Glenn,
I don’t want to nudge you too far out of your comfort zone, but all you have to do is look at the external workings of the stone-simple Apollo impulse to understand how it works.
The lower arrow in photo 1 shows a catch-weight (pawl) resting in its slot on the Apollo impulse coupling. There are two catch-weights 180° apart. As the name implies, they engage by weight alone. The upper arrow points to the non-impulse, direct drive coupling on the right mag.
The left arrow in photo 2 shows the direction of rotation. The right arrow points to the very shallow step or catch. As a catch-weight approaches the 12 o’clock position, it falls within its slot and is then caught by the step. Once caught, the internal impulse spring is wound for start-up. This engagement is rather tenuous and the shallow step is easily jumped by the catch weight if the rotation is too fast. Furthermore, since these parts are open to the environment, the step area and catch-weights need to be kept super clean and dry. A film of oil can keep a catch-weight from free-falling and even the slightest ramp of oily dirt at the step will make the catch-weight jump free like a California skateboarder.
The impulse stops functioning when the Kinner is turned faster than 80 r.p.m.
The next time you’re near Mark’s Fleet, open the left cowl door and check-out the Apollo.
Best,
HT & V
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