I am a part of MICAV 2013, we're a 4-man team. http://www.nal.res.in/micav2013/
We need to build a fully autonomous air vehicle for surveillance. and we chose to go with a multirotor.

Now the concept is, we need to build a quadcopter that has a overall diameter (including props) of not more than 330mm, it must have FPV and should have a flight endurance of at least 15mins-- as per the rules of the competition. 

We have an ArduFlyer 2.5 flight control board-- is it compatible with such small multirotors?

The prop-to-prop distance in the quadcopter is compromised (only 12mm) in order to get the dimensions right-- How bad can a quadcopter handle with such less prop-to-prop distance? Is it a very serious downside?

What kind of materials are suitable for constructing a very light weight frame?-- any special building techniques or materials?

In what unconventional ways can the flight time be maximized?

It also needs a small FPV Tx unit, preferabally 5.8GHz with minimum 200m range. We already have a 2W Tx, but it's too heavy.

How to choose appropriate parts for the quadcopter to achieve the above requirements?-- I have selected a few parts, it would be helpful if someone can tell me how suitable the parts are.

Motors: http://www.hobbyking.com/hobbyking/store/__5431__AX_1806N_2100kv_Brushless_Micro_Motor_19g_.html
ESCs: http://www.hobbyking.com/hobbyking/store/__5431__AX_1806N_2100kv_Brushless_Micro_Motor_19g_.html
Battery: 3S 1000-1500mAh
Props: 5"

I'm guessing the quad is going to have an AUW in between 300-500g at most.

Also, we're not able to find 5X5.5 or 5x6 quadcopter props, anybody know where it's available?

 

Yes, arduflyer should be compatible with small quads, with proper tuning.

Using carbonfibre tubes for frame would save a lot of weight, with self made mounts out of 2/3mm ply or balsa etc

Flight time can be maximized by using good efficient motors to begin with such as t-motors.

For fpv you can use 5.8ghz 200mW tx/rx with cloverleaf/skew antenna, should give you more than a km of range.

But fpv with 15 mins flight time with an auw of 300-500 gm is like rope walking.Its achievable, but increases the costs. So if you can spend more $$ its achievable.
 
Then again you would be using hobby grade stuff, which can be replicated rather easily.
All you would be doing in miniaturizing something thats already been done.
So you should think out of the box for such competitions given there focus areas such as
co-operative flying,multiple vehicle co-ordination,etc.

Anyhow, best of luck

Thanks.
I am looking into building the frame entirely out of CF.
The T-motors dont seem to be available in high KV versions, I'll need motors in the range of 2000KV+ I guess because the design limits the prop size to 5" at most from which I need to draw close to 1KG of thrust from all four motors.
The problem I'm facing right now is in choosing the right components. We have just one shot at this as the competition is scheduled for early Jan, 2014.

This is actually not out first attempt, we have already built 5 tricopters and none of those worked right.

use these motors, same kv but weights five grams less http://hobbyking.com/hobbyking/store/__5378__C1822_Micro_brushless_Outrunner_2100kv_14g_.html
esc: http://shop.afterbuy.de/public/catalog_xmlxslproducts.aspx?art=viewproduct&suid=2344&productid=39444363

for airframe you can also use a monocoque frame design made up of 1mm balsa sandwiched between fibreglass, its exceptionally strong, but i don't have the data for a direct comparison with carbon fiber.
also i recommend you go for a hexa or Y6 configuration for added thrust and redundancy, not to mention the added benefit of higher payload capabilities

Right now not willing to experiment with new multirotor configurations, quadcopters are proven to fly properly in tiny sizes, so just want to go by that.
Thanks for the motor and ESC suggestion, will look into it.

Let me tell you something... as you are restricted in size and need good flight time..
Go for motors like ntm prop drive or t motor
As prop size is limitted instead of 5" normal prop go for 5" 3 blade prop..
Which will give you more lift with less A consuption..
small av tx rx( no need of 200mwt and all)
Apm will suits you very well..
As the size is 330mm I thinj this is easily achievable..
All the best..



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Frankly i dont think 5" props would be able to develop such 1kg thrust with the efficiency you need,
Here are links for t-motor 1306 3100kv & 2206 1200kv, please check them for performance details,
you will get an idea on what im talking about.

http://www.rctigermotor.com/html/2013/Professional_0912/41.html

http://www.rctigermotor.com/html/2013/Professional_0912/42.html

The hobbyking motors you selected may give you required thrust, but then you will lose flight time.
Either you will need to increase prop size or reduce more weight.

Start weighing the stuff you have as of now, accordingly make new selections.
Anyways tricopter is better suited if it gives room for bigger props, what happened to your earlier tricopters?

And neither could I find the prop sizes you wanted. The only thing close was
http://www.gravesrc.com/APC_ELEC_5_25X6_25_SPEED_400_p/apc053625.htm

Thanks.
Apparently, there aren't any NMT prop drive motors that I can use for the project. I will keep looking for suitable ones.
Its proving harder everyday to find 5" quadcopter props, we're searching for 3-blade ones too. Please let me know if you come across any.
As for the FPV Tx, we need a range of 200m at minimum. What power do you suggest for such a range?

