Al,

Depending on exactly which housings you have, that method may be off by more than 10 degrees.  See the attached photo.

Steve Boese

Of course there is always the way that doesn’t require any parts – well; maybe a piece of wire, or something to use as a pointer near the teeth on the flywheel ring gear.

-Remove the rotor 1 spark plugs (and one from rotor 2 to relieve the compression).

-Turn the engine until the tip seal on rotor 1 is in the center of the leading plug hole.  Mark the gear tooth at the pointer.

-Turn the engine until the same tip seal is visible in the trailing plug hole. Mark the tooth at the pointer.

-Now turn the engine back to the gear tooth at the pointer that is half way between the 2 marked.  The tip seal is now at TDC.

-The center of the combustion chamber is 60^o on the rotor from the tip seal; or 120^o on the E-shaft.

- Count the total number of teeth on the ring gear, and divide by 3. Now rotate the engine by that number of teeth (either direction) and rotor 1 will be at TDC.

Al G

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Steven W. Boese
Sent: Sunday, February 27, 2011 4:10 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Steve Boese TDC Finder

I like this better than what I came up with.  It will be easier to find the parts and assembly will also be easier since none of the initial parts need to be modified.  As long as one is careful not to draw the water or oil into the engine, it will also be easier to use.  Although there always seems to be a better way to do something, this seems as good and simple as it can get.  No more excuses for not knowing where TDC is.

Steve Boese