Hi Guys,

Pete Pete just put up this new video on youtube showing how he solved massive stick shake issues, its an excellent example of both fiddling about in the bush fixing thing as you go and also following a very scientific approach.

https://www.youtube.com/watch?v=uqcHWBPXiYg

The solution was very surprising and I suspect has something to do with 2 per rev and resonant frequencies building at different rpm. However am not sure about this, only just watched it 10 minutes ago and need to ponder more. Just look at how smooth he got those rotors at the end though and then go look at any number of people flying $100000 + machines taking up passengers and justifying massive stick shake on the basis of 2 per rev. Girodreamer I'd really love to hear your take on this given your experiments with pre-rotators (pausibly also something to do with balance in the system somewhere).

sling em don't string em!



if pulling the heavy ass pre-rotator off the spindly long arm of a mast solved his problem, and he was flying that way a long time, I would sure as hell inspect the holes at the bottom of the mast!

A mass hanging on a stick would detune the shake as well as removing the offending mass on the mast... Nice work.

Like James [VCSD pilot] looked as the 2 per vanished on the 205 with a Simplex tank after I played with it.

What'd you do? Secret sauce boss

Yes and how many of these $100 000 + machines have we seen online with exactly this level of shake and they just put it down to 2 per rev? Very good advice though. It was interesting to note the manufacture said it was a particular issue with the 28ft rotors, this might suggest that the frequencies were building some sort of resonant frequency. Particularly as it only happened at high speed or certain loads then would go away. A good thing he bothered to fix it rather than just buying a new set of rotors.

My comment was:

I think you will find it is coning angle... it would be my guess that the root cause is the machine is over rotored. My thoughts are that the rotors are turning too slowly and due to the low speed, the tips are higher than the teeter height (lack of centrifugal force). You seem to have got it smooth as possible, well done! I think I would prefer shorter rotors and keep the prerotator haha

My opinion is that rotors need to turn at a minimum (and maximum) RPM... 26" Patroni rotors on such a light weight machine... doubt the rotors are at 300 rpm... I always found over rotored machines to be too 'floaty' on landing... I personally prefer rotors (single seat) to be on the smaller side and turning faster. To me, a smaller, faster turning disk feels more 'solid'

I wonder if that insulation sock is rated for 12v? (that is what we call 'Aussie ingenuity' (AKA: Redneck ... here, hold my beer)

Well what to say ???

I have helped my mate building dozens of averso rotors .. he never had any complain about vibration from clients .. except one time from TRIXY factory ... who's boss made a real fuss and threatened to complain on face book etc etc

Pascal had to travel to the factory and test flight the rotor on the trixy gyroplane .. and of course he found out that the rotor head was out-of roundness ...

As I said before we first find pairs of comparable aluminium extruded blades interms of center of gravity placement and in terms of twisting

then we take the heavier blade and find it's CG location.

then we correct the CG position of the second blade adding small screws at the end of the blade or at the foot of the blade

then we mount the blades on the rotor hub (aligning the blades with the help of the string of course) and check if the rotor is well balanced .. if it is not the case we go on adding small weights at the tip

then we mount the rotor on a Xeeleex gyroplane and fly it,

we firstly tune the track with the help of a stroboscopic light this is the most important it must be perfect and removed all perceivable 2 per rev vibs

then we use the vibrex (with sensors on the mast etc etc) to measure vibrations ...

most of the time there is not need do anything else

sometimes small adjustements are necessary to perform with the help of the vibrex to get rid of residual vibs

it is useful to say that the teeter block is fitted with a system that makes it possible to modify the lateral position of the rotor hub

my rotor doesn't vibrate at all, I mean I can't feel any vibration on the stock whatever the G load, of couse if I release the stick a small vibration is visible if I focus on the stick but it is negligeable

we all use powerful violent pre rotators with heavy flex shatfs connected to the bendix and no rotor has never started to shake after years of European pre-rotations

to give you an idea it takes me 40 seconds to pass the rotor from stop to 240 RPM ..

it does not harm averso rotors at all ..

but those rotor blades are thick .. nothing to see with Autogyro blades

all of this is what we experiences on straight hub bars (straight but flexible permitting conning)

when the german Dulv (certification body) asked pascal to make hub bars with a pre-cone shape it did not lower the residual vibration and did not worsened vibrations figures ...

for me this guy is simple thinkering his gyro in the bush .. and this is not a good solution to make a good job...

it is clear the removing the car started at the top of the mast limits the 2/rev vibrations but in mu humble opinion he treated the symthoms rather then finding the real causes of his vibrations ...

