BeeDifferent Update

[GeneWeber]

Hi Folks,

I don’t spend much time on the forum these days. Not trying to be anti-social, just trying to focus on building my plane. It seems like folks are genuinely interested in the progress of others, so here are a couple pictures showing current status. Still hoping to bring my kids and a completed plane to Mentone this year.

Regards,

Gene

[Friendly]

Gene , based on the parts I purchased from you in the past , I knew you would build a quality machine. Keep the pictures coming, I have a friend building a bee as well. He will enjoy these.

[Alan Coats]

Thanks, Gene.

You're right, we really are interested in the progress of others, and it looks like you have made plenty. Your Bee looks great!

Alan

[GyroRon]

Gene, a hint or observation if you don't mind. That quicksilver fuel tank will work better for you if you can make the gas cap a non venting cap and drill and tap the center of the cap and using fuel line run up to a higher position and do a remote vent.

I had a engine out landing in Barry gyrobee due to the quicksilvers standard venting cap failing to vent causing a vacum in the tank that starved the engine for fuel.

Also that tank was designed to be installed on a quicksilver which tends to keep the cap up higher than the bulk of the rest of the tank, allowing you to fill the tank nearly full of gas without spilling. On a gyro the tank is installed backwards from it's normal designed installation and that causes it to spill gas if you fill it much more than half full.

I personally wouldn't use that tank at all, I like the clear plastic square shapped tank much better.

[GeneWeber]

Hi Ron,

Suggestions, especially when based on practical experience, are always welcome. I’ll seriously consider the venting suggestion.

If I understand what you’re saying about not being able to completely fill the tank, it’s due to the tank angle when the gyro is resting on the tail wheel. So, I’d guess I need to put a block under the tail wheel when I fill the tank.

Thanks & Regards,

Gene

[GeneWeber]

Thanks Mark & Alan,

Compliments regarding this machine should really be passed along to my friend John Mealey. Something I built on my own wouldn’t be anywhere near as good. God bless him.

Regards,

Gene

[KDOG]

Hmmm, I'm thinking of getting my fuel tank from Starbee. I assume that its vented correctly?

[Al_Hammer]

You're really making progress, Gene. Congrats. It's looking good. :)

[Doug Riley]

Gene: Are those main gear axles fiberglass rods?
Given the cantilever, I assume they're not the usual metal tubes.

[GeneWeber]

Hi Doug,

You are correct sir, they are fiberglass rods. It’s just about the only remaining Honeybee feature. But they have been shortened 3” on each side. They are heavy, and since the braces up to the mast were then trimmed to fit, it dropped several ounces of weight in total down low. The braces running from the keel tube to the main axles were also replaced. The Honeybee used an unconventional piece of rod in a tube arrangement that allowed a bit of fore-aft play but no adjustment. It now has rods with end bearings. This provides adjustment (toe-in/toe-out) with no play. :)

Best Regards,

Gene

[CLS447]

I was wondering where you were ,Gene ! It is looking real good, keep up the good work! Maybe an award at Mentone?

Have you done any training/flying yet?

Come & see us at K-town soon, ya hear!

[GeneWeber]

Hi Chris,

You flatterer ;) , I’ll pass your praise on to John who deserves it. If I get to Mentone with a completed plane for Tom Milton to inspect I’ll be more than satisfied. I did get an N number for the plane, N45575.

I did a few hours of training with Ron Menzie over a year ago, and then realized my plane wasn’t close to done. So I decided to suspend training until the plane was closer to completed. Perhaps it will soon be time to start up training again :D . My goal then was to get a Private Pilot Certificate. Now with Sport Pilot a reality, that seems to be the best route for someone like me.

Yes, I’d very much like to meet you at Kutztown this spring and see your Air Command SS in person. She looks like a beauty (although your co-pilot shown in this months RotorCraft looks like a dud :p ). When I’m finally flying N45575 instead of building it, I’d like to revisit the idea of an East Penn RotorCraft Club.

