Then they adjust flight tracking by small weights added to one tip - if necessary. The uniform aerodynamic shape along the length of the blades, and the fixed bolting of the blade to the hubbar, with no tracking or blade AOA adjustment, requires that each blade be exactly uniform in weight distribution and airfoil cross section - so they are serious about no distortions from materials in the blade that would have different coefficients of expansion during the heat cure step.

- Greg

PS: The accident was a low time pilot in an M14 that tried to do a vertical spin. He did the spin OK, but never stopped the spin or picked up airspeed 'till he hit the ground flat vertically - I was there at Magni's Day and saw it. I got to see the wreck after they picked up the pieces - the rotors were split but still attached. One steel wheel axel broke - the landing gear "spring" was intact - to my amazement! The tail boom was bent up bad and the tail was destroyed. The mast was not bent, but the rotor head looked "stressed". The nose wheel was bent back. The cockpit was mostly intact - the pilot walked out of the wreck.
 
Greg - think about a lawn mower engine. It has a flywheel and a governor. If the response rate of the flywheel is similar to that of the governor, as soon as the two get out of phase, for whatever reason, the engine starts "hunting". If the governor response rate is double that of the flywheel, it is much less likely to enter harmonic oscillations.

Back to gyros - I believe that, with the exception of birdy and his fellow moo chasers, there is no disadvantage for a highly pitch-damped airframe. A pitch damped airframe does not minimize the pitching rate of the gyro, as commanded by the pilot - rather, it makes the gyro feel like it is flying on rails - tracking straight and true into the relative wind. Unlike a fixed wing plane, where the pitching rate is commanded by changing the curvature of the tail - a command that all by itself is damped by the tail - on a gyro the pitching rate is not damped by the tail. The gyro is changing it's flight path as soon as the rotor AOA has changed.

The one thing a large damping tail does not allow for (and is something birdy et al want to do) is to pitch the airframe faster than the flight path that the rotor is commanding allows. Basically, they use the RTV moment about the CG - not the flight path - to pitch the airframe quickly. Like a quick in-air high speed breaking. I have never heard anyone other than birdy express a desire to perform this maneuver.

So I agree with you that strong aerodynamic damping by the tail does not hinder agility in gyros. But a strong damping by the rotor does.

Yes - the pitch damping rate by the tail should be proportional to the MOI of the airframe. The greater the MOI - the greater the damping rate should be. These two should really work in tandem (no pun intended ;o).

Now if we get back to rotor-airframe feedback - some rotor damping is a good thing. You don't want a rotor with zero mass that would respond in no time at all to any input. That would be disastrous. Just like a car steering wheel needs to provide feedback resistance to the driver, also a rotor should provide some resistance to change. The questions is how much, and for what purpose. Having flown the DW rotors, I think that Ernie came up with a good rotor damping rate in all size rotors. The rotor feels solid in your hand, but it responds quickly to moderate stick pressures. When flying into gusts, you can hear the rotor responding to the changing AOA briskly, but not instantly. Since the aluminum construction of the DW rotors is so light, rotor inertia, and the corresponding damping rate, is governed by tip-end weights. These were optimizes with a process of trial and error.

Now, I can see how a fast responding rotor like the DWs can become a problem with a low damped airframe like the RAF or any other no-tail gyro. The rotor response rate may be very close to the (no damping) response rate of the airframe! That is when pilots get into PIOs. This problem may be minimized by either using a highly damped rotor like the Magni rotor or any other high inertia rotor OR by damping the airframe properly. A highly damped airframe will not PIO because you cannot get it into harmonic oscillations with the rotor!!!

I don’t follow this Udi! I think we want the airframe to respond to gusts quickly. Especially so that the airframe can feedback into the spindle to cause the rotor disk to respond also to that gust quickly – to compensate for it with a change in lift the opposite direction to the wind gust – negative feedback! This would be a very tight, high gain, feedback loop that serves to minimize the actual disturbance to the whole system. In such a tight “loop”, the high gain feedback actually minimizes the pitch attitude reaction amplitude – prevents a lot of pitching in turbulence. This is the normal desired reaction to turbulence – the airframe pitches almost imperceptibly – but enough to change the rotor disk angle (spindle tilting) slightly – enough to compensate the change in rotor lift from the gust. The result is that the gyro penetrates turbulence with minimal pitching – to not excite the pilot into cyclic actions. The pilot feels up and down G-Load disturbances with minimal airframe pitching. I suggest this is precisely because the airframe pitches quickly in response to the wind gust – provide negative, high gain feedback to the rotor – and therefore not actually have to pitch much in the closed, high gain control loop.
First of all, let start with the assertion that the rotor, all by itself, has a limited AOA stability. Rotor AOA stability is limited to what's provided by RRPM and the corresponding blow back angle change. When the rotor is entering a gust, at first nothing happens. Due to the change in loading, the rotor accelerates or decelerates, and the rotor blow-back angle changes in a statically - stable direction. But this is a somewhat slow process.

