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Old 09-19-2007, 05:49 PM   #16
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Sounds like you should start with a 25 or 26 pinion on that size track. Make sure its a 64 pitch pinion though to match your spur.
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Old 09-19-2007, 08:13 PM   #17
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is more teeth = faster for slower.........i bet everyone of you guys are like wow this guy is a retard, with gears im not good so lol i understand though if you guys are pissed
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Old 09-19-2007, 08:15 PM   #18
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Quote:
Originally Posted by TEM View Post
Read the 12th scale thread and do a search on "rollout" or "roll out"
sorry but i just think going through 900 pages is the way to help me lol, i might kill myself before that
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Old 09-19-2007, 08:26 PM   #19
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I don't think thats a retarded question but you did get some crappy answers!... Rollout is your only real answer! I mean foam tires change size as you run them. People also true them down to a certain size right out of the box! So just a plain gearing ration is NOT going to solve your problem! Rollout is a number in mmpr which means millimeter per revolution. That is also equivalent to how far the car travels per revolution of the motor.

rollout (in mmpr) for a 12th scale = pinion/spur*pi* (rear tire diameter in mm)

I haven't run stock for a long time but you can try starting with about a 46mmpr rollout and see how the car behaves (how much batt you have left after 8 mins and how hot the motor is after 8mins). An easy way to do it is to ask the locals what rollout they are running!... I typically run spur gears of 96 or 100teeth (64 pitch). Lets say if I run a 96 teeth spur, my rear tire is mesured to be 46mm diameter and I want a 46mmpr rollout, plug those numbers in the calculation and solve, I get a pinion of 30.5ish, so I would use a 30 teeth or a 31 teeth pinon. If your tires are different size, or different spur size then you use the formula to calculate your own gear ratio. After a run you can determine if you are under/over geared and then you gear for a sweetspot for the track.

Some guys use a rollout chart (you make a chart with excel) so you won't have to use the calculator everytime....

Does that answer your question?
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Old 09-21-2007, 02:24 AM   #20
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Quote:
Originally Posted by TEM View Post
I don't think thats a retarded question but you did get some crappy answers!... Rollout is your only real answer! I mean foam tires change size as you run them. People also true them down to a certain size right out of the box! So just a plain gearing ration is NOT going to solve your problem! Rollout is a number in mmpr which means millimeter per revolution. That is also equivalent to how far the car travels per revolution of the motor.

rollout (in mmpr) for a 12th scale = pinion/spur*pi* (rear tire diameter in mm)

I haven't run stock for a long time but you can try starting with about a 46mmpr rollout and see how the car behaves (how much batt you have left after 8 mins and how hot the motor is after 8mins). An easy way to do it is to ask the locals what rollout they are running!... I typically run spur gears of 96 or 100teeth (64 pitch). Lets say if I run a 96 teeth spur, my rear tire is mesured to be 46mm diameter and I want a 46mmpr rollout, plug those numbers in the calculation and solve, I get a pinion of 30.5ish, so I would use a 30 teeth or a 31 teeth pinon. If your tires are different size, or different spur size then you use the formula to calculate your own gear ratio. After a run you can determine if you are under/over geared and then you gear for a sweetspot for the track.

Some guys use a rollout chart (you make a chart with excel) so you won't have to use the calculator everytime....

Does that answer your question?

That was awesome thank you

well i didnt measure my tires but heres a picture of them, maybe you can tell from here.....

also, now when the tire tread goes down, when you change your gearing, do you add teeth in ur spur and/or pinion or get less teeth??
And for rollout, is 46 good or can you get further than that??
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Old 09-21-2007, 06:09 AM   #21
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No.. eyeballing from a picture is not the best way to do things.. why don't you bust out a caliper or ruler to measure?... As the tires get smaller, you change the pinion size! Keep around a set of pinions probably around 25 to 35 teeth for 64p to run 12th scale stock/19t.

46mmpr is a ball park to start at! It varies depending on motor, battery performance, track layout, traction level, driving style, etc... You are looking for an optimal for the 8min run..
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Old 09-21-2007, 10:18 AM   #22
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ok so you change the pinion size, but do go with more teeth or less when your tires wear?
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Old 09-21-2007, 10:35 AM   #23
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You would add a tooth when the tires wear down.

Have a look at www.gearchart.com and click Gearchart Creator

For a pan car, give it a transmission ratio of 1.0 and fill in the # of teeth on your current pinion and spur gears. Set Target rollout to yes then click the rollout button. This will show you the number of teeth to run on your pinion as the tires get smaller.

If you started with 46mm tires and a 100t spur/32t pinion combo, you would change the pinion to a 33t when the tires get to 45mm. This combo would be a fraction faster, (mildly higher top end, mildly lower bottom end torque because the rollout is changing) but should yield close to the same driving experience and heat generated by the motor.

I generally pick a target rollout and take the closest gearing option within .5mm high or low.

Hope you find this helpful.

Chris
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Old 09-21-2007, 10:49 AM   #24
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that was very helpfull thank you..............I forgot one thing, my spur on my L3, is it normal for it to kinda wobble a bit if i grab and wiggle it, remember my chassis is currently a roller so no motor is mounted, but is that normal?
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Old 09-21-2007, 10:55 AM   #25
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my spur on my L3, is it normal for it to kinda wobble a bit if i grab and wiggle it, remember my chassis is currently a roller so no motor is mounted, but is that normal?

No that is not normal! Is the whole axle moving or just the gear?
If it is the whole axle then you need to tighten it up and make sure any bearings are in good shape. If it is just the gear then you need to make sure that you have diff balls in all the holes. Also you need to be sure that your hub is attached properly and there is no play there. Replace washers, bushings or bearings as needed.
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Old 09-21-2007, 10:58 AM   #26
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no just the gear, i was thinking of replacing the whole rear axle and get all new hubs, what company would you recommend?

and for people that are helping me out with rollout, my motor is a c027 pro
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Old 09-21-2007, 11:26 AM   #27
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ttt help
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Old 09-21-2007, 12:19 PM   #28
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?
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Old 09-21-2007, 02:48 PM   #29
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I think i get it now..........30t pinion/96t spur would probably have more acceleration than a 30t/100t pin/spur (both 64p) am i correct or wrong, and if you add a tooth or more on the pinion it would have a further roll out and if you remove a toothor more from the spur it would also have a better roll out........is that all correct?
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Old 09-21-2007, 06:41 PM   #30
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?????????
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