LARRYEBOYER
Gold Member
I'm sure RAF put a letter out on it's blades and the hubbar as a change up item at 500 hrs. I'll get the notice and post it.
Raf rotor blade cracks!!!!!!!!!!
- Thread starter Aussie_Paul
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GyroRon
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quadrirotor said:
EXACTLY!!!! Paul give us more info....
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Doug explained exactly what is wrong with the design. It is not best practice to make such errors. I beleive that his observations would fall well outside of what would be called opinions.
It is my opinion that the reason that this hasn't come up more is because most Expermantal aircraft don't fly very many hours per year. For most people 500 hours would be ten years of flying.
I beleive that the point here is to remind everyone to inspect critical components often and replace them on time. Cycles are what caused the cracks. Bad design just makes it happen sooner or makes the part heavy. You can't tell how many cycles a part has had by looking at it.
I have seen documention on more than one RAF and I haven't seen that life limit. That doesn't mean that RAF doesn't have the limit, only that most people are a little haphazard about their paper work or even that I didn't pay enough attention. I feel that paying attention to critical components is very important. I would have trouble enjoying my flight if I hadn't done everything I could to maintain and inspect the machine. Thank you, Vance
It is my opinion that the reason that this hasn't come up more is because most Expermantal aircraft don't fly very many hours per year. For most people 500 hours would be ten years of flying.
I beleive that the point here is to remind everyone to inspect critical components often and replace them on time. Cycles are what caused the cracks. Bad design just makes it happen sooner or makes the part heavy. You can't tell how many cycles a part has had by looking at it.
I have seen documention on more than one RAF and I haven't seen that life limit. That doesn't mean that RAF doesn't have the limit, only that most people are a little haphazard about their paper work or even that I didn't pay enough attention. I feel that paying attention to critical components is very important. I would have trouble enjoying my flight if I hadn't done everything I could to maintain and inspect the machine. Thank you, Vance
KenSandyEggo
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While you're checking the non-radiused parts of the hub-bar, do the same on the big reduction plate. I had mine crack as did many others over the years. I have some dye-penetrant in my hangar that I used when I had the RAF rotors and bar. I'll get the brand name and post it later. But like someone said, from beginning of crack to breakage can be a short time. Your crack may start a day after you check it.
I believe RAF has put a 500 hour life-limit on their bars and blades, which is unheard of in the gyro industry. A poor design is a poor design as was so clearly described here. I wouldn't see how different blades would have anything to do with it. Even if they shook like crazy (wait a minute...a lot of RAF blades do anyway) a hub-bar should be designed to withstand almost anything. Non-radiused turns and cross-cuts as Doug and Victor described are just plain ignorant design work. All they would have had to do was have a first-year engineering student at the bottom of his class that skipped classes half the time at the University of Saskatchewan or wherever take a look at it and go "Yikes!"
If you put Michelin tires on your car and a wheel falls off, I don't think you can blame the tires. What are you going to say if you have RAF blades and bar and Paul was flying different blades? "Oh, he was flying non-RAF blades, so I don't have to worry about it." I don't think that would be a good idea. It has been clearly pointed out in detail here that the RAF hub-bar is poorly designed, even if they're holding RAF blades. This poor design has been pointed out before on Norm's Forum, many years ago.
I believe RAF has put a 500 hour life-limit on their bars and blades, which is unheard of in the gyro industry. A poor design is a poor design as was so clearly described here. I wouldn't see how different blades would have anything to do with it. Even if they shook like crazy (wait a minute...a lot of RAF blades do anyway) a hub-bar should be designed to withstand almost anything. Non-radiused turns and cross-cuts as Doug and Victor described are just plain ignorant design work. All they would have had to do was have a first-year engineering student at the bottom of his class that skipped classes half the time at the University of Saskatchewan or wherever take a look at it and go "Yikes!"
If you put Michelin tires on your car and a wheel falls off, I don't think you can blame the tires. What are you going to say if you have RAF blades and bar and Paul was flying different blades? "Oh, he was flying non-RAF blades, so I don't have to worry about it." I don't think that would be a good idea. It has been clearly pointed out in detail here that the RAF hub-bar is poorly designed, even if they're holding RAF blades. This poor design has been pointed out before on Norm's Forum, many years ago.
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Hi Ken, Different baldes put different loads on the hub bar and the life span is changed. I don't think that is reasonable to expect RAF to anticipate someone using different blades and I beleive they are carefull to recomend against that.
