SamL

Titanium sounds good! Not sure if it work hardens over time or not????
As long as the blade conning angle is set correct for size of blades and weight of machine, then the blades would see not difference.
One material I would love to see used is fiberglass. In my opinion it would allow a central conning angle and during loading should flex with the blades, further minimizing blade flexing in high G manuvers. As far as its work life is concerned, it should last forever.

Sam......

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Scorpion

Sam,

Fibreglass wouldn't take the loads and stress that are put on a Hub Bar, it would start delaminating very quickly, don't even consider using it.

Metal (Alloy, Titanium etc.) is the only material that should be used for any rotor parts other than the blades.

Graeme

SamL

Graeme
I'm no fiberglass man, but I do know that there are many types of glass fiber and techniques designed for different applications. Now days many 2 seat gyro undercarrage systems are also made of glass, and seem to be standing the test of time.
Some examples are, Owen Dull, GTG Kruza, Magni, ELA, Patroney, and MT-03, to name a few.
It would be interesting to see what others with glass knowledge think ?

SamL

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Scorpion

Sam,

Yes, composite is a very good material to use for landing gear, but landing gear does not go through the extreme stress, bending and twisting that a Hub Bar is subjected to.

In composite you have two materials; one is the fibreglass itself and the other is the bonding agent (resin, epoxy etc). It is the bonding agent that breaks down through stress and twisting which then causes the fibreglass to delaminate and disintegrate.

There is also UV breakdown of the resins and epoxies to consider.

It would be nice to have Hub Bars made of this material, but I think it will be many years before they have anything to sustain the punishment that the Hub Bars cop.

Graeme

niquenaque

An additional problem with laminates is the connection to it. FRP [fibre{glass} reinforced plastics] do not have the same bearing pressures as metals, as Graeme has noted the plastic in the mix is the weak point in this equation, so you have to install metal ferrules in the FRP to reduce the bearing pressure on the FRP down to a level where it does not delaminate due to bearing pressures. The other thing that goes wrong with it is that the connections - even with ferrules - tend to flog out. This is overcome by giving the FRP a very bulky connection system as you see with propeller blade roots which are usually set up so the fibres of the FRP are locked in by a wedge or wrap around system so as to trap them into a very large bearing area with a largely tensile connection.
A composite hub bar is not an impossibility as demonstrated by the use of Graphite fibre composite blades on the apache helicopters. They are merely beyond the budgetary constraints of most gyrocopter buyers, metal is certainly less expensive due to the fact that you don't have to spend hours making up a block of metal as you would to laminate up a composite hub bar, then cure it, etc, etc.

Hope this helps,

Nic.

Graeme

I have no idea but what was the old SkyWheels hub bar made of?

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disco

I flew a set of skywheels this morning and they are old as. I inspect them but dont know if I'll see any signs of problems... I've asked on here about the life of them but nowbody seems to know. I recon they're great blades and most people I've ever asked said their one of the best. For those who don't know, they have a fiberglass (or some thing like it) hub bar that the blades plug into snugly and then you put the 4 bolds in each side.

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Scorpion

Hi Disco,

I stand corrected on the use of composites for Hub Bar's. I looked up the Skywheels site, Sky Wheels - Home and this is what they had to say;

CENTER SECTION
We have replaced the standard aluminum hub bar system with an airfoil shaped composite section, which minimizes drag and contributes lift. Similar to the rotor blades, the center section is constructed with S-glass oriented at +/- 45° to provide torsional strength, and S-glass and carbon fiber oriented spanwise to provide tensile and bending strength. A 12-inch deep socket is molded in each end of the center section to accept the blade roots, and four AN6 (3/8" diameter) bolts per blade provide blade retention. In addition to improving performance, the wide chord of the composite center section (approximately 10 inches) and the wide spacing of the four (per side) blade retention bolts provide the in-plane bending stiffness and rigid blade pattern alignment that is necessary to minimize stick shake.

I'm impressed.

Graeme

bones

yep they been making them for bout 20 yrs, unfortunately not still in business, as far as im aware

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Scorpion

Hi Disco,

I would like to have a look at some photo's of the Skywheels system.

Any chance of posting some on the site for us to have a look at.

Graeme