Accident involving rotor bearing

[John_Read]

In an earlier thread someone made mention of an accident caused by "a known fault with the rotor bearing" - or words to that effect.

Does anyone know the details of this incident?

John

[KenSandyEggo]

Tom Milton posted the details a few days ago, but I don't recall what thread it was in.

[Dean_Dolph]

Here is the thread! http://www.rotaryforum.com/forum/showthread.php?t=2362

[rehler]

It happened many years ago - I think at the Middletown Ohio fly-in. A man and his wife (don't recall the names) were flying to the show in a McCullough J2 certified gyroplane. The main rotor bearing, which had rusted badly, gave out and the gyro went down killing both of them as I recall. Some of the "old timers" like Tom Milton should recall the facts more accurately.

[John_Read]

Thanks for the information.

John

[Mike Nelson]

The accident can be pulled up on the FAA accident database. It was N4354G with 312hrs TT. The accident occured at 2:15pm on June 17th 1989 near Oxford, Ohio. The pilot was a 57yr old male with a student certificate and no other ratings. He had a total of 229hrs of pilot time and 30hrs in the J2. The weather was VFR with wind from 250 deg at 10 to 18kts and 74deg F temp. Witnesses stated that the rotorblades slowed and folded-up, one separating from the aircraft. Inspection of the wreckage showed that the main rotor mast thrust bearing was galled and had seized. The FAA listed the cause of the accident as the failure of the pilot to replace the main rotor bearing that had expired its service life at 300 hours and witnesses further reported that the bearing was making noise prior to the accident flight and that the pilot was told to not fly the aircraft until he had the main rotor bearing replaced. The pilot and his wife died in the accident.

[KenSandyEggo]

Hey, Mike. I almost forgot. Thanks for those great photos of the J-2 you sent.

Hey! I just noticed that this is my 1,000th post! (Get a life, you ditz!) Maaaaaa! This is a great place and keeps me out of the bars and casinos.

[pwendell]

Hey! I just noticed that this is my 1,000th post! (Get a life, you ditz!) Maaaaaa! This is a great place and keeps me out of the bars and casinos.


Sheesh Ken, get with it and find a bar with a wireless hotspot...you ought to have at least 2000 posts by now :D :D

[gyropilot]

The pilot and his wife died in the accident.
Sheez... that gives a whole new meaning to the word "togetherness." Very sad and very preventable.

John L.

[Doug Riley]

A good little preflight trick is to give the rotor a whirl by hand before starting the engine and listen for squeaks or grinding sounds.

[RHerron]

This rotor bearing failed as a result of the ball seperators rusting and collapsing, allowing the balls to "group". These bearings would never wear out in normal service. However, they are 40% packed with grease and are sealed. Trapped moisture from condensation just sits and corrodes things when the aircraft isn't flown regularly.

The upper transmission bearing is subject to this same kind of damage as water from rain drains right into it (it isn't sealed, only shielded).

[jucie]

...It was N4354G with 312hrs TT....the failure of the pilot to replace the main rotor bearing that had expired its service life at 300 hours...

Ok. In this specific case there is no doubt it was a pilot failure, because obviously he knew he had to replace the part, and he didn't (very sad), but as an general rule, would you trust a part that will break just after 104% of the expected service life?

[Doug Riley]

All machine parts are subject to failure at or before the end of their rated lives if neglected or abused.

I don't believe this accident is representative of gyros in general. Gyros should not be parked out in the weather continually. Rotor heads should use sealed bearings, not merely shielded ones, or (as Dominator does) should be designed so that the bearings are simply not exposed to water running down from above. Bearings should be checked before flight and should not be flown if they are noisy. Bearings should be purged with fresh grease periodically (at least once a year). If signs of rust are apparent, get a new bearing. They are cheap.

[KenSandyEggo]

Didn't this J-2 sit out for years without any maintenance or flight?

[John_Read]

I started this thread because I discovered my rotor bearing to be very slightly noisy when I twirled the head while the blades were off. Being a DOG (Deaf Old Git) I could not hear the roughness, but I felt it through the fingertips as I turned the head.

There is no way I would have noticed this unless I had removed the rotor to give the blades a good polish. Subsequently I found the roughness could be felt very well through the control rods.

