Build Thread: Flight Tested CarbonCore Cortex 6.0Kgs Naza 3 Axis Gimbal 30min+

[CarbonCore Multicopter]

Hello Multi-rotor readers!

This is Adele & Cam at CarbonCore.
We';ve been making and selling multirotor (or "drone") airframes for about four years now.
The motor arm tubes with the steel threads are still the same, but we';ve also become a limited company,
and started a family.

In this thread we';re going to build a boxed Cortex Carbon Airframe, just as we';d deliver one to you.

We made more this time so we can offer them to the UK for £550 + VAT + P&P!
If you';d like to get one, please write to us through our website at www.CarbonCore.com
Before purchasing a carbon airframe, we ask that you are confident in your choice and combination of electronics and that your flight controller is known to work in X8 configuration drones. We do not recommend a Cortex as your first drone.

To get a Cortex that has been flight tested, with a well-tested set of electronics, please ask one of our Resellers for a Cortex RTF (Ready to Fly).


As we work through this build we';ll talk about all the components and thier installation and setup.
And have a close-up at the carbon and a check-through everything that';s installed.

So here it is! Delivered in a plain white box. about 425 x 360 x 80mm.  1490g.


Opening the box. There are four motor arms with mounts pre-fitted, taped to the bubble wrap around the assembled centre frame.


Motor arms up close


Emptied the box


And un-wrapped everything.


We guess anyone at this stage can';t resist standing the frame on the legs, but then you';d have to take it apart again...

These are 100% carbon laminate. So they';re a little lighter and more expensive to make.



The centre frame, retracts, motor arms and skids are all pre-assembled, ready to bolt together, after fitting electronics.
There';s a few little hardware bags, red thumb screws, short bolts for the skids, long bolts for the arm pivots, retract pins and motor X plates - we';ll explain them as we go.


And a quick look at the retracts that slot through the frame plates.


Next post we';ll have a look inside the frame and open some new motors!
Thanks for reading :)

[Desmoboy]

Hi Cameron and Adele
At this price these are a steal.
Can you tell us what the price for the parts is now going to be should we have the unfortunate need to replace arms , legs etc ?

[CarbonCore Multicopter]

Hello We hope everyone had a lovely Easter Holiday!

All spares will be at the same pricing as when the frames were £659+vat.
Please write to us if you';d like an order form!

[CarbonCore Multicopter]

Next the pre-assembled skids were bolted to the legs. Four, M3x6mm torx bolts for each leg.

[CarbonCore Multicopter]

Retracts and arms slotted in to frame just for looks



The carbon plate tolerance can vary by +/-0.05mm, which doesn';t sound much, but it can be the difference between a loose fit and not being able to slot the tabs through the frame.
So we check them all before assembly. And if they';re too thick, they go in a special drawer. It';s really important to us that the parts fit together and work. We';ll look at fastening the retracts and setup in a later post.

[CarbonCore Multicopter]

Motors and ESCs. Any 8 should do - they';re all the same! We chose the Tiger 4010 370Kv motor and 30A OPTO Pro ESC for the Cortex. We have an equal amount of propellers in stock (more on props later). After testing a load of motor brands, types and props, we settled on this combo. We should probably get some more soon...



Motors, ESC and props all come in sealed bags with part numbers. So we open them and check a few things before bolting them to the Cortex.
Notice the small bags of prop plates, bolts and rings have NOT been opened - they';ve been saved in a little tray for later.

Also saved 2x Tiger ESC instructions.

[CarbonCore Multicopter]

(We weighed everything while it was open and separate)



Centre Frame:            510g
4x Arms:                    215g
Retracts:                    355g
1x ESC:                       20g
1x Motor:                   125g
8x Motors + 8x ESC: 1220g
Hardware bags:          120g

All:                          2565g

[CarbonCore Multicopter]

Next is to just look at each and every motor from above and below:
We';re looking for: foreign objects, anything in the motor/coils, bad coil enamel, anything that looks abnormal, damaged insulation on coils and cables, C-CLIPS on, all motors spin freely and sound the same.



At this stage it';s also worth getting the multi-meter out, setting it to Ohms and checking that the three combinations of pairs of motor cables all read the same resistance, about 0.05.  (Cable combinations are red-blue, blue-black and red-black.

The meter should also ring-though every pair as a dead-short. if it doesn';t... that means broken stator wire.