So - we don't want to leave the gyro AOA stability for the rotor. If we want a gyro that is AOA stable (a pre-requirement for airspeed stability), we must take advantage of the tail to do that. On the other hand, you don't want the airframe to be so twitchy to gusts that it's uncomfortable (too static stable). So the happy answer is an airframe that is very pitch stable, but adequately damped to prevent this twitchyness... Makes sense?

The next thing we want is for the rotor to go along with what the airframe is telling it to do. If the airframe is pitching down into a gust - you want the rotor to pitch down with it. This is the DEFINITION of AOA stability. If there is one thing I want to see more of in gyros is AOA stability. We have been talking about some gyros that suffer from "runaway" airspeed dives. This is the direct result of poor AOA stability - nothing else!

OMG... my posts are starting to look like Greg's :eek:
 
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Not saying that Magni is doing anything wrong - their safety record speaks for itself - but there are other ways to achieve safety without compromising agility. For me, flying gyros is all about agility. If I want to fly cross country, I take a Cessna.

Also my thoughts exactly.
I cant see why one would engineer the gyro out of gyros.
The thing a gyro has over a FW is its [ among other things], responce rate and control precision.

So, I guess I’m questioning that why, for agility, you would want the rotor to have a much quicker response rate than the airframe – it is the airframe that the pilot wants to see respond – and quickly too. I think I’m suggesting that “agility” is all in the rotor, how quickly it changes disk attitude with pilot cyclic input. This adjusts the “agile” flight path, not anything the airframe does aerodynamically. The rest of “agility” is up to the inertial response of the airframe. The strong dynamic damper does not hinder this or make it more sluggish, it just helps re-direct the airframe to the attitude the rotor is determining by its flight path re-direction.

You seem to be contradicting youself here Greg.
On the one hand you say; it is the airframe that the pilot wants to see respond – and quickly too. I think I’m suggesting that “agility” is all in the rotor, how quickly it changes disk attitude with pilot cyclic input.

Then you say; it just helps re-direct the airframe to the attitude the rotor is determining by its flight path re-direction

If the airframe cant overshoot [ damped] then how can you increase the cyclic rate of the rotor?
IOW, a highly damped machine [ and rotor] can only pitch as fast as the HS will allow.
A stable but undamped machine will have a higher pitch rate to a highly damped stable one.
And RATE is wot agility and precise control is all about.

Because the airframe pitch and roll rates seem to be about the same, this suggests to me that the strong dynamic pitch damper is not really affecting or slowing down the pitch rate, because the roll rate does not have such a large dynamic damper – but it still has the same responses as does pitch!

The strong dynamic pitch damper has no effect on roll, only on pitch.
Its the heavy stick thats slowing the roll AND primarily the roll rate.
You can engineer your cyclic control to be heavy in pitch, or roll, or both, or neither.

both roll and pitch seem to respond about the same
Thats because they both have the same 'heavieness' engineered into the stick.
If you took the HS off the magni, itd be just as heavy. The only difference would be overshoot in manouvers and no stability.

Chuck, this is what I was thinking, so you don't need to be sorry for me. I am suggesting too that this is not THE big contributor to stick forces (in the Magni), this actually would be a reducer of stick forces - as compared to higher teeter heights on heavy gyros with even more teeter height.

And if you consider the fact the my wasa still has the very high teeter head [ RAF] and as heavy, or even heavier blades than the magni, bout the same all up weight, but still has much lighter stick forces................. .
The only real difference between the 2 machines that can be atributed to the weight of the sticks, is the leaverage.

Geez Udi, i dont know wether i agree with you or not. ;)
First you say;
with the exception of birdy and his fellow moo chasers, there is no disadvantage for a highly pitch-damped airframe
Then you said;
The one thing a large damping tail does not allow for (and is something birdy et al want to do) is to pitch the airframe faster than the flight path that the rotor is commanding allows.
Dose it make a difference or not?
One line you say, there is no disadvantage in highly pitch dampening, then you say, pitch the airframe faster than the flight path that the rotor is commanding allows.
Im generaly in agreeance with you mate, but your startn to confuse me now.
 
