Hello,
We're working on a drone meant for research purposes, aiming for 30~ flight time with a payload of ~1kg.
I've been given the task of building it, however I have almost no RC experience, we're starting from scratch.
I thought to use the following parts:
Frame: Tarot 650
Motors: 4x Foxtech motor W50-10 KV288
ESC: 4x DYS 40A OPTO ESC V2(Simonk Firmware)
Props: 17x5.5 CF
Telemetry: RFD900
Flight controller: Pixhawk
Receiver: ?
BEC: RCTimer 5A 5V
Power Distribution Board: Foxtech
Battery: 6s 9000mah
Remote control: Taranis?
Battery charger/balancer: ?
A few questions,
1) Is the Taranis a good choice for a remote? What receiver/transmitter do I need in order to use it with the pixhawk?
2) What else do I need?
3) Can the frame hold 4-5kg in total? Are 17' props okay?
Technically there Is enough space for 17' props but I could add longer motor mounts to increase the distance between the rotors.
4) I'm assuming extra 250gr for misc items (Screws, cables, mounts and other things I forgot) we're at 3.1 kg weight without the payload. With approximately 950 gr of payload (Camera, gimbal, computer, high bandwidth communications) we're hitting 4.05 kg.
In order to hover each motor needs to output ~1kg of thrust, which according to the graphs on foxtech website, would draw 3.3A * 4 = 13.2A. That should give us 40 minutes of hover time, correct?
Assuming 1.5 thrust/weight ration in forward flight the motors would draw 5.9A * 4 = 23.6A which should give about 22 minutes of flight, still correct?
Couldn't find these motors on ecalc so did it by hand.
If you have any comments or recommendations for other parts please don't hesitate to share.
Thank you for reading (And sorry for the wall of text).
Replies
I think the Taranis Tx/Rx combo is an excellent choice. If I were not so far into the Futaba world, money-wise, I'd just on a Taranis.
Note that the performance specs for this motor on the Foxtech site are with one of their 18x6.1 props. The 17x5.5 you are proposing will likely generate less lift as they are smaller diameter and have less pitch. But if you are thinking about the Hobbyking ones they are very cheap. I use those HK 17" props and like them a lot. Amazing for the price.
I haven't run any numbers but my sense is that the 17" props won't be enough for 4-5 Kg, or at least for as long as 30 minutes. I know you are getting near that frame's limit with 17" props, but you could always buy some 16 mm CF tube and cut new lengths for the arms, any length you want. The only "machining" on those arms is a hole at the body end of the tube which allows a clamping/retention screw to pass through.
eCalc is pretty good and your figures look reasonable. I've found its hover predictions to be fairly close. If you can get a design with a hover at 50% throttle or less, you should be golden.
I'm not sure I'd agree with a forward flight multiplier of 1.5. If you read discussions about record attempts at hover time, it's brought up often that gentle forward flight is more efficient than a stationary hover. That seems to jive with my experience watching my current consumption. Of course if you fly like a crazed ferret all bets are off.
Per the Foxtech specs you are under 20 amps per motor at full throttle. For ESCs you could consider Castle Creations 25 amp Multirotor quad pack. They will run all day happy at 25 amps and run very cool. They are amazingly small and light and will fit inside the space between the frame's top and bottom plates.
Oh and one last tip....A Pixhawk won't fit well in between the 650's top plate and the very tippy-toppy plate. Best course of action is to get yourself some thin G10 fiberglass (Amazon sells it cheap) and make a longer tippy-toppy plate. Get some 40 mm standoffs (RMRC carries some nice ones) and you will have a nice and protective location for your Pixhawk.
I should add I'm currently in the process of a build with that Tarot frame using some T-Motor MN3110 470KV motors and those HK 17" props, running at 4S.
Thanks for your reply!
Is there a receiver/transmitter you can recommend to work well with the Pixhawk?
I'd rather get a frame and stick to it, not very comfortable cutting stuff on my own :)I can get extended motor mounts which allow for ~20' props if need be, but maybe I should go for another frame that can also handle 4kg total weight well?
Is there a way to use custom motors on eCalc? Or are there very similar motors I can get instead that appear on eCalc?
Any idea if there is a build log of a similar quad? Mostly found logs of folks trying to break flying records.
The most popular Rx that I've seen with the Taranis is the FrSky X8R. I've never used it but have heard good things. It's sometimes packaged with the Taranis Tx.
I suspect if you really need to lift a total of 4 kg you might have to look at hexas or octos. It is rather trivial to create longer arms for the 650 by just acquiring 16mm carbon fiber tube and cutting it to the length you want with a fine toothed hacksaw. I'm doing that very thing at the moment. Keep in mind that unless you want to spend a great number of thousands of dollars for an S800 or S1000, this is a very DIY field. You need to get comfy with cutting and modifying things. You will learn a lot. Mostly from your mistakes.
You can use custom motors on eCalc by filling in the various motor data fields. I've never been sure how accurate that is though.I don't know anything of the motor you have in mind, but if you know enough of it's specs you might be able to find an equivalent in eCalc.
I'm not familiar with any other quads that might do what you want. Your lifting requirements, if they are firm, are equivalent to lifting high end video and camera systems. You could look at multicopters for those, but you will likely find they are hexas or octos, and a great deal of money.