You can';t beat just taking the time to look at something :)

Luckily, all these motors seem OK!

[CarbonCore Multicopter]

At this stage we';d normally fit the motors to the arms, but we';ve learned that it';s best to remove ALL the M3 grub screws and then glue them ALL back in...  They come to us with a little glue on them, but they';re not really tight and take very little to undo. 

If this is done after the motors are fitted to the copter, it can get confusing to remember which one has been done etc. (OK there';s no harm in labelling things if that';s how you build).

A few customers have had motors start pulling-apart before, resulting in the motor stopping as the magnet can (with propeller) gets out of line with the stator. So we';ve given discounts and replaced motors before.

We hope all new customers can get to read this thread, and get flying quickly and trouble-free!



Using an M2 Hex driver, two M3 grub screws were removed from each motor.

Look at the flats in the right photo. We have found motors where the flats were not lined-up with the grubs. they need to be. We used a helicopter tool with a one-way bearing, designed to stop a 4mm shaft rotating, so we could turn the magnet can against the tool to line the flats up with the grub holes.

Each motor was checked for free-spin and "float" along the spindle. What we mean by this is the magnet can (the top bit the prop bolts to) has not been pressed all the way on to the shaft. So the fix is to put it on the bench and press down on the top of the motor (not the shaft).  One of the eight motors did have some float and it "clicked" while pressing on it, and then it was fixed!

Thread Lock was applied and the grubs re-fitted to every motor.

[CarbonCore Multicopter]

 :popcorn:Fitting motors to the arms:
All that needs to be done with your new Cortex Carbon airframe, is remove the TOP motors plates. The top and bottom are the same, but please check what way up the CarbonCore logo is on the arm, before attempting to remove the LOWER bolts, that don';t need to be removed. 

We thread lock the ALL the lower bolts and pillars when we assemble the airframes.
Here';s a look at the Carbon Motors arms with steel threads fitted.

[CarbonCore Multicopter]

The motors are fitted to the motor mounting plates, by feeding the motor cables through the small grommets, one-at-a-time. This must be done from the counter-sink side of the motor mount as shown in the photos.



Now the hardware bag with a stack of little X-plates and some bolts.



The motor bolts are M3x8mm.  32 bolts are needed to fit all 8 motors.
*The frame plate bolts are M3x6mm and are NOT suitable for the motors - they';re just too short.

[CarbonCore Multicopter]

With the cables pulled-through the motor tight up against the plates, the motor threads for the 45-45 hole pattern "X" all get a small drop of thread lock.
Then the M3x8mm bolts can all be bolted-up to the motors through the X plates and motor plates.



We also like to put one bolt in first but not tight, and then the other three. Only tightening once they';re all in.

[CarbonCore Multicopter]

We tape the three cables for the top motors to themselves, to keep them separate from the lower motor cables.
Then all the cables can be fed down the arms,
Thread Lock applied to both pillars and steel thread on each arm,
And the top motor mounts bolted-on.

There';s a knack to it: Sit the top motor plate slightly past the bolts holes and press it back on to the arm. This gets the lip of the grommet over the edge of the carbon tube, and avoids it getting caught between the motor mount and motor arm tube.



That';s all the photos for this week!

We don';t mean to rush this thread: but so far there';s not been much to discuss. And we want to do a few more threads too

www.CarbonCore.com

[CarbonCore Multicopter]

Next week we will be adding braid to the wires, Motor/ESC testing, ESC fitting, Powerboard soldering, Regulator install and voltage set.

However... What Flight Controller should we fit?!?

We can try a Naza, which means we';d have to do slightly different-to-normal wiring. And we';ve heard the Naza';s not great at X8';s. (OR is it???) Or we could continue the thread with an X4 Quad-Cortex. We can also get an A2... But why use an FC from a company that don';t do an X8? We also have a ZeroTech courtesy of CopterSquad.com and we';re sure there';s at least one-hundred other controllers we could consider. We';d really like to try something cheap and tuneable, with sensors...  Looking forward to your suggestions for next week!

[Desmoboy]

3DR Pixhawk since you are asking

[Hands0n]

+1 the 3DR Pixhawk.  Supports the X8 of course.  And bristling with ports for sensor technologies using I2C and/or CANbus. Built-in redundancies, and ability to add a backup GPS for increased redundancy there also.  The Pixhawk will complement the air frame perfectly.