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Not saying that Magni is doing anything wrong - their safety record speaks for itself - but there are other ways to achieve safety without compromising agility. For me, flying gyros is all about agility. If I want to fly cross country, I take a Cessna.

Also my thoughts exactly.
I cant see why one would engineer the gyro out of gyros.
The thing a gyro has over a FW is its [ among other things], responce rate and control precision.

So, I guess I’m questioning that why, for agility, you would want the rotor to have a much quicker response rate than the airframe – it is the airframe that the pilot wants to see respond – and quickly too. I think I’m suggesting that “agility” is all in the rotor, how quickly it changes disk attitude with pilot cyclic input. This adjusts the “agile” flight path, not anything the airframe does aerodynamically. The rest of “agility” is up to the inertial response of the airframe. The strong dynamic damper does not hinder this or make it more sluggish, it just helps re-direct the airframe to the attitude the rotor is determining by its flight path re-direction.

You seem to be contradicting youself here Greg.
On the one hand you say; it is the airframe that the pilot wants to see respond – and quickly too. I think I’m suggesting that “agility” is all in the rotor, how quickly it changes disk attitude with pilot cyclic input.

Then you say; it just helps re-direct the airframe to the attitude the rotor is determining by its flight path re-direction

If the airframe cant overshoot [ damped] then how can you increase the cyclic rate of the rotor?
IOW, a highly damped machine [ and rotor] can only pitch as fast as the HS will allow.
A stable but undamped machine will have a higher pitch rate to a highly damped stable one.
And RATE is wot agility and precise control is all about.

Because the airframe pitch and roll rates seem to be about the same, this suggests to me that the strong dynamic pitch damper is not really affecting or slowing down the pitch rate, because the roll rate does not have such a large dynamic damper – but it still has the same responses as does pitch!

The strong dynamic pitch damper has no effect on roll, only on pitch.
Its the heavy stick thats slowing the roll AND primarily the roll rate.
You can engineer your cyclic control to be heavy in pitch, or roll, or both, or neither.

both roll and pitch seem to respond about the same
Thats because they both have the same 'heavieness' engineered into the stick.
If you took the HS off the magni, itd be just as heavy. The only difference would be overshoot in manouvers and no stability.

Chuck, this is what I was thinking, so you don't need to be sorry for me. I am suggesting too that this is not THE big contributor to stick forces (in the Magni), this actually would be a reducer of stick forces - as compared to higher teeter heights on heavy gyros with even more teeter height.

And if you consider the fact the my wasa still has the very high teeter head [ RAF] and as heavy, or even heavier blades than the magni, bout the same all up weight, but still has much lighter stick forces................. .
The only real difference between the 2 machines that can be atributed to the weight of the sticks, is the leaverage.

Geez Udi, i dont know wether i agree with you or not. ;)
First you say;
with the exception of birdy and his fellow moo chasers, there is no disadvantage for a highly pitch-damped airframe
Then you said;
The one thing a large damping tail does not allow for (and is something birdy et al want to do) is to pitch the airframe faster than the flight path that the rotor is commanding allows.
Dose it make a difference or not?
One line you say, there is no disadvantage in highly pitch dampening, then you say, pitch the airframe faster than the flight path that the rotor is commanding allows.
Im generaly in agreeance with you mate, but your startn to confuse me now.

I need another bottle cause your starting to confuse me shyte :lalala::phone::suspicious:
 

The only real difference between the 2 machines that can be atributed to the weight of the sticks, is the leaverage.


Ever tried to turn a car quickly with broken power steering? The wheel forces are so high it takes effort to change direction. No matter how hard you tried you'd never get the car to spin off the road.

Those of us with old VPM 16's have altered the gearing in the controls as much as possible (until the rear stick touches the front seat) to allow for lighter stick forces. The Magni's geometry won't allow longer sticks like say a MT-o3 whose seats sit higher.

I don't think there is anything about a Magni which restricts it's ability to change direction quickly other than stick forces. I've seen them change direction pretty quickly. Don't think you could do eight hours of it though Birdy.

Stick forces don't explain why a Magni is so pitch stable though.
 
Thanks bpearson!

