S.S.Bearing

[Verne Koester]

It's the only bearing I've used to date that's lasted more than 5 gallons. Two weeks before the Nats, I went through 2 bearings, both of which appeared to be heavily corroded. Closer examination revealed that the "corrosion" was in fact, burnt oil. I had numerous discussions with many experienced O.S. 1.4 RXers and got many different responses ranging from reducing the oil content so the balls don't skid in the race (had already tried that), to machining out the web adjacent to the counterbalance on the crank, to using the EFI bearing with the shields in, to using a stainless bearing with the shields out and grease flushed away (already tried that and it didn't work for me). 

I think there's a lot of factors involved explaining the wide variance in results. In some cases, including mine, I think the tuned pipe might be scavenging the crankcase too efficiently leaving too little oil behind to lube the bearing. I had one stainless bearing last exactly two flights and it appeared very dry and was covered with burned oil which looked exactly like corrosion. I tried another stainless bearing with the shields and grease intact and it lasted about 4 flights. Along the way, I tried boring two, evenly spaced 3/32" holes through the web to let some more oil through which only helped slightly, if at all. I then put in the EFI bearing with the shields intact and have been flying it ever since (about 6 or 7 gallons so far). I don't think that's enough to draw any absolute conclusions, but so far, it's the only thing I've had that's held up beyond 5 gallons and it still "feels" like new. 

One of the people I talked to about this was Mike Stokes from Great Planes. He told me their recommended fix was the EFI bearing. I think removing the web away from the counterbalance would also probably work and I've been told (not by Mike Stokes) that this has no impact on performance. However, the EFI bearing has been fine so far and I'm going to continue running it until it feels gritty or loose. I'm very pleased with the engine in every other aspect and intend to buy another one for my next plane. Don't take anything I've said as an "expert" opinion because it's not. This is just the experiences of a junkyard mechanic that wants to concentrate on flying instead of engine problems. Don't intend to get into any long debates on the issue either because I don't have enough experience with the engine to speak with any authority on it. I only know what has worked for me.

Verne
  ----- Original Message ----- 
  From: mdarr00 at comcast.net 
  To: discussion at nsrca.org 
  Sent: Monday, August 04, 2003 5:59 PM
  Subject: Re: S.S.Bearing


      Dave, I was unaware of the differance in size, but I know for a fact that Verne Koester is running one in his O.S. 140 RX, and I got that p/n off of his spare bearing package.  What was the differance in the bearing size?  If it is slightly wider or narrower, it will most likely not make a differance, as long as the i.d. and o.d. is the same size.  Maybe Verne will chime in on this thread and let us know for sure.

  Mike
    ----- Original Message ----- 
    From: Dave Smith 
    To: discussion at nsrca.org 
    Sent: Monday, August 04, 2003 5:29 PM
    Subject: S.S.Bearing


    "  learned from other peoples experience that the best stainless steel bearing
    is the O.S. FI factory bearing p/n 29430010.  That is the bearing I will be
    using next, and I was told to leave the seals in the bearing to maintain the
    factory grease in the bearing."


    Mike:     On checking with Tower,the stainless bearing will not be available until October.

    Also,their specs show it to be very slightly different in size than the one they list for the 140RX.    Would this be a problem?

    Dave
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