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Old 07-25-2006, 08:55 AM   #1
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Default Newbie Questions on Gear Ratio and Rollout

I would like to know the basics of selecting gears and gear ratios. I've been doing some searching but haven't found any solid info yet. I've been to gearchart.com and have been able to make a chart based on my current setup but I don't know exactly what I'm looking at.

My current setup is 98 tooth spur and 21 tooth pinion for a ratio of 11.38. Is there a certain gear ratio range I'm looking to hit?

I also understand rollout to be distance traveled per revolution of the motor. How does this relate to gear ratios?

If there is a good explination of all this somewhere please point me in the right direction.
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Old 07-25-2006, 09:14 AM   #2
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slamman,

you're not alone. many have asked this question in the past, and many will ask it in the future. the answers should be found in the following links:

http://www.rctech.net/forum/showthre...hlight=rollout
http://www.rctech.net/forum/showthre...hlight=rollout
http://www.rctech.net/forum/showthre...hlight=rollout
http://www.rctech.net/forum/showthre...hlight=rollout
http://www.rctech.net/forum/showthre...hlight=rollout
http://www.rctech.net/forum/showthre...ighlight=ratio
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Old 07-25-2006, 09:18 AM   #3
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How are you getting 11.38? Even if that's your final drive ratio, it's way too high, unless you are running a 7 turn mod. Gearing will depend mostly on your motor and the track size and style. Stock motors are usually geared at 6-7.5. 19T usually gears higher (meaning a lower gear ratio) and mod gears down (higher ratio).
Rollout is exactly what you said it was. Rollout changes directly with gear ratio, and is the same thing (in essence) however it takes into account your tire size. It's mostly used only by people who run foams because the tire gets trued smaller and you need to re-gear to compensate for a smaller tire.
Gear up: bigger pinion/smaller spur, FDR gets smaller (closer to 1:1), rollout increases
Gear down: opposite of above
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Old 07-25-2006, 03:37 PM   #4
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if you want to accelerate quick what ration to use high or low? and how about if you want more torque?
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Old 07-25-2006, 04:04 PM   #5
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im not gonna start a new thread with this , so quick question in related to my other post,, having hard silver brushes and heavy spring would it affect my acceleration? how about having a soft springs? and also having a heard and medium springs on earch side whats the advantage?



thanx
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Old 07-25-2006, 04:16 PM   #6
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acceleration and torque are proportional. higher gearing gives you more torque, lower max speed; lower gearing the opposite.

well, hard brushes dont break in as well, or as fast- but they last longer. harder springs- also give you longer motor life(as the brush deteriorates, spring becomes less compressed, so there's less brush pressure on the comm..you need a certain amount of pressure for it to work.

softer springs give you faster acceleration(to a point), but you'll have to replace brushes more often because a brush only has to deteriorate a little before the spring is relaxed. spring pressure basically results in friction between the brush and comm- more force, more friction, less speed. however, since you're new- just leave motors well enough alone. keep em clean, you'll be fine for now.
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Old 07-25-2006, 05:43 PM   #7
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im not really that new, and i know how to take care of the motor i just wanna get the most out of it.. couple of guys on our club are so fast on their stock motors. just wanna know how they do that. i have a c027 with 767 brushes with trinity red springs. and it wont do much. i have been messing up with the g ratio. and if you think my comm is dirty, its not i got a comm lathe.
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Old 07-25-2006, 06:56 PM   #8
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well for starters, you're way overgeared. Fix that, and you should increase your top speed about 60%. Drivetrain issues could also slow you down(or speed them up)..but I'm not the one to ask about that. If your comm is in good shape, get some softer brushes, and medium springs. when you start getting into weak springs and really soft brushes, motors are more of an art than a science.
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Old 07-25-2006, 07:22 PM   #9
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Getting stock motors (especially) fast requires more than just picking brushes and springss. Polish the bushings and shaft, properly tweak and align the hoods, and keep it clean. Of course there are always other little tricks you can do
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Old 07-25-2006, 07:42 PM   #10
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care to share?
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Old 07-25-2006, 07:45 PM   #11
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Quote:
Originally Posted by pinggoy
care to share?
www.motortuningsecrets.com
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Old 07-26-2006, 02:16 AM   #12
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FYI, gear ratio, rollout, speed, charting link here:
http://www.gearchart.com/index.cfm?f...n=chart.create

Last edited by cyber3d; 07-26-2006 at 02:18 AM. Reason: addendum
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Old 07-26-2006, 06:33 AM   #13
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everybody knows that link. but thanx.
but do you know how each ratio work in relation to quick acceleration and more torque? and for what type of track?
cause if a person ask for a gear ratio no. wont matter i think if somebody ask for an advice for that, probably its better if you explain what it does like lower ratio(6-1) have top speed and higher ratio(1-6)have torque. giving a linik to a person who doesnt even know what those no. does to his car doesnt make sense.
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Old 07-26-2006, 08:15 AM   #14
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Thanks for the links, Seaball. Those were informative.

Quote:
Originally Posted by XrayFK
How are you getting 11.38? Even if that's your final drive ratio, it's way too high, unless you are running a 7 turn mod. Gearing will depend mostly on your motor and the track size and style. Stock motors are usually geared at 6-7.5. 19T usually gears higher (meaning a lower gear ratio) and mod gears down (higher ratio).
Rollout is exactly what you said it was. Rollout changes directly with gear ratio, and is the same thing (in essence) however it takes into account your tire size. It's mostly used only by people who run foams because the tire gets trued smaller and you need to re-gear to compensate for a smaller tire.
Gear up: bigger pinion/smaller spur, FDR gets smaller (closer to 1:1), rollout increases
Gear down: opposite of above
XrayFK, I got to 11.38 by way of (98/21)x2.4375. So a good gear ratio starting point for a stock motor is 6-7.5?

Am I better off going to a much bigger pinion gear, much smaller spur gear, meet in the middle or does it matter as long as I'm in the correct gear ratio range? Are you better off keeping one of the gears larger or smaller?
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Old 07-26-2006, 08:27 AM   #15
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11.38 is way too high for a stock
Try a smaller spur and bigger pinion. 87/32 should be much better. Or you could switch to 64 pitch, that way you would have finer increments between gear ratios.
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