On dismantling the head I found some rust on the upper surface of the bearing, and clearly there must have been water penetration. I imagine this must have happened while the machine was on its trailer on the road. I remember having to take it through some pretty heavy rain.

I think the bearing might well have run on without trouble for a few more hours, as there was no play in it ... but that is what this poor couple thought! In the end it could easily have brought me to grief also. :eek:

I suppose the moral is to take care after being out in the rain. And to make sure to check it for noisiness from time to time. Maybe spinning the rotor and feeling the control rods (if you are a DOG) would do the trick!

Would there be any point in pouring a bit of lubricant over the bearing from time to time? If so, what whould you use?

[automan1223]

John,

I have been in the Automotive Repair business technically since I was 9 years old. If you dont count child labor laws I have been spinning wrenches for 25 years now. It never ceases to amaze me how quickly a good part can go bad with relatively little humidy and neglect. Since I moved to the steamy south 8 years ago I have become even more amazed at what mother nature can do with condensation and just a little bit of salt / river air. At 3 am if you go outside the condensation is almost rain sometimes.

John, you have learned a very good lesson, thanks for sharing it and make sure you put the high capacity bearing back in.

Somebody jump in here and recite the bearing info. I got a bogus bearing once in a good box. (another napa story)
The number of balls / load capacity was not the high cap bearing I needed.

Doug, even with seals, nothing is fool proof. Inspect, lube, be a FUSSPOT. with your equipment. ITs your LIFE !

Jonathan

[Victor Duarte]

john, is the type of bearing imposed ?
there are sealed bearings.. btw is it possible to fill them with grease ? i think in graphite grease. whats your opinion.
i suppose you have heard about graphalloy, ( http://www.graphalloy.com/ ) tough bearings, no lube, hi temp, submersible, did you have opportunity to hear about them or test them?
thank you ( and change that damn bearing ;) )

[Doug Riley]

The basic bearing # for all of the Bensen-clone rotor heads is 5206. Various letters are added to the basic number to signify seals or shields (seals are better).

High-capacity bearings have a higher load rating than standard units. This type is signified by yet another letter suffix. CAUTION: High-cap bearings have a slot in the race through which the balls are loaded. This slot MUST be on the non-load-bearing side of the race! The bearing will fail almost immediately if it's installed incorrectly. Since in a gimbal head the load is applied to the outer race, it's tricky to identify the loaded and unloaded portions of the bearing. Be absolutely certain that you've put the bearing in properly... or just don't use high-cap bearings. Some people whose judgment I trust (like Chuck Beaty) advise against using them.

[Victor Duarte]

thanks for the info doug...

there are so much valuable infos here, they sould be stored in a special thread that could be very usefull (time and life-saving).

i had an idea about that, imagine you have a picture or a plan of a gyro, then the user could click on a part (rotor, blade, wheel, tail etc) and have all the precious infos some people like doug and other skilled persons gave, like the kind of bearing, the kind of metal, the kind of bolts, maintenance recommendations etc..

hey todd, if i have perpective views of the gyros, i can make a Flash movie with links for free.. lets say it would be my contribution..

thanks

[Harry_S.]

Doug, the 5206.2RFC3 bearing has been the main staple for umpteen years, and as you stated, it had to be installed correctly or you have a dire problem.

The new bearing...3206.2RFC3 does not have a loading slot and can be installed without consequence. This is the bearing that RAF installs in the rotor head. This is also the bearing I had AAI install in my modified dual bearing rotorhead.

[Mike Nelson]

I know most of you do not fly J2s, but the J2 rotorhead uses Aeroshell #14 grease and it has 10 zerks on the head that calls for grease every 10 flight hours. In addtion, the manual also calls for the rotorhead to be covered with a waterproof cover if left outside. The J2 uses the same rotor system as the Hughes 269 helicopter. The old saying around many Hughes 269 rotorheads is that "when the rotorhead stops throwing grease around all over the airframe, its about time to grease it again". It's true.

[Ron Marlett]

I rather liked the idea posted on Norms old forum many years ago by Craig Wall. You bond a small electret microphone to the rotorhead structure, such as the main torque bar, with epoxy. You run this mic audio to a small amplifier. The output of this amp could be sent into your headset and you could listen to the head bearing under load any time you liked. A permanently installed mechanics stethescope.

