Quote:
Originally Posted by babetta80
aah, ok. thanks, the according to the pp manual, a fewer teeth on the pinion give the truck better torque, and more teeth give it better acceleration hmm...
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The Propulse manual statement is a little misleading. It should say 'use more teeth for higher speeds' instead of 'best acceleration'.
There's a couple/few things that you need to know to understand how to apply gearing. One thing is gear 'ratios'. The other is the difference between 'high torque' motors and 'high rpm' motors.
Gear 'ratio' is the difference in rpm's between pinion and spur gear. Another way to look it is.. Ratio is how many rpm's the motor is turning in relation to 1 revolution of your rear axle. For example, the stock Propulse pinion is a 13T, the stock spur is 54T. To equate ratio, divide the number of spur teeth by the number of pinion teeth.. 54(t) divided by 13(t) = 4.15
The ratio at the axle in this case is 4.15:1, this is considered a 'low' gear.
Meaning, the motor turns(rpm) 4.15 times for every single revolution of the wheels.
Using a 17T pinion and a 54T spur you get a ratio of 3.17:1, this is considered a 'high' gear.
Meaning the motor has to turn fewer times to make the axle turn one revolution.
High torque motors have more 'low end' power providing fast acceleration. The drawback to high torque motors is most typically won't provide high rpms, hence not being able to reach very fast top speeds. But you can use a higher gear ratio to compensate for that.
High rpm motors have more 'top end' power and can spin faster than most high torque motors. The drawback to high rpm motors is they typically do not have a lot of 'low end' torque and initially will accelerate slowly till they reach their 'power range'. To compensate for that, use a lower gear ratio.
What does it all mean? For faster low end acceleration, use a low gear or a high torque motor. For more 'top speed' use a higher gear or a high rpm motor.
The best situation is to have a strong motor that has a combination of good torque and high rpm's, couple that with a mid-range gear and you have excellent acceleration and good top speeds.
But, when deciding motor/gear options you need to use what is the best set-up for the type of racing and the surface you are racing on.
I am sure that is all as clear as mud..
cheers
(Just to add more confusion: The reason high rpm motors accelerate slowly is due to another ratio.. 'power to weight'. Less torque means less power to get all that weight moving, so a high rpm motor will struggle with a high gear from a standing start)