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700 Class Electric Helicopters 700 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar. |
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06-08-2015, 10:20 AM | #1 (permalink) |
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560Kv motor in a 12S 700
A bit of background. I tried asking in the manufacturer specific forum but I figured I might hit a larger audience here because nobody replied and all my searches are coming up with very little answers. I have the option of trading to trade my current Scoprion 500Kv for an equivalent 560Kv motor. I've been really crunching the numbers on all possible scenarios and my assumptions are as follows:
Motor speed @ 560Kv assuming an 85% efficiency: 21,705rpm (at 80% battery discharge) 23,800rpm (at full charge) 9:1 gear ratio w/11t pinion (99t main gear) 21,705 / 9 = 2411 headspeed (fully discharged/100% throttle) 23,800 / 9 = 2644 headspeed (full charge/100% throttle) If I set up a governor (or throttle curves) I believe I could end up with numbers like this: Idle 1 2411 (low) @ 70% throttle = 1850rpm headspeed 2644 (high) @ 76% throttle = 1850rpm headspeed Idle 2 2411 (low) @ 92% throttle = 2220rpm headspeed 2644 (high) @ 84% throttle = 2218rpm headspeed I just wanted to know if the numbers were close or if I was way off on my calculations. I know a 520Kv or 530Kv motor would probably yeild the best efficiency to power ratios, but my options are my current 500Kv motor or trade for a 560Kv. I just want to avoid too much overshoot and if I have the numbers wrong I'd like to know before getting a motor that's way too hot for my application. Thanks!
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Tim KBDD TEAM PILOT --Si vis pacem, para bellum-- |
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06-08-2015, 11:08 AM | #2 (permalink) |
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Join Date: May 2011
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First of all I would use 90% efficiency of motor...
then use the following formula 100% RPM at the end of the flight = Kv of motor x Volts (3,7x#of cells) x 0.9 x number of teeth on the pinion / number of teeth on the main geat this will then give you the RPM at the end of the flight depending on your ESC you can govern it down a little.. but if you use Castle Creation do not go below 80% as it will get too hot.. gh |
06-08-2015, 01:36 PM | #3 (permalink) |
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I used 85% efficiency because of total system losses which seems to be pretty consistent on most other setups I've messed with (600 class and smaller). The 700s are admittedly a new animal and that was why I wanted to ask about the setups before making any changes. I tend to prefer longer flight times so I don't really need blistering speeds, but it's nice to have it there if I want to use it. Going with a 560Kv motor might push me well above my comfort zone and I wanted to see if anyone has used one or if they are even a viable option at all. I suppose if I put it at an 80% throttle it might actually be lower than that when it's governing on a full charge and I'd rather avoid the possibility of charring it (aka sticking with ther 500Kv or waiting until I can get a 510, 520 or 530Kv instead)
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Tim KBDD TEAM PILOT --Si vis pacem, para bellum-- |
06-08-2015, 02:34 PM | #4 (permalink) |
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Join Date: May 2011
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I think that it is a smarter idea....
If you like longer flights then you should look at lower RPM... Check the low head speed thread here... There are a few ways you can achieve that but the easiest is to change the motor for lower Kv... |
06-08-2015, 07:28 PM | #5 (permalink) |
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Join Date: Aug 2010
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http://heli.dacsa.net/calcv3/
You can select different governors. It is pretty close what you will get in real life. Highly recommended.
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HD750, TDR II, TDR, Logo 700, Logo 700 XXtreme, Logo 550SX V2 |
06-08-2015, 08:26 PM | #6 (permalink) |
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Do any of you know what this means:
Results from the calculation:* Estimated lowest voltage during flight:*34,80 Lowest RPM (due to voltage and efficiency) :*1948 Castle program warning that max is at:*1968 a little over that is OK, it's just a warning
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Tim KBDD TEAM PILOT --Si vis pacem, para bellum-- |
06-10-2015, 02:57 AM | #7 (permalink) |
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Join Date: Jun 2010
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I was just wondering why the way high head speed? You are talking some very high head speed for a 700.
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Trex 700L Ikon 2 / Trex 700L Ikon V. 2 / SAB Goblin 500 Sport Ikon 2 / HD Cell 500 Ikon 2 It isn't about if, it is about when! |
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