To take this idea another step, several mics could be used in addition to the rotorhead, such as on the engine crankcase or propeller reduction gearbox. This audio could be switched into the headset manually or monitored by a processor/level detector. If any of the audio levels increased above a set threshold then the pilot would be notified as to which mic had a high noise level and the audio from that mic would automatically be sent into the headset for the pilot to evaluate. "Boy that rotorhead didn't sound like that yesterday".

[Victor Duarte]

ron it s an interesting idea, the signals coud simply be processed in a common "programmable automat" (i dont know if its the right english term) and displayed through an LCD screen, but with al the background metals noises, the pilot could need a submarine acoustic specialist ;)

thank you

[birdy]

Another thing bearings don't like is heat.
I don't know wot sort of crappy grease the factorys pack these bearings with,but I know it don't like git'n hot.
On a hot summer day,if parked out for more than 5 mins,the alloy in the head can excead 100c and the "moisture" in the grease melts and runs out,leaving you with a dry bearing.
Before I fit a new rotor bearing I cearfuly remove the seals and repack the bearings with a "real" grease,and now git twice the hours before I need to change [6oo hours].
The last one I changed had bout 650 hours on it and still felt like a new one,but I changed it anyway.

[John_Read]

Thanks everybody for your responses. I was especially pleased to learnthe part number, as I didn't know what it was and my local motor parts outlet was not sufficiently interested to look through the stock to find out! :o

The bearing I took out has identical faces - nothing resembling a loading slot, and no obvious way to put in more lubricant. I think - in order to be on the safe side - I will order the new kind where it makes no difference which way up you fit it! :D

John

[Doug Riley]

Harry S., I hadn't seen that part # 'til you posted it. 5206 is an industry-wide number, but the letter suffixes seem to vary from maker to maker. In the "Black Beauty" rotorhead we (AEROTEC) sold for awhile, the number was 5206MZZ. The "M" was for the heavy-duty, loading-slot version and the "ZZ" meant rubber seals (not just shields) on each side.

The selection is a bit less critical in a 2-bearing head. Jim Mayfield and crew at Sparrowhawk are quite professional and ought to know what's best.

[Jim]

Doug, Harry and everyone else,

In his JT -5B plans, Jukka Tervamaki calls for a 3205 2RS main bearing. Do any one of you know the characteristics of this bearing? Are the dimensions of this bearing the same as for the 5206MZZ or 5206.2RFC3?

Thanks
Jim

[Dean_Dolph]

Hey, Jim, since Ken J. has a real job these days and can't police the Forums I'm going to set in for him and ask you to fill out your profile so we'll know a little more about you.

ThanX!

[Greg Mitchell]

Doug or anyone else, can you tell me more about this bearing and whether or not it needs to go in one way or the other.

MRC 5206CZZ USA 08 0092........that last 2 may be a Z, even with my readers it's hard to tell. On the inner black section it has CPI marked and 13 opposite each other. On the other face on the inner middle black section again it has CPI and 27 directly opposite.

Thanks for the help guys.
Mitch.

[Mike Nelson]

In response to monitoring the rotor bearing and heat, I use a Tel-A-Temp strip right on my rotor mast right where the bearing is seated. This is a strip of laminated paper with adhesive on the back and has various tempature boxes on the front that go from white to dark gray depending on how high the temps get on the surface where the Tel-a-temp is attached. The Robinson helicopters use these strips to monitor heat on their gear boxes and rotorheads. It's one more way for the pilot to know what might be going on inside a part that should not be generating a high amount of heat. Of course, you can also climb up to the rotor head as soon as you land and check to see if the bearing is still cool to the touch with your bare hand, but the tel-a-temp can be seen from the ground and are very acurate. It will also permanently record the highest amount of heat (by how many temp boxes turn gray) during the flight.

[Doug Riley]

Greg: We used MRC's in the Black Beauty head. The writing on the SIDE of the bearing housing was upside down when the bearing was correctly installed. It is best to get the instruction sheet that comes with the bearing, however, and follow it closely.

[Harry_S.]

Jim: Go to a good Bearing shop/store and they can cross reference practically all bearing numbers and mfg's. DON'T tell them it's for an aircraft. If they ask, tell them it's for whatever you can think of...self designed lawn mower; exhaust for a paint booth...whatever.

[Harry_S.]

Some years back, a short story was printed in the PRA Magazine about two buddies flying together. This was back in the days when most everybody was flying single seat Bensens. Some of you old timers may recall this story and make any corrections to it; please.