Ever tried to turn a car quickly with broken power steering? The wheel forces are so high it takes effort to change direction. No matter how hard you tried you'd never get the car to spin off the road.

Those of us with old VPM 16's have altered the gearing in the controls as much as possible (until the rear stick touches the front seat) to allow for lighter stick forces. The Magni's geometry won't allow longer sticks like say a MT-o3 whose seats sit higher.

You got the words and example I was searching for.
 
I imagine at least one Magni owner has access to a ruler and a protractor. Hopefully, he will post stick rate; stick travel per degree of rotorhead tilt. It need not be a dark mystery.

I’ve flown high inertia blades –Hughes OH-6 having 5 lb. brass slugs in each tip- on gyros with stick rates ranging from 1 inch/degree to ½ inch/degree and in both cases, controllable with fingertip pressure. Certainly, the greater rotor lag resulted in some increase of stick pressure but nothing startling.

I once bought a truckload of run out OH-6 blades from Ft. Rucker so a number of people in Florida flew with OH-6 blades. Most sawed off the last 6” of the tip to get rid of the brass slugs and to speed up response rate.

I generally left the tip weights intact but there was a very noticeable difference in handling as compared to contemporary gyro rotor blades; Bensen, Stanzee, Rotordye, etc. The Hughes blades required more time to accommodate changes of G load.
 
Ever tried to turn a car quickly with broken power steering? The wheel forces are so high it takes effort to change direction. No matter how hard you tried you'd never get the car to spin off the road.
Believe it or not bpearson, thats zactly wot im on about.

Stick forces don't explain why a Magni is so pitch stable though.
I never said it had anythn to do with its stability.

You got the words and example I was searching for.
Angelo, ill change the question then.
DO you know the weight of the Magni blades???????????

The Hughes blades required more time to accommodate changes of G load.
CB, wot RRPM and loading were they at?
 
Before getting too worked up over the harmony, or lack of, between rotor rates and moment of inertia of the gyro, etc, consider the following:

Pure roll and pitch about an axis can only be achieved by applying a pure torque. For example, in an airplane, roll is achieved by applying up aileron on one wing and down aileron on the other.

A gyro body is essentially a weight on a string. There are no balanced , equal and opposite forces.

To "roll" the weight about the cg requires "swinging the rope" by tugging at the top of the mast with the rotor.

It is well known in physics that the rate of swing of a weight on string depends only on the length of the string and has nothing to do with the mass at the end of the string.
(the formula is slightly more complicated if the mass is spread out, as in the case of a tandem gyro. but the principle is the same.)

"But, but....." you say, "everything has rotational inertia and a heavier object requires more torque to turn it. Shouldn't a heavier gyro rotate more slowly for a given stick input?"

Not really. First, it is impossible to generate torque about a teetering rotor hinge. All the rotor can do is pull (or push!)

The object on the rope provides its own torque about its own cg by resisting the tug of the rope at the attach point. A heavier object resists more, thus the rate of rotation is always the same. It only depends on the "acceleration" of the top of the mast, or rope.
 
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I need another bottle cause your starting to confuse me shyte :lalala::phone::suspicious:

Bones, Me TOO! - Greg

Good discussions, but it is just not possible to try to address every point that's being made. I am very happy to see Udi and Al and Chuck all chiming in - and I think I need to bow to their expertise in a lot of these areas.

Udi, I don't think I disagree with much you are pointing out, but I am not sure I followed all the rotor “damping” point. I am not sure if the "rotor damping" you are commenting on is really damping. In my way of thinking, inertia (of the rotor) is different than damping:

Inertia is something that tends to keep a mass moving in the direction it is moving, or tends to slow its acceleration or deceleration of movement. It is not something that tends to stop the motion.

Damping is a force or moment that tends to stop a movement - not resist its acceleration. The force or moment derives FROM the motion.

By this distinction, I think we are mostly talking about the rotor's inertia due to its weight. I don't really understand the mechanism for "rotor damping", but I'm sure it has some because Chuck has said it does. But I think we need to make a distinction between rotor inertia and rotor damping - even though both are "DYNAMIC" elements, they are different dynamic mechanisms.

This is analogous to the airframe that has MOI about the pitch axis (inertia) and damping from the vertical MOVEMENT of the HS (damping). Without a tail, it still has MOI. With a light weight or small MOI, it still has damping.

