Spur Gear Size

Old 08-09-2004, 03:42 PM
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Default Spur Gear Size

Ok, this has probably been fought our before but I cant find the post. My question is : Staying at the same gear ratio, how will changing the size of the spur gear affect acceleration or top end?
For example a 100/25 for a ratio of 4:1. Now change the gears to 80/20 for a ratio of 4:1. Now does the car seem to accelerate quicker because the motor winds out earlier? And with the 100/25, the motor pulls longer because it takes a little longer for the motor to reach top end?

Does this even affect anything. I would like to know for sure before I go out and spend 40 bux on gears to adjust for the different style tracks I run on. One is tight and small and another is a pretty flowing, open large track.

Thanks for any help
T
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Old 08-09-2004, 04:17 PM
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the bigger the spur, the smoother the acelleration.....
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Old 08-09-2004, 06:05 PM
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Default Re: Spur Gear Size

Originally posted by Torqer
Ok, this has probably been fought our before but I cant find the post. My question is : Staying at the same gear ratio, how will changing the size of the spur gear affect acceleration or top end?
For example a 100/25 for a ratio of 4:1. Now change the gears to 80/20 for a ratio of 4:1. Now does the car seem to accelerate quicker because the motor winds out earlier? And with the 100/25, the motor pulls longer because it takes a little longer for the motor to reach top end?

Does this even affect anything. I would like to know for sure before I go out and spend 40 bux on gears to adjust for the different style tracks I run on. One is tight and small and another is a pretty flowing, open large track.

Thanks for any help
T
As a general rule of thumb, the larger the spur you will get more torque from the motor. The smaller the spur, the motor will spool up faster.
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Old 08-09-2004, 06:27 PM
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Default Spurs/pinions

So....what spur/pinion combo is better for stock touring cars and which one is better for racing mod?
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Old 08-09-2004, 07:13 PM
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If your ratios are the same, where you top out is the same. 25/100 is the same as 20/80. The only difference is in the weight distribution on the chassis.
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Old 08-10-2004, 01:10 AM
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theoretically there will be differences in performance (can't remember exactly what those differences are) but not the sort of differences you would be able to notice... the only thing even worth noting is the change in weight balance as the motor is shifted, but even that would be a subtle difference.

IMO, not really worth changing gears (to achieve the same ratio) unless you are a really top level driver
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Old 08-10-2004, 01:53 AM
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Default Weight distribution DO matter...

On my chassis, the motor sits lower with a bigger spur, so with a bigger spur I gain lower center of gravity. And the motor is quite heavy, about 10% of the total weight of the car, I think...

If the motor move in / out side, while adjusting gear mesh, you in general want it to be as close to the center as possible.
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Old 08-10-2004, 02:52 AM
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Dosen't your motor hit the ground when you race
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Old 08-10-2004, 03:21 AM
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No. The lowest part of the motor is aligned with the lowest part of the chassis buttom.
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Old 08-10-2004, 10:27 PM
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Ok, well thanks for the help guys. I run an Atlas ym34 type t so weight distribution isnt that big of a deal as the motor moves up and actually moves very little when it does. Thanks anyways and again I appreciate the help.

Torq
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Old 08-11-2004, 04:55 PM
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Another point for a larger spur gear is the smaller pinion would be lighter!
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