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Esc Placement and wire length

nilsen

Senior Member
#1
Hi everyone,

I built a nice Aerial image and video platform on the Tarot Fy680 frame buying the motors and ESC's from buildyourowndrone.co.uk, upgrading to 11 inch props and larger 30 amp ESC's from Jdrones.
So far so good, flies so well, it's very powerful and has no problem lifting the cam and gimbal, well this compared to a phantom 1 which I crashed into the ocean :D

Nevertheless on a flight yesterday evening at 100 meters up the thing started conking out badly (I could see it though fpv) but luckily the APM2.6 and loiter mode managed to keep the hex on a relatively straight down trajectory and I managed a to soft land it in some bushes with no damage.

I rearmed after changing my pants and saw that one of the ESC's was spinning the motor very slowly and irregularly, kind of twitching it, very strange, like a 4 cylinder car engine only running on 3 cylinders.

So here I am, ordering some better quality ESC's and larger 700kv motors and was thinking that I would put the ESC under the props next to the motors as it would simplify the wiring on the hub but then after some googling quickly found a lot of opinions on extending the battery leads to the ESC. Apparently it's a VERY BAD IDEA due to the inductance in the wires.

At climb the copter only draws about 32 amps from the 4s so I'm not sure it would be a problem but I would very much appreciate the expertise from the wonderful folks on this forum.

Thanks a lot!

Cheers from a rainy Zürich.

Nils
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#2
So here I am, ordering some better quality ESC's and larger 700kv motors and was thinking that I would put the ESC under the props next to the motors as it would simplify the wiring on the hub but then after some googling quickly found a lot of opinions on extending the battery leads to the ESC. Apparently it's a VERY BAD IDEA due to the inductance in the wires.
Nils,

It is a problem and is already accounted for in the ESC's CAPs. Any added length at our scale is negligable, unless you're planning on wire runs in the order of meters not cm. Depending on the quality of the ESC, you might have issues with the signal line noise (fixed with a ferrite), but I'd worry more about *Resistance* of you power feeds long before I'd wory about their inductance. Make sure you use a suitable gage wire, but beyond that, it should be fine.
 

Cyberdactyl

Misfit Multirotor Monkey
#3
Also, insure your ESC heat sink plates have plenty of air. Your idea of putting them in the thrust column solves that. Mount them on their side if possible.
 

nilsen

Senior Member
#4
Hey Guys,

Thanks for the tips, that's kind of what I had thought myself but there was a lot of fear mongering out there so I'm glad it should be ok, I think it also looks a lot neater.

By the way I like the idea of mounting them on their side, the motor mounts on the FY680 frame have a lot of holes so I think it should be possible.

Thanks again folks,

cheers!
 

nilsen

Senior Member
#7
Ok great!

Here is a video of the reason I came here to ask you guys in the first place about ESC placement since I'll be replacing my JDrones ones with some higher quality ones:


Here are some images of it with Gimbal:

Hex-1.jpg

Hex-2.jpg

And here is a quick video of the Gimbal I made to explain to people what a gimbal actually does (I had a lot of questions from my friends).


I'll add more images and some video once I get my new components and put it back together.

I also just received my GHT Gimbal so that's exciting... Looking forward to seeing how well that works!

Cheers all, have a great weekend.
 

FinalGlideAus

terrorizing squirrels
#8
Nice copter mate and lucky save there too! The APM is lovely board for that setup. I loved how well it still flew the copter after the esc failure.
 

nilsen

Senior Member
#9
Hey there,

thanks a lot, I was so happy, really I was sweating at the thought of it crashing and dying after the effort and money spent (I watched some crashes of the DJI S800, imagine that)

Anyway my 14AWG wire arrived today so I started the assembly by threading the wire through the arms and soldering to the PDB.

Copters-1.jpg

Copters-2.jpg

I have a APM power module which powers the APM and also provides current and voltage measurement and I had a revelation to solder it from the top to keep the bottom clear for batteries and the gimbal without this massive power cable obstructing the view.

I'll post a pic when I have done it to demonstrate what I mean.

Cheers!
 

nilsen

Senior Member
#11
Well here it is, complete...

As soon as I get bigger motors I'll replace these small ones...

No connectors used as I am trying to keep weight down as well as reliability up.

Hex-1.jpg

Hex-2.jpg

Hex-3.jpg

Hex-4.jpg

Hex-5.jpg

Complete
Hex-6.jpg

Here is the GHT (Grouse House Tech) Gimbal but I have no a6000 yet so I won't be using it with anything other than a gopro.
Let's see how well it lifts it.
Hex-7.jpg

Cheers!
 

nilsen

Senior Member
#13
So I finally received my back ordered motors from HK.