I don't think of the big reduction plate as quite so critical to flight saftey. That does not excuse the bad design.
Ken, I sure hope that I don't ever get on your bad side. Thank you, Vance
I don't think of the big reduction plate as quite so critical to flight saftey. That does not excuse the bad design.
Ken, I sure hope that I don't ever get on your bad side. Thank you, Vance
Chuck_Ellsworth
Platinum Member
I can't believe the comments here in an effort to smoke and mirror the fact that RAF
"Are not capable of designing any component that is safe for any flying machine.".
To try and fuzzy this fact with statements such as these idiots put a five hundred hour life on their blades and hub bar is incredible.
If they do not have the ability to design a component as critical as a hub bar that can last longer than five hundred hours how in hell can you have any faith in their five hundred hour life time?
How did they arrive at that number?
Chuck E.
"Are not capable of designing any component that is safe for any flying machine.".
To try and fuzzy this fact with statements such as these idiots put a five hundred hour life on their blades and hub bar is incredible.
If they do not have the ability to design a component as critical as a hub bar that can last longer than five hundred hours how in hell can you have any faith in their five hundred hour life time?
How did they arrive at that number?
Chuck E.
Victor Duarte
troublemaker
here's an info i got from a tech crew on choppers , he told me thats the product he uses for dye penetrant inspection :
https://www.corvib.com/ardrox/
cheers
https://www.corvib.com/ardrox/
cheers
quadrirotor
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bones
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Paul also why nothing about this on the Aussie site (yet) ???
Jerseywing
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While in the the Navy I was trained as a nuclear grade welder ( we all had second specialties on the Sub.) We used a dye penetrant that didn't require a light. It was a red dye that was applied to the surface, allowed to stand for 5 minutes then wiped off. A white developer was then applied and any red would stand out real clear. A magnifying glass would help too. Any hard edge is a stress point thus the reason for fillets and rounds. Metal may brittle fracture due to defects These defects can be the result of impurities (carbon atoms in cast iron - also known as interstitial defects), overheating, overcooling, or creating a stress point from machining a sharp edge into the grain of metal. This defect will cause a brittle fracture (Cracking) of the metal instead of a ductile failure (Bending or distortion). One of the destructive tests done on metal is called a Charpy V notch test where a notch is cut into a test piece and then struck with a hammer (actually a pendulum) to determine it's brittle fracture point. Without the Vee it will deform, with the Vee it breaks. The result of poor machining/design is that a Vee is created for you...Thank god you found it
Victor Duarte
troublemaker
big up , michael, for this very interesting explanation, a pleasure
i see in your profile you have a RAF, what will be your reaction ? and what do you spot on preflight ?
thanks
i see in your profile you have a RAF, what will be your reaction ? and what do you spot on preflight ?
thanks
automan1223
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Paul, Whew.
Thats one for the poop sheets.
You say your blades were about 500 hours old.
How many years is that ?
Did they hold raf blades ?
How many ft ?
How heavy is your gyro ?
What rotor RPM do you average ?
How were the blades supported when not in use ?
Did they get flapped recently ? ever ?
This is the first time I have heard of a hub bar failing in this way.
Let us know what RAF has to say.
If they in fact do want them changed in 500 hours then I would half that for safety.
Jonathan
Thats one for the poop sheets.
You say your blades were about 500 hours old.
How many years is that ?
Did they hold raf blades ?
How many ft ?
How heavy is your gyro ?
What rotor RPM do you average ?
How were the blades supported when not in use ?
Did they get flapped recently ? ever ?
This is the first time I have heard of a hub bar failing in this way.
Let us know what RAF has to say.
If they in fact do want them changed in 500 hours then I would half that for safety.
Jonathan
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Aussie_Paul
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NO, NO, NO, it was not me...........
NO, NO, NO, it was not me...........
.........Thank God. It was on a Raf in NZ. The owner, who complained about the cabin hop, has done training with me and I was to go and test his machine after they had modified it with the list of RAF mods that I have designed and tested.
I must say that all the "concerns for my well being" is very humbling!!!!
Aussie Paul.
NO, NO, NO, it was not me...........
.........Thank God. It was on a Raf in NZ. The owner, who complained about the cabin hop, has done training with me and I was to go and test his machine after they had modified it with the list of RAF mods that I have designed and tested.
I must say that all the "concerns for my well being" is very humbling!!!!
Aussie Paul.
Aussie_Paul
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Bones I couldn't post pics last night on the oz.....
