Xenon trouble again

[greg vos]

I thought I would post some info of my ongoing woe's with the xenon...

Seen in my previous thread wherein I rebuilt the Xenon I documented in great detail what I found, what I liked, and what I thought were good and bad, along the way I made new Friends and further alienated myself from some other quarters for being rather outspoken...after-all who am I to have an opinion? who am I to pick on AP's and the workmanship we see daily from these back yard mechanics who work on our Gyrocopters?

Ok so whats this all about, the Xen was rebuilt test flown signed out and by all accounts a nice gyro (with the Best Panel ever seen in a Xenon ) ...well being the anal perfectionist that I am I went in pursuit of a vibration I feel exits, despite my local AMO (AP) saying it cant get better, I even had another well respected AMO (AP) and helicopter builder fly it and again confirm that the vibration I seem to think is there??? is in fact not, moving on we did find the following rather alarming The rotor made a slight ticking sound as it spooled down after a flight, so I was told to check the bearing... in Springs they mos check things out like we do in Benoni

Here is how we do it in Cape Town



The craft has 200 hours on it so the thought of a head bearing being faulty was unlikely? not detoured I consulted with a piece of equipment that could remove any doubt, the dial gauge, well IMO the bearing read as if it had over 2000 hours on it.

So out it comes




Myself not known for my academic qualifications decided to follow the OEM manual...for once




and while Im not a great lover of burning things did this by the book, so some heat...




Now for the kick...out it comes.... with the help of a press (its so lekker to have all the toys in the workshop)



Get on with it Vos where is this going


Gosh its a 6206.... a single row ball bearing and not to be used in the Rotor head of a gyro copter (unless you have two, as seen in say a Magni arrangement) The Xenon OEM manual says it must be a 5206, so I decided to contact Oliver Bennit Head of Technical at Xenon in Malta and a test Pilot, he confirmed that the craft should not be flown with a 6206 and that I must fit the 5206.

So guys be very aware of what monkey tinkers with your plane, most Ap's are to old to be BEE compliant but the work I have seen the work I have repaired makes think that many AP's are now very qualified for BEE and the standard we associate with BEE type qualifications..

In a day or so I will assemble the head to OEM specifications and can only hope that RDY does not throw another curved ball into my net.....I may not catch it


He he and and some of these AP's have god like status....Eish here is the comment from Oliver copied from my email

oliver.bennett@celieraviation.com <oliver.bennett@celieraviation.com>
1:36 PM (4 hours ago)

to me

Hi Greg,

PLEASE DO NOT FLY, it is a single row bearing ! The correct part is 5206.

For clarification a single row B/bearing does not offer the integrity for this application, and this head could have come off in flight, and then people would say ja well greg worked on the thing.... I can post a schematic drawing of a 6206 and a 5206 if any one wants to see the detail? the drawing i paste below will make it clear

5206 OD62mm x ID30mm x 23.4mm

6206 OD62mm x ID30mm x16mm



In the mean time Im going for cold one

[nomie]

That is scary. I would have something stronger than a beer if I found that on my gyro!


5206:

Dynamic Load Rating (Cr) 29,600
Static Load Rating (Cor) 21,200


6206:

Dynamic Load Rating (Cr) 19,500
Static Load Rating (Cor) 11,300

[stevenoc]

Jeez Greg. And I flew in her like that.

[FO Gyro]

Well done on finding the problem there.

[Hub-Bar]

Hi All

I am horrified by the pic showing the use of a blow torch used to heat up the head. This is WRONG! – regardless of what your manual says. This is an uncontrolled process. The correct way, if you have to use heat at all, is a temperature controlled oven and an independent temperature measuring instrument to confirm what is happening to the part. Obviously you also have to know the appropriate safe temperature range for what you want to do. I recently saw a RAF teeter tower insert onto which the teeter bearing inner race was installed and the race was nonuniformly discoloured blue. This tells just one story : the bearing race, which is a hardened heat treated part which comes polished and shiny from the bearing manufacturer, was subsequently heated up using a flame to fit over the boss of the insert. This assembled part was unfortunately supplied by RAFSA. (I have addressed the issue with RAFSA and I can only pray they have changed their assembly process – a simple press and self made up alignment tools does the trick for me – easily.) This post is not meant to be a stab at anyone or anything. A flame is only good for cutting and welding – NOTHING ELSE! – keep it well away from safety critical parts.

Rgds
F

[greg vos]

Thanks HB, I to was concerned about the heat as you refer to, I used very little to just break the bearing seal from the old lock tight. Johan Van Ludwig advised this as well as the OEM manual, but in reality the bearing required very little pressure from the press.
The teeter tower was stil cool enough to handle with bare hands.
The new bearing (a 3206 let's not get into the confusion with bearing companies and the 5206) went in without a press and the assembly process was painless.
Tomorrow I hope to install it all and do a test fly.

