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Old Oct 28, 2010, 12:20 PM
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United States, NJ, Roseland
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Amp x Volt = Watts Somethings wrong.

Look at these rimfire 1.20 numbers:
Max. Constant Current: 50A
Max. Surge Current: 80A
Max. Constant Watts: 1480W
Burst Watts: 2360W
No Load Current: 2.3A
Input Voltage: 18.5-22.1V (5-6S LiPo)
RPM/V (kV Rating): 450

If I take the max. constant current 50 amps and multiply it by 22.1 (6s) I get 1105 watts?? too low compared to their specs. Or if i take the max burst rate of 80 amps and mult. by 22.1 I get 1768 watts. Still too low for theit max. burst watts. Am i doing something wrong?

Now if I take their numbers and want to figure out the motors amp capacity. I'd take watts (max surge) 2360 divided by volts (6S) 22.1 = 106.7??? WAY higher than their 80 amps listed. SOmethings fuzzy......Could be me.

-Dave
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Old Oct 28, 2010, 12:40 PM
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A fully charged lipo will be 4.2v per cell...
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Old Oct 28, 2010, 12:51 PM
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USA, MI, Grand Rapids
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bartricky is on to something there, I think. Rimfire appears to have used something a touch higher than "nominal voltage" when they calculated their numbers. Reverse the math with their numbers to find out what voltage they calculated from...that will tell you how bogus or not the numbers are.

fresh lipos are 4.2 per cell.....under load that number drops to maybe 3.8 when fresh, 3.4 when half depleated.... They could have use any number of cells at any voltage within that range to generate their numbers.....and any answer within that window would not be technically wrong. Motor specs are always a ball-park sort of a thing...your milage will vary a bit due to the specifics of your set-up.
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Old Oct 28, 2010, 01:02 PM
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just went back to post one and ran the numbers......29.5 volts is the answer for the constant and burst numbers. So they used a seven cell fully charged (29.4)to get those numbers?? OR an 8 cell at nominal (3.7) voltage, which is 29.6 volts???? Seems to me, somebodys asleep at the wheel at rimfire....

Have you looked into Scorpian brand motors? they have motor/prop charts that state truthfully what voltage and prop were used.....they have at least 8 different numbers combos graphed for every motor they make. Mountainmodels.com sells them.

CommonsenceRC.com also has accurate usefull number charts for their motors....also worth a look for you??

I hate buying things from manufacturers who just print random bogus things and expect us to follow the herd.....call rimfires bluff and buy from someone who publishes true numbers.
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Old Oct 28, 2010, 01:22 PM
The building never ends!
Tucson, AZ
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If you multiply 8S voltage by those current numbers, you'll find that the advertised numbers fall out (though the burst wattage is eight watts lower than what my calculator says it should be, assuming a per-cell voltage of 3.7V) So I'd guess they tested the motor at 8S to make their power numbers look better. Can you use the motor at 8S? I wouldn't recommend it.
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Old Oct 28, 2010, 01:52 PM
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United States, NJ, Roseland
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Now funny thing is that the eflite power 110 has lower numbers but its rated for 8S??? Im just trying to figure out if this motor can stand more amps??? if you look at the burst watts its 2360 Thats a lot of watts. So if its rated for 2360 burst, the motor must be able to handle 80-90 amps right?!?!?!?!?!? Either their AMPS or WATTS are off. Question is which? My guess is the AMPS. I hope : )
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Old Oct 28, 2010, 01:53 PM
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Tower Hobbies really needs to get their act together. They are missing the E-Power boat.
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Old Oct 28, 2010, 01:54 PM
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United States, TX, Fort Worth
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Nothing wrong with showing max values for max watts continuous and max watts burst at levels beyond those achieved using the suggested cell count and amp draw. Shows the amount of safe operating envelope available out past the normal max cell count and amp draw.

Do you run your car engine at max temp and max rpm on the dial all the time? Nope.

I predict that GP set a conservative operating envelope for the Rimfire to keep reliability high and warranty work low.
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Old Oct 28, 2010, 03:08 PM
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So they crank up the numbers with a huge battery, and then turn around and tell you not to use that battery....that means that the ratings they are advertising are beyond what you can acheve with the reccomended equipment?? That's a load. I want numbers that are relavent to a real world set-up.

I choose usefull data with my wallet!! NUF SAID
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Old Oct 28, 2010, 05:20 PM
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looks like im going to scorpion in the future....so since i have this one rimfire, if I use their watt numbers 1480 max constant 2360 burst, could i use a 8, 9 10S lipo as long as I keep the watts within those parameters?
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Old Oct 28, 2010, 05:44 PM
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Sounds locical enough.....but a guess is a guess, and yours is as good as ours..
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