Chuck Beatty's gyro and CMDR Wallace's lil' Nellie?

[SnoBird]

I've always admired CMDR Wallace's gyros and of course am incredibly impressed with his longevity with flying - and surviving. And although most of his machines don't have a horizontal stab, it looks like he either instinctively or technically understood how to incorporate features that enhanced longitudinal stability in his now 50+ year old designs. Are there any resources (online or otherwise) that can reveal the overall design of his machines in more detail? I'm thinking about modifying my stock SnoBird and want to gather some facts and info from the old masters before I do.

Also, I've seen Chuck Beatty's machine on youtube and am very impressed with its design. Knowing the level of knowledge and experience that Chuck has, it looks as if he's built the perfect pusher gyro by incorporating all of what is currently known about gyro stability into his own machine. I especially like the way he's decided to hang the tail support from the upper part of the mast instead of down low. I'd like to know in more detail how this machine is designed and if possible any tradeoffs (barring any "trade secrets", of course ;-) that had to be made in order to achieve the design. Hopefully this is not a case of bad manners to ask such things, but it would be nice to know what's already known before trying to reinvent the wheel on my own machine. Thanks in advance for any help...

[C. Beaty]

I’ve never seen a picture of one of Wing Comdr. Wallis’ gyros with metal blades. Always wooden blades with external nose weights.

My speculation is that he has discovered the stabilizing effect of over balanced, torsionally flexible blades.

When the center of mass of a rotorblade is located a substantial distance forward of the aerodynamic center (nominally ¼ chord), the rotor can become auto stabilizing; an upward gust, for instance, acting on the AC produces a torsional deflection that tends to keep the rotor headed into the relative wind. The rotor tends to remain in position when a disturbance affects the airframe.

If so, there is less need for stabilizing tail surfaces and CG/propeller thrust line location becomes less critical.

There are a couple of downsides. External nose weights increase rotor drag. The cyclic stick becomes very heavy, depending upon the degree of overbalance.
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My gyro is constructed from 3” dia. X 0.065” wall aluminum tube. Connections are by bucked hard rivets wherever possible and by the use of gang nut plates (channel nuts) where not.

There’s a set of dimensioned sketches floating around somewhere. Larry Goodhind had them but I believe he’s sent them to Tim O’Connor.

[Mac]

Chuck's sketches of his unique gyro design are located at Tim's Gyrowiki.com / shared documents / Dudley folder.

Chucks Sketches (http://gyrowiki.com/Shared%20Documents/Forms/AllItems.aspx?RootFolder=%2fShared%20Documents%2fD udleyScans&FolderCTID=0x0120001B8A4E515AAA624FBDD3EA16F1078C3 9&View={C6E56DDF-7A3A-4C7D-A021-308373D3AE19})

[SnoBird]

Thanks Chuck and Mac. Chuck do you have any clear, detailed pictures of your machine that you would be willing to share? Like a front, left, right and rear view? And maybe some close ups of critical features? That'd be really neat to see the inside story behind how and why you built this unique machine. And being that you have so much experience with nearly all types of gyros over the years, how does your gyro compare handlingwise to other gyros you've flown? I'm sure it's more stable than an old Bensen type, or HTL models, but do you ever feel it's too stable? By that I mean is it as maneuverable and "flickable" as you'd like it to be considering your level of flying experience? And did you find there were any unexpected tradeoffs or perhaps unexpected benefits? One thing I wonder a little about is rotor vibration. By mounting the tail boom high, did this change the amount of vibration transmitted to the airframe? On the one hand I would think the tail boom connecting close to the rotor might produce a mass damping effect, but then on the other hand it might also diminish the vibe absorbing flexibility of the mast. I dunno, was hoping you could comment on it in a genral sense if you wouldn't mind. Looks to be a very well thought out machine, would love to learn more about it.

And is CMDR Wallace available online? I know he's very old now, still wouldn't surprise me if he reads a little online. Would be nice to hear/read what he has to say about his design. Thanks to all...

[SnoBird]

Incidentally Chuck, I apologize spelling your name with two t's. Didn't mean to mix you up with Warren or Ned!

[karlbamforth]

Chuck,

Is the overbalance trial and error or do you have a magic formula to calculate it ?
I know that we suspect magni have done it with composite blades but do we know anyone who has actually done it ?