My confusion, or the question I think we are working on, is the stability of a Magni due to its airframe damping and dynamic response, or to the heavy rotor (and rotor damping?)? I still maintain it is both, and that even without a heavy or heavily damped rotor, some of the stick feedback comes from the dynamic damping of the airframe tail – increases as a function of increased airspeed while RRPM is about the same. (Actually, the Magni stick gets much lighter at speeds below MPRS, where RRPM is also about the same. By this observation, I conclude that the rotor is not all of the stick “heavieness”. I believe the stick would still be somewhat heavy with or without the tail, but I do believe the airframe tail and the airframe inertia provides a lot of the stick heaviness due to the dynamic damping in the tail. Everything contributes to the overall stability and harmony of control – it is a “harmony of all the parts that make the whole “harmony”.

Case in point may be the ELA and MTO3. Both of these are similar to Magni aerodynamics – at least in a power off glide where HS embedding on the ELA and MT03 are not a factor. I believe pilots that have flown these and the Magni say that the stick forces are less but not as light as might be expected with a light rotor – comment from ELA/MT03 guys! This would support that the rotor dynamic response (from inertia and damping?) is part of the stick feel. But these gyros are also reported to have Magni-like stability. With still somewhat heavy stick forces, and with stability and (so far) no reports of PIO or buntover, this suggests the tail and tandem MOI are playing their part in stability and stick feel as well.

Chuck, I’ll try to measure the Magni cyclic stick ratio today.

Birdy, I apologize if I don’t reply to your points directly. I am not sure I am following your points, and I am not sure there is a real need to try to change your intuitive understanding – I don’t think anyone is worried about your safety – you are a skilled pilot who probably is a better stabilizer or damper than any hardware. But, I can’t keep up with everything, and I would rather focus on helping those less experienced with making good decisions about what they do. I feel the Magni has “secrets” to offer – that nobody may fully understand, and, with its safety track record, I’d rather spend more time exploring the “secrets” than defending its performance.

- Thanks, Greg
 
The Hughes blades required more time to accommodate changes of G load.
CB, wot RRPM and loading were they at?
The Hughes OH-6 rotor blades, usually with a 24’ rotor and a disc loading of ~1lb/ft², typically ran at 300-320 RPM on my old Bensen style machine, depending on whether it was with Mac or VW.

The most noticeable effect of rotor inertia was during a landing flare.

With low inertia Bensen blades, the customary way of alighting was a single pop of the stick and the blades would speed up and catch. If that sort of landing was attempted with Hughes blades, it would mush through and thump in.

The showiest landing with Hughes blades was to land after rolling out of a tight turn with excess rotor RPM and chop the power. The machine could be held at a foot above the surface until airspeed and excess rotor RPM bled off and plop down with zero roll.
 
Magni cyclic ratio

Magni cyclic ratio

The ratio of control linkage, stick travel Vs. rotor head tilt, is simple to measure. No need for speculation.

Most gyros will be near ¾” of stick travel per degree of rotorhead tilt.

Chuck, I measured the Magni control ratio to be .53 inch per degree of head travel. This was measured at the middle of the joystick grip. Actually, I measured this at the forward stick position - not the neutral stick position. So, we could expect a bit more head travel at the mid-range because the rear control fork has a bit more range at that point - like any Brock-type cyclic control. So, it looks like the design is intended for 1/2 inch per degree of head travel. Doesn't look like they were going for a metric number!

This puts more stick leverage than your suggested norm above - .5"/degree vs. .75"/degree - a quicker control and a heavier stick and an explanation for some of the higher stick forces.

But, again, the stick forces change very signifcantly from slow speed to high speed - neither the stick length or the RRPM are changing to account for that. But, the airflow over the HS does change from slow speed to high speed. - and the effectiveness of the Dynbamic Damper changes a lot with airspeed change.

- Thanks, Greg
 
Thanks for posting stick rate, Greg. A rate of ½”/degree is quite high.

There is argument in some quarters (which I happen to disagree with) that a fast stick makes control too sensitive.
 
If it was possible to fit a horizontal stabilizer sufficiently powerful to prevent an RAF from tumbling out of the sky, you wouldn’t have to be concerned with chopping the throttle.

With as much as 500 ft-lb of tumbling torque, the stab would have to generate 500 ft-lb of nose up torque. In all situations where full throttle might be applied.
 
With as much as 500 ft-lb of tumbling torque, the stab would have to generate 500 ft-lb of nose up torque. In all situations where full throttle might be applied.

Can't think a Magni stab at low airspeed and full throttle generates anywhere near that Chuck?
 
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