Carbon fiber

[Sonnyj]

Hey Gents
You too Russ! :lol: :peace:
I was wondering, would carbon fiber make a good hub bar? It's supposed to be lighter and stronger than aluminium. You could lay it up to any size.
Would it be flexable enough? I dunno, maybe something to think about.
Cheers
Sonny

[russ]

Hey yar rat.......still makin that moonshine licker :cheers:
Rob Patroney here in Oz is the guy to speak with, makes composite blades and props, knows his shit

cheers.......

[BeefBear]

Sonny, I'm sitting here looking at a piece of carbon fibre and....I wouldn't like to fly a hubbar made out of this stuff. The company I got the sample from is involved in building nose cones for the Collins class subs. So they know thir stuff. Currently inside the factory is a 16metre ocean going pleasure craft. All constructed out of Carbon fibre. Wasn't allowed inside the boat to see the layout or any of the engine mounting points but it seemed to me that any vibration would see a drilled hole simply grow in diameter.

Ted

[Sonnyj]

Thanx Ted
I was just throwing something out on the table for folks more knowlegable than me to chew on. :chew:
I personally caint say that I know much if anything about C\F and can say for sure I have never worked with it.* :cheers:

Thanx again :buddy:
Sonny

Hey Russ
When ya gunna give us another one of your most excellent story's? :rockon: :crazyas: :drunk:
The tosser huntin trip was really great. :yikes:

Cheers and best regards
Sonny

[JOE NELSON]

Sonny,

I found a website yesterday that has fibre glass straps, lord mounts and vibration isolators. This might be a good resource for you. The website is lord.com

:cheers:

Ohio joe

[SamL]

Sonny. they make aircraft spars and props out of the stuff. I think it is only time before someone makes a composite hub-bar for a gyro.

Sam............ :eyebrow:

[Echo 2]

The assembly that holds the 3 blades on a Squirrel chopper is made from some sort composite material.

[niquenaque]

Composite Hub Bars...

They are entirely possible and workable. I'm not sure I would use carbon fibre due to its properties. From what I understand of it if it exceeds 1% deflection it simply goes bang! So, you would have to design for less than 1% deflection in the worst possible loading case ever for a bar, ie, roll over at full rotor RPM. Would it be advantageous for it to snap on a rotor strike? I don't think so, I can well imagine being speared by the loose end of a rotor blade and hub bar in a roll over incident, especially if you happen to wheel barrow it in. I have seen three such incidents - two on Jack Allen rotors, and believe me there is nothing wrong with the rotors or the bars - only the pilots or some dodgy welding - where the blades and hub bars remained intact and the rotors did not cause any harm to the pilots - a very critical thing, so, that is the reason for my belief in a solid bar which will not fail under anything but the most adverse condtions.

The critical thing to do with composite designs is to get the 'bearing pressure' right at all the connections, ie, where the hub bar connects to the the teeter tower and teeter bolts, where the blade roots connect to the hub bar and/or teeter towers[magni]. At the bolt level the composite will probably not handle the pressure caused by a bolt being forced into it by centrifugal loadings, shear stresses and any combination of oscillations from same. To fix this you have to bush the composite with a metal sleeve so the bearing pressure - which the metal can cope with - is reduced to a level the composite can cope with at, say, double the diameter of the bolt. Another option is to make the bolt big enough to make the bearing pressure on the composite acceptable, or use so many as to reduce the bearing pressure below elastic deformation levels. The next trick is to make sure that when the blade is loaded up that the connection copes with the compression loadings equally as well as the tension loadings, not such an easy thing to do when you are trying to lay one up as you have to get solid connection on both sides of the bolt top and bottom of the blade.

It requires alot of thought and careful design consideration.

Hope this helps,

Nick.

[Fencing Wire]

Wot were McCutcheon hub bars made of?

[russ]

Glass..........

Rob P, is toying with this idea also.

We already got glass axles [ newo ] seem to stand up to the flexing no probs