As I recall, one of these fellows performed some maintenance on his gyro, including some work on the rotor head. One thing he did was to replace the main bearing (5206) in the rotor head. After all the work was done, they went flying together one day. After they formed up at about 200 ft. and were flying along, this fellow looked over at his buddy, who was slightly below his level and as he was looking, his buddies complete rotor seperated from the gyro and the gyro dropped to the ground. Examination later revealed the 5206 bearing came apart and the main bolt pulled thru the bearing. It was determined the 5206 bearing was installed upside down.

The loading groove (half moon) should be installed FACE DOWN .

If you old timers find any of the above to be in error...please correct.

[Greg Mitchell]

Doug,
Thanks for getting back to me. I haqve some detail on this Bearing MRC 5206 CZZ.
The C Suffix on the 5206CZZ stands for:

“Double-row angular contact, non-filling notch ball bearing, with outwardly convergent contact angles, rigid design.”

The ZZ Suffix stands for two shields.

It doesn’t matter which way you turn this bearing.

The dynamic load rating of this bearing is 6,660 lbs.

Regards,

Mitch.

[John_Read]

Thanks again, folks. I have installed the 3206 bearing which can be either way up....

Better safe than sorry!!!

John

[Jim]

I have a few catalogues from manufacturers such as BCA and SKF. These are usually free :) :) from industrial supply stores who carry bearings. They have very good information.

Recently I also went on line to http://www.ina.de. They have an excellent site. Type in the number of the bearing in question and a description and sketch of the bearing comes up. Answered all my dumb :eek: questions in an earlier posting. I found that http://www.skf.com is also good.

Jim

[gyroplanes]

Doug,
Thanks for getting back to me. I haqve some detail on this Bearing MRC 5206 CZZ.
The C Suffix on the 5206CZZ stands for:

“Double-row angular contact, non-filling notch ball bearing, with outwardly convergent contact angles, rigid design.”

The ZZ Suffix stands for two shields.

It doesn’t matter which way you turn this bearing.

The dynamic load rating of this bearing is 6,660 lbs.

Regards,

Mitch.

I have installed many MRC5206MZZ bearings as they were standard equipment on Air Commands for many years. We also used them on our SnoBird "Black Beauty" rotorheads.

At some point, several years ago MRC started to enclose a little piece of paper in every MRC5206MZZ bearing box which told you to install it a with the thrust loads on (or away from?) the bearing side with the part number etched in.

I'm certain that of the hundreds of Air Commands sold that half of the MRC5206MZZ bearings were installed without regard to orientation as most were sold before this warning was enclosed. I haven't heard of any failures.
Just wondering.

[Doug Riley]

Tom, I've heard a story or two from people who changed the bearings in their rotor heads and claimed that "it was trash after an hour of flying." No way to prove it, but one explanation might be that they put a loading-slot bearing in upside down.

When AEROTEC had its turn building and selling the "Black Beauty" heads, I used to take that MRC instructional slip you mentioned and staple it around the teeter bolt to (I hoped) catch people's attention.

[gyropilot]

From the MRC catalog:

MRC double-row ball bearings are manufactured in
two main types: C-type (conrad construction) and
M-type (maximum capacity with filling notches). Each
row has a 30° contact angle.

C-type

Conrad construction, or C-type, double-row ball
bearings have contact angles that converge outside
the bearing, thereby increasing resistance to
misalignment. This type does not have filling notches.
These bearings are recommended for applications
where single-row bearings are inadequate, but radial
loads are not so great as to suggest a filling-notch
bearing. They will take heavy radial loads, and axial
loads equally in either direction. The C-type design
fully meets the requirements of American Petroleum
Institute Specification 610.

Both the inner and the outer rings have closure
grooves. These bearings are available with seals,
shields, and snap-rings.

M-type

This type has filling notches on one side to permit
assembling the maximum number of balls into the
bearing. Contact angles converge outside the
bearing. All inner and outer rings have closure
grooves. These bearings may be equipped with seals,
shields, or snap-rings; or a combination of these. The
M-type bearing has very heavy radial capacity. It also
has thrust capacity in one direction, with the ability to
accommodate light thrust load in the reversing
direction.

