ROTOR HUB BAR DESIGN DISCUSSION ON DESIGN

[Gyrodes]

I AM NOT A PERSON WITH ENGINEERING QUALIFICATIONS. :blahblah:
The fallowing is for discussion only and not to be regarded as fact or recomendation in any way. :paper:
With the number of hub bar failures in the near past I aim to get people to discuss the posibility that we may have a possible flaw in the design changes of the hub bars on our gyros.
On the lighter machines the hub bars are 19mm thick by approximatly 63 to 65 mmwide.
Then the blade lengths have increased and the hub bars increased in thickness by 33.33% to 25mm with the hub bar width remaining the same at 63 to 65 mm.
Question is should the width of the hub bar be increased by 33.33% also, Would this help prevent the failures we as an industry/group/organisation are experiancing in the training machines and high G force machines. :confused:
I REPEAT I AM NOT QUALIFIED TO ADVISE ON THESE MATTERS JUST THINKING ALOUD TO PREMOTE DISCUSSION. :poke:

[rotor]

Hi Des,

I am not up on the exact science of rotor engineering either.

I did talk to some one from Bundaberg the other day after the second recent hub bar failure. Apparently the owner of the second machine was Rusty Ferguson and the blades in question were Rob Patronies. The hub bar didn't fail in flight but was picked up on the ground - whether through proper inspection or shake I'm not sure. Although these blades are heavier he thinks the reason for the hub bar failure was the amount of spin they generate during flight. Exact figures I cannot give you but he indicated that they were not spinning as fast as the lighter blades - I must surmise that the angle of attack or the amount of lift generated is the cause of this. However, without the amount of centrifugal force due to less rotation of the blades, the moment on the hub bar must be all the greater placing more stress here.

The gyro that crached and burned in WA had AK blades on. No further info available.

I guess if the stuation concerning hub bars was dangerous, we'd have heard something by now. Do your prefilght meticulously as allways.


rotor

Edited 21/08/2005 05:15AM