[CarbonCore Multicopter]

Thanks for the recommendation on the PixHawk - some of our customers have/are using them in the Cortex. We want to read the instructions before deciding on which FC.



8x 200mm lengths of cable braid and 8x 40mm lengths of heat shrink tubing were cut and fitted over the 3-bundles of ESC cables.




The purpose of the next step is to make sure an ESC is working normally, and then make sure the motor spins the right way.
Next is to check if the ESC works. So a 2.4Ghz transmitter (we go flying with this one) was bound to a matching receiver (Spektrum works with JG), powered with a JR NiMh 4-cell battery that came with the Tx. The end points of the throttle channel were checked in the Tx menu, and they were set to 150%, instead of the normal 100%. Some say that this increases the resolution of the control signal, as the range would now be 300 steps instead of just 200. A good check is to plug in a servo - directly into the throttle channel on the receiver that the ESCs are going to be plugged in to. And go high-low on the transmitter throttle stick to see if the servo goes its full range. This one passed the test so it';s safe to assume that when the ESC is plugged-in, that it will receive the full throttle range from the transmitter. This is curtail should you want to calibrate the throttle range of the ESC. So we';ll first read the ESC manual before attempting calibration.

The last photo shows an edge-view of how the upgrade retracts set builds into the retracts. One-piece pillars that can';t spin. And adjustable metal servo arms.
More on retracts later when this Cortex gets upgraded!

[CarbonCore Multicopter]

The battery used to power the ESC is a 6-Cell Lithium Polymer rechargeable. or LiPo. They';ve got a good energy-density which means they';re light with lots of capacity or flight time. Also the larger the capacity typically the more current you can draw. The advantage depends on if you need to keep the batteries warm or cool.

Cortex 4010 370Kv motors are rated at 20A max working efficiency. If they were to draw any more then there';s a problem, as motors then just turn the extra current in to heat. So 8 motors times 20A is 160A. 200A power distribution board should be fine.

Checking the main motor/ESC battery while the soldering iron is warming-up. We';re going to need to fit a plug to the ESC to power it to spin the motor.
All the cells are to within 0.01V of each other and are mostly the same voltage. So that looks like a balanced pack with good charge in. If the cell voltages were below about 3.2V then the pack should be charged some more before use.  One of the ways lithium polymer batteries can get damaged is when they get over-discharged, then the next time they are charged the chemicals are a bit different and the cells can inflate potentially causing a fire. So charging batteries are kept close-by.



Now normally the ESC cables would be trimmed to length for the designed fit in to the Cortex centre frame. But we might build this one a little differently depending on the choice of flight controller.

[CarbonCore Multicopter]

So now an XT60 connector that fits the battery is fitted to a partner and clamped in a vice by the terminals. This sinks the heat away and stops the 40W soldering iron melting the yellow plastic. If the solder joints can lift the vice then they can';t be too bad. they look OK. e.g. not dray and crispy like a dry joint. Cables and plugs are tinned and soldered together, then heat shrink fitted and tucked inside the plugs. This can now be temporarily solder and insulated to the ESC we';re going to test on the throttle channel of the receiver.

Do NOT do this if you are soldering a plug to a battery. That would result in a short-circuit and maybe a fire.
For fitting a plug to a battery we would also insulate the partner plug';s terminals and clamp the plugs by the body. Insulating the vice would also be good.

[CarbonCore Multicopter]

Here';s the test setup on the bench. Top left: RD600 receiver, receiver battery and transmitter.
Middle row: ESC (plugged in to throttle on receiver), motor arm with lower motor connected to the ESC.
Bottom of photo: The connector cable we just soldered and the 6S 10,000mAh LiPo battery.

The transmitter is switched on first, then the receiver battery is plugged in to the receiver, then the big battery can be plugged in to the ESC.
It';s probably not a good idea testing a motor on the bench like this - it could easily touch the bench and "drive off".
The ESC played a tune when powered-up, and the motor stayed still at low throttle and spun at full speed as the throttle stick reached the top (not before).
That was the results we wanted. So it looks like the motor cable colour sequence top-to-bottom (of the ESC with the black cables at the top), is black-blue-red.

All eight motors can now be plugged in to all the ESC';s: Black-Blue-Red as shown in the photos.
This is for the X8 setup where all top motors spin counter-clockwise (when viewed from above) and all the lower motors all spin clockwise. This setup then only needs two types of props, instead of potentially four types.

