Hub Bars and whats happening?

Brian · 04-07-2007, 12:03 PM

I see Adrian posting here lately and am asking the question, "what is happening in regard to hub bar cracking"?

It could be construed that ASRA was more concerned about punishing 2 certain TA's than why hub bars were cracking. Certainly, the actions of ASRA could be seen to not make members or non members willing to come forward and report further hub bar crackings etc..

So, have there been any more hub bars cracked since the infamous one last year ?? and to my limited knowledge, the last hub bar reported. And, where are we at in the investigation??

Adrian S · 04-07-2007, 02:33 PM

Brian,

I am a little offended by the tone of your email as it suggests that Allan , Myself and others have been sitting on our hands!
Sure it is true that some of our time has been taken up by other events but I can asure you that we continue to act on your behalf.

A significant amount of research was undertaken based on 6 samples of cracked hub bars that were presented to me over the last three years. Work was done with Metalurgists and NDT experts which then led to the implementation of the AD requiring Hubbar testing at diferent life stages based on use types such as Recreational vrs training and mustering.
ASRA expended more than $6000 of members money along with probably 200hrsof my time to get to this point.
It is important to note that before we released the AD we tested a number of NDT processes before we accepted the published approach, this was done to make sure the approach was not suceptable to errors. For example the tests showed that dye penetrant testing was proven to be in some cases unreliable in detecting the commencement and propergation of cracks in hubbars.

Since the implementation of the AD the only cracked hubbar that has been presented is one that had been in service for more hours then recommended in the AD.
Anecdotal evidence also suggests that most gyro operators who do the high hours now order an extra hub bar with the blades and just discard the old hub bar when it is due for testing. This may explain why we are no longer seeing any more cracked hub bars - the AD is clearly doing what it was designed for - saving lives.

I have also been doing some more research into improved designs for hubbars - all of the Australian manufacturers have now made changes to their designs to further reduce the risks of early fatigue.
I have also just commenced a review of the hub bar design used on the German MT03 - to do this I purchased one of the hubbars, modified a head to accept its metric dimensions and have subjected to 100hrs of abuse measuring changes every 50hrs . I will continue to do this untill I exceed 1000hrs or find cracks or right them off through pilot error. On paper the MT03 design looks to be good but it is important to realise that there is nothing wrong with the present designs as long as you abide by the manufacturers and ASRA requirements.

I am currently doing tests on the impact forces from high energy pre-rotation systems and have found evidence in some cases of the impact forces causing the elongation of the holes in the hub bar through sudden twisting forces being transmitted from the instant of engaging the pre rotator with the head transmiting this force to the hubbar block retaining bolts. This elongation is causing stress raisers where cracking is then likely to start as the fatigue cycles get closer to its point of cracking. Of the six hubbars that I have done detailed testing - four showed signs that the cracks started from the holes in the hubbar where the pillar block is attached. This risk can be minimised through initialy hand starting the blades before you engage the prerotator or having a soft start system.

Although I had to stand down from the Tech Managers role at the the end of last year due to personal and work pressures rest assured that I am passionate about gyros and helping the movement continue to move forward.

The greatest risk we face is people thinking the hubbar problem has gone away - it has most definatly not it is just that while responsible gyro pilots follow the AD to the letter the risk is being managed.

As always dont hesitate to call me if you want clirification or more info.

Adrian.

russ · 04-07-2007, 03:13 PM

Adrian............have just had a new set of blades made by Rob P, they are going on my new build [ Raftorr ] The hub bar is completely different to the norm, ...........much thicker, blade straps much longer, and the strap securing holes, are now centrally located, in line, down the bar, and the bolts are bigger as well.

Question...........this "new type" hub bar, is it exempt from the current rulings. This redesign, is to add to strength etc etc, Rob plans on only doing this system to the heavier machines, 2 placers etc.

cheers...............

Brian · 04-07-2007, 04:56 PM

Thanks Adrian for the up date on whats happening and whats being proposed for the future.Your 's and other's time and effort is appreciated as we all have lots of spare time [not]. Its encouraging to hear that our blade manufacturers are making changes, hopefully, changes that will improve hub bar life and pilots safety.

Thanks to what happened last year, I'm not sure that [all /some] pilots are so anxious to report problems and this brings about another topic and that you and Allan are definately not guilty of but the general policing of AD's, rules regs etc etc must be done in such a way to encourage members and non members to be forwith with all incidents and accidents so that gyro flying can be made safer, not to wield the big stick. Sure, there are going to be times when punishment is needed and thats the way it should be but the emphasis must be on as Birdy says, "fess up if you stuffed up"

No, I was in no way saying or hinting that you or Allan were sitting on your hands, in fact after meeting you and Allan at Lameroo, I'm assured that anything you guys are doing will be done and done well. Its just that I'm aware of some things that are going on and while that issue is important to get resolved [for the sake of ASRA] and having some time on my hands, I was wondering what was happening in regard to hub bars.

I have re read my opening post and it could be construed that I was having a crack at you or Allan [I will stick to those names as I do not know who else is involved]. I apolagize for that.

It can be said that I'm not happy with some goings on in ASRA but I'm sure that you well know what I'm talking about as I openly discussed a few things with you at Lameroo.

Adrian S · 04-07-2007, 05:26 PM

Russ,

Good question. Yes both Rob and Jeff have been good at taking most advice on board and updating its a pity that the US dont want to listen and learn from our experience!

My view at the moment is that we need to build up some history with the new designs before we suggest that they are not subject to the same AD requirements. For instance if we can track 4 or 5 of the new hubbars through their life(current AD life) and it can be shown through testing that that particular design should have a extension of hours then I would certainly be recommending it to ASRA.
The only other way would be for the manufacturer to engage a suitable organisation to build a computer based fatigue model to predict a revised safe history. This wont be a simple task because of the variables in gyro design, weight, power etc.
This is unfortunatly beyond my capability and finances and probably the finances of most OZ blade manufacturers so we will use the "history of safe operation" approach.

Russ in short the current AD applies to all Hub bars on Aust Reg gyro's unless the manufacturer has conclusive evidence to the contrary i.e The RAF factory have stated that their hub bar must be discarded after 500 hour regardless!

I hope that this clears this up.

Adrian

Adrian S · 04-07-2007, 05:35 PM

Brian,

Thanks for the above clarification.
I certainly appreciated meeting you face to face at Lameroo and have found you to be a reasonable bloke when we have talked on the phone or face to face even when we might disagree on one or two things.

Mate - keep asking the questions as it can only help fellow gyro pilots like me and you and all of the other guys out there.

Adrian

russ · 04-07-2007, 06:28 PM

Thanks for the info...........

Will get those hours up real quick........let's see how they hang in there.

Birdy2 · 04-07-2007, 07:49 PM

An occasional post like Adrian's first on this thread is a good reminder of how much these blokes [ and shealas] do for us............., for no reason but coz they give a sh1t.

Thanx people.

its a pity that the US dont want to listen and learn from our experience!
Listen to us??? :

We who hang off the bottum of the globe???

Mate, we peasents wouldnt know jacksh1t.

RHGraham · 05-07-2007, 01:15 AM

I'm a newb so please excuse my stupid question, but, I assume from the conversation that most hub bars are aluminium?

Birdy, those of us who sit on top of the globe often have the same thoughts...

rotor · 05-07-2007, 06:37 AM

Well,

I reckon it's us that's on top of the globe ... you blokes are the ones down under ...

- heat rises to the top - that's why we have such a warm climate and you blokes get all the snow and ice!!

Here's a pic of the correct way the earth sits ...

rotor