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Originally Posted by Chuck Merja
Interesting, but a couple clarifications.
Do you really direct drive an 8" wheel - seems like you would be getting surface speeds on the wheel of almost 4 times the max ball speed, so you are either losing a lot of energy in the energy transfer to the ball, or your exit velocity might be too high.
I think you get backspin, not topspin, so you're shootin' a 9 iron, not a 3 wood (I'm not a good enough golfer to use a driver)  This is probably fine for "short" shots, but might limit your range. |
Yes, we're direct driving the 8 inch wheel with the big CIM. I wonder where you get your 4x estimate? Here's the calculation as I see it:
As a rough estimate, we assumed the wheel would present only minimal load on the motor once up to speed, so would be spinning at about 2400 RPM, near it's no-load speed. The speed at the edge of the wheel will be about
(2400 rev/min) * (1/60 min/sec) * (8*3.14 in/rev) * (1/40 meter/inch) = 25 m/s
With a single wheel system, the speed of the ball is half the edge speed of the wheel, assuming no slip. So we're pretty close to the 12 m/s limit right at the wheel, and there will be loss in the shooting track. I doubt we're over speed at all.
You're right, this design is all about backspin. I'm not a golfer, but in tennis backspin slows down and lifts the ball, flattening out the curve and lengthening the range. This seems like all goodness.
Bill