For nearly every oil seal there is a double lip oil seal that fits in the same space.  I used these on rotary engines and transmissions. I also installed a thin "O" ring in the base of each hole so no matter what might happen, the seal would always seal. A seal retainer also was applied so that the seal could not move out of the cavity any amount at all.  When using a double lip seal, add a bit of synthetic grease between the lips so that both lips are lubricated always.  On the main seal I shortened the spring a bit to add a bit more pressure. 

 

My engines did not leak at all but a failed side seal or oil scraper can suddenly dump sump gasses or oil into the case.  Better a few more minutes of power than not.  I also glued them in with GE 100% tub and tile caulk.

 

I had one oil seal escape the tail shaft of a transmission early in life. The tranns got real hot, the hole got bigger than the seal, the seal fell out. The trans lost all of it's oil. I lost the transmission. 

 

Rotaries require a crank case breather to keep such loading off of the seals. Actual airplanes have such breather separators.  Excessive blow by can turn seals inside out and ruin a day, or just generate annoying leaks.

 

Lynn E. Hanover 

 

 

 

In a message dated 2/26/2021 9:00:38 AM Eastern Standard Time, flyrotary@lancaironline.net writes:

 

Finn,

 

Steve posted a picture of three different 5mm bearings back in 2019. The AZK35525 I ordered and received has a bronze inner and steel outer race. I have no idea on the oil seals.

 

Bobby

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Thursday, February 25, 2021 3:28 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: RD-1C input shaft oil seal

 

Thanks Bobby!

When I Google AZK35525 most pictures don't show any races. Not included?

Any significant difference between the Timken and National 350909 seals?

Finn

On 2/25/2021 3:59 PM, Bobby Hughes BHughes@qnsinc.net wrote:

Finn,

 

A few us are / were using the bearing Steve identified. I had 34.5 hours on the new bearing when I sold the RV10. The bearing still look new.

 

5MM needle cage assy  bronze inner race / steel outer race 35mm    AZK35525

35mm

52mm

5mm

7000 rpm

 

My oil seal was leaking and replaced at the same time as the 5MM bearing. The leak was only detectable at idle. A small streak of oil was form below the seal. In flight the oil would blow everywhere making it impossible to located the source.

 

350909

Rear Oil Seal  National Oil Seal

 

 

Bobby – S21 kit has arrived.

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Thursday, February 25, 2021 12:46 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] RD-1C input shaft oil seal

 

So there's a bunch of posts of input shaft oil seal failures.

But what is the recommended oil seal?

I think I've traced my oil leak to that. (Tricky because found drops on
fittings near oil filter base after last flight. But after wrapping
paper towels around the fittings and doing a ground run-up, only traces
of oil is on the outside of them -- likely slung up from the input shaft).

On a different note. January last year I bought a  “INA 81107TN
Cylindrical Roller Thrust Bearing, Polyamide Nylon Cage, Open End,
Metric, 35mm ID, 52mm OD, 12mm Width, 6500rpm Maximum Rotational Speed”
on Amazon for $18.40 to replace the input thrust bearings on my RV-3B.
(The stacked bearings are cutting a groove in the shaft.) Now the same
bearing set costs $135 and up. WTF! Did find SKF 81107TN on eBay for
$30.50. But dang! No inflation?

Finn


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