what is your calculated mph?
05-10-2005, 10:49 PM
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what is your calculated mph?
I just did the calculations that skrap has posted and came out to be 29.2 mph! That seems a little quick to me. I am set up as follows:
spur/pinion: 86/19
motor: Reedy Quad Mag 19t (27000 RPM peak)
battery: Epic 3000 NiMh
spur/pinion: 86/19
motor: Reedy Quad Mag 19t (27000 RPM peak)
battery: Epic 3000 NiMh
05-11-2005, 07:47 AM
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RE: what is your calculated mph?
ORIGINAL: usmcrc
I just did the calculations that skrap has posted and came out to be 29.2 mph! That seems a little quick to me. I am set up as follows:
spur/pinion: 86/19
motor: Reedy Quad Mag 19t (27000 RPM peak)
battery: Epic 3000 NiMh
I just did the calculations that skrap has posted and came out to be 29.2 mph! That seems a little quick to me. I am set up as follows:
spur/pinion: 86/19
motor: Reedy Quad Mag 19t (27000 RPM peak)
battery: Epic 3000 NiMh
When you do that calculation, you need to figure on about a 12-15% difference between the theoretical top speed, and the true top speed. The 12% drop is due to voltage inconsistencies, friction loss, wheel slip, aerodynamic drag etc. That percentage becomes exponential, the faster you go. I really need to develop a bell curve to illustrate that.. My brushless B4 for example, has a 28.7% difference between real speed and theoretical speed. (85.44mph calculated speed, 61.2mph measured speed.)
When you figure the loss in, you are probably closer to 26-27mph.
05-11-2005, 04:05 PM
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RE: what is your calculated mph?
When you do that calculation, you need to figure on about a 12-15% difference between the theoretical top speed, and the true top speed. The 12% drop is due to voltage inconsistencies, friction loss, wheel slip, aerodynamic drag etc. That percentage becomes exponential, the faster you go. I really need to develop a bell curve to illustrate that.. My brushless B4 for example, has a 28.7% difference between real speed and theoretical speed. (85.44mph calculated speed, 61.2mph measured speed.)
-Wes
05-12-2005, 12:42 PM
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RE: what is your calculated mph?
I have a XXX graphite touring car.
GP 3300 cells
lrp Automatic no limit esc.
Trinity D6 8X2 motor
Anyways a cop on my street radared it at 46mph, and I ran out of room lol.
GP 3300 cells
lrp Automatic no limit esc.
Trinity D6 8X2 motor
Anyways a cop on my street radared it at 46mph, and I ran out of room lol.
05-12-2005, 11:45 PM
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RE: what is your calculated mph?
Calculating speed from printed numbers don't mean squat,...go to th park with a TAPE measure,.. measure out 300 feet,...time your ride (example:300 divide by time(7 seconds) 300/7=42.85 (FEET PER SECOND) NOW TIMES 60 (FEET PER MINUTE) NOW TIMES 6O(FEET PER HOUR),....DIVIDE BY 5280(MILE)=29.22 mph.
THATS REAL,,,,,,NOT NUMBERS OFF MOTORS
THATS REAL,,,,,,NOT NUMBERS OFF MOTORS
05-13-2005, 12:00 AM
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RE: what is your calculated mph?
34.26 mph. and with a hacker on 18 cells rated at 1.18 volts per cell and are matched, is 128,000 rpm's! with 20% deducted, i got 134 mph. somewhere around there.
05-13-2005, 07:10 AM
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RE: what is your calculated mph?
ORIGINAL: RNelson
Calculating speed from printed numbers don't mean squat,...go to th park with a TAPE measure,.. measure out 300 feet,...time your ride (example:300 divide by time(7 seconds) 300/7=42.85 (FEET PER SECOND) NOW TIMES 60 (FEET PER MINUTE) NOW TIMES 6O(FEET PER HOUR),....DIVIDE BY 5280(MILE)=29.22 mph.
THATS REAL,,,,,,NOT NUMBERS OFF MOTORS
Calculating speed from printed numbers don't mean squat,...go to th park with a TAPE measure,.. measure out 300 feet,...time your ride (example:300 divide by time(7 seconds) 300/7=42.85 (FEET PER SECOND) NOW TIMES 60 (FEET PER MINUTE) NOW TIMES 6O(FEET PER HOUR),....DIVIDE BY 5280(MILE)=29.22 mph.
THATS REAL,,,,,,NOT NUMBERS OFF MOTORS
You need to make at least 3 runs, and take the average of all 3. differences in reaction time can skew the calculations between two runs. Just a .030 difference in start and stop due to reaction time, can mean a difference of 5-17 mph in your answer! You cannot get an accurate reading, without expensive, electronic timing
The best way to measure how fast you are going is buy an inexpensive pocket gps. It's accurate to +/- .05 mph.
