Mailing List flyrotary@lancaironline.net Message #68005
From: Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] PSRU REAR Seal
Date: Sun, 12 Apr 2026 18:25:23 -0400
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Thanks, yes I looked at that.
0.25" wide but should be OK. Also the slighter less than 1.5" seal OD can be handled with RTV or other sealant. 

But look at this from  SKF's web site:
Limiting speed 3 840 r/min
Maximum operating temperature 212 °F
Minimum operating temperature -40 °F
Permissible circumferential speed 1 002 ft/min
Rotational speed 3 840 r/min

Limited to 3,840 RPM?

Shaft circumference: 1"*Pi/12 feet.
1002/Pi*12 = 3,827 RPM.

This is for the input shaft where we might see as high as 7.500 RPM (at least on the Renesis).

Doesn't mention max pressure but I've seen 7 psi elsewhere. Shouldn't be a factor if well vented (big PSRU oil return line and good engine "crankshaft" (oil pan) vent).
I'm increasing my PSRU main oil return line to 1/2" NPT -- 3/4" ID hose and also cutting a small groove in the mount plate behind the input shaft thrust bearing race to allow oil that makes it to the seal to drain.

Finn

On 4/12/2026 4:39 PM, DOUGLAS LOMHEIM dlomheim@aol.com wrote:
Fin:  this is the PSRU “rear seal” that Dennis installed in the “C” model on my 7A w/Renesis in 2024ish.  
Doug


Sent from my iPhone

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