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Hi All,We have been sent a hub bar from a set of Australian built Advanced Kinetics blades.The hub is 1 Inch thick 2 feet long,with no inbuilt coning angle.There are also no washers under the hub block bolt heads.TT in service less than 700 Hrs.3 cracks are visible,one from each bolt hole the full thickness of the bar(All the way to the outside) and one from a bolt hole going across 3/4 of the width.The hub will be sent away for further analyses.All operators using these blades are advised to thoroughly check your hub bar before each flight.If in doubt contact you nearest ASRA Technical adviser or an ASRA Board member.
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Murray,I would be keen to be kept in the loop on this one.
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Murray,Is this only on the hub bars with offset (or diagonally placed) bolt holes? This is why I prefer the hub bars with the bolts placed along the centre of the teeter blockMark
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holy ****, he was lucky. i"m with mark on this one.
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Mark I think the biggest problem with this type of bar is its constantly trying to bend as close to the centre as it can. The later AK bars have the coning angle pressed into the bar instead of the angled spacers at the ends.There is also a preferred diagonal placement patern of the hub block holes.We found this out during an investigation into a fatal a few years back.As Waddles Junior said in his thesis on hub bars its also a good idea to have a washer under the bolt head.Investigations continue.
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Yeh, a [ honest] history would be interestn.
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This one from SA?
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i can see what you mean with washers and coning angles etc. but when you think about gerry"s bigger hub bars . they have counter sunk[into the hub bar] only one bolt and obviously no washers. less holes further from the edge etc. actually one bolt and 2 small dowels. this is going to be my option for a while to come. the owner of that hub bar should buy some lotto tickets.
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I wasn"t aware that any of the AK hub bars had the coning angle bent into them. I bought a new hub from Geoff"s family just before the business went to NZ. The bar that I bought, presumably the latest type that he made, is a straight bar without coning built into it and with the teeter block being machined from round stock and the two bolt holes are along the centre axis of the bar, rather that diagonally across the corners of a square teeter block. Please let me know if there"s another later bar. Rob Patroney bends his hub bars to accommodate the coning.
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Yes Murray,and the other thing with using the washer to spread the load of the head over a larger area, is to not wind the crap out of the nut!While the bolts need to be torqued to the right tension, Waddles Jnr was adamant about not deforming the hub bar material through over tightening, as this is the quickest way to produce a fracture.If anyone wants to think about it, the bolts or dowels are only there to locate the teeter block on the hub bar (and to stop it flopping about if it wasnt tightened enough) there is no need to tighten the bejesus out of those bolts.Mark.
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Danny,Jeff developed a hubbar designed specificaly for mustering and high energy operations it was short & 1.5" thick and had the lower surface tapered with wedges on the top surface to build in the coning angle. The teeter block was from round stock to distribute any bending loads over a larger area. I am not sure if the new owners are also providing this option as the 4 sets I have seen coming from
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Ok thanks for that...I"m v interested in this of course.
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Murray,Is this only on the hub bars with offset (or diagonally placed) bolt holes? This is why I prefer the hub bars with the bolts placed along the centre of the teeter blockMarkHi MarkHaving the holes in the middle has its pros and cons. Having the holes on the sides means if a crack occurs it will usually travel to the nearest edge meaning you still have about 75% of your hub bar intact rather than only 50% or less when holes are centred. The choice is yours
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Yeh,I can see that in the second picture above????Mark
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sam how many hub bars with bolts in the centre have had cracking problems. ?
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