flyrotary@lancaironline.net Mailing List Archive

Guys,

There are several reasons for "transmission fluid" in an automatic transmission. First the TF is highly detergent to suspend particles and water. Second the viscosity is usually matched to the converter. The fluid also has to be a good high pressure lube for the gears. And lastly, the reason for the need for particulate suspension? The clutches, or bands if you will are what actually changes the gear ratios by usually stopping the ring gear of a given planetary set.

Now, for our use a separate lube source would be fine. We do need a moderate viscosity though and circulation for the needle bearings in the planets, (or the plain bearings in the planets) There was a big discusssion on the ACRE about the use of a Bell Helecopter #47 transmission planetary. The unit is big designed for high power, which is great, but usually turns at a slower RPM which isn't great. The gear pitch line speeds are near the high limit which is less of a problem, but the needle bearings in the planets are near max recomended speed for that size bearing. Too heavy or too much oil can cause the bearings to skate. This is a VERY BAD thing. Think of a big plane landing. The tires chirp and slide as they are accelerated up to the landing speed. Now think of the same thing happening with the steel bearing roller and the races. Obviously the bearing can't dissipate that energy by "burning rubber" like the tire. The steel on steel contact that can happen can destroy bearings pronto!

Bill Jepson

George - don't get me in trouble. I'm NOT saying Tracy is wrong, I was just wanting to learn why things are designed the way they are.

so, the high HP on the redrive requires better lubrication than simply grease, I.e. spray lubrication, and for simplification, the engine oil system (synthetic oil) is used rather than a separate system.

how is the C-6 lubed in trucks? I'm sure it's average HP requirements are less than the PSRU. where are the c-6 planetary gears actually located in a truck? trans, rear end, o/d unit...?

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

From: George Lendich

To: Rotary motors in aircraft

Sent: Tuesday, December 05, 2006 10:40 PM

Subject: [FlyRotary] Re: redrive lube

Kevin,

I guess this will be one of a hundred responses, however -

1.Tracy's way of doing his PSRU is OK.

2. Motor oils is likely to get contaminated with 2-stroke oil if your using it (most are) and carbon particles from the combustion process which act as an abrasive.

3. Motor oils need to be changed after 12 months even in low use situations.

4. Heavy duty of the gears ( as in aviation use) may need pressure directional spraying, whereby most gearboxes have splash lubrication.

An ideal situation would be a separate cooling of PSRU oil with synthetic lube oil, with pressure fed directional spraying of the planetaries and their bearings from it's own pump and reserve/ cooler.

Just my opinion.

George ( down under)

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

From: kevin lane

To: Rotary motors in aircraft

Sent: Wednesday, December 06, 2006 3:39 PM

Subject: [FlyRotary] redrive lube

i am asking this question with only the experience back in college years of putting a buick v-6 in a 1953 willys, no race car experience etc......

auto transmissions have special fluid and coolers because of the torque converters, right? manual transmissions just have gear lube, which, it seems, you put in and basically forget about. what is different about the PSRU redrive from a manual transmission? why can't it be self-contained with gear lube and forgotten? are planetary gears different from a manual transmission? are they fed with an oil flow and coolers in trucks? i'm sure all of this has already been answered and thought out. ken said he keeps his redrive lube separate from the dirty engine oil. why are tracy's redrives plumbed as part of the engine oil flow? kevin (just curious)