Ceramic Bearings

[Njoro]

A few years ago when I was burning lots of Nitro and destroying crankshaft bearings a lot I was looking for the original type of bearings that OS used to use the type with a metal cage for the balls and not the cheap plastic cage which is fine for novice learning to hover, when I came across ceramic bearings from a US site.

I bought two for testing and since I used to keep a maintenance log and general flying log I ended up with data that the supplier was very pleased with and had it up on their webby.

The bearing from its first ignition to its last rotation was logged, the bearing failed under the strain of the starter, the cage disintegrated into tiny bits and I did get a tiny score mark on the piston and liner. This failure could have been in the air but since I knew from the engine noise that the bearing was about of fail I refrained from aerobatics and just flew lazy 8s'.

The bearings' start to failure rotations 20,124,000 revolution +/- starter revolutions.
Head speed a constant 1950/rpm.
Total fuel used 10 gallons 25% nitro.
Price then $76 rate then £1 - $2.2.
The bearing was far superior in terms of smoothness and apparent power from the engine and the helicopter felt light and powerful, the down side of the bearing is the fact it's only as good as the steel race that the ball run in. Once the race pits that is the end of the bearing. I've still got one left and since the Redline is due a service I'll fit it.

[Coyote]

The ceramic certainly does its job then, but again the weak link is steel. Pretty impressive data recorded and impressive results too.

Price wise was that the price per unit, or as the pair ?

Amazing to see the from such a tiny component the performance increase was so apparent. :)

[Njoro]

 The price was per unit since the front bearing was not ceramic. Thing is I can't remember where I bought it!

[Coyote]

Oh right you said so you got two for testing so was unsure, £30 quid a bearings pretty high, but if its really that good still worth it.

I would have thought after using your findings they would as a kind gesture of thanks send a free one out for you lol :)

[Njoro]

Yep I waited for an email to say thanks and here is some new bearings for free, I got the thanks but no bearings :'(

Thing is I was trashing the OS bearing so quickly and at £13 each it was worth testing a different make.

[Coyote]

The buggers, that was nice of them :(

At least they were of an improvement though :)

[Njoro]

 I think if I just flew or someone just flew mild circuits and run a head speed of say 1750/RPM the bearing would have lasted far longer and the money spent would have been worth it in the long ran.

I'll upload a picture of a good one.

[foamystuff]

Would cageless bearings be suitable or does the vibration destroy them? In my turbines I have cageless, angular contact ceramics, the problem is that if you push the wrong way the inner race pops out with very little force and can only take load in one direction. The only time I had a cage fail on me was with a KJ66, which went from 80K something RPM to zero in about a tenth of a second and there was hardly any damage!  :laugh:

[Njoro]

Cage less bearing may work, are they steel race or do they come all ceramic? The killer blow in an IC engine is the hammer effect at ignition the few thousand of an inch play is all it takes to start chipping the race. If jet bearings have zero play then that could mean a longer life. I'd try one and see if they were available in the right size.

[foamystuff]

Hardened steel race as far as Im aware..