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Gear size?


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#1 Upfront slot cars

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Posted 21 July 2016 - 07:48 AM

What is the OD of a Parma 31t crown gear?


Andrew Ford




#2 Ramcatlarry

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Posted 21 July 2016 - 11:54 AM

31t: 0.760";  30t: 0.743"


Larry D. Kelley, MA
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#3 John Luongo

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Posted 06 August 2016 - 08:31 AM

Don't forget tire roll out (circumference) when making gear ratio calculations. For example: for every .020" trim or increase in diameter for a 1" spec tire, your driven gear should change one tooth to maintain the same tire roll out, the distance covered by the tire's circumference. So, shorter tire with same gear ratio will cover less distance on the track needing a numerically lower gear ratio to cover the same roll out.

 

I have found that sometimes, depending on the local rules regarding tire size, a slightly different tire diameter change up or down will allow me to retain the same gear ratio that my motor likes without sacrificing torque/RPM.

 

Ever drive a car that for "some reason" got faster as the race went on? Overall gear ratio was altered by tire condition/wear to a combination that the motor liked.

 

Best,

 

John


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#4 John Luongo

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Posted 08 August 2016 - 08:03 AM

nice gear ratio chart on pro slots web  that takes into account tire size in relation to final drive ratio.


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