Can someone answer this questions, if = the timing=20 is set at 25 degrees BTDC and the leading fires at 25 degrees BTDC and = the=20 Trailing fires 15 degrees later (10 degrees BTDC) - when does the = third spark=20 event fire, is that another 15 degrees with the leading firing=20 again?

The pulley end keyway points = to 9.00 at=20 TDC ( plug sides) on the housing closest to the pulleys ( = Front/ our=20 rear) - is this what is referred to as No1 housing?

George (down = under)

<snip>

In a message dated 04/26/2005 12:00 Central Daylight Time, = Lehanover=20 writes:

<< In a message dated 04/25/2005 07:00 Central Daylight Time, = jwvoto@itlnet.net writes:

I can look into the spark plug hole and see the apex seal go by, so = are you=20 calling apex seal crossing leading plug TDC?

There are a number of gags to locate TDC close enough to get the = engine to=20 run.

(1)

Remove one spark plug from number one housing. Screw a length of = hose into=20 the plug hole. Put your tongue on the end of the hose. Gently turn = over the=20 engine. When you get a null, where there is no pressure and no suction = on your=20 tongue, that's TDC. Good to within a few degrees.

(2)

Or,

Bend up a piece of welding filler rod so as to make a pointer that = can=20 touch a flywheel (flexplate) tooth. Bolt or clamp the wire to the rear = iron.

Take both plugs out of number two rotor housing.

Turn the engine until you see an apex seal in the center of the = trailing=20 plug hole.

Bend the filler rod so that it points to the center of a flywheel = tooth.=20 Put a white paint drop on that tooth.

Turn the engine in the running direction, until that same apex seal = appears=20 in the center of the leading plug hole.

Put a paint drop on the tooth the rod is now pointing at.

Count the teeth between the paint dots. Divide by 2.

The point half way between the two paint dots is TDC in the number = one=20 housing.

Good to within a few degrees.

Also, you can count the total number of teeth and divide that = number into=20 360 to get the number of degrees per tooth. Paint the correct tooth = yellow and=20 make the rod a permanent piece, for setting accurate timing in an easy = to see=20 location.

(3)

Or,

(Similar to above)

Take both plugs out of number one.

Turn engine in running direction until an apex seal appears in the = trailing=20 plug hole.

Gently turn the engine backwards until an apex seal appears in the = leading=20 plug hole.

Half way between those two events is TDC. With practice, accurate = enough to=20 do by just feel and rocking back and forth by hand and to find TDC = within a=20 few degrees, or close enough to drop in the distributor and have the = engine=20 fire instantly and run fine.

(4)

If you used grease or Vaseline on the side seals, you can have a = plug=20 prepared with the center knocked out of it and a plug in place with a = piece of=20 brake line soldered through the center. Screw this special plug into = the=20 bottom plug hole. Push a length of plastic tubing over the piece of = brake=20 tubing. Pour auto trans fluid through the top plug hole. Reinstall the = top=20 plug. Hold the hose in the vertical. Turn the engine until the fluid = level=20 nulls.

That's TDC number one with a degree.

(5)

The flywheel end counter weight is centered between the plugs on = number two=20 rotor housing. That's TDC number one within about 10 degrees. But you = can get=20 good at it, and get more accurate.

(6)

If you have the front pulley bolt and washer off, looking from the = front=20

pulley end,

the keyway in the 9:00 O'clock position is TDC number one within a = few

degrees.

My TDC rig is for setting up port timings and requires a = disassembled

engine, so that won't help you. Good for inside of one degree.

(6)

Quick and dirty.

Take out either plug from number one housing.

Wet a finger. Hold it gently over the empty plug hole. Turn the = engine in=20

the running direction. When the air quits pushing past your finger, = that's=20 TDC

within 10 degrees or less.

Lynn E. Hanover

<snip>

On 9/19/07, bmears9413@aol.com <bmears9413@aol.com> = wrote:=20

Changing=20 the subject a bit, I want to make sure i have my motor on TDC to set = my=20 timing marks on the flywheel. This is my plan, tell me what you = think. I'm=20 building a fitting to screw in the spark plug hole, and running a = vacuum=20 line to a small suringe (like a insulin suringe). I can eyeball the = rotor=20 location close to TDC, the install this contraption and rotate the = motor so=20 the suringe moves out to the end and starts back in. then back the = motor up=20 again till the suringe tops out. I figure that outa be and accurate = TDC.=20 Whadda ya think???

Bob Mears
Supermarine=20 Spitfire

-----Original Message-----
From: Ed Anderson = <eanderson@carolina.rr.com >
To: Rotary = motors in=20 aircraft <flyrotary@lancaironline.net>
Sent: Wed, 19 = Sep 2007=20 1:16 pm
Subject: [FlyRotary] Re: Strange Ignition?

I do not believe that is a significant = factor, either,=20 Al. After all, we're suppose to do our ignition checks on the = ground=20 before take off {:>). My understanding is that best power = on the=20 13B has ignition timing between 25-28 deg BTDC, so not surprising = that the=20 20B would fall in that range also. Sounds reasonable to me.=20

Ed

----- Original Message ----- =

From: = Al Gietzen =

To: Rotary = motors in=20 aircraft

Sent: Wednesday, September = 19, 2007=20 3:08 PM

Subject: [FlyRotary] Re: = Strange=20 Ignition?

I = wondered if=20 perhaps one issue was that I was doing the ignition check static, = on the=20 ground; where the combination of RPM and MAP would be different = than in=20 the air. But on checking with Tracy 's = spreadsheet=20 on the timing settings, over a fairly broad range above about 4900 = the=20 timing is (should be) in the range of 26 to 28 degrees=20 BTDC.

Al

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