We're being a bit generous about the 1KG thrust, expecting the final AUW to be in between 300-500g. I dont know how heavy it will turnout to be in the end.
Efficiency is a bit of concern and we will do everything to keep the weight low.
Thanks for the motor suggestions, will look into them.

Do you have any idea about minimum Watts/g requirement for hovering in multirotors?

For hovering thrust requirement is atleast double the auw. Thats all I know about hovering.Not sure about watts.
Check the link, ppl are talking about it, however I couldnt grasp the technicality.

http://www.rcgroups.com/forums/showthread.php?t=1312463

http://www.wattflyer.com/forums/archive/index.php/t-68668.html

google blackout quad, spanky quad, QAV 250. see the specs of those. they use tmotors of similar specs as u need. they all weigh 500-600gms and are250mm motor to motor. 330 motot to motor is easy.
but for 330mm u can use 8 inch props also without any problems so u dont have to use tiny motors. fit 8inch props, 2000mah3s, 2204 or 2206 motors. will give u what u need i.e run time.
vtx is fine, u need to remove the filter portion from vtx and make it smaller and run it off 5v from bec, not many know how to do this so they avoid it.
use sunnysky or tiger motots, ntm and all are junk, i havent seen any guy who knows what he's doing use it. not my personal experience but i do see ntm quad users crying a lot. they are fine on planes.
use ecalc for rc maths. lol


edit, please omit the 330 quad advise. dint know ur requirement was 330 OD

SideWinder, thanks for those links. 

Pravesh, how do you suggest I use 8" props? The maximum prop size that I can accommodate with all props on the same plane is 5".

if u take 330 motor to motor. dint read it properly but now i get it that 330 is outer dimension.

hi there are some fun props i recently got it delivered

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=25101

Bhanu, thanks a ton! 

Till now i had build 2micro quad which had acamera recorder so i can help u ib both fpv and quad building jst call me 9595634361

I studied on ur project a lot  its possible n im also interested in helpin u out u jst call me as soon as possible bcause i hav a very light frame for u jst40gms weight call me soon

Please post some pics of your quads, It'll be helpful.

You cannot use a 5" Prop for a project where your Prop tip to tip has to fit in side a 330mm Sphere

5" Prop gap 1" 5" Prop say 10" one side of Quad then 10x10 + 10x10 = 200 square root of that = 14.14" = 359 mm

Maximum you can use a 4" Prop. Safely without any prop wash interference only 3" -3.5" Prop.

to Use a 3 Inch Prop you need a High KV Micro Motors preferably more than 3000KV on a 3S capable motor and ESC setup.

Under any case you are not achieving a thrust of 1Kg in such a Quad may be in a X8 in WOT in that size. Any how in  50-60% throttle you may not achieve  thrust more than 300gms for such a micro setup.

For APM you really need to knock down on all of extra weights components of all electronics from heat shrink to wires and connecting pins.

You may have to custom design and etch and laser cut your own very Thin PCB based frame with all tracks of wiring integrated in the frame and all component soldered on the frame itself to make it light to fit under AUW of 400gms including Lipo for a 15 Min flight time endurance.

I couldn't understand Sundaramji's calculation. Thats a 5030,3 blade prop placed approx 300mm apart, with 30mm still left to use.
A 3" gap is approximately achievable. So I think 5" props can be used, we can even try a 6" prop if it permits.

Im not aware of the term "prop wash interference", but if it means interference in fpv view due to props, then fpv setup can be placed under the frame or the cam can be placed on an extended boom. I mean the frame has to be made accordingly.

A quad (blackout mini) mentioned by Pravesh earlier looks promising,the frame is apt for fpv. Check the link

http://www.rcgroups.com/forums/showthread.php?t=1959559

Sundaram ji, I dont understand your calculations. I have a CAD design of the 330mm quad in Reaply #11 and according to that, 5" prop fits right in.

Right now it would be too ambitious to think about a PCB frame, we just have a month to get this done.
We will work out the lightest possible frame.

SideWider, the Blackout quad is a nice one, but I cannot use the design as it is, H-quads don't fit neat into 330mm diameter.

also consider this

http://www.hobbyking.com/hobbyking/store/__22319__Micro_Integrated_PCB_w_ESCs_Quadcopter_Frame_235mm_KIT_.html

here is mine one

sure the auw is 250gms with turnigy 1811-2900kv motors kk 2.0 with 1.6 firmware 2cell 1300mah battery with 5x4.5 props


frame weight is 82g with esc's,

previously i was flying it with a 500mah battery and now with 1300mah one but there is no difference in the thrust, so i think it will carry 50 gms more easily.

the problem is that i forgot from where i purchased 5x4.5 props i checked every invoice in my emails and on hobbyking's order history page but no clue, may be from satya but not sure..... hope you find them      

That looks amazing! Can you give me some technical data on that? Overall diameter including props, weight of current setup, thrust and flight time with the battery you're using?
Also, can your quad carry an extra payload of 50-60g as it is?