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Old 06-19-2003, 10:06 AM   #1
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how do I figure out what pinnion to put on my mod

Hey I was just wondering how to figure out a starting point on gearing for my mod motor...I am running a Mission that has a spur of 87 th and 48 pitch.....the motor is an 11double I just want a starting point something that is at least close
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Old 06-19-2003, 10:18 AM   #2
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Check your manual, they usually give decent starting points for different motors with different turns and stuff.
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Old 06-19-2003, 02:04 PM   #3
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Default and I forgot to mention

the manual doesn't have anything about gearing
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Old 06-19-2003, 02:31 PM   #4
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DOH!!! mission, guess I should have read better...

from what they have on the schuie web site your internal is 1.8:1 or 2.1:1 depending on how you have it set....
the equation is this:



(spur gear/pinion gear) * internal ratio = final drive



for mod motors.. anywhere between 9:1 to 12:1 final ratio would be a decent place to start.

working backwards with 2.1 internal ratio and a 84T spur:

9 = 2.1 * (84/x) solve for X to get your pinion gear, round up or down as needed

in this case X = 19.6 rounding up use a 20T pinion...

this will help you get in the ball park for gearing, from there you refine by going up or down teeth on the pinion.

hope this helps a bit...
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Last edited by RAP66; 06-19-2003 at 02:42 PM.
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Old 06-19-2003, 02:33 PM   #5
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Default as I stated in my first post

I am running a Mission (schumacher)....I just don't have a clue and what I started with just doesn't seem to work 18 tooth pinnion with 87 tooth spur
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Old 06-19-2003, 02:43 PM   #6
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read below... hehehe I just glanced over your post initially.

anothr thing to remember.... the closer you are to a ratio of 1:1 the higher your top end will be, how ever the expense is torque. meaning it will tak you longer to reach full speed, than say a gear ratio around 5:1 the further away from 1:1 you get results in more torque at the expense of top end.


the gearing you posted give a final of (@2.1:1 internal) 10.15:1 you not fast enough go up a few teeth on the pinion... if the speed is fine but the car bogs drop a few teeth.

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Old 06-19-2003, 02:49 PM   #7
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Here is what I found on the Trinity site:

9) What gearing should I start with on my Sedan?
(Drop one tooth on the pinion for every turn you drop on the mod motors)
Losi XXXS 48 pitch (Stock - 25/90) (10T Mod - 19/90)
Assoc. TC3 48 pitch (Stock - 26/72) (10T Mod - 21/72)
Schumacher Mission 48p (20t pulley) (Stock - 23/90) (10T Mod - 19/90)
Yokomo MR4 48pitch (Stock - 26/81) (10T Mod - 20/81)
Hudy X-Ray 48 pitch (Stock - 27/93) (10T Mod - 22/93)

90/19 = 4.74. 87/18 = 4.83

So you are pretty close. If the motor is not hot after a 5min. run, try a 19T pinion.
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Old 06-19-2003, 05:03 PM   #8
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Default sweet thanks that kinda what I was looking for

sorry didn't want it to sound like I was being snotty or anything hehehehe that just the way it came out..so sorry and thanx for taking the time to answer my question.....

yes the motor seemed to get hot after 3 minutes of driving...and I wasn't leaving it fully open either......it seemed to bog early and wind out fast...so I kinda knew I was on the right track.... I think I will try a 19 or 20 Tooth pinion...se if that makes a difference
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