Spur Gear Ratio: Optimal Ratio Explained

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In summary, the optimal spur gear ratio is one that meets the needs of the application, with a range typically between 1:1 and 1:6 and a pitch line velocity of up to 25 m/s. The minimum number of teeth for a gear with a normal pressure angle of 20 degrees is 18, and the preferred number of teeth includes integers that do not share common factors to ensure even wear. A good search term to use is "optimal".
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Single stage spur gears ratio
What is an optimal spur gear ratio?
 
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The ratio that best meets the needs of the application. A good search term is the word optimal.

That answers the wrong question, then you need to more carefully word your question.
 
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About 6.5 to 1
 
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https://roymech.org/Useful_Tables/Drive/Gears.html#Design said:
A single spur gear is generally selected to have a ratio range of between 1:1 and 1:6 with a pitch line velocity up to 25 m/s. [...] The minimum number of teeth on a gear with a normal pressure angle of 20 desgrees is 18.

The preferred number of teeth are as follows
12 13 14 15 16 18 20 22 24 25 28 30 32 34 38 40 45 50 54 60
64 70 72 75 80 84 90 96 100 120 140 150 180 200 220 250
 
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The p/q ratio should involve integers p and q that do not share common factors, so the gears will wear evenly, with a "hunting tooth".
 

FAQ: Spur Gear Ratio: Optimal Ratio Explained

What is a spur gear ratio?

A spur gear ratio is a measure of the relationship between the number of teeth on two interlocking gears. It is calculated by dividing the number of teeth on the driven gear by the number of teeth on the driving gear.

Why is the optimal gear ratio important?

The optimal gear ratio is important because it determines the speed, torque, and efficiency of a gear system. Choosing the right ratio can improve the performance and longevity of the gears.

How do you determine the optimal gear ratio?

The optimal gear ratio can be determined by considering the desired speed and torque of the system, as well as the size and number of teeth on the gears. A higher gear ratio will result in greater torque but lower speed, while a lower gear ratio will result in higher speed but lower torque.

What is the difference between a high and low gear ratio?

A high gear ratio means that the driven gear has more teeth than the driving gear, resulting in a slower output speed and higher torque. A low gear ratio means that the driven gear has fewer teeth than the driving gear, resulting in a faster output speed and lower torque.

Can the gear ratio be changed after the gears are manufactured?

Yes, the gear ratio can be changed by replacing the gears with ones that have a different number of teeth. However, this may require redesigning and rebuilding the gear system, which can be costly and time-consuming.

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