Flywheel Seals etc

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103

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My Cygnet SF2A has a 2276cc VW assembled from Great Plains kit. The engine was assembled ~2014 from parts acquired 5-7 years earlier. Currently has about 150 hours.

I grounded it August 4 when it looked like I had a rear main seal issue with oil slinging out of the accessory case. Ordered a rear seal and proceeded to separate the engine from the plane.

It became apparent the main seal was perfect but the face of the crank and flywheel was leaking making a mess. I have a 8 dowel crank and a fiberboard gasket that had failed.

After reviewing situation I have a non o-ring flywheel. We examined options to machine in a groove but there was insufficient parent metal.

Happy to report after calling Art at Great Plains they have updated the 311- 4 dowel and 312 8-dowel flywheel to include a O-ring groove. After confirming I have a O-ring compatible crank I ordered one. It is too much work to pull a engine and a new fiber gasket was just asking to do this again in 1-300 hours.
REF
https://www.thesamba.com/vw/forum/viewtopic.php?t=692467

I will install the new flywheel and source whatever shims I need to set the end play. If you find yourself leaking around the dowel pins review this area and consider upgrading to the O-ring solution.

It is also recommended if you have a 8 dowel crank to use the larger diameter HD washer under the gland nut. I will do this also while I reassemble everything. Hope to be flying again next week I need to do my cross country and schedule my check ride!

Please share your experience with sealing this end of the equation.
 

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Pops

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I have never had a problem from oil leaking from the rear main seal unless the seal was getting wallowed out from a wore out rear bearing. Using stock parts for the flywheel, o-ring, etc never had a leak like you had. I think the o-ring will stop the leak. Why wasn't it there in the first place. Was the flywheel that was used for the 1200cc crank in the 40 Hp that is designed to not use a o-ring, on your crank designed for the latter model flywheel with the o-ring ? Hope I said that correctly :)
 

Hot Wings

Grumpy Cynic
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Why wasn't it there in the first place.
It's my understanding that the 'flywheel' was designed long ago to be a universal fit, thus the larger inner diameter to clear the non o-ring crank.

About lost a finger one time grinding out an o-ring flywheel to fit an older crank using a burr and a drill press.
Had my finger in the "T" slot when the burr snagged the flywheel. :eek::oops::mad: It's still crooked.

Note to OP: Use the metal gasket with the o-ring not the paper. You will need to source one for the SPG 8 dowel pattern. They don't come in the stock gasket kits. Think Porsche 356.

In my experience >50% of the time, with stock VW parts, you get correct end play with 2 30s and a 24 shim. It's a good starting point.........
 

103

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To answer both inquires... I cannot say why the original GP kit did not contain a O-Ring flywheel. Someone elected a fiber seal which rubs me the wrong way when using precision ground shims to remedy. Thus I have a O-Ring flywheel in transit form GP. Confirmed I have a GP O-Ring compatible crank with force one hub near the prop.

Metal 8 hole seals are unavailable off the shelf but I sourced a 4 hole local at Mofoco and used the old flywheel and a custom turned punch to modify the steel seal. Note: 8 holes are not symmetrical ala Porsche architecture to key/lock in the crank flywheel position with respect to the crank with each assembly. I plan to have both the steel face seal and the O-Ring. Too much work to repeat.

I like a dry clean engine compartment and airplane belly. Might be Teutonic dream flying a VW but I will do my part to achieve the ideal!

I will look for the 356 SPG8 gasket! Good to know.

My rear seal was fine but I will replace it with new since I have to pull the shims and re calibrate the stack with a new flywheel. I own two new "elring" rear seal that hail from Germany! I will reset with a fresh one.

Just say no to fiber seals!

Lunch is over...elring main seal.jpeg
 
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