flyrotary@lancaironline.net Mailing List Archive

Don't mind at all, Al. I like to do it - as at least it gives a sort of ball-park figure of what to expect.

Sounds like to me that your temps are not out of line. 243F with a 210F input would lead me to 'expect" around 210F with a 180F oil temp going in which I would certainly think was reasonable.

I agree, I think a temp reading is more useful than a chip detector - could give you a warning long before metal chips started appearing.

----- Original Message -----

From: Al Gietzen

To: Rotary motors in aircraft

Sent: Tuesday, May 22, 2007 4:36 PM

Subject: [FlyRotary] Re: Gear box oil temps

Figures I found on the web indicates 3% is a fairly standard figure used for a planetary gearbox efficiency.

So 3% of 160 HP = 4.8 HP which is mostly converted to heat.

Tf = 180F + (203/((7.3 *.5) *0.4) = 180F + 69F = 249F

So using this example and assuming I haven't screwed up, I would expect the oil temps coming out of the gear box to be around 249F.

Ed;

I really appreciate when you take the time and effort to do the math that I’m to lazy to do.

I think at the time I noted the re-drive temp out it was 243F, shortly after leveling off from a climb, and the oil temp (after cooler, into drive) was still about 210F. I’m gonna guess the power at that point was about 140 hp. So it seems that the efficiency and/or the flow rate is a bit higher. In any case; I’ll proceed on with worrying about that outlet temp.

Thanks.

BTW; I think that monitoring the redrive outlet is important. It can give you a heads up on problems with the redrive. It is nice to be able to set a limit in the EM to alert you of a potential problem.

Al