flyrotary@lancaironline.net Mailing List Archive

For the mechanical engineering comment of the day; Most o-ring seals REQUIRE a 32 microinch finish. This will NOT happen with a drill. For your injector o-rings you are sealing gasoline. (obviously) No halfway measures here! You simply MUST have a totally leak-free seal. Get the correct reamer. They are easily available in metric sizes. For the best finish leave .002-.005 in. of material when drilling. A 32 microinch isn't mirror-like, rather it is flaw free. (no scratches at all) Usually a shiny surface.

Bill Jepson

-----Original Message-----
From: dale.r@cox.net
To: flyrotary@lancaironline.net
Sent: Wed, 25 Oct 2006 7:50 AM
Subject: [FlyRotary] Re: Rotary Roundup

Hi All, This sounds like a "what I learned from that" moment. Good practice for holes that need to be fluid tight is to drill or bore the hole slightly undersize and then finish the cut with a reamer. Reamers come sized in thousandths of an inch, so it's not usually much of a problem to get exactly the correct size. Moreover, a reamed hole is going to be truly cylindrical, something you can't count on when honing or polishing a drilled hole. A chucking reamer - suitable for use in a drill press - will run about $20 from suppliers like Rutland and ENCO, sometimes considerably less, depending on the size and what's "on sale" at the moment. Good Building, Dale R.
Stephen Brooks wrote:

It appears that I won't be able to attend this years round up, htough I was hoping that I would have time to get there.

I came to SC yesterday, intending to finally take my plane to NC. I've only flown it once in that last 4 months, so I pulled the cowling, checked things out, and started the engine.

After a couple of minutes run time, I shut it down, and checked everything out. I found that I now have a fuel leak from one of the injectors, at the fuel rail. Apparently I have an o ring that is not leaking. I've ordered a new set of seals from Mazatrix, and I'm going to go back to the airport today, and remove the fuel rail so that I can take it back home with me.

When I drilled the fuel rail for the injectors, the holes are not perfectly smooth. I think that the roughness of the bore probably led to the o ring failure. I'm going to polish the bore, without hopefully enlarging it any. I think that I'm going to use a dremel with a fine stone on it.

This weekend I also have to help our yougest dughter and son-in-law frame up a new house they are building.

I hope that everyone has a great time at the roundup, and I hope to make it next year.

Steve Brooks

Cozy MKIV N75CZ

Turbo Rotary 13B

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