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Arducopter with 8 motors - First aerial photos

Posted by Markus Jahn on February 21, 2011 at 2:00am

3689390322?profile=original

Had again a really nice saturday flying with my Hashcopter. Took first images from the copter with my 800 gram camera. Pictures didn't turn up to be anything spectacular but copter flew nicely at high altitude and was very controllable. I'm still waiting for parts to arrive for my camera stand and FPV equipment. For that reason camera stand was just taped to nice position and images shot by feeling.

I actually had some difficulties with cheap ESCs not arming the motors properly. This was due to it being -25 degrees Celsius temperatures and electronics just needed some warming up occasionally. Actually so did the pilot. Eventually one of the ESCs broke down and flying was over for the day.

Because ESCs did some tricks on me I accientally ended up testing what happens when one of the motors shuts down. I was landing the copter still hovering at around 20-30 meter height when one of the motors just stopped. It was nice to realise everything was still controllable and I was able to land to copter nicely to a snowy field. It could have been flown with just 7 motors despite the heavy camera hanging under the copter.

 

3689390554?profile=originalAll saturdays pictures with better resolution:

http://www.markusjahn.net/gallery2/main.php?g2_itemId=47419

Previous two parts of the story:

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

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

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Comments

  • Ground Loop February 27, 2011 at 2:53pm

    Thanks!  Nice drawing -- that explains it very well.

    So you're just using the straight-up QUADcopter code, then, no octocopter software trickery.

    Did you have to do anything special to get the pairs-of-motors calibrated to the same power curve, precise endpoint agreement, or it just works itself out in stabilization?

     

    How did you arrive at your rotor-to-rotor distance?  If I want them equidistant, as you have in your picture (uniform octogon), and as close as possible, the frame intersections are at rotor-diameter (motor-to-motor) divided by the square root of two.  The math works out, but I notice the Arducopter frame sticks the motors out a bit further than it has to.  I'd like to keep it as compact as possible -- maybe +2cm between the props tip-to-tip.

  • Markus Jahn February 27, 2011 at 12:47pm

    3692174581?profile=originalHere is how my motors are rotating. If you counter rotate the pairs you won't have any yaw. This is one thing I was concerned when building my copter because nobody seemed to have tried it before. Now I can say it works really well.

    Here is couple of nicer aerial photos taken this week:

    3692174606?profile=original3692174417?profile=original

  • Ground Loop February 27, 2011 at 1:21am

    Can you explain a bit about rotation direction on the eight props?  Did you pair two identical props on each side, or counter-rotate them?

    Like this:

    http://www.mikrokopter.com/ucwiki/mkm?highlight=%28mkm%29

     

  • Markus Jahn February 23, 2011 at 5:14am

    I have not let the copter stay out to cool down. Actually if I do that my ESCs don't want to initialize. They just start beeping like no radio signal. That could be caused by APM but I believe it's just the speed controllers.

    I've noticed no other problems caused by coldness. I haven't been able to see any gyro drifting happening during flights. 

    At first I did some jumps upside down and weird yawing but that was due to starting the flights in stable mode. If you keep your copter in stable mode some time it is alway going to some direction when trying to fly. Way I avoid this is to keep Copter in acro mode start the motors and give them some power to almost lift off the ground. Then switch to stable mode and take off the ground.

    What kind of issues do you have?

  • Tom Hastie February 22, 2011 at 9:03am

    Hi Markus,

     

    Have you had any issues with the ArduPilot Mega and IMU shield operating in cold temperatures? It's also winter here in Canada, and I've noticed some "odd" behaviour with my ArduCopter using ArduPiratesNG software. Generally the problems seem to be fixed by reboots of the board, or letting the board "cold soak" to the outside temperature before flying.

     

    I'm still trying to track down the source of the issues. And I'm wondering if it might be the gyros and accelerometers drifting at cold temperatures. Do you let your arducopter sit outside in the cold before flying?

     

    Tom

  • Markus Jahn February 22, 2011 at 12:51am

    There is also one positive side more on twin battery setup. Even when flying with 25C battery current with eight motors is so big that when flying the battery down to 3.7 volts it warms up. With two batteries you might avoid this phenomenom which wears down batteries.

    About saving a falling copter I wouldnt count much. Hashcopter can survive a motor failure and ESC failure and I don't believe batteries ever fail suddenly and totally... Of course learned that anything can happen when you are flying. :)

  • Ground Loop February 21, 2011 at 10:40pm

    I just ordered a batch of motors & ESCs.. I'm going to with the Arducopter setup, eight times:

    2830-13 850kV motor

    10x.4.5 EPP props

    20 A ESC

     

    Would it make any sense to run four of the ESCs off one battery, and four off a second battery?  Two power rails, in the event one system has a failure, dead battery, etc.  It seems like the loads should naturally balance between the two anyway.

    I'm not certain four props could hold it up, but at least it might come down more gently?

  • Markus Jahn February 21, 2011 at 2:06pm

    http://www.markusjahn.net/gallery2/main.php?g2_itemId=47664

    I too consider this to be best way to make eight motor frame. It is a bit heavier than the type with arms attached to each other with two center plates. It is also little stronger and that pleases me when flying with heavy camera.

  • Markus Jahn February 21, 2011 at 1:42pm

    About the evenly spaced motors in a circle shape I would say don't change it. For some reason it makes the copter more stable than any other shape. The 83cm diameter comes mostly from the fact that it is still fits to my car and can be transported more easily.

     

    My ESCs and motors are from RCTimer and I am quite happy with them despite one ESC is broken right now. They are 11$ ESCs and 10$ motors so if one breaks I'll fit another. No trouble...

     

    Running 4S 5000mAh 25C batteries. Frame is bolted through the lower bar and top bar has access holes on top bar(it just looks better). Same bolts also attach the "legs" to the frame. I put couple more pictures on the build page where you can see middle part of copter:

    http://www.markusjahn.net/gallery2/main.php?g2_itemId=47667

    http://www.markusjahn.net/gallery2/main.php?g2_itemId=47658

    http://www.markusjahn.net/gallery2/main.php?g2_itemId=47661

    There are no hidden spacers inside tubes, just bolted through. The top bars bottomface and leg work as washers keeping the lower bar in shape when tightening the bolt.

    My props are Graupner E-Prop 10x5. They are strong props but propably bit less economical that Arducopter standard/Maxxprod/APC propellers. As you can see my prop savers are quite rough. But that is how I want to make my copter. If simple things work there is no need to change them:

    http://www.rctimer.com/index.php?gOo=goods_details.dwt&goodsid=146&productname=
  • Ground Loop February 21, 2011 at 9:12am

    I found some of the info in your first post:

    Motors are bolted through one layer of aluminum, with access holes.

    Motors are 750kV / 100W

    You are running 4S 5000mA, yes?

    Bars are 80cm long, 15x15mm 1mm tube.

     

    Prop?

     

This reply was deleted.