Hang Test (Method of hanging)

[asra]

I am just about ready to hang my machine to check it's degree's nose down hang.Question, Can I use a fork lift to lift the machine from the hub bar ?Orshould I make up a lifting block to be used with block and tackle ?My rotors are Jack Allan with 3/4 inch hub bar.The machine is an open frame fitted with Rotax 582.The machine below is not mine, its just an example of what I am thinking of doing with mine. Regards Sam. [?][?][?]Image Insert: 61.97 KB

[NiqueNaque]

Sam,Looks like a good idea but I'd be making sure the fork hasn't got any creep on the ram before you get under it, consider propping the fork mast with a post to prevent it from coming down as what is shown in this photo is very naughty - OH&SA.You will note that the axles on the gyro do no line up and the photo may be skew to the centre of gravity, putting it out by a fraction, this is why I advocate the use of a pair of plum bobs to get it right. I've just had one of my rare flashes of brilliance! for the test only replace the teeter bolt with some bright bar of the same diameter, only make it about 2.5 m long, hang the plumb bobs off the ends of the bar to get the true centreline of the COG.You would still have to do the COG off the main wheels to make sure that your three vectors intersect, or at least the thrust vector was slightly below the COG.Cheers,Nick.

[asra]

Nick your profile states your a trouble maker, but I am now questioning that !!!![]My main concern was if I would or could damage my hub bar in any way by lifting my machine with it, since it is one of those vital parts to safe flying.I will use a plum bolt during this test as a reference to work from.Thanks Again Mate !!!!Regards Sam. [][][]

[NiqueNaque]

Sam,On a point of logic, what does your gyro hang off when flying?You'll note the person who did this one used some cloth on the fork tynes to put the hub bar on, you could use thick sponge or styrene foam to good effect for same, just move the fork very slowly around your precious gyro (careful Gollom!) so you don't damage it.I wouldn't lift the bar on the knuckles, ie, where the blade roots join to the hub bar, though, again, the whole machine hangs off all of it in flight, it just doesn't appeal to me to lift it at a connection point.If you are worried that much about the hub bar you could just put a heavy lifting strap under the bright bar for the test, feed the fork tyne through the strap and then lift it by the strap, those blue 50 mm load binders I have are good for 2 tonnes, so your precious won't fall to the ground,make sure you undo any tie downs before you lift with fork, might stretch the mast if your don't.Cheers,Nick.

[asra]

NickDuring flight the hub bar is lifting the machine, but it has a huge amount of centrifical force also acting on it, helping make it more ridgid and less prone to bending.During a static hang test and being only 3/4 inch and made to support the total amount of weight, I am worried I may stress it.Has anyone else done this with a 3/4 hub bar and survived !!!!.Sam.

[Tim]

Yes, I have seen them hung this way many times. Make sure that you hang it as close to the centre as possible, and not out at the ends of the hub bar.Nick is right about the accuracy of the positioning of the camera and the gyro. Must be dead square with the machine and the vertical line taken from a plumbob (or even better, two) for accuracy. A small amount out in the accuracy can mean a large amount out in the C of G. The good news is that it is just as easy to do it accurately as it is to do it incorrectly.Tim McClure

[NiqueNaque]

Sam,The vertical load is always there while in flight, what ever your rotor RPM.You might note that the centrifugal / centripetal forces act at right angle to the weight, so your hub bar will not be challenged by the absence of them, it might even be happy about it.The last time I looked I calculated 5 tonnes of tension in the hub bar, so if this is not present, the hub bar should not be stressed.Cheers,Nick.

[asra]

I will use a fork lift and ensure all given advice is considerd during the test.Thanks Sam.

[asra]

Howdy SamlOne other small thing that should be pointed out,When I hung my gyro the other week end it hung at 0* I weigh 195lbs or about 87 kg.Then I put my son who weighs 140 lbs in the seat and the gyro hung at 4* noseup.So if your going to fly it you need to sit in it for the hang test.Just a thought.Regards SonnyIntelligence is not a privilege,it is a gift and should be used for the good of mankind.

[asra]

I weigh 195lbs or about 420 kg.Then I put my son who weighs 140 lbs What the...Sonnyj i think you pushed the wrong buttons on your calculator mate, 195 lbs is only about 87 kgs,i'm only jokin with ya...Mark

[asra]

Sorry Mate I aint too good with that metric stuff,Thought it made me sound kinda FAT[:I].What would it be if measured in "stone"?[)]No Worries[]Cheers SonnyIntelligence is not a privilege,it is a gift and should be used for the good of mankind.

[asra]

As long as you've still got two "stones" it doesn't matter if you weight 195LBS or 87KG.

[asra]

I have been told that if the hang test is under 9 degree's, it only means you loose some forward stick, and gain more back stick.Is this true ?Sam.

[asra]

Perhaps I missed something, but in the context of that last post, I'm not sure if the importance of chocking the head at mid position was recognised. Apart from providing one part of the C of G calculation, the hang test is done to ensure there is sufficient control travel for safe flight.LlewellaA sceptic is a person who, when he sees the handwriting on the wall, claims it is a forgery.

[asra]

Don't blame Llewella for that last post, it came up as her because I hadn't logged myself on.BTW that picture shows a slim young lady being used for ballast, it really should be done with the usual pilot , or someone of equivalent weight in the seat.John EvansThink logically and do things well, think laterally and do things better.