S.S.Bearing- What to Do about it??

[Verne Koester]

I'm currently using Powermaster Mean & Green with 18% synthetic oil and 15% nitro. Since I bought this fuel at Toledo, they've released a new fuel called 16/15 Power which is supposed to be geared toward the 2-strokes in this size range. As I understand it, it's basically the same as what I have except the oil has been reduced to 16%. I contacted them and tried diluting my fuel to about 16.5% oil by adding methanol (didn't have any nitro) but it didn't seem to matter much. I'm absolutely convinced that in my particular application, the bearing simply wasn't getting enough oil/fuel to it. It's not too hard to see when you put a brand new bearing in it, have it go "gritty" in two ten minute flights and then pull it right back out with a layer of burned oil on it that looks just like corrosion. The engine ran just fine through all of this, BTW and still has the original glow plugs (Mintor head) that I started the season with. I think there are more factors in the mix here that will give different results with different setups. I suspect the tuned pipe plays a large role in all of this and may be scavenging the case too efficiently. In any event, the EFI bearing with the seals left intact is working where nothing else I tried would. I have a spare, BTW, and checked the manufacturer and part number. For those interested since Tower is currently out of stock, the EFI bearing is an NTN 6904LU. I called my local bearing supplier who normally stocks that exact bearing and just happened to be out at the moment. They charge $40+ dollars as opposed to the $25 or so that Tower's getting. Maybe someone else can find it cheaper. However, I'd stick with the NTN because I think the grease they're packed with makes a difference.

Verne


  ----- Original Message ----- 
  From: Wayne Galligan 
  To: discussion at nsrca.org 
  Sent: Tuesday, August 05, 2003 4:30 PM
  Subject: Re: S.S.Bearing- What to Do about it??


  Verne,

  So what is the oil content of the fuel your are using?  I use Cool Power 15/17 and the original set of bearings lasted about 125 flights.

  WG

    ----- Original Message ----- 
    From: Verne Koester 
    To: discussion at nsrca.org 
    Sent: Tuesday, August 05, 2003 2:54 PM
    Subject: Re: S.S.Bearing- What to Do about it??


    Bob,
    The general consensus of pilots I talked to at the Nats (many of whom were long time competitors) was that the engine should have less oil, not more. The general idea was that more oil causes the balls to skid instead of roll. However, little or no oil, which was the case with my engine, causes the bearing to deteriorate rapidly. So far, the sealed, EFI bearing has worked just fine. 

    Verne


      ----- Original Message ----- 
      From: Bob Pastorello 
      To: NSRCA 
      Sent: Tuesday, August 05, 2003 7:17 AM
      Subject: S.S.Bearing- What to Do about it??


      Assuming that OS doesn't offer a solution to lubrication of the rear bearing on the 1.40, what other options are available?
          What mods could be made to the crankcase to permit more oil flow back there?
          Would increasing oil content of fuel make any difference?

      If the real core problem is undersizing of the bearing for the load application the motor endures, then a real fix would be a redesign of the crankcase to use a larger and wider bearing.  Pretty unlikely that would happen, I would guess.
          So what's the solution besides keeping the bearing suppliers well-funded??

      Bob Pastorello, Oklahoma
      NSRCA 199, AMA 46373
      rcaerobob at cox.net
      www.rcaerobats.net


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