NRC 5206CZZ bearing

Alan_Cheatham : So being all that said which bearing number has been replaced by the old MRC 5206CZZ


SKF owns MRC but the MRC brand is still used.


Look for SKF 5206E2RS
Look for MRC 5206MZZ

These are the preferable MAX bearings (they have a few extra balls) and rubber seals on each side. Max bearings have an extra margin of safety in my opinion but in order to put the bearing together there is a loading slot cut on one side of the bearing, this slot must go DOWN (face toward the ground) in the rotor head or there could be premature bearing failure.

Download this file: http://www.skf.com/files/519959.pdf
It will help you to identify where the loading slot is.

If you can not find MAX bearings:

Look for SKF 5206A2RS
Look for MRC 5206CZZ

These are the non MAX bearings (called Conrad), there is not a loading slot to worry about so the bearing can go into the head either way. Load-wise both max and non max bearings are fine but I believe a bearing with extra balls is safer if the cage should somehow suffer a failure and the balls congregate to one side of the bearing.

If you have a RFD head I would think one seal could be removed from the bearing.

The 3206 bearing number also appears to interchange with 5206 and some use this bearing in their heads as well, you can search the forum for info.

.
 
Last edited:
Alan_Cheatham : Got this e-mail this morning and wanted to share it....

The new part number is SKF3206A2RSC3 $51.50, stock in Macon, Ga

This has 2 Rubber Seals.

this is a different place than above.
http://www.wbds.com/htm/5206CZZ-MRC.htm
 
Last edited:
Alan_Cheatham : Got this e-mail this morning and wanted to share it....

The new part number is SKF3206A2RSC3 $51.50, stock in Macon, Ga

This has 2 Rubber Seals.

this is a different place than above.
http://www.wbds.com/htm/5206CZZ-MRC.htm

That would be an "A" bearing which is the non-MAX bearing, also the "C3" means the bearing has additional axial internal clearance. I don't know if that extra clearance would have any effect on a gyro rotor head but I would suggest not getting the C3 bearing, look for a bearing that has no "C" number (which would be the standard size).

Try here for SKF specs and info: http://www.skf.com/portal/skf/home/products?maincatalogue=1&lang=en&newlink=1_3_21

.
 
Alan_Cheatham :
Thanks for the help here......:yo:
 
Well I got my friend that works at NAPA to order me a bearing. Well it came in I open it up in the store and looked at it and you could see where some one installed it and beat on the bearing edge to install it or take it out one. I sure didn't want it.......
 
Hi Dog

WOW!! Is somebody skating on THIN ice. These bearings are made to carry Heavy loads so it doesn't make any difference whether it was going into a rotorhead or some othere heavy loaded piece of machinery, to put a bearing like that BACK INTO INVENTORY after it had been sold and not looked at upon return is just asking for major liability problems. Store policies need to be SERIOUSLY reviewed there. Glad YOU checked it out !!!

Tony
 
WHY :
I could not belive the (Friend ) asked me so do you want it? when I said no he said what about the shipping here? I told hin as the people that took it back. You exect me to fly with a bearing like that? Some friend....

Makes me scaredto order thebearing and have it drop shipped to me....Is it the good one or a cheap one. I want a SKF brand or the MRC one......
 
I have always used the MRC 5206 MZZ from Bearing Headquarters (formerly Berry Bearing).... even before they had the information paper about the "notch" in the box.
I called MRC and talked to an engineer (I told them it was for wind generator blades) (Not much radial load, but a lot of axial load)
It turns out he mentions gyros and rotorhead bearing use.. he was a pilot.
He explained the difference in thrust capability from each side. The "bad side" was still well within our safety range (I'm glad, because there are a ton of Air Commands and other gyros built without regard to loading slots)

Alan, I don't have the paper here, that comes with the bearing. It clearly shows the preferred axial load path.

I believe the loading slots may actually face UP on a rotorhead. IIRC.

Check the drawing and follow the preferred load path. Think about the weight of the gyro trying to pull the center race out of the bearing downward, with the rotor trying to pull the outer race upward away from the center race.
 
Last edited:
I believe the loading slots may actually face UP on a rotorhead. IIRC.

Check the drawing and follow the preferred load path. Think about the weight of the gyro trying to pull the center race out of the bearing downward, with the rotor trying to pull the outer race upward away from the center race.

The center race goes down ,the outer race goes up and pulls the balls to the top, center race also loads balls to the top--so,loading slot goes down and will not have a load on loading slot in flight.
 
Alan, I don't have the paper here, that comes with the bearing. It clearly shows the preferred axial load path.

I believe the loading slots may actually face UP on a rotorhead. IIRC.

No, if you examine the load path as per the instruction sheet and as mentioned in the previous post the loading slot must go DOWN. You can also search the forum, that information is posted over and over again, slot DOWN.

.
 
What is the maximum weight of the gyro for a 1 piece bearings? (5206)
From what weight should be 2 bearings in the head?
My gyro will weigh around 1100 - 1200 lbc.
Currently, I have such a 1 bearing in the head. I wonder if this is not enough for such a weight? Enough? Will do 2 for 2 head bearings?


Janusz
 

Attachments

  • IMG_0032.JPG
    IMG_0032.JPG
    50.5 KB · Views: 2
What is the maximum weight of the gyro for a 1 piece bearings? (5206)
From what weight should be 2 bearings in the head?
My gyro will weigh around 1100 - 1200 lbc.
Currently, I have such a 1 bearing in the head. I wonder if this is not enough for such a weight? Enough? Will do 2 for 2 head bearings?


Janusz

I would say at 1100 - 1200 lbs. you should go to a two bearing head. The second bearing is not for added load capacity but for increased resistance to forces trying to pry the bearing apart.

.
 
Bearing napa tried to sell me. You can tell it is used ~
 

Attachments

  • 0211111509a[1].jpg
    0211111509a[1].jpg
    66.7 KB · Views: 1
  • 0211111509b[1].jpg
    0211111509b[1].jpg
    59.4 KB · Views: 1
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
 
Just FYI, but the bearing at the above link is double shielded and not the double sealed bearing used in most rotorheads.

.
Thanks Alan I know they are I bought them on purpose I love them metal shields opposed to the plastic seal :)
 
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
The stamped side down to be quite simple :yo:
 
The stamped side down to be quite simple :yo:

Yea that what everyone is saying and even the bearing specs....I have some rotorhead bearings lying around I think there are all the non-directinal type but I have an old AC bearing I jerked out from the 80's maybe I can see the loading slots and better analys there reason for loading agaist the retainer.
 
Top