05-13-2005, 08:02 AM
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RE: what is your calculated mph?
Yes, it probably does slow you down. But at most, you lose 1-2mph. Given the accuracy of GPS, it is an acceptabe trade off. I'd rather KNOW that my truck is REALLY doing 45mph, than guess.....
05-13-2005, 08:22 AM
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RE: what is your calculated mph?
Yes, but check the accuracy of your radar gun. Unless you have access to police band radar, your readings can be skewed by as much as 5mph +/-.
Again, using a 'hobby grade' radar gun is still NOT the final answer.
You need to use a professionally calibrated radar gun, with an accuracy of +/- .01 mph to be considered accurate......
Again, using a 'hobby grade' radar gun is still NOT the final answer.
You need to use a professionally calibrated radar gun, with an accuracy of +/- .01 mph to be considered accurate......
05-13-2005, 10:03 AM
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RE: what is your calculated mph?
hey skrap,
i think i am gjoing to have to break down and get the gps. i found an upgrade to the software for my data system and i am going to try a new sensor mount fist, but i am itching to see the real speed. I talked to mike ar rc-monster (where i bought my stuff) and he did a 60+ run with a T2!! and a t2 is much heavier and more inefficient. so i believe i should officially be joining the 60+ club with you very soon.
i think i am gjoing to have to break down and get the gps. i found an upgrade to the software for my data system and i am going to try a new sensor mount fist, but i am itching to see the real speed. I talked to mike ar rc-monster (where i bought my stuff) and he did a 60+ run with a T2!! and a t2 is much heavier and more inefficient. so i believe i should officially be joining the 60+ club with you very soon.
05-13-2005, 11:58 AM
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RE: what is your calculated mph?
I must be the only guy on this board that doesn't care how fast he's going =) I care more about turning clean laps and keeping my mind focused on the race than I do about how fast I'm going. If I'm winning, it was fast enough. If I'm losing, it wasn't.. Pretty simple, ehh?
But, for the sake of argument and fitting in with the group, here's my setup so you can do the math for me...
SS5800
7c pack 1.185+
26/86 gearing
3.145" tires
Keep in mind, that's a qualifying setup, meant to be ran only a few laps at a time. Last week in practice, I kind of forgot to pull it off and ran about 50 laps with it. Ended up thermaling the ESC and when I finally found a temp gun to borrow about a minute later, it was still popping at 193 degrees.. So it got pretty warm. Thank goodness the thermal shutdown worked!
But, for the sake of argument and fitting in with the group, here's my setup so you can do the math for me...
SS5800
7c pack 1.185+
26/86 gearing
3.145" tires
Keep in mind, that's a qualifying setup, meant to be ran only a few laps at a time. Last week in practice, I kind of forgot to pull it off and ran about 50 laps with it. Ended up thermaling the ESC and when I finally found a temp gun to borrow about a minute later, it was still popping at 193 degrees.. So it got pretty warm. Thank goodness the thermal shutdown worked!
05-13-2005, 12:43 PM
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RE: what is your calculated mph?
you have to remember though munkey, for those of us that don’t race, top speed and handling are theonly braggin rights we have….that or who can spend the most money on an rc….
05-13-2005, 03:54 PM
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RE: what is your calculated mph?
ORIGINAL: Speedmunkey
I must be the only guy on this board that doesn't care how fast he's going =) I care more about turning clean laps and keeping my mind focused on the race than I do about how fast I'm going. If I'm winning, it was fast enough. If I'm losing, it wasn't.. Pretty simple, ehh?
But, for the sake of argument and fitting in with the group, here's my setup so you can do the math for me...
SS5800
7c pack 1.185+
26/86 gearing
3.145" tires
Keep in mind, that's a qualifying setup, meant to be ran only a few laps at a time. Last week in practice, I kind of forgot to pull it off and ran about 50 laps with it. Ended up thermaling the ESC and when I finally found a temp gun to borrow about a minute later, it was still popping at 193 degrees.. So it got pretty warm. Thank goodness the thermal shutdown worked!
I must be the only guy on this board that doesn't care how fast he's going =) I care more about turning clean laps and keeping my mind focused on the race than I do about how fast I'm going. If I'm winning, it was fast enough. If I'm losing, it wasn't.. Pretty simple, ehh?
But, for the sake of argument and fitting in with the group, here's my setup so you can do the math for me...
SS5800
7c pack 1.185+
26/86 gearing
3.145" tires
Keep in mind, that's a qualifying setup, meant to be ran only a few laps at a time. Last week in practice, I kind of forgot to pull it off and ran about 50 laps with it. Ended up thermaling the ESC and when I finally found a temp gun to borrow about a minute later, it was still popping at 193 degrees.. So it got pretty warm. Thank goodness the thermal shutdown worked!
Based on that setup, you could realistically be running 58mph flat out! Damn, that's fast![8D]