MTO rotors, why they crack?

[birdy]

Just read the gyro news thing on the MTO blades LATERAL cracking and think there may be a point missed.Lookn at a side view ofa MTO, it seems the rotor is very much restricted against movement fore n aft to allow reliefe from the 2per that every ridged teetering blade needs.For one, its a SS mast, welded to a long body, not very flexable.And 2, most of these europian machines have a forward rake in the mast. [ most oz machines have a vertical of backwards leaning mast].This configuration, even with a flexable alloy mast, still restricts the free flexing needed, and the stress is constricted to the rotor itself.For the mast to be able to take the pulsing drag forces out of the rotor, the mast SHOULD be at 90* to the tip plane so it has maximum freedom of movement.Any angle either side of 90 is restricting the masts ability to take the pulse, coz its nearing an inline situation. An inline setup will allow for 0 flexing.I know, most will say that if the pulse was be"n absorbed by the rotor, then the stick would shake.I bet it dose.But this shake can easily be masked by a fluke in machine resionance.

[bones]

Matey all I got to say is throw away your can opener, u don"t know what your dealing with

[Tsemler]

But Birdy, These are "Modern Day" "NEW GENERATION" Gyroplanes how could this still be so ??

[Disco]

For the mast to be able to take the pulsing drag forces out of the rotor, the mast SHOULD be at 90* to the tip plane so it has maximum freedom of movement.Any angle either side of 90 is restricting the masts ability to take the pulse, coz its nearing an inline situation. An inline setup will allow for 0 flexing. Birdy, I been thinking about this on n off for months, considering designing another machine for myself.I wasn"t able to convince myself that I was right in either of my scenarios i ran with in my head but since you"ve brought it up...

[Adrian S]

Birdy,Spot on with your analysis. Trouble is that those of us that study, design,build or fly gyros here in Australia are considered to know squat by some factorys. Two blade tetering semi ridged rotor systems and ridged mast designs are not compatible if you want a low stress environment.As usual just my 10 cents worth.Adrian >

[birdy]

I was wondering if it may not be 90 degrees to tip path but 90 degrees to drag. Gess I shoulda bin more clear on this point.Yes, your rite, if you only fly at cruise speed.But no one dose that.I said the tip plane path coz its closer to the AVERAGE angle of rotor drag.Wen your hangn off the prop, theres a very distinct drag pulse that"s angled much lower than the airflow.Never spent the time to figure why, but I know its there.Mite have sumthn to do with haven so much extra rotor disc area flyn through the prop wash.Either way, a mast aligned 90* with the airflow or the tip plane is much better n one lean"n forward.A 9 degree top trailing mast being perpendicular to the disc will obviously carry our weight in forward flight down its length but the stuff is strong enough to not have to run it that way anyway.Not clear wot your tryn to say ere Disco??Trouble is that those of us that study, design,build or fly gyros here in Australia are considered to know squat by some factorys.Mate, I don"t design or build [ rebuild aint buildn ], im justa SCG sitn init.

[mad max]

Mick"s Gyro here in Darwin has rubber mounted teeter bushes. I always felt it was unnecessary on good old fashion T6 bolt on masts but it sounds to me a good mod. for ST. steel ridged welded masts.

[Brian]

It was only yesterday I thought that things were a bit quiet but thanks to you Birdy, I"m sure all thats about to change ;D

[birdy]

Mick"s Gyro here in Darwin has rubber mounted teeter bushes.That"s a new one Max.How much freedom do the bushs allow for?

[mad max]

Looks like I"m talking through my **** Birdy. Mick asked me to test fly this craft and i felt uneasy sitting halfway up the mast and tried to raise the nose wheel early, knowing that I would receive an early warning stick shake if my rotor revs were a bit low. Instead the rotors and stick suddenly went berserk, the old girl reared up on one wheel and took off into the scrub like an insane horse. I looked up at the rotor head and it looked like the pillar block had rubber bushes around between the housing and the normal bush housing. I simply jumped to a conclusion that it took away the feel. Mick has since informed me that the rubber is on both sides only forming an optical illusion. I am so used to the Rosco rotor head which has early warning feel. I think such systems really require a rotor RPM instrument, Mick has since fitted one.