Part numbers on M-type double-row bearings are
normally located on either the side face or the O.D.
The side face marking is always on the side opposite
the filling notch and the O.D. marking is offset from
the center away from the filling notch. Therefore,
double sealed or shielded bearings with the filling
notch covered from view can be oriented correctly.

Ball Cages and Types

The cage supplied with C-type and M-type bearings is
one-piece, heat-treated steel for maximum retention. It
is snapped into place after the full quota of balls has
been introduced between the inner and outer ring.

Load Ratings (lbf):

Dynmaic Radial = 6,430

Dynmaic Axial (thrust load)= 5,208

Static Radial = 4,590

Static Axial (thrust load) = 3,029

Speed rating when grease filled and double seals = 7,000 rpm

[RHerron]

Harry,

I guess I am an old-timer. As I remember it, the fellow left the large-area washer off the main (vertical) spindle bolt and only the press-fit center spool held the head together long enough to get him airborne.



Some years back, a short story was printed in the PRA Magazine about two buddies flying together. This was back in the days when most everybody was flying single seat Bensens. Some of you old timers may recall this story and make any corrections to it; please.

As I recall, one of these fellows performed some maintenance on his gyro, including some work on the rotor head. One thing he did was to replace the main bearing (5206) in the rotor head. After all the work was done, they went flying together one day. After they formed up at about 200 ft. and were flying along, this fellow looked over at his buddy, who was slightly below his level and as he was looking, his buddies complete rotor seperated from the gyro and the gyro dropped to the ground. Examination later revealed the 5206 bearing came apart and the main bolt pulled thru the bearing. It was determined the 5206 bearing was installed upside down.

The loading groove (half moon) should be installed FACE DOWN .

If you old timers find any of the above to be in error...please correct.

[Aussie_Paul]

I would have thought that the extra balls that the loading slot allows would spread the load over a larger suface area and that tiny loading slot would not cause any problems at all. Maybe in an industrial application, where the bearing is being used to its maximum capacity, a problem may develop.

I flew many hours, before I knew about loading slots, with the loading slot the wrong way and after 1000 hours I bought a new bearing but I never installed it as the was more manufacturaing tolerance movement in the new bearing than the was in the old one installed the wrong way!!!!

Aussie Paul. :)

[C. Beaty]

I have no recollection of someone falling from 200 feet as the result of an upside-down bearing. In fact, the older MRC catalogues I have don't even list a loading slot bearing. That's not to say it didn't happen.

I did hear a report that Bob Arnt (Commander Bob) reassembled his rotorhead with the bearing block upside down which places the thrust retaining lip on top and the rotor went its own way during a high speed taxi as the blades approached flying speed. I think I recall hearing he did the same thing all over again.

I believe the entertainment took place at Cross City, Florida.

Too bad no one got it on film. It might have been a winner on that Stupid Tricks TV show.

[Douglas Riley]

Aussie Paul, a footnote for others reading your post: new bearings often feel sloppy when they come out of the box. That's because there is a calculated amount of play in the assembly, to make room for the grease. Some manufacturers ship them dry or nearly so. Once they're packed with grease, they tighten up and even become harder to turn. But, of course, they are supposed to be packed.

[Victor Duarte]

Doug, can i ask you a question, have you heard about the use of GRAPHALLOY bearings ?
thank you

[Harry_S.]

That would have been a classic Chuck; if caught on film. I take it...he wasn't hurt...physically?

[C. Beaty]

I'm pretty sure Commander Bob didn't lose any skin in that episode, Harry. The rotor would fly upward and rearward until it lost stability and tumbled; the rest of the gyro would shoot forward from the loss of rotor drag.

That was a long time ago. I'll have to ask David Seace; if he wasn't there, his stepfather, Slim Rosenberger surely was.

We used to call the crew that hung out at Cross City the "Over the Hill Gang;" most were getting long in the tooth and appeared to go to Cross City mainly to ogle the airport manager's wife in her skin tight short shorts.

She reminded me of Hermione Gingold; on the other hand, I was a lot younger and perhaps a bit more discriminating in those days.

[Aussie_Paul]

Thanks Doug, I forgot to mention that.

Aussie Paul.:)

[Harry_S.]

AH SO Chuck!!! :cool:

[RHerron]

Aussie Paul, a footnote for others reading your post: new bearings often feel sloppy when they come out of the box. That's because there is a calculated amount of play in the assembly, to make room for the grease. Some manufacturers ship them dry or nearly so. Once they're packed with grease, they tighten up and even become harder to turn. But, of course, they are supposed to be packed.


