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From: Lehanover@aol.com
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Date: Sun, 24 Apr 2005 10:59:45 EDT
Subject: Re: [FlyRotary] Re: Apex Slot Wear/ Grinding for 3mm Seals
To: flyrotary@lancaironline.net
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In a message dated 04/24/2005 03:21 Central Daylight Time, 
lendich@optusnet.com.au writes:

<<  Lynn,
      Ken Welter reported accelerated slot wear after machining his rotors
   for 3 mm seals.......Granted Ken is pulling about 300 HP for takeoff using
   nitrus oxide........It was mentioned that the hardened layer at the rotor 
   tips was lost due to grinding for the 3mm seals........Do you  know what
   hardening process is used (induction, etc) and whether it could be 
   restored........Your take on this please Lynn or anyone !!
   --
   Kelly Troyer 
   Dyke Delta/13B/RD1C/EC2 
  >>


I was unaware of the hardening process if any. I have only seen 5 or 6 rotors 
with worn grooves in 30 years of looking. 

Any number of processes are available, like electron beam, induction. Spray 
metal and maybe ceramic buildup and remachine. I try not to build more than one 
engine per year, and that would be one of mine. I rebuild the engine spare 
engine from last year to be the race engine for this year, and include any ideas 
or changes. Last years race engine becomes the spare. 

I have a guest engine to do shortly, but even that engine has good grooves, 
and it has been raced for years with iron seals and a stock oil pump. One 
rebuild on this engine was required when a piece of safety wire about 3/16" long 
found its way into the intake, and took out an apex seal, rotor and housing. 

I just picked up a set of lightened rotors in exchange for the rebuild. They 
look fine to me. I have repaired damaged rotors. Filling in dents and gouges. 
Even along the seal groove. They weld up well and a diamond file in the groove 
gets things straight again.

I note that Racing Beat uses large amounts of top oil in when pulling huge 
numbers from their turbo 3 rotor. I don't know if that is injected through the 
housings or premix (or both).

When my wife's RX-3 ate a seal, the groove was an obvious "V" shape. It was 
not a case of metal pushed aside. It was missing. Plus, the seal was much too 
short 
(it fell out of the groove) and much too thin. 
The side seals were alarmingly too short. It should not have started much 
less pulled the car around. The car was owned by a teenaged girl who drove it 
through 4 years at Ohio State University. I may have been the first person to 
remove the oil drain plug. I think in that case, the lack of lubrication was the 
cause of the failure. 

I think a good synthetic oil supply as premix, and an effective air cleaner 
prolong engine life to the degree that it just becomes boring. A good thing in 
an airplane engine.

Lynn E. Hanover