Ball Park Sizing

[sirch]

First off, hello. I'm new to this forum and I know you must get a load of newbie questions about self build drones but here is another   . I want to build a drone to carry a camera because I already have a decent quality smallish WiFi enabled camera. My main aim is to just just it to lift the camera, take a still photo and come back again. I am not after massive range or speed and don't expect it will ever get more than a few hundred metres from me.

The camera plus lens weighs around 700g. I have been pondering what size of drone I need to carry this and I have used  https://www.ecalc.ch/xcoptercalc.php  to do some calcs but there are so many dependent variables that it is hard to know whether I am in the right ballpark.

It seems to me that with a 700g payload I am on the verge of needing a hexacopter rather than a quad but I was hoping that someone could tell me if a quad would be capable of lifting 700g? Also any recommendations for motor/prop combos for this application would be appreciated.

[shawdreamer]

your suspicion of likely needing a hex for a 700g load is probably more correct than what you realise, for more reasons than just its lifting capability.

A quad would have to have pretty substantial motors and props aswell as a large frame size and power system to cope with its own weight and your payload while maintaining enough power to perform maneuvers also, in short its possible but likely very expensive.

however more pressing a question in my opinion is would you really wish to take a 700g camera and lens into the air without some degree of redundancy is something go's wrong?, one of the main reasons Hex's are used over quads for heavy lift camera ship work aswell as their superior lifting ability of course is the fact that if I hex loses one of its motors during flight (for whatever reason) it more often than not can still retain a large degree of control, atleast to a point were it can be brought down in a controlled manner sufficient enough to save the frame and its often precious payload, where as when a quad loses a motor/prop its pretty much game over straight away, the pilot will lose almost all control authority and have zero chance landing the frame in anything remotely resembling a controlled fashion.

[Reman]

Hexacopters or Octocopters don't automatically equate to more lifting capacity, It's more about having an extra layer of protection if something goes wrong. In most situations your average hex should be able to be safely landed even if a motor or ESC dies mid flight. With an octocopter you could even carry on filming with one or two motors out of action, And depending on where around the frame the dead motors/ESC's are, You may even be able to have a controlled landing with up to half the motors being out of action (Though if you ever found yourself in that situation I'd say you REALLY needed to rethink your maintenance schedule !!! LOL !!!).

So, What you need really depends on what you'd be flying around, How expensive the camera is and how how p*ssed off you would be if it crashed and broke.

If you're not particularly worried about the camera and won't be flying near anything that could cost big money if you crashed into it (company carpark, or solar farms spring to mind) I'd probabbly risk going for a larger (6 to 800mm) quad frame. The benefits of this are that motors get pretty pricey as soon as you get into the larger sizes, So only needing 4 keeps the cost down a bit.

If you're somewhat attached to the camera you'd probabbly want to go for a similar sized hex. It gets more expensive because you need an extra couple of most of the expensive electronic bits, But at least you'd have a minimal level of protection against a motor or ESC going bad in flight.

....... So, What are you after it to do?

[sirch]

Thanks for the info, I hadn't considered the survivability aspect so it looks like a hex is the way to go despite the extra expense.

Any thoughts on good prop/motor combinations?

....... So, What are you after it to do?

As I said it's for photography, quite often there is a decent landscape but there are trees and the like in the way of taking a photograph so I'm just looking to get above trees, hedges and other obstructions and take some photos of the landscape, sunrises, cliffs, etc.

[ched]

I really enjoy researching components and building multi rotors but sometimes it has been done cheaper and better by a decent company. Have a look at the cost to build your own and then have a look at DJI quads. They are very very good camera platforms, easy to fly, and long flight times.

If you do decide to build your own please post your idea of components and we will try and advise.

[Bad Raven]

The other way to look at this is that you are intending making a Multicopter to fit an existing camera, a camera that might not take and transmit any better images than one far lighter and likely quite cheap, cheap enough that you'd save so much on the MR build it would effectively pay for itself.

Just Saying............................   ::) ::)

[sirch]

Thanks for the welcome ched999uk   

Even the DJI Mavic 2 with the Hasselblad camera which is about £1200 isn't as "good" as the camera I want to use (Olympus EM5 ii) for what I want to use it for, also I really don't need all those Mavic bells and whistles. This really is about photography for me, think of it as an extension to to a Tripod, I want to get the camera a bit higher or may be into a physically inaccessible place, for example over a river.

I've done more digging/research and the current shopping list looks something like this and comes in at about £550

Frame	Tarot 680
Battery
Controller	Pixhawk
GPS	Ublox NEO-7M GPS
TX/RX	Flysky-FS-I8-2-4G-10CH
Camera Mount
Power distrib
Motors	hobbypower 2212 920kv
ESC	SimonK 30A
Props	10 x 4.5

There are probably some bits missing...
which gives, on ecalc.ch
[attachment id=0 msg=212861]

[ched]

