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Old 07-10-2008, 06:34 PM   #1
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Default Gear Ratio Question.

I have a question about gear ratios, the question is what is the effect of going higher in number value verus going down. Meaning going from like a 6.57 to 6.80 or going in the other direction 6.57 to 6.36. (brushed motor)

I know one gives more torque less top speed the other gives less torque more top speed.

Also Im finally switching over to brushless motors is the gearing going to be the same or is there a big difference in the gearing?

Any help would be appreciated



Steve P.
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Old 07-10-2008, 07:08 PM   #2
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There will be a HUGE difference in gearing between brushless and brushed. As the FDR numbers go up, gearing will decrease, meaning that the motor will make more revolutions compared to one revolution of the entire drivetrain. The higher the FDR, the more the motor turns to turn the drivetrain once, this equates to more tourqe and less motor strain. Running a high gear ratio will be a low FRD, meaning that the motor will spin less compared to one revolution of the drivetrain. this means more top speed and more strain on the motor, batts, and speed control.

To find the FDR of a car, take the spur and divide it by the pinion, then multiply that number by transmission ratio.

In simple terms, a 6.36 will have more top speed than a 6.8.

Hope this helps.

-Kyle
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Old 07-10-2008, 08:15 PM   #3
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Thumbs down I like your post.

A good post.thanks ofr out standing.acer
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Old 07-11-2008, 05:45 PM   #4
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Thanks for the info, Kyle.

I have another question if anyone wouldnt mind answeringthe track that I run at everybody with a brushed motor gear at about 6.5, I will be running in the 17.5 class. Could someone suggest a starting point with the gearing.



-Steve P.
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Old 07-11-2008, 07:41 PM   #5
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I run on a 80x20 carpet track as well as a 120x60 outdoor asphalt track and I've been running the Novak SS17.5 at 4.2 and lower depending on the track layout. The 17.5 is a torque monster and you've gotta use some low ratios to get the speed out of that motor.....just my 2 cents.
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Old 07-12-2008, 11:39 AM   #6
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Thanks. The asphalt track I run is pretty close to the same size, I will give it a try.

-Steve P.
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