About a month ago I decided to invest into a hexa for the purposes of aerial and ecological mapping. Over two weeks ago I ordered a range of parts online, in total 5 different shipments. The beginning of this week the frame arrived from mikrokopter.de. The rest should follow shortly or next week.

This build is based on the description of the concept design from Stephen here:

Concept Design for a Long Endurance Hexa

I followed most of it to the letter, but acquired arched landing gear and spares. The arched landing gear is useless in the end, as it's a lot shorter and weighs the same as 3 struts, which is the maximum I'm going to use. When the equipment arrived I felt a little bit underwhelmed by how thin and fragile everything looked, but as I started to put this together I recognized how the construction actually wasn't too bad.

Before going for the hexa I also considered an octo or a quad. An LE quad has more 'airtime', but it doesn't have any reserves for payload. I may want to hook up 500g or so at some point. The octo can carry a lot of weight, but the airtime and complexity is a lot worse.  So I settled for something inbetween.

First thing to do for the frame was to see whether the weights were correct as reported on the site. if these deviate too much, then all of the calculations will be wrong. I found them all to be correct as reported down to the last gram.
Here's a little list to save you some time:

  • 2x GFK center plate    30g  = 60g
  • 6x Arm 460mm ( Octo XL ) black or red,  58g = 348g
  • 3x HiLander gear complete with mounting brackets  28g = 84g
  • 4x large vibration dampers  = 6g
  • 4x small vibration dampers (lipo holder)  = 5g
  • Lipo Holder = 53g
  • 12x metal bolts+nuts in construction = 18g

Total frame weight: 574g

Expected AUW: 2375g one battery or 3250g for two batteries.

The photo shows the size of the frame vs. the TBS Discovery which I have around. On top of the plate is a computer mouse to provide another indication. The prop is a 10"x5.5" APC one which is typical for the smaller Arducopter hexa. Eventually this machine will use 15x5.5" carbon props.

Calculations on flight duration for a 143g payload (Canon IXUS 230HS) show that I should expect to get around 41 minutes out of this machine on a single battery with 11Ah. A second battery of the same size adds 12 minutes to 53 minutes flying time. I'm always a little bit skeptic of such numbers, so I'd be happy for 25 resp. 40 minutes already.

More to come!

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Comment by Jonathan Dandois on August 17, 2013 at 9:28am

Awesome work Gerard.  What kind of camera / sensors are you going to equip?  Our work so far has just used red-green-blue point-and-shoot digital cameras and we have recently had great success using a Canon ELPH 520-HS housed in a waterproof case.  

The case is no longer waterproof, we removed the rubber button pressers, drilled holes in it for mounting on the copter, and removed the lens cover after it cracked on a hard landing.  But we found that using the case makes securing the 'continuous shooting mode mechanism' (CSMM, a.k.a. a plastic nut, electrical tape, and a velcro strap) much more secure and have never had a problem with the camera turning off or not taking pictures during flight.  We also suspect that the case holds the camera more tightly than just a 1/4-20 screw or our previous methods of strapping it on with a velcro strap.  The result is nice crisp photos and fewer lost cameras on rough landings. Win-win!

Jonathan

Comment by Gerard Toonstra on August 18, 2013 at 5:47pm

I plan to use the Canon IXUS220HS for normal photos and another Canon Powershot SX220 using a filter as sold by publiclaboratory.org.  There are some issues there getting pictures that are comparable to other pictures over time (they don't have an absolute reference yet, only a relative one), but I hope to get that sorted at some point.

I made a little script for taking pictures on the IXUS using CHDK. The camera is turned on before flight and then the flight controller sends a short pulse of 250ms to trigger. It can also send a longer pulse to shut the camera down to protect the lens. I still have to see how I can trigger that mechanism using the APM.

Good idea about watertight housings to secure cameras. I planned to do something with velcro straps or rely on the lipo holder casing itself (just drill a hole in it.). This is yet to be sorted.

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