If a vent is installed without providing a drain larger than an6, oil will be pumped out of the vent even if the vent is installed in the top of the gearbox.

David,

You are correct.  The references I found recommend not running gears mostly or completely submerged in oil.  They said the oil churning by the gears absorbs power and produces heat.  However, after the installation of the larger drain and the vent, I didn’t observe a measurable change in the temperature of the oil exiting the gearbox compared to the original setup.  The reduction of the internal gearbox pressure still may be worthwhile.

Steve Boese



Steve,

               Looks like I will have to add the vent line as already have the  an6 drain.

Thanks Neil.

 

From: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Friday, April 30, 2021 4:00 PM
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: PSRU thrust bearing/washer

 

Neil,

 

With a -6 drain line to the crankcase, air that was initially inside the gearbox is mixed with the oil and this mixture is forced out the drain by an equal volume of pure oil coming in.  Eventually all the air is eliminated and the gearbox is completely filled with oil.  An RD (Tracy Crook) redrive fitted with a -10 (5/8”) id drain and a vent from the upper part of the redrive to the upper part of the crankcase will not fill up with oil and only have crankcase pressure inside.

 

Steve Boese 

On Apr 29, 2021, at 4:25 PM, flyrotary@lancaironline.net wrote:



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Mat,

                Oil into the redrive is needed mainly for lubrication and also heat transfer.  Very little is needed as lubrication needs little with oils these days.  It appears that In most cases the redrive actually fills and does not drain readily.  Why I do not know.  This puts pressure on the seals back and front, which suggests it may be beneficial to hold both seals in with small screws to prevent them getting pushed out.  Screws are good insurance as in flight a detached seal could ruin a good day.

Neil.