I also think that the car staters are really not the good solution .. they are by far starting to violently ... there is no mean of regulating acceleration ... it can end up if harming the rotor head and bending the rotor

a system aimed at starting a diesel engine should not be used on a rotor head ...

our traditionnal mechanical pre-rotation accelerate smoothly even if they are capable of bringing the rotor to 240 or even higher rpm

the belts are always spliping a lot and we alway pay attention to press the lever smoothly which gets rig of the shock of car staters pre-rotators

you have helped me to understand that pre-rotators were not the only tool to take off properly but on the other hand when they are well designed and properly use there is no reason to bend the mast, harm the rotor head or the rotor itself ..

just my 2 cents of course

I think that it is necessary to learn how to properly build and tune a rotor .. but again I am a luck man Averso aviation does it all for me ..

murray we are using long rotor turning at 320 rpm .. it is slow and does not causes vibrations

I never start rotors from stationary with a car starter Gyro... I always give them a push to get them started

Hey Cameron... can you try to get Omeobandit to sign up here... I have emailed but being a hotmail, it might get caught in his junk filter.

Every comment I have made suggesting he signs up here, gets deleted by the yoo choob gestapo...

Hi guys omeobandit here. Yeah it sucks that you cant PM on youtube anymore, thats why I put that email up there, thanks for reaching out muz

I gotta say that the shaking issue only arose when I chucked the 28 patroneys on. You can see the shake i was getting from the 26ft AK's but it wasnt as bad as it looked, but now that i know what its like to have smooth as buggery stick i dont think i'll ever settle for less

My mate wolfy suggested something similar to you about the teeter block height and coning angle muz

Its all a bit complicated for me, im not very technically minded and i was just ringing up all the old boys and doing what they recommended to try, im glad it was as simple as removing the prerotator. Rob patroney said quite a few of his rotors back in the day at the 28/29ft length had the same issue on machines with electric prerotators and he always told them to remove it.

Rob reckons having a heavy prerotator at the top of the mast is silly to begin with, and built his gyros with the prerotator down low on the mast and ran a bendix shaft thingy to the top. Rob is really interesting, he thinks that lots of things that we consider normal on gyros, to be silly inefficient engineering, i wish he had better health to stay in the scene and innovate for us

Welcome to the mob mate...

Will be good to hear about some of your antics out there...

How many other flyers are there out your way?

Have you got a link to those 'electrical insulation socks'?

Bugger all :(

Birdy up north and another old mate from APY went the dark side an converted to those little rotax ch7 helicopters. Come to think of it it seems like most of the stations that used to run gyros have ridden the beef boom last few years and all you see now is 22's and 44's and brand new landcruisers

Theres one bloke with a couple of gyros down finke way but i dunno if he gets up often.


Dunno if any of you fellers are on facebook but i posted the other week about my gearbox failure. Was flying back to alice from titjikala and the old hirth shit itself. I had planned to embark on a 150km curve over tiger country to get around the restricted alice airspace and even planning to fly roudn the cliffs of east macdonnell ranges looking for caves, but when i took off i thought it too boring to head on due course straight away and sit at 1000ft so i went down followed the road for a while so i could see whos coming in n out of town and wave to my friends. Was just before the next station where i was planning to head away from the road, that i felt and heard the big clunk and luckily shut it off immediately and put it down on the road underneath me. Shortly after a car came through and i hitch hiked into town then came back later that night with the trailer.

I just left OZ about a few months ago.
Where are you exactly?

Muz, you know where we were, is that anywheres near where Petes at?

im everywhere, i was out at maryvale on the video, been in alice the last month, heading up to darwin in the next couple days and will hop between there n kununurra WA for a little while

Welcome in our tiny forum Omeobandit, I am more then happy that we can discuss altogether here thanks to MadMuz who has taken over the stick of the forum .

Back to the vibrations it is clear that the source of vibration in a gyro is the rotor and rotor head ... all comes from there, the better the rotor and the better the rotor head roundness the less vibrations.