Best Regards,

Gene

[chuter]

Thought I should take a minute to express my concerns about the fiberglass rods used for suspension on HoneyBees.

I had a powered parachute that used these rods, and it wasn’t uncommon for them to break. They didn’t break “a lot”, but I went through 2 or 3 in the 60 hours I put on my ppc. We took off exclusively from cow pasture type fields, and I had a rough landing or two that could account for part of the problem. But rough landings happen on gyros too.

On a powered parachute it wasn’t such a big deal, but if one collapsed on a gyro with the blades spinning causing it to tip over, this could be really bad news.

On the up side, they make for a really nice, smooth ride over rough stuff.

Just thought I should mention it, I hadn’t seen it come up here before.

[GeneWeber]

Hi Michael,

Thanks for the “heads-up”. Can you give me more details either here or in an email?

What was the diameter of the rods used? I assume they were solid? What was the length of the spans between support points? Where did they break along the span? Do you have any photos (broken or unbroken)? Just how hard was the impact that broke them?

Thanks & Regards,

Gene

[scottessex]

Curran3 used the fiberglass rod suspension on his gyrobee, He might be able to give you sone insight.

[chuter]

Gene,

I believe they were 1 inch in diameter, solid, about 1 foot long. I'd guess there was about 8 inches or so of exposed rod between the wheel hub and the main axle. (It's been several years, so this is just best memory).

They would sort of shread, not break cleanly. Just kind of collapse and what you had left was a mushy bunch of shreaded fiberglass that wouldn't support any weight.

Sorry, but I don't have any pictures.

I seem to remember one broke after a pretty hard impact, but I think one surprised me and I never really new why it broke. May have been defective.

[chuter]

Another memory just popped up (getting old is so much fun).

I remember one of them broke in such a way as to not totally collapse, just obviously weak, and you could see where it had started to shread or come apart.

[GeneWeber]

Hi Michael,

Thanks again. Looks like I have some homework to do.

Does anyone have any suggestions to where I might be able to find strength specifications on commercially available fiberglass rods? For that matter I don’t even know where to purchase replacement rods. I’d also like to find strength VS aging data, and flex cycle data, on them.

Thanks & Regards,

Gene

[scottessex]

Just on a hunch, try.....www.mcmaster.com

[Sonnyj]

Hiya Gene
I do a lot of work on buckit trucks,I know they dont look anything like a gyro but,they have the fiberglass rods in the boom instead of solid metel cables for insulation.They will hold a lot of weight in a strech situation but they will break under compression.
Just a heads up
Sonny

[GeneWeber]

Hi Scott & Sonny,

Thanks for the inputs. Unfortunately McMaster-Carr does not appear carry anything this size. The bucket truck example sounds like a column failure whereas an axle break would be a cantilever beam failure (I think :D ). But it underscores that fiberglass rods do fail under certain conditions, so I appreciate the heads-up.

I was working on the plane last evening and took some measurements. The rod diameter is 1.24”, the inner and outer spans are ~7” and ~6”. Since they’re 25% larger diameter and ~half the length of the PPC axles, they’ll definitely take more stress before breaking. I didn’t think to measure the total axle length, but I’m pretty sure it’s slightly under 3’. So I need to find 3’ lengths of 1.25” diameter rod if I ever need replacements.

I did a lot of Googling yesterday. Did get some hits that indicated that PPC’s breaking fiberglass axles is not that uncommon. Michael, what did your PPC weigh? I didn’t find any definite replacement parts or spec sheets.

Again, if anyone can point me to a possible source of replacement parts and specification sheets I would greatly appreciate it.

I did find some mechanical engineering information online. IF I can get a grasp of it, I’ll work through some beam flexing and breaking formulas and post them. Then hopefully smart folks will correct them for me. ;)

If anyone has any interest, these documents seem somewhat useful:
www.deltacomposites.com/lit_library/DelDesMan.pdf
http://ceaspub.eas.asu.edu/imtl/HTML/Manuals/MC101_Modulus_of_Elasticity.html
http://www.tiniusolsen.com/tmech.html
If you know of other good sources please post them.