[Hub-Bar]

Hi Greg

Even just a little bit of WRONG is not RIGHT! A blowtorch flame burns at several thousand deg C. So, even if applied carefully to a part, how much of that heat is transferred to the part and what is the temp distribution on the part? We cannot tell, so for safety critical parts it is a NO-GO, not negotiable, period. For what it is worth, these are the methods I use when replacing bearings on my gyro. If you have to install an interference fit bearing onto a shaft, place the bearing (still in it’s airtight packaging) in the sun and place the shaft (also in a plastic bag) into your freezer for a while. If it does not fit into your freezer, wrap it with cling wrap and pack it with ice. You will find that more often than not, the bearing then just slips over the shaft. If the bearing fit is on the OD, place the bearing (in it’s airtight packaging) into the freezer and leave the part in the sun. If that does not work, place the part in your kitchen oven and dial up 100 – 120 degF – that is about 40 deg C and no harm can be done and heat distribution on the part is uniform. For the rest, a simple press with alignment tools does the job. On bearings – never use oriental cheapies. Stick with a well known and trusted bearing manufacturer. My RAF kit was originally supplied to me with NSK and Timken bearings, so I stick to these suppliers.

Regards
F

[Hub-Bar]

And??? How did the test flight go?

Rgds
F

[greg vos]

And??? How did the test flight go?

Rgds
F

The test flights were not as good as I had hoped, the bearing now replaced and the control surfaces (roll & pitch) rebuilt to remove the slight play they offered when I stripped it down did add a significant improvement, but I am still concerned about the shake in the top part of the mast.
The old mast has Engineering data, that mast is 2.3mm thick and for those of you who recall Rafiall Cillear stating on rotary wing that 2.3mm mast was a design breakaway safty feature?
So in my quest for perfection you can appreciate that I now speak Polish and understand bikini clad Blondes in Malta, (new home of C/Aviation)

However Oliver Bennit the new head of technical despite his willingness to help certainly does not have the basic fundamental understanding of his product and my many sometimes rather technical questions had him referring to his head of design to get me answers, because I ask questions from a Tech point of view and one cannot gloss over the answers as if they were juts talking to a pilot, after all I have standard two and sums and my questions have relevance.

So what we did glean is that the new mast profile at 3mm wall thickness has no recorded or tested data and it is what is referred to as temporary fix or temporary solution wtf? yes that email had me reaching for Scientific calculator and I had to extrapolate my own data so since that day I have decided to throw all my interest into stamp collecting and model train sets, because this thing appears to be dangerous ...on the surface.

However as luck has it Im a fortunate man and recently had a visit to Surrey the home of the finest super car manufacturer in the world..Vos get on with it! what you are saying? well here is the luck a week ago I had the pleasure of flying a honey around CT, she must have a weight of some 42-44Kg and a lekker pop, turns out her husband is the Chief design Engineer for Mclaren based in Woking.

So Louis van Wyk got a RT from me who was flying lead and I asked him to please bring that man to Aerosport safe cos I need to talk to him. After landing I proudly admitted I was one of those oaks who got a tour through the factory and much later him and I were drooling over his Hp and my sharp calculator was now no longer needed. I extended the invite to join me at Mclaren in the V&A the next day and introduced him to Andrew Mayer so 'quid pro quo' as he was unaware that Mclaren had an office in CT so typical of engineers, they can build stuff but have no idea how to sell it - that takes a genius

We calculated max stress and some frequency (not having actual polar chart data) and Mr Carbon fiber god of the car world declared that with a max weight of 560Kg and an imbalance despite annoying and frustrating the aircraft should hold together for a few hours so I can continue to do flight testing.

That I now have done, below in a nother post I will add some comments to the 7 or so test flights I have done over the last week

I must just say that the team at CA have serous titles Im certain if I go to the factory I will be addressed as Captain Lieutenant Colonel Greg Vos (gooi a salute) Eish

[greg vos]

So having to assemble the head had me calling a few tool companies for a spanner like this



faaark not easy to get and impossible to assemble the head without it, because the castle nut needs to be at 90Nm... no not a hammer and blunt screw driver as it seems this is how it was assembled...cos this thing comes from the North where it was exposed to backyard mechanics...and men who are seen as gods by SAGPA and the board at RAASA ...if only they knew that their top tech guys are real boxes and have a good theoretical knowlege but when it comes to throwing spanners they should rather .....not
Anyway Im not going to go into AP bashing tonight, even I am too tired and and just happy that my lawnmower shop has the top guys working for them because my lawnmower is possibly my most precious instrument and it needs the hand of surgeon at least once a year ...and I have posted pictures of some of the AP's I have met on their walls with a saying do not employ these men we in the Northern sub of CT love our lawn

So to be expected I just made the tool, its not perfect but its more than adequate, I even calculated the extra length from centers and reduce the Torque wrench from 90Nm to 86Nm



Now the head on, a quick flight... its still vibrating and difficult to see in this pic.... I will ask Gyro pilot to upload a video of the shake Im chasing



I have now flown almost 30 hours since the rebuild, I have Flown with Louis van Wyk, Peter Goldsmith both AP's and Im told it cannot get better and I must not concern myself with the vibrating top part of the mast assembly.

Im hoping to fly RDY to Braam at FAGG in few days and let him fly it, if he says it within spec then I will have to rest, as far as Im concerned there is still shake although I admit the stick is dead still and the water in the bottle will take a deserning eye to notice (i cant spell such a big word)

I got my M16 to fly with almost zero stick shake and for a Gyro with heavy blades it was challenge, but with some work it can be done, I have flown clients Gyros and the things vibrate and shake terribly and if it were mine it would drive me crazy so in many cases I am my worst enemy always looking to make it better...has it got me beat

I have trick or two left before I get back to the stamps and the model trains

[gyropilot]

https://youtu.be/g1D8sk7YC3M