ORIGINAL: jeff naul
hey brett thanks for the reply. i just got it back from gabe and he had done alot of work to the engine. he did say something about some tubes being stopped up. can debris from my flying field be the problem. i get some grass in the fog screen because this time of year we are not mowing so the clippings arent getting blown off? but it happens always on the third flight, thats whats strange. jeff
Hey Jeff,
What you describe about the grass and debris contaminating the lube line is indeed possible but I feel it's quite unlikely, the lube line exits behind the compressor wheel and just in front of the front bearing. When servicing the engines after ~20-25 hours of use we find a lot of the debris normally ingested into these engines shows up on the diffuser vanes and not under the comp wheel. There's not a lot of room between the comp wheel and diffuser for dirt and debris to get in there, plus with the rotatives spinning @ 100k+ all the crud ingested will tend to go out through into the combustion chamber area via the diffuser vanes rather than behind the comp wheel.
The pressure differential between the underside of the compressor wheel and the bearing tunnel is what does the lube work for us, it is possible for your particular engine to not quite have the differential required, but again it's unlikely. I believe it's more likely for any possible blockages to be coming from the lube line fuel/oil supply, all I can suggest is that the fuel and oil you use is maticulously filtered, the lube line restriction is very small and it doesn't take much to cause problems.
Also, as Paul has mentioned, any slight imbalance will cause bearings to fail pretty quickly no matter how good the lubrication is, does the engine tend to "howl" at any rpm region, normally any imbalance will show up at various rpms harmonically rather than at all rpms.
I'm sure Gabe will be able to fill you in on the details, hopefully he'll be able to help you out, he has a great service and does very good work.
Cheers,
Smithy.