Thanks & Best Regards,

Gene

[chuter]

Gene,

As far as weight of my ppc; it was a two-seater and I'm thinking it weighed about 350 lbs empty.

[Jazzenjohn]

Gene, Mcmaster has fiberglass rods in the size range you specified. They have 1", 1.25", and 1.5" solid fiberglass rods. A 5' piece is $36 and is rated at 30,000 psi lengthwise; 7,000 psi crosswise for Tensile strength. Look under materials/plastics.

[Doug Riley]

Knowing the tensile strength (and assuming the compressive strength is the same or greater), you can easily calculate the beam strength of the rods by using the section modulus (I/c) for a solid round beam.

The still-unknown factor is the fatigue properties of the material. My one experience with a fiberglass spring was with the tailwheel on my little U.L. plane. It got floppier and floppier with use, as, apparently, one glass fiber after another broke. I finally replaced it with a rigid tube cushioned in rubber. Meanwhile the manufacturer came out with a metal spring as a retrofit. Others must have had problems, too.

[GeneWeber]

Hi John,

Thanks. Yup, there it is. Not sure how I missed it. Sorry Scott, you were correct. Page is attached.

Hi Doug,

you can easily calculate the beam strength of the rods by using the section modulus (I/c) for a solid round beam. Easy for you perhaps. :( I’m not yet understanding what I’m reading. They talk about frequency of oscillation in formulas applying Young’s modulus. Too many moduli and other unfamiliar terms as well. Electronics is much easier. ;) I’m seriously considering buying a length of rod, and doing a destructive test to see how much force it takes to break a 7” cantilevered length. I’ll have to see what kind of scales John has.

The still-unknown factor is the fatigue properties of the material. Agreed. But is it just number of flex cycles or do temperature cycles, UV exposure, etc all play a role. I'd imagine so to some degree.

At least I know that the axle setup on my plane is stronger than the PPC setup, and the load is less.

Regards,

Gene

[Doug Riley]

Gene, you're holdin' back on us, or being modest.

The strength of a cantilever beam is most easily expressed as a moment (or torque). That way, you can play with different lengths of beam with the same section while doing only minimal additional arithmetic.

The section modulus is a number that measures how efficiently the material in a beam is distributed to resist bending loads. For example, I-beam sections have a very high section modulus for the amount of material in them -- they're an efficient shape. A round rod is a lousy, inefficient shape for a beam -- but that's what we've got, so let's do the numbers.

Formulas for the sec. mod. of various beam section shapes are given in engineering reference books. For a 1.25" round rod, the sec. mod. is 0.19165 cubic inches. To derive the maximum moment that the rod will take (assuming you're working with a material that fails first in tension), multiply the tensile strength by the section modulus. This little multiplication is typically expressed as M=S(I/c). M equals the moment, S is the strength and I/c is the sec. mod. The moment in this case is 5749 in-lb, or 479 ft.-lb. So the rod will break if a load of 479 lb. is applied a foot out from its fixed mounting point. If the lever arm only 9", the load is 639 lb.

These are one-time loads. I don't know anything about the fatigue behavior of unidirectional fiberglass, except to say that my fiberglass tailwheel spring lasted only a few dozen hours.

Young's modulus is the modulus of elasticity (how far it bends under a given load). You can use that to figure the deflection of the gear in a landing of X G's, and/or its period of oscillation.

Sometimes undamped, springy gear will resonate with the rotor at certain RRPM to create a little hiphop. I haven't found this to be a big deal with a teetering rotor. It can be a very big deal with lag-hinged rotors, though.

