Flathead question

[fuel pump]

I have a question about the function of the chamfer on a flathead ring gear. I know the chamfer on the pinion gear (on the starter drive) helps the pinion fully engage the teeth on the ring gear during the starting cycle. But the teeth on flathead ring gear (unlike a small block Cevy) also have a chamfer on them. Why is it the chamfering needed? My guess is it helps disengage the pinion after the engine fires and you turn off the starter. The sbc starter has a spring to pull the pinion out of engagment but the flathead starter does not. Is this the reason? http://www.jalopyjournal.com/ubbthreads/images/graemlins/confused.gif

[Bruce Lancaster]

I think your reason (disengagement) is correct--my slightly fuzzy perception is so: The pinion gear is screwed forward to engage by the spinning of the flyweight as the electric motor turns; It then spins backward as the flywheel whacks it on startup. I think the chamfer aids engagement in one direction and then cams the gears the final fraction out of engagement the other way. I'm going to go home and stare at some hardware on this one--I've never studied the flathead starter drive much because I've never actually had any trouble there!

[mtflat]

Doesn't the flathead starter spring help retract it from the ring gear? I've replaced a bunch of them. It engages by means of the worm gear and the spring assists it's return. I suspect the chamfer on the ring gear helps the process.

[hatch]

It has something to do with the "Red Wheel" effect.

[286merc]

Winter must have arrived in force for you guys.
Instead of studying ones navel for the next few months we resort to the deep dark mysteries of one of Henry's finest.

[Digger_Dave]

As Bruce said; flathead starters have a shaft that has a "thread" on them. When the starter is energized the shaft rotates and "pulls" the pinion gear into the flywheel. Ford found that without a chamfer on both the pinion gear AND the ring gear, the pinion wouldn't always engage. (the pinion is rotating by the time it gets to the flywheel)

The spring on the flathead starter acts as a "shock absorber" on engagement.

SBC starters are "pushed" staight into the ring gear (by the solenoid) before the starter starts to spin. (only needs chamfer on pinion teeth)

[Bruce Lancaster]

"Winter must have arrived in force for you guys.
Instead of studying ones navel for the next few months we resort to the deep dark mysteries of one of Henry's finest."
Oops--too late. Couldn't get the flywheel chiseled loose from the permafrost--will have to study navel instead.