The following is a concept design for a long endurance- low cost alternative to the Ecosynth octo design.  The design is based off of Steve Westerfeld's (of DIYDrones) high performance hexacopter.  It caught my eye when Steve posted his (winning) entry in the T3 Multirotor challenge.

Steve Westerfeld's hexa.  It has an all-up-weight of 2.8kg,1050 RCTimer motors with 15" carbon fiber propellers, and two 6000mAh lipo batteries in parallel. It can fly for 42 minutes.

Based on Steve's design (I contacted him for some advice on replicating his results), I designed a hexacopter with Mikrokopter frame (for lightness), Arducopter electronics (for ease of use, since our lab is already familiar with them), and the pancake motors plus carbon fiber props that Steve used (for efficiency).  

I calculated the weight of this hypothetical copter (camera+dog tracker payload included), and included two 8000 mAh lipos.  The all-up-weight was just under 2.8kg- mainly due to the lighter frame and landing gear freeing up extra weight with which to use heavier batteries.

Due to the near equal weight but increased battery capacity, I predict that the hypothetical hexa could fly for 45 minutes or longer.  The only other significant factor besides all-up-weight and prop/motor choice (which I kept the same) is the choice of ESC's.  I chose Arducopter ESC's over Steve's specialty ESC's; I don't believe that the difference in efficiency of those ESC's would be significant.

Compared to the Ecosynth Octo, our current mainstay for large area mapping, 45 minutes is a major improvement over the octo's 30 minutes.  2.8kg is also safer than the octo's 4kg weight.  And most especially- the cost.  The current Ecosynth octocopter costs nearly $2,500.  As I've detailed in the following budget, the long range hexa costs under $900. 

.

    Component(s)     Price

.

.

    APM 2.5+GPS+Power module

    $234.98

.

.

    3DR Radio Telemetry     $41.94

.

.

    Power Distribution     $19.99

.

.

    ESC's     $108

.

.

    Electronics Plates     $15.99

.

.

    LED Strips     $15.85

.

.

    Copter Arms     $131.7

.

.

    Center Plates     $59.9

.

.

    Landing Gear     $56.85

.

.

    Plastic/Rubber Mounts     $18.65

.

.

    Brushless Motors     $109.08

.

.

    Carbon Fiber Propellers     $65.98

.

.

    TOTAL:     $878.91

The Electronics for the long endurance hexa.  Shown above is an ESC, the power distribution board, two electronics plates, the APM 2.5 + GPS + power module, and the 3DR telemetry set.

 

The frame for the long endurance hexa (not shown to scale.  Arms are longer, landing gear is bigger.)  Depicted above are the center plate, the red and back arms, and the landing gear.

The "pancake" style motor and the 15 inch wide carbon fiber propellers (not shown to scale- props are larger in comparison to motor.)

The 8000mAh 14.8V lipo battery.

The frame uses the long arms intended for the Mikrokopter Okto XL, but places them in a hexa configuration.  This is what allows enough room for 15" props.  The electronics will be mounted on two tiers- one for the power distro board and one for the APM+GPS+RC Reciever+Telemetry, like the other recent Ecosynth aircraft.  A tupperware dome will cover the electronics as usual.  One red led on the front arm and two LEDs on the back arms will help identify which direction the copter is facing while in flight.  Three landing gear legs would be mounted: one on the back leg and two on the front legs.  The camera mount would be the same system as the octo.  Because of the high ground clearance afforded by the landing gear, the propellers and motors will be mounted facing downwards so as to extend the life of the motors and marginally increase motor efficiency.  

In brief: the long endurance hexacopter is a low cost high performance alternative to the current Ecosynth octocopter.

Update 12/19/2013

This is now my battery of choice:

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Gerard

Thanks a bunch for the info! I'll wait to hear your success on this concept design and make the purchase based on your findings!

Appreciated!

Nima

Well, the motors finally arrived. They look quite good, but I haven't been able to test anything yet. The motor mount is a triangular shaped oddness which also uses 2.5mm bolts to the frame. This requires some sort of custom adapter work before it can be fitted. What I read about the motor though is that it seems to perform well. I now have a wattmeter and the rest to be able to make good measurements on the performance with the 14x8's. More to come.

Hi Stehen et al.,

sad news!

RCTimer updated the motors. Actually, the new ones look better and also "sound" better. They have a new shaft with a larger diameter and the housing also looks a little more robust. The downside is that i) they are a little heavier and ii) - much more important - they do not fit on the MikroKopter arms any more because of the bigger shaft and the larger clamping ring. Moreover, as I learned from a MikroKopter staff, the thin 1mm arms are no longer produced. So as it looks i) more tweaking, ii) a different frame or iii) other motors and the heavier arms are needed to build a hexa like this...

Best regards,

Thorsten

Thanks Thorsten for letting us know. Does that mean the clamping ring is also bigger than 10mm in diameter?

There's not a lot of protrusion from the end, shouldn't a simple spacer solve the problem?  Assuming the distance between the screw holes didn't change much.

Here's what a US guy did on mounting the motors on these arms:

http://www.quadframe.us/collections/octoframes/products/medium-weig...

Those 1mm 10x10x460 alu square tubes should be standard enough to find different suppliers. Even if we need to saw the lengths ourselves to be honest, the length doesn't have to be too precise. Drilling a couple of holes shouldn't be too difficult either. Another possibility is using carbon tubes like Ferdinand does.

http://www.metricmetal.com/products/sq_alumtube.htm

http://www.wickes.co.uk/tube-anod-alum-square-10x10mm-x1m/invt/188275/

http://www.marchesironmongery.co.uk/square-tube-1m-x-10mm-silver-an...

http://hobby-miracle.com/index.php?route=product/product&produc...

Hi Gerard, the clapping ring is about 9mm and does not fit into the hole. I'll post some photos the next days. Some washers may help but based on our experience with the yaw I am not sure if it is the best idea, but i'll test it. The main issue is weight. The heavier arms and the heavier motors will add about 100g to the system. But some DIY alu tubes are an option for sure. 

It would be interesting to know what frame Steve Westerfeld used for his hexa. 

Some photos (left: old version, right: new version):

Hi all, I had a new maiden flight today with an all new hexa. Same motors  but 17'' props and a new frame. No crash :-) More to come after balancing the props...

Sounds like a teaser... :)   Any chance of disclosing the frame that you used?

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