NRC 5206CZZ bearing

Yes you are right apparently they are non directional. I am sure there are experienced builders here to chime in on it though. I am not one of them by any means :)
 
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I have never used the sealed bearings, only shealded because I seal them in the head block.
The head bearings we commonly use are the "Conrad Type" deep groove angular contact bearings. They are bidirectional. These bearings are rated at around 6,000 lbs at around 6,000 rpm as I recall.
As Alan stated above, the only reason for using two in the really heavy machines is because the increased undersling adds additional over-turning loads to the bearing.
 
It is best to avoid loading slot bearings altogether in a rotorhead. As others have mentioned, axial capacity is ample so that the extra ball or two that can be installed via loading slots is redundant.

The important thing is tolerance to moment loads (overturning) and loading slot bearings aren’t forgiving in such applications.

The only thing I like about a Magni is the Jukka Tervamaki rotorhead that permits wide spaced bearings. European gyro designers would be well advised to copy that rather than the fiberglass frock.
 
I deal with loads on bearings all the time in some of my rotary gun stuff and you never want to put the load pushing on the side of the bearing where the snap ring or retainer is.
Remember the load on a rotor head pulls the outer race up and inner race down....why would you want the load in the event of a snap ring/retainer failure to go down and pull the guts out of the bearing and detach the rotor.....???? I may retract this after I get my coffee tonight but something is amiss

There are no loads on any snap rings, only compressive loads between the balls and the race faces.

The primary load path for axial loads on a rotor head bearing is through the upper balls and the reason why on loading slot bearings the slot goes down.

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There are no loads on any snap rings, only compressive loads between the balls and the race faces.

The primary load path for axial loads on a rotor head bearing is through the upper balls and the reason why on loading slot bearings the slot goes down.

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Makes sense Alan....I always thought that both rows of brearings were loaded. After seeing the pic I can see that only the upper bearings are riding agaist the race and both would engage during a radial load. I guess the only way this type of bearing would fail is if the center part caved in or the outer housing blew out...of course this should never happen properly assembled in the bearing block.
 
I finialy got my MRC bearing,got it installed yesterday. When I took the bearing out it came out with the numbers and letter facing down so that is the same way I installed it back in.....
 
This double row bearing has a notch [or opening large enough for a ball] for inserting & assembling the balls in manufacture. This bearing should be installed with the notch's DOWN. This puts the loaded balls riding on the notchless races. Picture it in your mind, it is real simple. Of the many I have checked over the years, about half were installed right and half wrong. It is not a life or death deal. That bearing even with notch will support 10 times our loads. To check a bearing, carefully pop off grease seal and look for notch.
Don't trust direction of printing, most are foreign made even with U S name on box. Do not over grease either. Use a good pressure grease. We will never wear one out if properly packed. If water gets in bearing from rain or what ever it can rust and be ruined. Every time rotor is removed, give it a spin with your ear near...

Alan, You are right. My wife, me, and my boy have dislexia. I changed my mistake. We want the load running on the race's WITHOUT the notch's...
 
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This double row bearing has a notch [or opening large enough for a ball] for inserting & assembling the balls in manufacture. This bearing should be installed with the notch's up. This puts the loaded balls riding on the notchless races. Picture it in your mind, it is real simple. Of the many I have checked over the years, about half were installed right and half wrong. It is not a life or death deal. That bearing even with notch will support 10 times our loads. To check a bearing, carefully pop off grease seal and look for notch.
Don't trust direction of printing, most are foreign made even with U S name on box. Do not over grease either. Use a good pressure grease. We will never wear one out if properly packed. If water gets in bearing from rain or what ever it can rust and be ruined. Every time rotor is removed, give it a spin with your ear near...
Awesome info Ed thanks. You know what would top it? Pictures for the ones who are lurking and don't speak much of English! There are a lot of them. A picture is worth well you know the saying.......although we are in recession so it must be worth even more :)
Thanks Ed!
 
This double row bearing has a notch [or opening large enough for a ball] for inserting & assembling the balls in manufacture. This bearing should be installed with the notch's up. This puts the loaded balls riding on the notchless races. Picture it in your mind, it is real simple.

No, I am sorry but you are mistaken, if the bearing has a loading notch it goes DOWN !!!!!!! If you have any confusion just look at the drawing I posted on page 3 of this thread, it's the upper balls that are loaded when the bearing is taking an axil load from rotor thrust so you want the loading slot down.

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It is best to avoid loading slot bearings altogether in a rotorhead. As others have mentioned, axial capacity is ample so that the extra ball or two that can be installed via loading slots is redundant.

The important thing is tolerance to moment loads (overturning) and loading slot bearings aren’t forgiving in such applications.

That sez it all!
Just use the conrad type bearing like most gyros always have and don't worry about which way to install it! Why complicate such a simple thing?:noidea:
 
Here’s how a Conrad bearing is assembled:

Image1.JPG
There are no loading notches and the cage keeps the balls properly spaced.
 
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That sez it all!
Just use the conrad type bearing like most gyros always have and don't worry about which way to install it! Why complicate such a simple thing?:noidea:

I've always wondered why this subject keeps coming up.
Dog, you have the correct bearing. Put it in any way you wish.
 
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The important thing is tolerance to moment loads (overturning) and loading slot bearings aren’t forgiving in such applications.

Chuck,

This is understandable but the rotor bearing is also carrying an axial load of several hundred pounds which will modify the loads a pure moment load imposes on the balls and races. Given such, do in-flight loads create a critical problem with loading slot bearings in small gyro application?

I assume a structural analysis on the head/bearing has been done in the past by someone, it would be interesting to see, if not I may need to crunch the numbers myself.

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I don’t know if anyone has crunched the numbers, Alan.

I do know that for a single place gyro, a 5206 Conrad bearing is bullet proof. Specific dynamic radial capacity is given as 5110 lbs in a very old catalog I have.

The calculated life expectancy with a pure thrust load of 500 lb. at 400 rpm is 23,265 hours, using the method listed in my very old MRC catalog.

Why mess around with loading slot bearings?
 
The only bearing failure I know of in all my gyro years was in a J-2 Gyro. My buddy Bob Wahn bought a super J-2 after riding in mine. It had been sitting outside for a while when he bought it. We all told him to change the bearing. It froze up on a cross country, his wife and he died in a terrible crash form 1000', into a lake. There was not much left of the machine. Later the bearing was looked at, rusty and galled. He was our electrician at our 3 biggest years of PRA conventions, 87/88/89. 140+ machines. Bob had electric for everybody. They were sorely missed after the crash...
 
I remember that incident. I never thought of that bearing while flying, till then.
 
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