Instead of usually one drive in a plane you have four drives in a Quadrocopter. Simple statement, but it means four times the cost and synchronism is important.
In order to allow good control, the total maximum thrust value should have a factor of 2 to the total weight.
In order to have best price/performance ratio, I like to describe 3 sets of low cost drives.
Because reliability is most important in the case of a Quadrocopter, I like to say a few words about it.
The brush less motor should have a low kv (turns per minute per Volt) value, in order to reach a good efficiency. Because the air flow speed must not be high, because of limited vertical speed, a low kv value allow larger diameter propeller and therefore better efficiency. Click on the picture to show it in full size.
At least from the measurement and calculation the 2213N shows the best efficiency.
DT750 - kv = 750 rpm/V, axis diameter 4 mm with M4 thread
Propeller: GWS 10x6" HD, 2 hex nuts
Voltage 10.5 V, thrust of 658 g
Current is 9.1 A and rpm = 6922
Efficiency of 6.9 g/W.
- 2213N - kv = 800 rpm/V, axis diameter 3 mm
Propeller GWS 9x5" HD
Voltage 10.5 V, thrust of 504 g
Current is 6.0 A and rpm = 7151
Efficiency of 8.0 g/W.
- FC 28-22 - kv = 1200 rpm/V, axis diameter 3 mm
Propeller GWS 8x4" HD
Voltage 10.5 V, thrust of 556 g
Current is 9.1 A and rpm = 10260
Efficiency of 5.8 g/W.
ESC, Electronic Speed Controller
TURNIGY Plush 10amp 9gram Speed Controller
This controller is small and light, has a 20cm RX cable, but I found examples which does not have the same RX pulse width to turns per minute factor.
Hobbyking SS Series 15-18A ESC
This controller is the cheapest one, with the drawback that the RX cable is just 10cm long, compared to the standard length of 20cm. Also it is not programmable.
All those mentioned propellers are from company GWS (HD type), or similar ones. I found that they have the best efficiency, when you look in the program Drivecalc.
Balance of the propeller is very important in this application. I cut off the heavier side some thin chips (upper side) with the help of a thin sharp steel plate.
10X6 Propellers (Standard and Counter Rotating) (6pc)
The weight is 11g, in principle a good set, but the drawback is the bad balanced R type propeller.
9x5 Propellers (Standard and Counter Rotating) (6pc)
The weight is 8g, in principle a good set, but the drawback is the bad balanced R type propeller.
8X4R Propellers (Standard and Counter Rotating) (6pc), Type R not tested yet
The weight is 6g
I like to have MPX plugs in the battery power distribution, see link, then it is easier to exchange an ESC. For the battery with high capacity now the XT60 plug is used, see link.
You should take care about a low voltage signaling, either with a buzzer on the MultiWii control, or external Voltage Detector, see link.
An other option is to have a currents sensor, which is supported by the MultiWii control. I am using a ACS715 break out board, see link. The output is an analog voltage (133 mV/A) that reads 500 mV for no input current and has a typical error of less than 1.5%. The sensor operates at 5 V, 10 mA.
Setup in config.h of MultiWii /* PLEVELDIV ACS715 = 133 / 4.9 * 10e6 / 19977 * 3600 / 1000 = 4891L */ #define PLEVELDIV 4891L // to convert the sum into mAh divide by this value, ACS715 #define PSENSORNULL 102 // for I=0 A my sensor gives 102 * 4.9 mV = 0.5 V for ACS715 #define PINT2mA 37 // for telemetry display: one integer step on arduino analog translates to mA, ACS715 1000 / 133 * 4.9
- Check especially all motor nuts or screws, if they are tight. I lost 2 propellers because of loose motor nuts.
- Ckeck all electric plugs for having good connection.
Nuts - you should use hex locknuts only, or plastic nuts where appropriate.
In case of the M3x3 mm grub screws in the motor stand I am using UHU-POR for securing the screws, because then it is possible to loosen the screws again.
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-- RudolfReuter 2011-10-14 04:11:24