[CarbonCore Multicopter]

The cable braid and heat shrink cut earlier has been fitted over the 3-bundles of motor cables.
All the motor cables without sellotape were plugged into ESCs - these are the lower ESCs and motors.
And numbers M5, M6, M7/F1, M8/F2 are all applied to these ESCs - the orientation of the labels is so they read the right way up and on the inside when the ESCs are fitted.
Then all the tape can be removed and the ESCs for the top motors can be plugged in. Labelled M1, M2, M3, M4.

In the photos top-to-bottom the arms will be designated 4,3,2,1.
Arm one is in the top right-hand corner of the frame, with the Cortex facing away from you.

Before heating the heat-shrink all the motors and ESCs were tested as shown in the above post with the transmitter, receiver and batteries to make sure the motors are all working and going the correct way.

[CarbonCore Multicopter]

16x M3x6mm bevel bolts removed from the top plate.
Top plate removed for a look inside.
All the cable ties to fasten the ESCs to the little vertical plates are already in place.
The ESC carbon plates are super-glued to the lower frame plate, and each have a bolt also super-glued in place.
This is just to fasten these plates to the lower frame plate, so they stay there and don';t just fall out when the top plate is removed.
All the 31mm and 10mm pillars are already fitted with thread-lock.

We might wire this one differently... removing the four 10mm pillars in the middle, that are intended for the 200A power board, and fit a small carbon plate there for a flight controller that needs to be fitted on the centre of gravity (the middle for now).  There';s a Naza in the photos but that doesn';t immediately mean it';s a good idea. There';s also a ZeroTech YSX4 ZeroUAV flight controller here, courtesy of Malik at CopterSquad.com but we';re going to read the manuals for both of these and others before deciding what one might be best and trying it.

[CarbonCore Multicopter]

Here';s how we';d normally wire-up a Cortex ARTF (Almost Ready to Fly).
This works for the WooKong and A2 flight controller. But not for controllers that need the sensor in the middle.











We';ll continue this thread next week with how we';re building the Cortex we';ve just un-boxed.
It';s likely we';re going to solder the ESC cables together with a wiring loom and centrally mount either a Naza or a YSX4, because they';re here.
The pixhawk sounds interesting but we need to do some reading first!

[CarbonCore Multicopter]

Adele & I have a read through a NazaV2 manual and not seen any reason we can';t use it, yet...
We';ve flown Hexa950 at AUW 6.5Kgs with Naza';s and they worked fine. Those were V1';s.

So the things that jumped out at us when reading the manual:
It';s got Attitude Mode which makes it self-levelling, and GPS mode to keep it still when there';s a GPS signal. And Manual Mode looks like it will let you roll the copter on it';s side until it crashes, so more like a normal RC heli or plane.

When we';ve flown with GPS, when it loses the signal, the FC will make the copter it "kick" back to level in Attitude mode, and then it might drift downwind a little until corrected by the pilot. But then when you get GPS signal back, it';ll noticeably "take back" an attitude to hold it';s position. The Naza says it';ll do this after 10 seconds of lost signal.

Naza Attitude mode is limited to +/-45 degrees of pitch and roll - that';s plenty.
And the Naza GPS should be on a mast because it';s sensitive to magnetic interference which can be made by batteries, cables and motors.

"For larger aircraft than 650, the WKM is recommended"...  Well we';re going to try a Naza in an 800mm quad...
"Make sure the aircraft CofG is in the centre"
"Try your best to mount to MC (Multi-rotor Controller Naza) at the centre of your frame"
"ESC ports face the front"
"Immediately Mode" sounds like it';s to be avoided.

Configuration -> Mounting - This appears to be for the GPS, ONLY. And the Naza itself has to go in the middle on the CofG.
The XYZ axis in these manuals have never been a standard convention and are only in whole centimetres. So it might be best to mount the GPS a round number away from the centre.

We can';t find any notice on aircraft weight limit or if ports F1 and F2 can be used for motors.
Page 31 has compass calibration.
Page 36 for V2.2 has only 6 Multi-Rotor configurations and the X8';s not on there... But then there might have been a firmware update since we got them, we';ll find out when we plug it in!

