Hub bar project - report published

[asra]

[Adrian S]

Steve,Well done. Your time and effort is appreciated.Regards,Adrian S

[asra]

Cheers Adrian - I didn"t end up scoring a swan over to WA, however I"m already planning my drive along the coast from Darwin to Perth next year, so I"ll be sure to stop in to have a poke around your shed...

[Adrian S]

Steve,Your welcome any time!Thanks,Adrian S

[Disco]

Thanks Steve

[Des Garvin]

Hi Steve,
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[asra]

I was recently asked my opinion regarding polishing hub bars in reference to my statement regarding the surface condition of hub bars - in the interests of including all in the discussion I thought I"d post my response....Ideally, a hub bar would have a residual compressive surface stress treatment such as shot-peening, as this will delay the initiation of cracks at the surface - there is some quantitative data on this in my report. In terms of a polished surface, without reference to any quantitative data, polishing would certainly minimise the size of any discontinuities in the surface, and it is at discontinuities that cracks will generally initiate - however cracks can still initiate at discontinuities that are smaller than the finish of the polish. If there are any small nicks, corrosion, fretting etc. in the hub bar, these should certainly be polished out, bearing in mind that the more material that is removed, the less cross-sectional area of the hub bar, and hence the higher the stress level, but if we"re just talking about a very slight buffing of the surface, I would say the amount of material removed would have an insignificant influence on stress level.In short, polishing a brand new hub bar would be better than nothing, but I can"t put my hand on my heart and say it would definitely significantly improve safety, however polishing out any obvious surface defects should be considered essential.

[Weedy]

Good Day Steve,Sorry for the highjack, but I need Help.I"m from South Africa and have the AK blades and hubbar (33 foot) fitted to my gyro. My problem is that our CAA is looking for data on the AK blades and bars.I am appealing to anyone that may have any test data, technical drawings, specs etc that I could hand over to them.Many thanksClaude Pullen

[asra]

Claude, Unfortunately I don"t have any specific data in my possesion - prehaps somebody else here may be able to help - however one of the challenges I faced with my project is that there is very little data available for many gyroplane products. Given the simple and affordable nature of gyroplanes, and the often relaxed regulatory environment, much of the manufactured products are designed and developed based on historical observations and acquired experience of what works best, as opposed to extensive (and expensive) fatigue testing and laboratory development (which is the type of data that I suspect your CAA is interested in). I understand that some of the major gyroplane manufacturers do have stress and fatigue analysis data for their components, however my experience in this regard is that this is well-guarded information that they are reluctant to release. In saying that, I"m sure that an enquiry from a relevant authority such as the CAA, for the purposes of certification, would carry a fair bit of leverage. Good luck sourcing your data...