Yes, if they are not sealed. Sealed bearings are usually only packed 40% full. That is a specification that is emphasized in the maintenance manuals of Hughes 269-300's. It is also in the bearing specifications for the McCulloch J-2. This is to prevent skidding of the balls as could happen if they were packed 100%. We used to clean the bearings of all original grease, dry them thoroughly and fill 40% of the spaces (per maintenance manual). Then, roll the bearing to distribute the grease and then install the seals.

One requirement for the helicopter bearings was that they have considerable play. Too tight in a rotorhead is a "bad thing". The bearings that were closest to "perfect" were used in industrial electric motors. The "rejects" were used in helicopter heads.

Bearings without seals could/should be purge-greased (100%)as the extra grease will work out after a few turns. The original Bensen heads all had shielded bearings but some people replace them with sealed.
If so, don't over-pack them.

[John_Read]

What? Pack them? How do you do that? My bearing does not seem to have any way to put grease in. I thought they just came as "fit and forget" items!

:confused:

John

[C. Beaty]

Open and shielded bearings, John, are frequently shipped with a rust inhibiting slushing compound and must be cleaned and lubricated before use.

One convenient way of lubricating a bearing if you have a vacuum pump is to immerse it in a can of grease, place in a bell jar, vacuum chamber or whatever and pull a vacuum. When the vacuum is released, grease fills the bearing.

The shields are a light press fit and can be popped off with care. Then the bearing can be hand filled.

On the other hand, you might have received a pre lubricated bearing.

[birdy]

Are these "shields" the things we call seals[rubber] or is it different again??

[C. Beaty]

Seals are seals and shields are shields, Birdy.

Shields are the metal closures that keep out everything but the smaller rocks.

With an open bearing, you can see its balls.

After additional thought, I think shielded bearings always come prelubricated and it's just open bearings that come with a rust inhibitor.

[birdy]

Thanx Chuck.
Was think'n maybe there was a yank/oz lingo thing happen'n.
Just I'v only seen rotor bearings with the rubber[or neoprean] seals.

[Ted Eggleston]

Doug,
I haqve some detail on this Bearing MRC 5206 CZZ.
The C Suffix on the 5206CZZ stands for:

“Double-row angular contact, non-filling notch ball bearing, with outwardly convergent contact angles, rigid design.”

The ZZ Suffix stands for two shields.

Mitch.

Its interesting to note the changes companies make to bearing descriptions from one country to another. For example here in Australia the 'Bearing Service Company' manual shows its method for describing bearings under the following method;

Bearings with 4 digits, normally are classed as follows:
1st digit - Type of bearing, 2nd digit - bearing series, Remaining digits 00 = 10mm, 01 = 12mm, 02 = 15mm, 03 = 17mm, all others are to be multiplied by 5 to give the Bore size in mm's.

Bearings with 3 digits use the 1st and 2nd digit descriptors above and the single remaining digit is the Bore Size in mm's.

Bearings with 5 digits use the 1st digit descriptor above, the 2nd to indentify the width of the series, the 3rd to indentify the Diameter series and the remaining two digits to define the Bore size.


Occasionally they may start a bearing number with letter M with 3 numbers for maximum capacity, or N,NU,NC,NF,NJ NUP,RNU with 3 digits for Cylinderical roller bearings.

It pays to seek good advice when trying to match bearings as noted in the forum particularly when quoted from members of differing nations

[scottessex]

So, let me get this straight, the MRC 5206CZZ bearing, is rated for thrust in both directions and it doesn't mater what side is up or down.

Normaly a thrust bearing will be marked on one side or the other, at least the ones I have used.

[Doug Riley]

As long as it's not a loading-slot bearing, then yes, it's OK in either direction.

These ball bearings aren't "thrust bearings" as such. They're made to take thrust loads alone, radial loads alone or various combinations of both.

[scottessex]

Thanks Doug, I am in the process of rebuilding my rotorhead, Good info to know!

[automan1223]

I forgot about the loading slot in the high cap bearing,

I only remembered that the hi load bearing had a few extra balls, it was on the old forum, something like 13 for the std bearing, and 18 for the high cap.

