Arducopter with 8 Motors - Crash, Rebuild and First Flights

Here is video of first flights with the new lighter Hashcopter. PIDs make it a bit agressive and unstable because of reduced weight. Also you can see the massive camera flying with the copter.

Story goes like this:

I had a bad crash after few hours of flight time with Hashcopter. Crash was caused by flying the battery too empty and one off the ESCs cutting power off. The copter is capable of landing with 7 motors but I made a mistake flying to the direction of the broken motor to get it closer to pilot. This caused it to lean on the corner with no power and from that it couldn't recover, flipped and crashed from 20 meter height. Frame bent badly and one of the motors was never found. Fortunately most of the electronics survived from the crash. Lost only two motors and one ESC.

For some time had been thinking how I would change things if starting to build the frame from scratch. This was the perfect excuse to start all over again. So here are the changes made to totally the new frame:

- Used 10x10mm tubing with 1mm wall thickness. This saved 160g of the frame weight and frame is still strong enough for all practical purpose.

- None of the wiring anymore goes inside the tubing. These things are always being repaired and taken apart for some purpose. I don't want to do any extra soldering just because I need to get something detached from the frame.

- Made much lighter landing gear from 6mm aluminium tubing. Saved 60g from that.

- Built really simple Camera mount with no servos from 6mm tubing. I take only still images and usually the camera stays in one position or can be manually turned on ground.

Overall I got the whole copter over 400g lighter and that means minutes of more flight time. Overall flight weight after lightening is still 2700g. This includes 730g of camera and 530g of battery.

 

And here is a nice sunset shot from repaired copter:

Earlier parts of the story:

http://www.diydrones.com/profiles/blogs/arducopter-with-8-motors

http://www.diydrones.com/profiles/blogs/weight-testing-of-8-motor

http://www.diydrones.com/profiles/blogs/arducopter-quad-with-eight

Views: 1082

Tags: Arducopter, Ardupirates, Hashcopter, Octocopter, Oktocopter, Oktokopter, camera, flying, mikrokopter

Comment by Cliff Dearden on March 29, 2011 at 4:57am
I like it.
Comment by ARHEXA on March 29, 2011 at 8:30am

That's nice, quite aggressive.

 

i was planning to build a version like yours (using 2 motors on each channel = 8 motors)

because of the reliability that you reported a successful landing with 1 dead motor.

 

now you fried another motor in another flight (why do they fry so much ?) but couldn't land safely with 1 motor dead....

 

I'm hesitating between a 6 motors version (one on each of the 6 channels) or 2 motors on 4 channels like yours.

i've been told that having 6 channels should increase stability over having 4 channels....

Comment by DougB on March 29, 2011 at 10:17am
You may have said somewhere else but I couldn't find it. What code are you using?
Comment by I.S. on March 29, 2011 at 10:39am

@Markus

Congratz, I think the weight is really low, for that big drone and camera

Do you know what was the cause of motor death?

And yes, the okto looks quite nervous on the air, but no heavy feeling at all!

@AR

6ch should make corrections more accurate than 2x4ch

Comment by Markus Jahn on March 29, 2011 at 12:28pm

@I.S.

The motor did not burn. I just flew quite long and the battery voltage got so low one off the ESCs cut off power. You can't turn that stupid feature off. When one motor is off, voltage is again higher and rest 7 stay on.

Copter can barely fly with seven motors and it was windy. So when tried to fly in the direction of shut off motor the copter could not stabilize itself. I should have just let the copter stay where it was and landed there.

 

@AR

I've said before that my next copter will be a Quad with big around 300W motors. You can build it so much simpler and lighter than 6 or 8 motor versions. It will have longer flight times because of that and it can be made stable enough.

Comment by Markus Jahn on March 29, 2011 at 12:39pm

@DougB

I fly with ArdupiratesNG code r.589. Will be switching to the new ACM code as soon it is published. Waiting eagerly...

Comment by ARHEXA on March 29, 2011 at 12:41pm

Markus,

what type of 300W motors ?

also, why not making it 6 channels if it can be more stable ? even if you don't need to be stable for stills camera,

if you go-back to quad - a single motor/ESC failure - you have no chances.

with 6, you still have backup, and more stability....

 

i see you use 8 of the jDrones 850kv purple motors (right ?)

how do they handle the heavy load ? do they suffer a lot ? are getting really hot ?

what about the relative throttle ? does it push relatively far ?

Comment by I.S. on March 29, 2011 at 12:53pm

Sorry, I read the post too fast.

and yes, low volt cut-off is quite dangerous, better to look for soft cut

Comment by Markus Jahn on March 30, 2011 at 3:23am

@AR

I have used 750kv motors from RCtimer. Those look exactly like Arducopter motors. My motors are these:

http://www.rctimer.com/index.php?gOo=goods_details.dwt&goodsid=...

Now they also have the same motor with longer 40cm wiring:

http://www.rctimer.com/index.php?gOo=goods_details.dwt&goodsid=...

Those have worked really nicely and none have failed(flied with 14 of those in two different copters) except in crashes. They didn't get even warm with the heavier 8 motor version. Hashcopter hovers about half throttle and has always had more than enough power.

6 motors/channels doesn't actually make it so much more stable. I mean for shooting video good result can be achieved by carefully balancing props/motors and building properly isolated camera mount. The good thing with only 4 motors is the simplicity and saved weight.

Something like that should have enough power for big quad that could carry same as my octo:

http://www.rctimer.com/index.php?gOo=goods_details.dwt&goodsid=...

Has anybody built big quad with arducopter electronics? It would be nice to see how it flies.

@I.S.

My ESCs have the Soft Cut-Off on but for some reason you can't feel, sense or see when power is being reduced close to cut off. I will next do some battery and flight time testing. Could at the same time check what happens when one off the motors cuts off and also does my wiring give equal voltage to all the ESCs under power.

Comment by I.S. on March 30, 2011 at 9:27am

@Markus

Might be because soft-cut is done reaching really low voltage (3v/cell) and you don't get that deep?

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