I doubt it much use to answer the questions but it is an interesting pic anyway.

[Resasi]

There was a thread where Mr Goodhind had offered to reproduce the plans. A number of people expressed interest but he did not respond.

Be interesting to know if he completed them and/or produced a machine.

[C. Beaty]

Chuck,

Is the overbalance trial and error or do you have a magic formula to calculate it ?
I know that we suspect magni have done it with composite blades but do we know anyone who has actually done it ?

I doubt it much use to answer the questions but it is an interesting pic anyway.Bensen, while still running the PRA, wrote a monthly column titled; “Design Classroom” where overblancing of rotorblades was discussed in one of the articles.

My recollection is that while experimenting, he overbalanced a set of blades to the extent that the rotor wouldn’t respond to anything including cyclic input by the pilot.

Someone needs to dig out that article.

I also have a fuzzy recollection of having read about overbalance as applied to an early helicopter for stabilization purposes. I believe there could have been a patent taken out toward that end.
*****
The original Magni dealer in the US was Bill Parsons who constantly bitched about the heavy stick of a Magni, blaming it on the horizontal tail. Not being interested in a Magni and knowing Bill’s abilities as a theoretician, I didn’t think much about it one way or the other.

Then along comes Birdy who says it flies like a “hard mouthed ying yang.” I don’t know exactly how that translates into English but my interpretation is that it flies like a dump truck with the power steering out of order.

The various explanations such as a secret mechanical friction damper or fast stick simply don’t fly.

The heavy stick could only result from a slow following rate of the rotor vs. control input, indicating a large amount of rotor damping.
*****
I have no idea as to how overbalance could be solved quantitatively, it’s an enormously complex problem. Cut-n-try is the only approach I can offer.

[RotoPlane]

Bensen, while still running the PRA, wrote a monthly column titled; “Design Classroom” where overblancing of rotorblades was discussed in one of the articles.

My recollection is that while experimenting, he overbalanced a set of blades to the extent that the rotor wouldn’t respond to anything including cyclic input by the pilot.

Someone needs to dig out that article.

Chuck - I typed this out of the Design Classroom - Fall 1963.

This section is on chordwise balance of rotor blades.

Before we leave the subject of balance of rotor blades, it must be pointed out that chordwise balance has another, less obvious, side-effect on rotor performance. Assuming that the airfoil is of "zero moment" type, chordwise under-balance produces an unstable rotor, while over-balance improves flight stability of the rotor. The permissible amount of under and over-balance depends on the rigidity of the blade and of the control system (remember, propellers are not balanced chordwise at all). With a "soft" blade, of course, we know the severe amount of under-balance (say, 35%) will result in a flutter. But it is quite possible to fly a slightly under-balance blade without encountering flutter. Many amateur-built rotors with fiberglassed skins, not compensated by heavier nose weights, fall in this category.

The rotor with under-balanced blades reacts with progressively greater violence to air gusts and tends to "dart" in pitch and roll, or to use a technical description, "reacts divergently to disturbance". To the pilot such a rotor feels "touchy", over-sensitive, and requires constant attention of the pilot, like balancing a broomstick vertically on the finger. Figuratively, the more under-balanced the rotor blade, the shorter the broomstick. In extreme flight conditions, such as at high forward speeds, dives, etc., the rotor may actually "get away" from the pilot momentarily and go into severe pull-ups, or will tuck under, in spite of pilot's controls to the contrary. In such cases aerodynamic force gradient on the blade is greater than its torsional stiffness, thus forcing it to feather in "toggle action".

An over-balanced rotor blade has a directly opposite behavior, it reacts convergently to the disturbance. Such rotors tend to stay put in space, respond slowly to gusts and to controls. To the pilot an over-balanced rotor feels "sluggish", nonresponsive, and at times requires drastic manhandling to execute rapid maneuvers. As a bonus, however, it feels immune to gusts and can be flown hands-off in calm air for extended periods of time.

There is a limit to the over-balance, too. An excessively over-balanced rotor will go into a "weave", which is instability of the rotor disc. Here again the gradient of aeroelastic forces becomes greater than torsional stiffness of the blade, and their tips lose the ability to follow the commands from the hub. A "weaving" rotor disc dips and tilts in random directions, sometimes momentarily going violently out of track and becoming totally non-responsive to controls. In marginal cases, as in the case of flutter, it occurs first on the advancing blade at high forward speeds. Thus it gives the pilot a warning that something is wrong, and the pilot should slow down to avoid courting disaster.