Jonathan

[Harry_S.]

I've used the 3206.2RFC3 numbered bearing since it was installed by the RAF factory.

I also had AAI install this bearing when they modified my head to a 2 bearing block.

This bearing has no loading slot and can be installed *any side up.* Don't know if there is any cost difference with the 5206.


Cheers :)

[mcbirdman]

I found this old thread concerning bearings. I have a 3206-J From what I have been reading it doesn't matter how it is oriented and I see it is sealed. I am have never flown the head but it hasn't been lubricated in two years. Should I try to add any grease and if so what should I use? a Lithium grease or something specific? I am getting ready to close up the control system after I installed the remote control wunderlich brake bracket and would appreciate any good or bad things pertaining to this bearing maintanance. Thanks much. jtm

[LAWOLF]

I found this old thread concerning bearings. I have a 3206-J From what I have been reading it doesn't matter how it is oriented and I see it is sealed. I am have never flown the head but it hasn't been lubricated in two years. Should I try to add any grease and if so what should I use? a Lithium grease or something specific? I am getting ready to close up the control system after I installed the remote control wunderlich brake bracket and would appreciate any good or bad things pertaining to this bearing maintanance. Thanks much. jtm
I not fimular with your rotor head bearing but I know they are needle type to hold the load simular to the type you have on the front wheels of a car. They should be tightened down just snug to just make the plate hold the bearing with a firm pressure. I would think the bearing is a sealed type and would not require grease. If not the bearing grease should NOT be a moly type since MOLY will rust over time this is what the military found out. Just use a high temperture grease used for front wheel bearings. NO fiber grease as well.

[mcbirdman]

Thanks Lawolf,

They are sealed but I feel that with the bearings almost accessable at this point I wonder if I should try to put more grease in them or if I should assume that they were already properly packed. I have always covered the head when travelling but the bearing has been up there in the garage for 2 years or so....... I am just trying to be prudent and learn about things I do not know.....

[Harry_S.]

James:

As regards the 3206 bearing...I'm only experienced in using the 3206B 2RFC3 bearing. This is the bearing RAF has installed in the head. It is a sealed bearing similar to the 5206. I have had no problems with it.

Over a year ago, I had AAI modify my head to a dual bearing block. I had them install the 3206 bearings. The 3206 cannot be installed wrong as there is no loading slot.

I wouldn't be concerned about the bearing in your head but I would disassemble the gimble portion and regrease the bolts...just to satisfy myself.

The 3206 bearing that AAI returned to me still rotated smooth as glass after 6 yrs. of use...over 300 hrs. flyin' time. ;)

.

[mcbirdman]

Harry, Rodger that....... Wouldn't worry about the grease in the sealed bearings but be sure to grease the bolts on the gimble as I put it together for use.....

I tried to read all the posts on this page and I was able to determine no up or down on this bearing but was puzzled at the 3206 "J". the first part of the numbers were matching yours but couldn't see what the J did. Thanks for your input I appreciate your viewpoint. take care, jtm

[Gyrodon1]

Anyone know the p/n for the main rotohead bearing

[phantom]

I remember the story that harry s read about in pra mag and it wasn't a bearing failure, when the bearing was replaced the owner didn't put the large washer on top and flew for a number of hours over several months with just the press fit holding the head together and when it seperated in flight the rotor came close to bringing another gyro down. I have seen things like this happen when people will take something that they are not use to working with apart and then order parts and weeks later when it is put back together something is missed or put in backwards. I was test flying a machine that the owner had rebuilt and the belt drive failed after less then 10 minuits because the snap rings were left out when the bearings were replaced.
With things like rotor heads if you are not sure it is best to send the whole thing to someone who works with the type that you have.

[Doug Riley]

The "classic" rotor bearing for gyros is a 5206. You might as well get the sealed version, not the shielded or open versions. Clean and re-grease it periodically.

Heavy-duty (loading slot) versions of the 5206 need special care upon installation and probably aren't worth the fuss for a light 1-place gyro.

Never mind the nonsense from Lawolf in that old thread about roller or needle bearings. The 5206 is a double-row ball bearing.

[L_Butler]

When I replaced the bearing in my rotor head over this past winter the representative at the supply house said that the 5206 was being phased out and being replaced with the 3206. They said that the balls were slightly larger and the axial load capacity was slightly higher.

Larry