For an engineering project for high school, I have chosen to build an automated delivery drone, capable of carrying 1 kg of cargo, in addition to the dropping system we are going to build.
I need help optimizing this build for flight time, flight range, durability, and low cost (under $300 at most).
I think the props need to be large, and motors at low kv, for decreased power draw as a trade off for maneuverability. However, I know little of how to select motors and props and I know there is a lot of complex factors in that choice. This is where I need the most guidance.
I envision a quadcopter being a good choice, but it does not need to be a quadcopter.
As for a transmitter, I will be buying a cheap one, if at all. The drone will be automated, so a controller will only be needed for the initial testing phase and will not be as important once it is up and flying.
Heres my hobby king shopping list:
Quantity Stock Product description Price Weight
4 OK 171000436-0 - NTM Prop Drive 28-30 800KV / 270W Brushl.. $60.20 320
3 OK 017000065 - 12x4.5 SF Props 2pc Standard Rotation/2 .. $13.08 240
5 OK HKz30A - HobbyKing 30A BlueSeries Brushless Speed.. $55.30 235
1 OK HKz-Prog - HobbyKing Programming card for BlueSerie.. $3.28 17
1 OK HK-T6A-M1 - Hobby King 2.4Ghz 6Ch Tx & Rx V2 (Mode 1.. $25.06 998
1 OK FS-L001 - Hobby King 2.4Ghz 6Ch Tx USB Cable $2.85 60
1 OK 015000095 - XT60 to 4 X 3.5mm bullet Multistar ESC P.. $3.36 34
4 OK SHT007 - NTM Prop Drive 2830 Series Replacement Shaft $3.28 52
4 OK NTM28-ACC - NTM Prop Drive 28 Series Accessory Pack $7.40 88
TOTAL: $173.81 2044g
Sky Tools 127 Piece Heat Shrink Tubing Assortment $6.99 1
Vktech 40x 3.5mm Gold-plated Bullet Banana Plug Connector RC Battery $3.99 1
SunFouder 2 pcs Ultrasonic Module HC-SR04 Distance Sensor $8.99 1
NEEWER® Useful HJ MWC X-Mode Alien Multicopter Quadcopter Frame Kit Red/White $16.99 1
Hobbypower Top Pin APM2.6 External Compass APM Flight Controller w/ UBLOX NEO-6M GPS $69.89 1
FTDI Cable 5V VCC-3.3V I/O $17.95 1
Hobbypower Power Module V1.0 for Pixhawk Apm2.5 Apm2.6 Ardupilot Mega Flight Controller $11.101
Neewer Servo Tester CCPM Consistency Master Checker 3CH 4.8-6V $6.95 1
Subtotal (8 items): $142.85
I am going to use a VEX robotics motor to drive the dropping mechanism, they are
reliable geared motors and it will cost me nothing. I will wire voltage from the battery and
servo signal from the APM, they never draw more that 5A so it shouldn't affect anything.
FTDI cable is to set baud rate and name of bluetooth module (JY-MCU slave)
-Can the APM 2.6 take serial input coordinates and route to them? (I am willing to code it myself)
I already have a battery and charger, so that saves ~$60
The Turnigy nano-tech 4500mah 3S 25~50C Lipo Pack is what I already have, and seems like a good choice to maximize flight time to increase delivery range, but is pretty heavy.
I have a mix bag of those little plug wires, and 3 wire ones at the school I can use.
The distance sensors are for collision avoidance, is there any reason not to use those?
-Can I add code to stop and rotate until it is clear of obstruction? We do that in vex with robots, any reason this would be hard on APM?
The frame is inexpensive, if it does break, then we will build a H frame, but I want something to start with.
(also it looks cooler than any welded aluminum frame I could make)
Anything I can cut cost on? $316 subtotal + ~$40 for hobbyking shipping (yikes!) is within the budget.
Anything I forgot?
Thank you for reading my post, if you have any knowledge that can help me succeed in this project, I would love to hear from you.
All of the parts showed up, put it all together today and took a test flight. It flies easily and deftly. I'll post a youtube video soon.
This is hobbyking's APM board, the reviews are positive and it should be able to do everything we need to too, and has telemetry for far less cost that 3DR's package:
The diy foam tube frame shown here: https://www.youtube.com/watch?v=5XinbTcQAAc
looks like a possible frame that would cost practically nothing.
Its very light, and the lack of hardness means it won't transfer vibrations to the electronics, but that also means it's flimsy.
What would be the advantages of something like that? If it's practical to use that kind of construction, the budget would relax a bit. Also, mounting the drop mechanism will be much easier with the H-style square frame.
I did some more research and came up with this:
flight computer: apm 2.6 with ublox gps
frame: Tarrot fy 650
motors: Rctimer 5010/14 360KV
$73 for four
props: 16x5.5" Carbon Fiber
$35 for four
battery: 4500 mah turnigy nano tech
Turnigy nano-tech 4500mah 3S 25~50C Lipo Pack
$0 I already have this
esc: 4 in one 20A Qbrain esc
$0 I already have this
3DR telemetry kit for data collection
$100, a bit too expensive to be justified for this project
apm, frame, motors, props, rxtx
240 + 130 + 73 + 35 + 25 =
The APM is expensive, but for a good autonomous system it seems to be the best value
The frame is still expensive and heavy- but cheaper frames only seem to get heavier.
Is there an advantage of the expensive CF props, or are the wide plastic one comparable?
assuming I can find a cheap frame or make one out of pvc, and get cheaper props, that puts it at
apm, frame, motors, props, rxtx
240 + 40 + 73 + 15 + 25 =
$393 which is better but I don't know if that's feasible.
The computer is 60% of that cost, but any cheaper APM's turn out to be Chinese knockoffs.
Thoughts on where to go from here?
Re the frame if you can find someone with a 3d printer locally maybe they can print you a frame. You can get a real nice frame for not much cost in filament. Look on Thingverse for many options.
We have a makerbot printer at my school, but to fit the large propellors, the frame has to have a 1 foot radius, and at that size I feel like it would get heavy; most 3d print frames are for smaller quads. Is there a particular print on Thingverse you think would work?
The large prop size is for the sake of efficiency at the cost of maneuverability, which is optimal for carrying a load in a straight line over a few kilometers. Am I correct in thinking that is how prop size affects performance?
you'll need a transmitter- I dont think flight without one is available with the firmware. Also be weary about going large- you'll have to fly in biigger places and flying near people/things becomes way more dangerous, and crashes can be more costly