[B8MFlorida]

Doug-
You and the other incredibly smart guys that can get down to the nitty gritty like this never cease to amaze me. Where else can one get an education like this for free. Sometimes I have to reread these posts and even then I sometimes don't get it. But I just wanted to say
thanks to you and the others for sharing such an incredible amount of knowledge in Physics, Engineering and in Gyros. Always looking foward to your next posting.
John Rocca
B8M
Gyrobee
Naples FL

[Doug Riley]

John: Thanks. In truth, any of us can look this stuff up. The following books are ones that a person thinking about gyro design ought to have handy:

Marks Mechanical Engineers Handbook
Abbott and von Doenhoff, Theory of Wing Sections
Gessow and Meyers, Aerodynamics of the Helicopter
Pazmany (forget the exact name - a designer's manual from EAA)
Evans (similar to Pazmany - an EAA designer's manual)

The Marks is a little pricey, but is the handiest of the bunch for everyday work on your gyro.

You can't fool around in an informed way with H-stabs or other airfoils without the info in Abbott and von D.

Gessow is THE bible of rotorcraft theory, period.

Pazmany and Evans give lots of user-friendly info about typical small-aircraft designs and materials.

[GeneWeber]

Hi Doug,

In my youth I knew I was one of the smartest guys around. ;) Then I had the wonderful good fortune of working for IBM and then Bell Labs where I met some truly gifted people. Now I know I’m neither the brightest nor dimmest bulb on the Christmas tree. At this point in my life I appreciate these lines from the movie “Harvey”. Elwood P. Dowd: Years ago my mother used to say to me, she'd say, "In this world, Elwood, you must be" - she always called me Elwood - "In this world, you must be oh so smart or oh so pleasant." Well, for years I was smart. I recommend pleasant. And you may quote me. At the recommendation of you and Chuck Beaty I purchased “Theory of Wing Sections” and a used copy of “Marks’ Standard Handbook”. They are excellent references, and I’m glad I purchased them. But they certainly aren’t “teach yourself” guides for neophytes in these fields. In the case of this beam, I couldn't find anything that stood out as the appropriate formula to calculate the breaking point of a cantilevered beam. (Then again I couldn’t find the fiberglass rod in the McMaster-Carr catalog, so my powers of observation haven’t proven too stellar. :o ) Marks’, in the section on beams, says: The moment of the elastic forces about the neutral axis, i.e. the stress moment or moment of resistance, is M = SI/c, where S is an elastic unit stress at outer fiber whose distance from the neutral axis is c; and I is the rectangular moment of inertia about the neutral axis. I/c is the section modulus. A few pages later it has a table that shows how to calculate I/c for various shapes. Until you explained this in your post, it wasn’t obvious that: “The moment of the elastic forces about the neutral axis, i.e. the stress moment or moment of resistance” was a breaking force. And, “an elastic unit stress at outer fiber”, didn’t exactly jump out as being the place to use the tensile strength value.

So I agree with John about folks such as you having wonderful insight, and being an invaluable source of education for the rest of us. I know that there are some who can, but Elwood P. Dowd and I are not going to educate ourselves simply by reading Marks’. :rolleyes:

Thanks for your tutelage!

Best Regards,

Gene

[GeneWeber]

Hi Doug,

I could use some more tutelage. I set up the M=SI/c formula in MS excel and played with some values. If I’m doing this correctly It looks like my gyroplane has considerably more strength than a PPC such as Michael described. I calculate that the gyroplane would have to sustain a 3 G load to break an axle whereas the PPC would do so with only a 0.65 G load. A pdf of my spreadsheet is attached. Does this look correct to you?

Given that, I started to question how much shock absorption the strong short fiberglass axles would provide. Looking through Mark’s, it appeared that the elastic curve formula, r=EI/M, was the correct one to calculate total deflection per load. Again I entered some values in excel. I found a more detailed specification sheet for the properties of fiberglass rods and have attached it. “Modulus of Elasticity” sounds like Youngs’ Modulus to me, but the deflection using that value was so small that I’m hoping it might be the “Flexural Modulus, LW” or the “Flexural Modulus, CW”. But, even using these, the calculated deflection of the gyro axles is SMALL. Am I making some mistakes? :confused:

The gyro axle is not truly a cantilever beam rigidly attached at one end. It is supported in the center and has some limited ability to pivot there, so that should provide a bit more travel. :)

I appreciate your help with this.

Best Regards,

Gene