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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.