For those of you who don't like stressing motors I'm sure you'd agree that my current tiny jdrones motors are well overstressed with the 1245 props and since I'm considering 1260 they would most likely catch fire :)

Anyway I am most impressed by the initial look of these multistars. I purchased 8 with the intention of making an octacopter but will stick them on the hex for now.
Now to decide if I need to add the 40 amp esc, well if I want to use 6s I will have to...

https://www.dropbox.com/s/1lrplgy8b1q5tdd/DSC_0028_2.jpg?dl=0

https://www.dropbox.com/s/ekjjwpugfxjlaqx/DSC_0029_1.jpg?dl=0

Cheers!
 

trigger

Senior Member
#14
That's a very nice build, congrats.

I investigated a bit into building an hexa recently (even though I have several other projects on the grill...), and I'm a bit surprised at your ESC and battery choice.
As far as I found, 20A ESCs, 12" props, a 3 or 4S lipo (and appropriate motors, I was looking at rctimer's 5010 series) are more than enough to lift around 2kg at 50% throttle (~1kg hexa + ~1kg payload).

So my question is : why do you need 40A ESCs and 6S lipo ?
 

nilsen

Senior Member
#15
Hey Trigger!

I had this mad idea to keep the Hex as it is and was toying with the idea of an Octa and it seems that 6s is nearly always the minimum.
I then started to mess around with eCalc.ch and found that indeed using 4s there was a lack in power, so I used 6s in the config and lo-and-behold it was much better. YES.
Oh but now we're in a whole new problem with ESC's not being rated for more than 4s, they're more expensive and heavier, even when considering that I don't need 45amp, 20 or 30 is more than enough... Now I have these monster ESC's and no Octa.

Thus the plan is:
Remove the tiny motors from Hex, keep it on 4s with the current ESC's and see how it goes. If the flight characteristics are similar than with the smaller motors, take them off again and go the Octa route with 6s power.

How does this hobby chew through money faster than my wife :D
 

nilsen

Senior Member
#16
So rememer those motors I had above? They are for the large Octa for professional video etc however I had some time and no money for the Octa frame as of yet so I decided to put them onto the Hex.
For some stupid reason I thought they were 700 motors when in fact they are 390 motors designed for 15 or so inch props on 6s (hence the 45 amp esc I ordered with the motors).

Nevertheless I spend a day removing the small 890kv motors and installing these huge beasts and it comes time for a test flight.
I didn't do any calculations on ecalc or anything, I just put them on, made sure rotation is correct and maiden it.
Throttle 50%, nothing, throttle 60%, nothing.
Recalibrate ESC.
Throttle 50%, nothing...
Throttle nearly 100%, we have lift off :(
So now I can finally say I understand the whole rotation kv thing.
I inserted all the parameters into ecalc and lo-and-behold it says that with those motors on the hex and 12 inch props I need 80% throttle to achieve hover. Well there you go :)
Motors are off again, now I'm thinking if I should install the old ones back again or if I should get some others, ideally I would want a hover at 40% throttle and enough capacity to carry a NEX size camera comfortably.

I'll keep you all updated.
 

nilsen

Senior Member
#17
Hello Everyone,

I thought I'd give you an update on how my hex is looking.

I took off the huge 320kv motors when these arrived and finally replaced the Jdrones ones which were actually ok but they were unfortunately a bit small and I was worried about the quality of them. They also got quite hot when using the 6 pitch props and larger cameras hence I upgraded to these little beautiues.

They come pre-balanced and run quietly and cool, I wish I could put 13 inch props on here, I know the electronics could handle it, I wonder if the frame would allow it.

I also had massive problems with the 3DR telemetry link as the range was less than 3 meters however after some research I see that the antennas which ship with the modules are made for 2.5 GHz or so, so I decided to make my own and now the range is unbelievable. Well to be honest, I haven't gone further than 50 meters but the link was still very strong which is a 1000% increase than before.

New 915MHz antenna
Hex (1 of 5).jpg

Green motors - Turnigy 3252-850kv
Hex (2 of 5).jpg

Antenna on ground station
Hex (3 of 5).jpg

Motor and 12x6 prop
Hex (4 of 5).jpg

APM planner on computer.
Hex (5 of 5).jpg

I really like the APM and now the hex is so stable and hovers with about 40% throttle with the gopro and gimbal, I recon with a larger payload it would hover at about 60%.

The APM really is so stable, I know most folks like the crazy acro flying but for my business as a photographer and videographer I need stability and reliability :)

Here is a short video of it flying and some shots of the area where I live.

Cheers!