But the remaining vibrations will be amplified or not by the gyroplane itself which will behave like an Antenna ... "just" a question of wave length and "antenna" length..

this "antenna" will dissipate or amplify vibrations according to it's length and according to the knots on it's length.

it is necessary to brake the vibration modes to avoid resonance ... a simple modification of the mast length can change everything.

removing the pre-rotator modified the "antenna" length but I don't think it would have the same effect on every gyroplanes.

I maybe wrong of course I am just an uneducated person ...

a pity that Chuck beaty has gone ... nevertheless he wrote so many thin on the RWF that I think it is possible to find back his literature on the subject ..

say hello to Wolfy for me (tell him this is from the french electric pre-rotator guy) .. I have been exchanging a lot of mail with him about electric pre-rotators back in times when he was re-building his last mono .. I need to get him a new email ..

thx for being here

cheers

Girodreamer

Thankyou girodreamer,

I stay in touch with wolfy on the rotary forum, he logs in there from time to time

For those of you from around the world, you would know what these places are.

Maryvale Station is [100 km ??] south of the Alice [Alice Springs]
Alice Springs is a [major - population 26 000] town in the middle of Australia [towards the bottom of the Northern Territory] Ayres Rock / Uluru is a couple of hours from the Alice.
Darwin is capital of the Northern Territory and located at the top of the NT. pop 122 000
Kununarra is a town in the Kimberley region, top NE part, of Western Australia. pop 5 500

https://www.worldatlas.com/maps/australia

Rossco

Yep Wolfy is a really nice person, I Love his mono-seater and admire his pilot skills

I also "met" him virtually on the RWF which use to be a fantastic place to discuss gyroplane building before the forum lost most of his home-makers ...

I remember back in times when I tested my first gyro, I would report my tests flights issues and got many nice help and nice and helpful comments from awesome smart people.... things deeply changed later when tried try to share about my new design and build ... no help and only nasty comments kind of "only experts should design gyroplane frames .."

I miss chuck beaty .. and I hate snotty people thinking that they are sorts of heroes because they are flying stock gyros .. they forgot that in America and elsewhere, long before Magni, Autogyro etc arrived on the market people would build bensens, dominators etc etc ..

Thx ross!

Hi I'm not sure who he is?

Hey there. I suspect his issue is likely one of 2 per rev being greater given the width and length of the rotors and that the extra mass was causing inertia in the rotor to pull back further than it would with less mass up top. I'm not certain about this by the way its also possibly something to do with conning angle. However I feel this might not be the case as it gets worse as he speeds up or adds load which should decrease conning angle with higher revs, but maybe with more load loading up. 2 per rev will increase with rotor size. Of course there is zero you can do about 2/rev other than flexible mast lead lag hinges or what Wallis did and build a spring into the rotor head to adsorb. Now if I'm right and again I'm far from certain I am then the extra mass up top causing inertia to vibrate back and forth too much is only something he can fix by removing excess weight. The lighter drives (this was a car starter motor) don't cause this vibration. I have flow Petroni's blades myself and they had zero stick shake dead smooth so I do not doubt he knows what he is doing but other factors can come into play like rpm range and therefore coning angle etc.

However my philosophy is if the vibration is gone then the problem - fatigue as a result of vibration is solved he has no problem. From my point of view these blades are far too big for a machine like this. these blades are 22ft 8 inch chord I was flying an only slightly lighter direct drive VW on 22ft blades by 7 1/4 inch chord and it performed well (not as well as this in terms of climb rate). I think you buy into problems going too much bigger than you need to. However his stick is as he says butter smooth this tells me whatever vibration is there is not sufficient to translate to the stick. There are a heap of vibration modes that can happen with rotors all we can do is what he's done, string-line, check for out of round, and in this case ask the manufacture and follow his advice which clearly removed his problem.

If there is some issue with balance you'd feel that through the stick, tracking you'd feel that through the seat. The only thing he could try is span wise balancing them but as out of balance manifests as stick shake and he no longer has any there is nothing he can do other than an exercise in curiosity. Just my opinion.

There are some nicely manufactured blades out there I was particularly impressed with an American set with a cool method for blade tracking using a Allen key and I'm glad some people have nice smooth rotors but too many put up with stick shake and the least they could do is check the string line as he did. Too many people are flying machines with massive stick shake.