In practice most rotorcraft blades are balanced right on the quarter-chord, or if anything, slightly over-balanced. In case of powered rotors with collective pitch controls, blade moments are kept as nearly zero as possible to hold down the effort required by the pilot to operate the collective stick.

[RotoPlane]

I am using chordwise balance this way:

My 0012 blades have a 9" chord and both the aerodynamic center and pressure fall at 26% of the chord. These blades are controlled by servo-tabs and therefore will be balanced with the CG at 24%, a 2% over-balance, without fear of excess control forces. The airfoil nose cavity is filled with a matrix of lead bb's, short glass fibers and epoxy. The servo-tab controls housing extends beyond the airfoil nose and that extension holds the added weight required for chord balance. I can add or remove weight from this location, to give the flight characteristics I desire.

[C. Beaty]

Thanks, Ed. That pretty much meshes with my recollection. The first post Bensen PRA magazine editor published the “Collected Works of Design Classroom” in booklet format. I had a copy but it somehow got away.

[RotoPlane]

Thanks, Ed. That pretty much meshes with my recollection.

Yes, I noticed.....you must have a photographic memory…..almost makes me sick ;).

[SnoBird]

Thanks to everyone for the info on the Wallace and Beaty designs. And Chuck after looking at the videos of Wallace's machine, like you say he's still using the old style wooden blades with the external counterweights. I agree with your analysis that overbalancing is probably a part of his stability equation. Although we can't know for sure unless we find out he truly does overbalance them (i.e. the mere presence of external counterweights does not guarantee overbalancing), I'd say that's a reasonable guess. Another observation is that the arrangement of his airframe puts the pilot into a recumbent position, sort of reclining with the legs up. The engine with its smaller direct drive prop also serves to keep the prop thrust TL/CG offset to a miminum. And the mast is short so that the rotor thrust line probably has a small offset with the CG in trimmed flight. Basically by the looks of it, he's gathered all the big mass items into a cramped, consolidated space and has put the thrust line just about where it needs to be (intentionally or not). And by keeping the pilot quasi-reclined with his legs up along with the associated pedal/stick controls/keel structure etc, he's done all he can to keep the weight distribution favorably high (with the possible exception of the fuel tank, which suspends below). I suspect this also serves to mimimize the offset between the airframe center of drag and the cg under most pitch attitudes as well. I also notice your gyro shares the recumbent type configuration with the Wallace machine. I think both of you have it right by doing it that way (something I'm sure you already know, obviously).

This is in contrast to the Bensen format (of similar vintage) which has the pilot sitting completely upright, as if in an office chair. I suspect a lower keel and apparently longer mast (although still relatively short compared to more modern machines), combine to probably put higher offsets between both rotor and prop thrust vs cg on the Bensen machine.

Anyway, that's a start. Overbalanced wooden blades, recumbent pilot position, centerline thrust and a shorter mast seem to be important parts of Wallace's design, and partially of yours as well (sans the overbalanced wooden blades). And even Wallace has a horizontal stab on some of his machines, but I notice he seems to only have them on his heavier machines (with large 4 stroke engines).

Ed do you have any more of those Bensen classroom lessons? Talk about some awesome info, would love to read a compilation of all that stuff.

[RotoPlane]

SnoBird - Ed do you have any more of those Bensen classroom lessons? Talk about some awesome info, would love to read a compilation of all that stuff.

Yes Bill, I do but the majority of my gyroplane information is in the "Collected Works of Design Classroom", published by the PRA in 1974. One reason I typed the above excerpt, was because the print in this booklet is so small and is not clear enough after scanning…at least with my equipment. I wish PRA would reprint this booklet, at least those sections that have relevance to today's gyros.

Perhaps Tim O'Connor knows a way to make the text more readable on screen. I do not know where on "earth" you are located, but if Tim thought he would like to try this, I would send it to him….for a while….I refer to it often.

Using this booklet frame-work, I would like to see Chuck Beaty, Doug Riley and others with hands-on experience add their comments and clarifications to Benson's work. Perhaps the PRA would consider publishing this revised work for sale to the public. I am sure many gyro enthusiast would purchase it.