Bones I couldn't post pics last night on the oz.....
........ forum, but I emailed it to all the Raf owners.
Besides, the way it was interpreted, the clapping and cheering around Oz would have been deafening!!!!!!!!! LOL
Aussie Paul.
Bones I couldn't post pics last night on the oz.....
........ forum, but I emailed it to all the Raf owners.
Besides, the way it was interpreted, the clapping and cheering around Oz would have been deafening!!!!!!!!! LOL
Aussie Paul.
Chuck_Ellsworth
Platinum Member
Jonathan :
Something to think about.
First: This is not the first time that cracks have been found in RAF hub bars.
Second: How can anyone possibly fly a gyro with the most critical part prone to failure in such a short time frame? This is 2004 and there is the technology to design a simple hub bar that will not be prone to failure in such a short time frame.
I know these are experimental / amature built machines, however getting killed in one of RAF's pices of junk will not change anything, you will be dead.
Chuck E.
Something to think about.
First: This is not the first time that cracks have been found in RAF hub bars.
Second: How can anyone possibly fly a gyro with the most critical part prone to failure in such a short time frame? This is 2004 and there is the technology to design a simple hub bar that will not be prone to failure in such a short time frame.
I know these are experimental / amature built machines, however getting killed in one of RAF's pices of junk will not change anything, you will be dead.
Chuck E.
Friendly
Platinum Member
Thank God, you caught it in time.
Aussie_Paul
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Raf owners this is serious.
Raf owners this is serious.
There have been many Raf blades done 1,000s of hours and now a couple that have failed. Raf have nothing to do with me any more, they have blocked my email!!! I sold 21 Raf for them as a representitive and they won't support these customers through me!!!!! It doesn't worry me, just my customers who appreciate my loyalty to them.
There have been a couple of failures. One after a ground strike BUT the damage was already there. That ground strike probably saved the US instructors and a students neck.
Jim Buttler conducted some eddy current NDT at one of the universitys. I can't recall all the details BUT I suggest that Raf owners like Stan etc should really dig deep for that info. This is not in the area of Raf bashing this is in the area of safety no matter whos product.
Stan and others, do not take this lightly. Some hubs doing 1000s of hours and 3 that I know of failing at less than 700 hours. That is a very wide margin for error. To me that suggests some sort of quality control problem.
I realise that it could be due to mishandling, but IS IT????
Aussie Paul.
Raf owners this is serious.
There have been many Raf blades done 1,000s of hours and now a couple that have failed. Raf have nothing to do with me any more, they have blocked my email!!! I sold 21 Raf for them as a representitive and they won't support these customers through me!!!!! It doesn't worry me, just my customers who appreciate my loyalty to them.
There have been a couple of failures. One after a ground strike BUT the damage was already there. That ground strike probably saved the US instructors and a students neck.
Jim Buttler conducted some eddy current NDT at one of the universitys. I can't recall all the details BUT I suggest that Raf owners like Stan etc should really dig deep for that info. This is not in the area of Raf bashing this is in the area of safety no matter whos product.
Stan and others, do not take this lightly. Some hubs doing 1000s of hours and 3 that I know of failing at less than 700 hours. That is a very wide margin for error. To me that suggests some sort of quality control problem.
I realise that it could be due to mishandling, but IS IT????
Aussie Paul.
automan1223
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My rear end.
My rear end.
Paul, Chuck and the gang.
I just wrote a post about my experience with raf and I gave their latest 24th gen blades the thumbs up. The only problem I was concerned about besides being unable to torque the big bolt without a custom socket and jig was the small dimple from extra resin on the top of the blade surface 3/4ths of the way down the blade. I thought that or I was at least told that the latest gen blade and hub bar was worked out and "not to worry". I am worrying now. I have a new set with maybe 6 hours total and if there is a gremblin or quality issue I hope we can find out the why of it. My personal opinion no matter what the time the factory says. I know metal fatigues on high stress parts and after 300 hours you have to be on top of things xrays etc. . I can visualize someone using the end of the bar to hold it during a torque of big bolt operation. Is it possible this bar was mis-handled ? or those smaller bolts over torqued ?
Eddy current NDT. What does that mean and what is it good for. ?
Electrical Destructive Testing ?.
Jonathan
My rear end.
Paul, Chuck and the gang.
