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Old 04-30-2005, 04:09 PM   #1
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Default how long will it last?

w/ 3300 mAh batteries, how long will the 23T, 19T, and 8T last?
thanks
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Old 04-30-2005, 06:35 PM   #2
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9.3 mins
8.5 mins
6.7 mins
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Old 04-30-2005, 08:06 PM   #3
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hi Johnny,

do you use a set forumula to determine those numbers?
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Old 04-30-2005, 08:14 PM   #4
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There's no formula. He's just making educated guesses.
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Old 04-30-2005, 10:06 PM   #5
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pretty darn accurate guesses. accurate as in significant figures. not as in ive tested. is this just from experience? (no im not flaming. please dont think i am. dont know how to word this "softer")
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Old 04-30-2005, 10:09 PM   #6
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go for the 8 turn, no one cares how long it runs just as long as it goes fast!
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Old 04-30-2005, 10:41 PM   #7
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Those figures are for touring cars with drag coefficients of .085
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Old 04-30-2005, 10:46 PM   #8
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I am going to guess that to be a theory ?
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Old 04-30-2005, 10:52 PM   #9
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Wont that theory be as though the motors are running flat out for the full runtime though, in a real race im pretty sure i can dump an 8T quicker than that
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Old 05-01-2005, 01:30 AM   #10
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Quote:
Originally posted by Johnnytc3
9.3 mins
8.5 mins
6.7 mins
what is your experience/calculation to determine this,
with my 8 turn motor id be lucky to make 5 mins,without a slight decrease in dumping.
how did you work out,the effeciancy of his car,the efficiancy of his motor,the current draw of the motor,the increase in resistence of all electronics from heat,his track conditions,how many mahs went into the battery,the condition of the battery,the gearing he was using,the timing he was using?all these are gona determine the runtime and no exact or even predictable answeres can be given,the only way to try is to go to the track and practice,using a stop watch time how long it lasts for.
as a rough idea,at a certain track i can make 4 mins 55 with a 7 turn,this was dumping towards the end and if it was a race would of just finished,this is with good pack of 3700.
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Old 05-01-2005, 07:24 AM   #11
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I agree... You gear and race an 8T to just make the racing time (5mins plus last lap). If you have extra, you correct your mistake next run.

Its almost the same for 19t. You gear up heaps and run the pack very low too.
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Old 05-01-2005, 08:14 AM   #12
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Quote:
Originally posted by Johnnytc3
Those figures are for touring cars with drag coefficients of .085
I knew your calculations were wrong just based on your statement above. There is not a simple way to detect the average /U of friction or coefficient of friction for a touring car with rotational, sliding, and starting frictions. You did not know any of the circumstances. You did not know the drivetrain.

To calculate the average friction and relate that to the runtimes of electric rc cars:

Every aspect of the drivetrain
-weight
-rotational intertia
-torque
-rolling friciton of bearings
-hundreds of other factors
Track
-surface
-turns
-average lap
-surface temp.
Electronics
-amp draw
-watts produced
-resistance
-heat dissapation

I can give you a physics lesson, but that would be a waste of our time.
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Old 05-01-2005, 08:17 AM   #13
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Quote:
Originally posted by greencactus3
pretty darn accurate guesses. accurate as in significant figures. not as in ive tested. is this just from experience? (no im not flaming. please dont think i am. dont know how to word this "softer")
Actually, they are quite off what the average racer experiences. I could probably make better guesses.

8 turn 5.08263517484 minutes
19 turn 6.827253420002
23 turn 7.2826254143749
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Old 05-01-2005, 10:03 AM   #14
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LOL wow you guys are way too serious, i was just throwing numbers out of my ass, obviously there is no answer to his very "general question".


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Old 05-01-2005, 11:10 AM   #15
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LOL I'm just having fun with physics
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