REFLECTOR: Breather tube

[Jones Nick]

Ruben, the best position is facing aft. The last thing you want to do is pressurize the crankcase. Also, on the certified aircraft there is a relief hole in the tube just inside the cowling to prevent the crankcase from becoming pressurized in the event the tube freezes up with ice.

The ideal situation is to create a vacuum in the crankcase. This helps prevent leaks, increases horsepower (and efficiency) although slightly. Back when I raced cars, I would weld in a fitting at the exhaust collector cut at a 45 degree angle to use the exhaust to pull a vacuum on the crankcase trying to get every ounce of power from the engine.

Best regards,

Nick and Connie Jones
Velocity XL-RG
N10CN
99% done 90% to go

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Ruben Creus
Sent: Friday, March 02, 2012 11:55 AM
To: 'Velocity Aircraft Owners and Builders list'
Subject: REFLECTOR: Breather tube

I had to temporarily remove the breather tube the other day to work on some wiring stuff. When I place the tube back in place and looking at it,  I thought that as the tip of the breather tube that exits the cowling is cut in a 45 degree angle, then I assumed that if I place it facing the nose I guess it would have air pressure pushing into the tube. If I place it facing the tail, then the air around the tube it might create low pressure and therefore pushing the air out of the tube creating suction. If I place it facing the wing, the air would just travel passing the tube with no effect.

I guess all this rational also depends on the air pressure inside the breather tube coming from the engine, so I did several tests, facing the tube in this three positions and flying a bit. My tests concluded that when the tube is facing the tail It seems I have more oil coming from it as the cowling seems more oily , but is was hard to conclude as the oil leaving the tube could end up how knows where. And where the tube is facing can also impact where the oil will eventually go. Showing all my test were kind of inconclusive.

So, guess the main question is that if you know what is the proper positioning of the 45 degree opening, nose, side, or tail, or if it really matters?


Ruben G. Creus
? +1.571.215.0025
* ruben at vainneg.com<mailto:ruben at vainneg.com>







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