OK sirch I didn't realise you were that into the photography  ::)
A couple of things to mention.
In the calcs it looks like you are using a 2S battery? I would suggest 3S or maybe even 4S.
The calc mentioned too low a C rating. Basically batteries have a 'guide' to the maximum current you can pull. This is expressed as a C rating. You look at the Amp Hr rating i.e. 3300mAh (convert to Ah = 3.3Ah) and times that by the C rating (20) which gives 3.3x20 = 66Amps max current draw. Your motors say max current of 20Amps so x 6 = 120Amps max draw. So you can see a 20C rating battery is too low for the motors you are looking at. Also the weight of the battery is way too low. My 3S 3300mAh weigh about 220gms.
The calc also seems to suggest a weight of 900gms. With your camera I doubt it will be an all up weight of much less than 3kg!
You listed a Flysky-FS-I8-2-4G-10CH while I fly with a FlySky i6 (at about £35. Modded to 14 channels for FREE) and find it great for the sort of money you are looking at for the I8 you could get a FrSky QX7 which is sort of the 'industry standard' in tx and is available for about £95. So I would say go for the QX7 (https://www.hobbyrc.co.uk/radio-transmitters?orderby=10).
GPS: If you can go for a M8N as it acquires sats faster and locks better.
The Pixhawk Flight Controller has a number of versions, which one were you thinking of?
I have a F450 quad with a 3 axis gimbal and use a Naza lite Flight controller flashed to the V2 version (FREE guide in the FC section on here) and it is great. Very stable and easy to fly and has return to home (in case of emergency :) ). But it is only carrying a gopro size camera.

Can you do a live via wifi to a tablet or phone on your camera to enable you to frame your shots?
Be aware wifi's range isn't great with all the motors and your transmitter which is also 2.4Ghz as well as wifi!!!
On mine I have a fpv (First Person View) little fixed position camera that I use to fly to where I want then flick a switch on my tx and can see the live view of my photography camera. I use a little video transmitter (VTX) to get live images back to a monitor or goggles that have a video receiver that gets the signal from the quad.

Well done for having a play with the ecalc it is good for getting an idea of what you need.

Have a search for a Tarot 680 frame and see if you can see what components others are using. Thats always a good place to start. 
Before you buy your components post a list here and I am sure you will get some comments.

Good luck and keep us informed, it's always great to see other peoples builds as everyone does things differently.

[sirch]

Thanks for taking the time ched999uk I really appreciate it. I'll take a look at those battery specs and the other stuff you mention.

[sirch]

So doesn't going from 2S to 3S increase the voltage from 7.4 to 11.1 and so increase the motor speed and current draw?

The weight in the calc is without drive and payload, bottom right is the drone weight as calculated -  1718g and a potential payload of 3774g. But I guess that is why I started this thread, voltage, KV, prop size, so many possible variables. My starting point was this kit which I assume is something like plausible

https://ebay.us/WLCbyX

[ched]

I have not really seen anyone using 2S for a heavy lift multi rotor. If you up the voltage you actually lower the current as it's all about watts.
Sorry I didn't notice the all up weight at the bottom.

One thing to watch is thrust ratio. i.e. how much lift the props/motors will give vs the take off weight. For a camera ship you want it to be 3:1 at absolute minimum. This is because you need extra power to maneuver and to overcome wind etc.

Have a look at https://www.ebay.co.uk/itm/DJI-F550-RC-Hexacopter-Naza-V2-FC-GPS-E300-System-ESC-920KV-Gimbal-FrSky-Drone/332748306313?hash=item4d79583789:g:WV4AAOSwMhxbY5MC
or https://www.ebay.co.uk/itm/DJI-Flamewheel-S550-F550-wookong-Turnigy-9XR-Black-Pearl-monitor-and-more/312219474579?hash=item48b1bb1a93:g:TFoAAOSwfHVbTONS

I would say 3S minimum.
For a tarrot 680 https://www.ebay.co.uk/itm/HEXACOPTER-TAROT-680-MULITICOPTER-FeiyuTech-Mini-3D-gimbal/323410629489?hash=item4b4cc69371:g:p04AAOSwEN9bXJqT

[sirch]

OK, thanks.

What's the deal with motor KV, I know it means rpm per volt and from what I have read bigger props should be driven with a lower KV motor but does the ESC not take care of the speed? I can see that a smaller prop needs to spin faster so needs higher top speed but what's wrong with running a higher KV motor at a lower speed? Or running higher KV motors at a lower voltage (resistance I guess, i.e. you get fewer AMPs into the motor at lower voltage).

The issue I'm having is finding motors that meet the KV and power rating that don't cost £££. But then may be I've jut got to accept that heavy lift motors are expensive...

[Digit]

The ESC does speed more as a percentage rather than RPM, so a 50% throttle signal is 50% of the motor's top RPM regardless of KV. You could run a higher KV motor at a lower RPM but that would require limiting the throttle range. Also as a very general rule bigger motors have a lower KV thus a higher KV motor may not have the power to drive the prop you want it to.
Higher voltage means fewer amps due to Power=Volts*Amps thus more volts mean fewer amps and (personal thought) a faster response to throttle input.
Heavy lift motors are costly.

[hoverfly]

Good advice on the G.P.S. go for the "8" For a F/C  this might be worth a look at
https://store.mrobotics.io/category-s/146.htm
Nice dupont connectors, I haven't used it myself but it comes recommended  by someone that uses it for long range  fpv.

[sirch]

Thanks again folks, this is a really helpful forum 

[sirch]

This is pretty much what I had in mind it's reassuring that someone else has done it

https://youtu.be/qo-V_2RipP0

[ched]

Motors: Don't forget that rpm isnt the only part to it. Torque also plays a big part. Bigger props need more torque to spin them. They also have more inertia so changing speed also needs more torque. Lower kv motors will, as a basic rule, have more torque.
So while you could spin a higher kv motor at a slow speed it would have difficulty spinning the 10" props.

It's always good to look at the components others use but make sure you have looked at quite a few as only looking at 1 may give you the same problems they had 

Unfortunately heavy lift motors are more expensive as they don't make as many. A large proportion of multi rotors are used for racing and freestyle acrobatics all requiring highish kv motors.