Yes, you have to use full perimeter length.
I LOVE this forum. You guys catch all the details and that's great.
I agree, in fact, I was going to have Racer do that as part of his homework assignment.
The actual max outside diameter of the gear is 4.4 mm. I put 5 mm in the equation to allow for a little extra length. And then hoped and prayed that no one would catch the lazy math. I was also hoping the lawnmower crankshaft would ignore the math error too.
But it is true, we need to take account for the entire gear profile. So we could be pushing the upper limits on the poor lawnmower crankshaft.
Although in truth, we're only guessing at what it can handle to begin with. I supposed I should actually look into what they can actually handle.
Just based on life's experience I can kind of tell that this should work. At worst case we might be pushing the crank to its limits. It'll be the battle between the crank and the brass to see who wins out.
My goal is 420 gears. If I can get it to punch out 420 gears before it goes kaput I'll consider that a win.
Just off the seat of my pants I'm confident enough here to continue with the build of the punch press. We're certainly close to being in good shape.
Obviously if we had a crank from a larger engine we'd have more leeway. But I don't have a larger crank. And I'm too cranky to go looking for one.
I trust this little lawnmower crank can pull it off.
I'm thinking of going with the half-hard brass anyway. These calculators aren't likely to be used extensively. Chances of them wearing out are slim. They'll probably end up being purchased to sit on a display shelf and only used on rare occasions to show how they can add a few numbers up.
As a practical matter we could probably go with soft brass gears. Not sure about that. But surely half-hard would be good enough?
What do you think?
Would full hard brass gears be better? Push the lawnmower crank to its limits?
I'm game.