Andrei Aldea
DeadCat MK1 Project Documentation
These are the project notes for my Quadcopter build. I will try to include as much information regarding everything that I have done as well as provide the best and most pictures that I possibly can.
The Frame: I decided to go for a frame that had not become very popular yet, inspired by the Orvillecopter.
What makes this type of frame unique is the angle at which the arms are spaced. In the Dead Cat type configuration (the origin of the name is obvious), the front arms of the quadcopter are pushed back, allowing for easy mounting of camcorders since the propellers won’t get in the shot. The rear arms are at the same angle as a standard X configuration quadcopter.
The frame I used is a modified XK450 frame, similar to the DJI Flamewheel. It is shown below with the optional extended legs, which I used. Its a standard X configuration, but I wanted more.
So this is the SK450 with the Dead Cat modification. The Long legs above are used on the arms.
The Motors:
For Motors I decided to go with Turnigy NTM Prop Drive 28-26 1350KV Motors. These are AC Motors, so they are very efficient, they will pull a max of 30Amps each, they also have a very good thrust to weight ratio with 8 inch props. According to the website, their specs are as follows:
Poles: 3
Motor Wind: 14T
Max current: 18A
Max Power: 227W @ 11.1V (3S) / 302W @ 15V (4S)
Shaft: 3mm
Weight: 56g
ESC: 25~30A
Cell count: 3s~4s Lipoly
Bolt holes: 16mm & 19mm
Bolt thread: M3
Connection: 3.5mm Bullet-connector
Prop Test Data:
8x3.8 - 11.1V / 158W / 14.2A / 0.736kg thrust
8x3.8 - 14.8V / 310W / 21A / 1.1kg thrust
.
This means that the motors will spin at 100% throttle 16200 RPM and 22005 RPM depending on the battery voltage
The Batteries:
Specifications:
Capacity: 2200mAh
Voltage: 3S1P / 3 Cell / 11.1V
Discharge: 35C Constant / 70C Burst
Weight: 199g (including wire, plug & case)
Dimensions: 115x35x27mm
Balance Plug: JST-XH
Discharge Plug: XT60
The Flight Controller:
Other Components:
How They Work:
High strand-count silicone insulated average Amperage tolerance:
- 8AWG 200 amps
- 10AWG 140 amps
- 12AWG 90 amps
- 14AWG 60 amps
- 16AWG 35 amps
- 18AWG 20 amps
- 20AWG 12 amps
- 22AWG 10 amps
Update October 17 2013: The Xbee Pro modules are refusing to change baud rate and have been soft bricked, I’m on the phone with Digi and Adafruit to see what can be done. Until I get them working, telemetry will not be active.
Update October 19 2013: A shipment from Hong Kong will arrive at JFK with the parts I need to finally assemble the quadcopter, it includes some video equipment as well as 10-14AWG wire and high diameter heat shrink tubing.
This is how my frame was destroyed… proving it was not a very good frame:
Now I’m waiting as of October 31 2013 for new parts from Hong Kong. Its extremely frustrating…
Update November 11 2013: I’m encountering some technical problems. I am going into deeper issues.
I have done some calculations on the motors, assuming Linear results rather than curves. They should provide a fairly close match to real life results:
Model: NTM Prop Drive Series 2826 1350kv
Kv: 1350rpm/v
Poles: 3
Motor Wind: 14T
Max current: 18A
Max Power: 227W @ 11.1V (3S) / 302W @ 15V (4S)
Shaft: 3mm
Weight: 56g
ESC: 25~30A
Cell count: 3s~4s Lipoly
Bolt holes: 16mm & 19mm
Bolt thread: M3
Connection: 3.5mm Bullet-connector
Prop Test Data:
8x3.8 - 11.1V / 158W / 14.2A / 0.736kg thrust
8x3.8 - 14.8V / 310W / 21A / 1.1kg thrust
This results in the following assuming linear curve (might differ slightly):
9x4.5 - 11.1V / 211W / 18.9A / 0.980 kg thrust
10x4.5 - 11.1v / 234W / 21A / 1.098 kg thrust
11x4.5 - 11.1V / 258W / 23.1A / 1.198 kg thrust
12x4.5 - 11.1V / 281W / 25.2A / 1.307 kg thrust
Note: We see that 4S 8x3.8 is equivalent in thrust with 3S 10x4.5 in amperage.
This is all assuming linear thrust, real data might be different as the motor has in reality a curved thrust.
Max Current for the motor is rated at 18A so it might be pushing it...
For the Sake of it 4S (14.8V) configurations. They are not faisable!
9x4.5 - 14.8V / 413W / 18.9A / 0.980 kg thrust //The calculations are not made yet. Results are 3S!!!!
10x4.5 - 14.8v / 234W / 21A / 1.098 kg thrust
11x4.5 - 14.8V / 258W / 23.1A / 1.198 kg thrust
12x4.5 - 14.8V / 281W / 25.2A / 1.307 kg thrust
Now to compare to predicted weight of the hexacopter:
Lift capacity = (Number of motors * thrust/motor) / 2 (50% capacity or less is ideal)
Overall theoretical lift by 3S:
9x4.5 -11.1V / 5.88Kg Overall - 2.94 Kg Ideal
10x4.5 -11.1V / 6.588Kg Overall - 3.295 Ideal
11x4.5 -11.1V / 7.188Kg Overall - 3.594 Ideal
12x4.5 -11.1V / 7.842Kg Overall - 3.921 Ideal
10x4.5- 11x.4.5 Ideal Overall
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