flyrotary@lancaironline.net Mailing List Archive

Brian,

I found the email explaining how this process should be done. Charlie was correct in that you use both leading and trailing plug holes.

Mark

<snip>

" Joe,

There was a posting some time back explaining how to find TDC, but a search of my archives didn't turn it up. I think it was Lynn Hanover who explained how to do this, but I won't bet my life on that. This process worked for me on my 20B. So, I'll try to explain it for you.

Remove spark plugs for easy engine rotation. On #1 rotor (nearest front cover) rotate the engine in the normal direction until you can see an apex seal in the exact center of the trailing spark plug hole. Mark a convenient tooth on the flywheel. (Helps to make a pointer) Then rotate the engine backwards until you can see an apex seal in the exact center of the leading plug hole. Make another mark on the flywheel using the same reference point as before. Now count the number of teeth between the two marks and place a mark on this tooth. Rotate the engine back again to align this tooth with the pointer. This will be TDC. Now you can mark the crank pulley at the pointer on the front cover, or just use the this new mark on the flywheel instead.

Mark S.

Bill B

Make the pointer so it can be replaced into the same place again and again, or make it part of the engine.

This will get you to TDC within a degree or so. Once you have a TDC tooth on the flexplate marked,

(Or valley between two teeth) count the teeth on the flexplate and divide into 360 to get the number of degrees per tooth. Put the TDC tooth or valley under the pointer on the rear iron (the one with the reduction unit) and turn the engine backwards the number of teeth to get to whatever degree of advance you need to mark. I think Tracy needs a mark at 35 degrees. Normally I run 25 to 27 degrees total at 4,000 RPM.

So mark the teeth with colored paint. Say red for TDC. Yellow for your correct timing say 25 degrees, and green for that set up number at 35 degrees. The 35 is for setting up the controller and you can adjust it back to whatever you want.

If the colors are difficult to see, add white paint to each side of your collors.

Anything between 20 degrees and 27 degrees is fine. The rotors operate at 1/3 the speed of the crank so actual timing at the rotor is very modest, so 27 degrees is 9 at the rotor and so on. Even 20 degrees on low octane fuel is good up to 9,000 RPM.

Lynn E. Hanover

Check under the back seat.

<snip>

On Thu, Sep 16, 2010 at 5:16 PM, Charlie England <ceengland@bellsouth.net> wrote:

Hmmm...

I've seen a variation on that technique for piston engines using a probe in the spark plug hole, but I'm having a hard time seeing how it would work on a rotary. If you do it using just one plug hole, wouldn't that put the center of the rotor face over that plug's hole? Or is that TDC, or is there some geometric characteristic of the rotary gear train that moves the TDC point?

Would the technique work if you used *both* plug locations, & approached one in the forward direction & the other in reverse rotation?

Charlie

On 9/16/2010 1:46 PM, Mark Steitle wrote:

Brian,

I was curious, have you verified that the timing mark you believe to be TDC is actually TDC? I recall it being mentioned before that you can't rely on the timing marks on the pulleys as sometimes pulleys get swapped from one engine to another and may not match up correctly. I feel it is worth checking. Lynn H. has described how to locate TDC (check archives). Basically, you remove the leading plug on #1 rotor, rotate crank until you see an apex seal in the center of the hole, put a mark on the flywheel (use a temporary pointer for a reference point). Then reverse rotation until you see another apex seal in the center of the hole, put a 2nd mark on the flywheel. Now split the difference between the two marks and that should be TDC. Check that it matches the mark on your pulley.

Mark S.

On Thu, Sep 16, 2010 at 1:33 PM, <bktrub@aol.com <mailto:bktrub@aol.com>> wrote:

I've got a 74 x88 catto. The Co was a result of the band clamp not
sealing completely, but I was going to change to 321 or Inconel
any way, so I figured I'd do it now and be done with it. I wanted
to be absolutely sure my timing was correct before going any
further down the tunig road. I checked the timing yesterday, and I
was getting the leading plug firing about 10 degrees in advance of
those two timing marks lining up at 1400 rpm. I adjusted it so
that it is now dead on at 1400 rpm. I set it there as a reference,
it's easy to change in Mode 8. There's no reason to go any further
in the tuning department unless I can be assured that the timing
is correct. I've got a factory manual, but have not found any
reference to the timng marks or exactly what they signify.
Brian Trubee

-----Original Message-----
From: Don Walker <drwalker@gbis.com <mailto:drwalker@gbis.com>>
To: Rotary motors in aircraft <flyrotary@lancaironline.net
<mailto:flyrotary@lancaironline.net>>
Sent: Thu, Sep 16, 2010 11:14 am
Subject: [FlyRotary] Timing

Brian,
Timing is one of the few things I didn't have to mess with. Once
all the other problems were taken care of and the CAS was spaced
correctly, the engine started and ran fine. What a day! I am using
the EC-2 default setting for the renesis as programed by Tracy and
have not even paid much attention to it or even checked it. Good
luck on your next flight. I assume you are using the EM-2 and
EC-2. What prop are you using? You make a good point on checking
for CO. I just have one of those stick on cards and should borrow
a real meter as I am running SS flex tube also.
Don
RV-8 renesis 76/88 cato

-- Homepage: http://www.flyrotary.com/
Archive and UnSub:
http://mail.lancaironline.net:81/lists/flyrotary/List.html

--
Homepage: http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html