Hangar Flying

Hangar Flying => Hangar Flying => Topic started by: PatrickMc on April 29, 2011, 11:10:56 PM

Title: Air oil separator.
Post by: PatrickMc on April 29, 2011, 11:10:56 PM
Ok, tired of moving the oil breather to find the best place to keep the mess down.  It's just all over the place. Looking through spruce and wicks there are many choices.  Anyone have first hand experience with any separators please let me know which one to get.  I really dont want to have to test a bunch to find the one that works best.
Thank you,
Title: Re: Air oil separator.
Post by: easyrider on May 06, 2011, 04:02:19 PM
I use the ACS Slime Fighter which is popular with Van's Air Force.
I have had it fitted for about 20 Hrs with no problems.


Title: Re: Air oil separator.
Post by: A. Bruce Hughes on May 06, 2011, 06:30:12 PM
Oil/air separators are important if the aircraft belly is BEHIND the
engine; you can save cleaning the belly.   The little oil that you
will be losing into the exhaust is insignificant.   I assume that you
check the oil before every flight and change oil often.  The separator
takes up precious space and is useless for pushers.   Save your $$$

Bruce Hughes
Title: Re: Air oil separator.
Post by: A. Bruce Hughes on May 06, 2011, 06:36:35 PM
Well, the email went on its own.   I meant to say that I was NOT an engineer.

I am just quoting a Longeze owner/mechanic that knows FAR MORE about
engines than I will ever know.   He (and I) just run a LARGE diameter flexible
tube (with a cut at the highest point to allow for pressure release in case
of a plugged tube)(and springs inside to prevent tube collapse).   The tube
goes to the trailing edge of the wing.

Bruce Hughes    :)
NOT an engineer or mechanic
Title: Re: Air oil separator.
Post by: PatrickMc on May 17, 2011, 09:16:44 AM
Actually I would not call it a waist for carard A/C.  Currently mine is making a mess on the cowl, in the cowl, and on the prop.  I have moved it several times and other then extending it far from the A/C surfaces to get it into the free airstream, a separator looks pretty good.  I was going to extend it to the end of the exhaust to have it burned up and carried away by exhaust gasses but a local A&P said he would be concerned that it might ignite!  Not sure if that would happen.  I have seen pics of this application on CSA.  Any experience out there with this application?
Title: Re: Air oil separator.
Post by: Bill James on June 07, 2011, 10:54:41 PM
The VariEze 0-290’s initial propensity for spewing oil vapor was calmed by repositioning the case breather outlet to a welded fitting in the mag hole cover plate. I had been warned of significant wet vapor expulsion from the stock case vent by the prop flange and they were right. But now the oil laden vapor loses some energy coming up into the accessory case before coming out the upward directed 90 in the mag hole cover plate. From there the exit hose crosses over the accessory case into a custom air/oil separator at the upper firewall, then aft under the pushrod tubes to the aft cowl opening.
The air/oil separator is made from an aluminum automotive air conditioner “dryer” I believe it's called, one of dozens discarded in the corner of a friend’s a/c shop. I cut it open and cleaned it out and fitted it with a middle baffle plate and some stainless steel mesh. If I had known exactly where I was going to mount it on the upper firewall I would have shaped it slightly differently. It already had one ¾ inch tube outlet at a good location and another was welded on for the breather hoses.
Another smaller tube is welded on the bottom corner of the separator with a gravity-return tube for the condensed oil. While the tube should be suspect of several irrational design flaws, including the fact that it would have equal and opposite pressure on both ends during engine operation, it has none of the negatives that I expected, and works splendidly probably due to an overall bow to gravity. The return fitting for this drain/return tube into the case is just above the case/sump joint where it does not spew diabolical green alien acid on the cam. I appreciate that concern and have taken defensive steps but have noticed several other things to actively pursue and defend against, like not running out of fuel or into the ground, and just let this contraption do what it does so well with a cleaner and dryer aircraft posterior. It is free flowing and retains the same diameter of the standard case vent through the entire length of the tubing and separator. The “clear” tubing adheres to the strict direction in the plans  :)
This air/oil separator is robust and could (and has been) mounted in many different locations. It was especially useful during the early engine operation, although the oil vapor floating around the aft end of the plane in flight revealed many things about how air does and doesn’t follow the rules back there. Very interesting and enjoyable, especially once I got to where I could control the blowby. And now there is no reason to remove it  :)
A side note -  early on, breaking in the steel cylinders and chrome rings, a sage A&P that helps with engine stuff every annual stated/suggested that everything else being equal, the rings and cylinders would seat and the blowby would calm down on its own at about 100 hours. He was exactly right.