flyrotary@lancaironline.net Mailing List Archive

Phil,

Like Ed says a template is good if you have one, personally I would check any template using Lynn's suggested method ( just in case).

Basically seals ( especially apex seals) don't like running over holes (voids). Also as Lynn said an early opening increases overlap and exhaust contamination and a late closing can add to inlet back pressure.

One suggestion to me was that early opening doesn't give much advantage. I would leave the opening as it is ( although there are differences, in different models) I would select the lowest ( earliest) standard opening and work from there. I say this because I got a template from a professional and found the lowest point to be standard in 12 Housings - funny that.

You can't go too high or you run out of inlet wall. I have seen porting ground past the wall and into the water jacket. I have also seen that welded- up with a welder experienced in cast iron welding.

Paul Yaw's web sit has the degrees and you can use Lynn's degree wheel method. I made my own degree wheel.

George ( down under)

Hi Phil

Several have already offered good advise on bits and tools to do the porting job, so I won't try to add to that. However, one question I do have is do you have a template to draw the outline of the port? I recommend one highly - particularly if this is your first porting job.

Porting is fairly easy provided you are careful with the tools and go gently - don't try to hog out to much at one pass. I put several layers of duct tape on the running surface of the side housing all the way up to the outline of the new port - if a bit gets away from you - this tape (or something similar) can prevent damage to the running surfaces by a run-a-way bit. Believe me it can easily happen. I found that out - fortunately on an old junk housing I practiced on.

Ed.

----- Original Message -----

From: wrjjrs@aol.com

To: Rotary motors in aircraft

Sent: Monday, December 03, 2007 11:14 AM

Subject: [FlyRotary] Re: Porting tools?

Phil,

Unless you have the patience of Job don't try to port with a Dremel. It's a fine tool but only for very small work. You need to get a 1/4" die grinder or drill motor. Mikita makes a electric 1/4" die grinder. This is a fine tool, I've been using the same one for 20 YEARS! I also use a flex shaft drill motor with a ball bearing hand piece, again 1/4". Mine is from Domore, but it's ancient. Recovered from a dig like 20+ years ago. It has a foot pedal speed control. I saw a good looking one just like it at a local Woodcraft store @ about $300 for the kit. The cheapest way is the Mikita. You will also need some carbide burrs. Google 1/4" shank carbide die grinding burrs. There are many types. The diamond pattern removes material fastest, and the straight flute smoothes the best. Lots of people polish but it isn't really needed. I like a bead blasted finish personally, but mask carefully or you can ruin the running surface. There are as many ways to do this as people doing it! Good luck. remember max size isn't as important as making all the ports the same size, be consistent.

Bill Jepson

PS. A variable speed unit helps prevent getting into a vibration phase for the cutter and getting "jitters" FWIW

-----Original Message-----
From: Phil White <philwhite9@aol.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Sun, 2 Dec 2007 9:21 pm
Subject: [FlyRotary] Porting tools?

For those who have done porting on the cast iron end housings; what bits/stones/burrs did you use to open up the intake ports? Does it take several types? Which for rough cuts; which for polishing up? I'm ready to work on my 20B, and want to do a mild street port on the intakes. I have a 'dremel' hi-speed tool, but my bit selection is down to 1 or 2 left. What to buy??
Phil in IL RV-10 in process

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