Quote: Maybe slightly interesting, how many note that only odd tooth counts are used on gears and why?
Not always odd count for both:
3:23 42 teeth ring 13 teeth pinion
4:57 32 teeth ring 7 teeth pinion
4:86 34 teeth ring 7 teeth pinion
As was explained to me once by an engineer:
The reason for having ratios that are in the decimals is that with each revolution a single tooth on the pinion will not contact the same tooth on the ring with every revolution.
The pinion tooth advances one tooth per revolution so that it will contact each tooth on the ring gear through numerous revolutions.
Hope I explained that correctly.
Frank
Find another engineer.
There are repeating and non repeating patterns, not to mention the one tooth theory is wrong. I'm going to use Ford 9" ratios, since they are the most common.
A 3.00 is a common pickup gear and has a 13/39 tooth count. Each pinion tooth hits the same 3 teeth on the ring and is a repeating pattern. A 3.50 ratio has 10/35 and each pinion tooth hits the same 7 teeth during 2 rev's and is (semi) repeating.
As to the "one tooth" theory. A 3.08 ratio has 13/40 teeth and each pinion tooth is one tooth off, so after 3 pinion rev's it has went 39 teeth and is one tooth off the 40th tooth. A 3.23 ratio is 13/42 - again, after 3 rev's has went 39 teeth, but it is 3 teeth away. A 3.55 has 11/39 so 3 turns, 33 teeth, 6 off. Follow?
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