flyrotary@lancaironline.net Mailing List Archive

Hi Matt

I wouldn’t imagine pressure is a contributing factor, however the quantity of oil and churning losses generates heat.

I found this study - "Experimental Investigations on Churning Power Losses Generated in a Planetary Gear Set" https://www.researchgate.net/publication/321990749_Experimental_Investigations_on_Churning_Power_Losses_Generated_in_a_Planetary_Gear_Set

This study references the following further studies below:

Is there SIGNIFICANT power loss or heat generation that can be easily rectified by enlarging the drain and adding a breather?

Could someone read summarise and present a conclusion 😀

I’m guessing Steve B has already done this work.

Steve, were you interested in losses and heat generation, or seal problems associated with pressurisation, or both?

Cheers

Steve Izett

Anderson, N.E., Loewenthal, S.H., Black, J.D., An analytical method to predict efficiency of aircraft gearboxes, NASA TM-83716, USAAVSCOM TR 84-C-8, (1984).

Boness, R.J., Churning losses of discs and gears running partially submerged in oil, Proceedings of ASME International Power Transmission Gearing Conference 1989, (1989) 355-359.

Changenet, C., Velex, P., A model for the prediction of churning losses in geared transmissions – preliminary results, J. Mechanical Design, 129, 1 (2007) 128-133.

Changenet, C., Leprince, G., Ville, F., Velex, P., A note on flow regimes and churning loss modeling, J. Mechanical Design, 133, 12 (2011) 5p.

Durand de Gevigney, J., Ville, F., Changenet, C., Velex, P., Tooth friction losses in internal gears: analytical formulation and applications to planetary gears, Proc. IMechE Part J: J. Engineering Tribology, 225, 5 (2013a) 476-485.

Durand de Gevigney, J., Changenet, C., Ville, F., Velex, P., Becquerelle, S., Experimental investigation on no-load dependent power losses in a planetary gear set, Proceedings of International Conference on Gears 2013, (2013b) 1101-1112.

Höhn, B.R., Michaelis, K., Völlmer, T., Thermal rating of gear drives: balance between power loss and heat dissipation, American Gear Manufacturers Association Document, 96FTM8, (1996).

Kahraman, A., Hilty, D.R., Singh, A., An experimental study of spin power losses of planetary gear sets, Proceedings of International Gear Conference 2014, (2014)

Kolekar, A., Anant, S., et al., Windage and Churning Effects in Dipped Lubrication, Journal of Tribology 136.2: 021801, (2014)

Krantz, T.L., Experimental and analytical evaluation of efficiency of helicopter planetary stage, NASA TP-3063, AVSCOM TR 90-C-001, (1990).

Luke, P., Olver, A., A study of churning losses in dip-lubricated spur gears, Proc. IMechE Part G: J. Aerospace Engineering, 213, (1999) 337-346.

Macmillan, R.H., Power flow and loss in differential mechanisms, J. Mechanical Engineering Science, 3, 1 (1961) 37- 41.

Pennestri, E., Freudenstein, F., The mechanical efficiency of epicyclic gear trains, J. Mechanical Design, 115, 3 (1993) 645-651.

Radzimovsky, E.I., How to find efficiency, speed, and power in planetary gear drives, Machine Design, 11, (1959) 144- 153.

Terekhov, A.S., Hydraulic losses in gearboxes with oil immersion, Vestnik Mashinostroeniya, 55, 5 (1975) 13-17. Velex, P., Becquerelle, S., Analysis of no-load dependent power losses in a planetary gear train by using thermal network

method, Proceedings of International Gear Conference 2014, (2014), 615-624.

On 24 May 2021, at 4:53 am, Matt Boiteau mattboiteau@gmail.com <flyrotary@lancaironline.net> wrote:

I've always had a crankcase breather filter on the engine, but while I was testing I wanted to see what kind of actual pressures were developed inside the system. It was more a FYI.

I guess in my subject I should have clearly stated this is Neils PSRU design. Waiting for Neil to chime in on the difference between his and Tracy's PSRU, but the prop shaft bearings ride on Tapered Roller Bearings. The oil inlet is on the front half with 1/4npt return on the side. There is also a 3/8npt return on the bottom of the rear section.

My whole post was basically saying, gravity return isn't enough. The psru still gets pressurized even with the smallest of restriction. Putting a vent line on top, turns into another pressured outlet for the oil to return. Still, a vent line on top I'd recommend to help the returns.

I have a temperature prob in the PSRU. I could be wrong, but having the psru gears pressurized would cause more heat? I'll see what the datas shows.

- Matt Boiteau

On Sat, May 22, 2021 at 12:10 AM David Leonard wdleonard@gmail.com <flyrotary@lancaironline.net> wrote:
Ok, Here is my third comment. Yes you should absolutely vent your crankcase. In addition to the stock vent located on the oil filler neck, I also eventually installed an additional 1/2 in. vent. Both of these lines go through an oil/air separator which is vented in the low pressure slipstream and drained out the gear leg. And still it is not perfect, but improved since the early hours.

As an aside, I can tell you that increased blow-by is usually the first indication that I am due for an engine rebuild (among several other more imminent indications like a sudden loss of power). I recommend keeping track of blow-by (how much oil is caught by the oil air separator). If you start getting a lot of oil in the can, you will need a rebuild soon.

Dave Leonard
Turbo Rotary RV-6

On Fri, May 21, 2021 at 6:19 AM Matt Boiteau mattboiteau@gmail.com <flyrotary@lancaironline.net> wrote:
I played around the past few days with oil and psru. I added a psi gauge on top of psru,and vented the housing back to the oil dipstick tube. I have an oil breather tube from the fill port. We should have a vent on the oil crankcase. Without it, I did a pull and turned off the engine and 5psi stayed within the system until I cracked open the dipstick to relieve the pressure.

On Neil's PSRU, the oil inlet is on the front half. The front drain is on the side, which connects to the back drain that is an10, then to the oil pan.

Anyways, the stock psru inlet restrictor was 9/64. Once warmed up and running at 2200rpm static on the ground, engine oil is about 100psi for me. PSRU pressure was about 2.5psi and lots of oil was venting back into the oil dipstick tube. I kept on sizing down the restrictor until 1/16th. That mostly kept the vent clean and clear of any pressure build up inside the psru.

I'm not sure why Tracy recommends having the psru fuel of oil, maybe uses different bearings then Neil's? From a truck gear case perspective, plantey gears only need a coating of oil, not full and pressurized. I'm probably wrong, but throwing it out there. ?.?

- Matt Boiteau

--
Homepage: http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html