Contrails ! Jabiru spark

Amazing pictures

Lynn Matteson is a clever photographer and Jabiru boy. Those most unusual distributor pictures are reproduced with his kind permission.

Playing with a distributor

Photo Lynn Matteson

I just replaced the caps and rotors on my 2200, and decided to have some fun with the old parts.

I bored 3/4" holes into one cap between the four spark plug wire terminals, and hogged out as much material as I could and still retain the strength of the cap. I then installed the cap and wires and fired up the engine.

Using my digital camera, I got one shot out of the seven I took which showed the spark jumping the gap from the rotor to one of the segments...no big deal, just for my amusement.

Camera settings

Shutter speed 1/90 sec

ISO 200

f/2.8

Focal length 6.7mm

I had set the camera to "sports action". The camera is a Kodak Easy Share DX6490

Calculations

The shutter speed vs idle speed calculations work out like this :
Idle speed of (say) 900 rpm divided by 60 sec = 15 rps crank speed divided by 2 = 7.5 rps cam (or distributor) speed times 360 degrees = 2700 degrees of rotation divided by 90 (1/90 shutter speed) = 30 degrees of rotation during which the shutter fired.

Now I ask you...how lucky was I to get the rotor in just the exact position to see the exact time that the spark fired ? DAMN lucky, I'd say.
And I just went back and checked, and I had only made 6 shots, of which this shot was number 4, so that makes it even more of a "lucky dog" shot...to borrow a phrase from NASCAR : )

Maybe somebody knows the speed of the spark as it occurs in a internal combustion engine, I don't. But given a pretty short duration, that makes this shot even more lucky.

Lynn Matteson