We think if we build a Cortex with the 4010 370Kv motors, that were intended for payloads up to 6Kgs, it';s only just going to be in 7Kgs AUW with a 3-axis gimbal, one battery and a compact camera. Ideally smaller motors would be ideal for this build like how CopterSquad.com sells the Cortex. - They even build them to be under 5.0Kgs!
But at least this one should be fun to fly with lots of power!

[CarbonCore Multicopter]

We';ve decided to fit a Naza.
The Firmware update showed it can do an X8.
And we aim to find out if this works in just a few days!

All ESC were calibrated as in Post #19
[attach=1]

8 ESCS were individually calibrated. And with the Same transmitter and receiver the Cortex is going to be flown with.

One ESC went into program mode:
Another ESC and motor went straight to full throttle!
(As if it was supplied from factory with reversed throttle).

The supplied manual does not seem to exactly match what happens...

The actual procedure is:
Turn on Tx.
Go to high throttle on Tx.
Plug ESC to throttle channel.
Power Rx with 4.8V.
Power ESC with 22.2V.

The ESC/Motor beep "1-2-3"
Then beep "beeeep-beeeep"

Then you must go straight to LOW throttle,
where the ESC/motor give a single long tone to confirm the low throttle end point has been set.
Then the motor RPM will correspond to the transmitter throttle stick position.
And this was done and all motors'; throttles all appeared to respond the same.

The manual seems to have an extra step where the it says the ESC will beep the number of LiPo cells after the "1-2-3" tones. But they don';t do this, and if you wait for the extra beeps, they seem to go into program mode. It';s probably worth thoroughly going through all the ESC settings just on case they do have some differences.

We have been advised that the NAZA WILL NOT WORK in an X8. But we';re going to try it anyway!

Build photos next!

[CarbonCore Multicopter]

The Naza instillation.  Dead centre. 3mm foam tape. 
All the ESC wires going to the Naza might act on the Naza to move it around slightly.
So it might be an idea to pad all the wires in with some foam. But we';re just going to fly it first.

These ESCs were soldered together with a wiring loom.
The left regulator has been set to 12.0V to power a gimbal and video transmission.
The right regulator has been set to 6.0V to power the retracts.

+/- 6.0V Out from the retract regulator goes to a Y-lead that powers the retract servo motors.
The white signal wire from this Y-lead stays in the plug and plugs into the gear channel on the receiver.
These retracts work like this. They might just need the endpoints setting - but after we';ve checked it';s OK to plug the battery in.

[CarbonCore Multicopter]

Electrical test before powering!!!

We don';t know what';s going to happen when the battery is plugged-in. So here';s a few easy tests to help make sure it';s going to be Ok!

The multi-meter has a Diode symbol on it. This is the continuity test that sounds a "beeeeep" when the probes find very low resistance or a dead short.
Probing the threads inside the pillars gives a dead short.
Probing the edges of the carbon to any bolt or pillar thread gives a dead short and "beeeep"

Probing the battery connector pins ON THE CORTEX (and NOT the battery) when the meter probes touch both the positive and negative terminals inside the XT60 connector, the meter sounds the "beep" for a few seconds while the capacitors in the ESCs charge-up. The resistance continues to climb and the beep stops, now at "infinite" resistance.
It';s the meter charging up the caps.

This also means when you first plug the battery in, there';s a bit of a spark inside the plugs. This is very normal.

IF when metering both the terminls inside the plug that the battery connects to, and the beep never stops, then somewhere the battery power wires must be shorted, and connecting the battery will result in a melt-down...

[CarbonCore Multicopter]

Here the retracts have been fitted and then the locking pins, each with a bolt from underneath. 

[CarbonCore Multicopter]

These pics show the Y-lead from the retract regulator and the plugs from the servos.
They';re plugged-in and pulled back into the frame.

[CarbonCore Multicopter]

Final wiring check before bolting-on the top plate.
The main thing is to check none of the wires are on the ends of the pillars, so they don';t get trapped.

Note the CarbonCore Velcro straps - two 200mm lengths have been stapled together and fed through the slots on the top plate before bolting the plate on.

The GPS mast is exactly 10cm in front of the CG (also the middle). This is important because we remembered from using Nazas before, that they only accept whole numbers.
And the carbon rod supplied for the GPS mast was a very lose fit in the metal GPS mounts, so we glued it with two-part epoxy and spun it round for a while to make sure it was as straight as it can be without knowing a proper method to make sure the GPS mast isn';t leaning.