I just wrote a post about my experience with raf and I gave their latest 24th gen blades the thumbs up. The only problem I was concerned about besides being unable to torque the big bolt without a custom socket and jig was the small dimple from extra resin on the top of the blade surface 3/4ths of the way down the blade. I thought that or I was at least told that the latest gen blade and hub bar was worked out and "not to worry". I am worrying now. I have a new set with maybe 6 hours total and if there is a gremblin or quality issue I hope we can find out the why of it. My personal opinion no matter what the time the factory says. I know metal fatigues on high stress parts and after 300 hours you have to be on top of things xrays etc. . I can visualize someone using the end of the bar to hold it during a torque of big bolt operation. Is it possible this bar was mis-handled ? or those smaller bolts over torqued ?
Eddy current NDT. What does that mean and what is it good for. ?
Electrical Destructive Testing ?.
Jonathan
Jerseywing
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Victor,
I'm training in an RAf I don't own a gyro yet.
Johnathan,
Eddy current testing is typically used in tubes where a probe is inserted and it generates a magnetic field around itself. As it passed through the tube thickness differences in the wall or scratches/scrapes change the magnetic field and register on a scope.
Quality Assurance is typically broken down into two groups
NDT is non destructive testing - starts with visual to laser measurement to magnetic (magnaflux) to radiography.
DT is destructive testing where the sample is tested to its breaking point. This is used when baseline data is being established or when you have a batch system where the manufacturing guidelines are traceable to the point of origin. Then you would take a representative sample lets say 5 per thousand (less- 5 per 100 -if the level of criticality is higher) and perform DT on them to ensure they meet standards, if they pass then the "lot" is assumed to be satisfactory. In the nuclear world things are traced to the point of origin of the ore and controlled throughout. Every nut, bolt, washer and rubber o-ring has it's own paperwork, all equipment is tracked throughout its life and any defect or issue found can be cause for re-certification or replacement of all similar product-thats why it's so expensive. Kinda like aircraft parts eh?
If the failure rate is like posted then it sounds like the boys at RAF need to post an AD and re-think the design. Poor handling can be subjective but when it's broke, it's broke and there ain't no denying it. IMHO This doesn't seem like it should be a 500 hour part - it should (if properly designed) last the life of the blades if not the craft.
I'm training in an RAf I don't own a gyro yet.
Johnathan,
Eddy current testing is typically used in tubes where a probe is inserted and it generates a magnetic field around itself. As it passed through the tube thickness differences in the wall or scratches/scrapes change the magnetic field and register on a scope.
Quality Assurance is typically broken down into two groups
NDT is non destructive testing - starts with visual to laser measurement to magnetic (magnaflux) to radiography.
DT is destructive testing where the sample is tested to its breaking point. This is used when baseline data is being established or when you have a batch system where the manufacturing guidelines are traceable to the point of origin. Then you would take a representative sample lets say 5 per thousand (less- 5 per 100 -if the level of criticality is higher) and perform DT on them to ensure they meet standards, if they pass then the "lot" is assumed to be satisfactory. In the nuclear world things are traced to the point of origin of the ore and controlled throughout. Every nut, bolt, washer and rubber o-ring has it's own paperwork, all equipment is tracked throughout its life and any defect or issue found can be cause for re-certification or replacement of all similar product-thats why it's so expensive. Kinda like aircraft parts eh?
If the failure rate is like posted then it sounds like the boys at RAF need to post an AD and re-think the design. Poor handling can be subjective but when it's broke, it's broke and there ain't no denying it. IMHO This doesn't seem like it should be a 500 hour part - it should (if properly designed) last the life of the blades if not the craft.
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StanFoster
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Paul: Thank god you caught that and you are still with us...ok? I appreciate the direct warning to me. I would be plain lying if this hasnt got me concerned. You guys all know how I love flying my RAF. I am going to thoroughly check my hub bar....and I am considering putting sport copter blades on it.
I remember just looking at that hubbar one day and just the look of it didnt appear to be a load spreading design...but instead a concentrating one.
In my business of building curved stairways...I bend stuff all the time and know how important gradual changes in thickness is as far as spreading strain.
I will at the least change my hub bar to another design.
I cant honestly say I will be enjoying my flying till I am satisfied this is taken care of.
Stan
I remember just looking at that hubbar one day and just the look of it didnt appear to be a load spreading design...but instead a concentrating one.
In my business of building curved stairways...I bend stuff all the time and know how important gradual changes in thickness is as far as spreading strain.
I will at the least change my hub bar to another design.
I cant honestly say I will be enjoying my flying till I am satisfied this is taken care of.
Stan
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