Re: [Paparazzi-devel] Newbee question Apogee or KroozSD

[Gerard Toonstra]

Agile and heavy load are not necessarily contradictory, but the power required to be agile with heavy load is really intense. If you're already running into the top
region of allowable current then I imagine the current required to become agile with that load is a factor 4 or 5 higher. You'll need to go 6s in that case. I don't think
multirotor motors are made for higher voltages, that'd be only heli motors going 12s. So I'm not sure you're going to be able to experiment with that 
right off the bat.

I'd start a bit calmer and look at tiger motors to start with, which are popular:
http://www.rctigermotor.com/show.php?contentid=132

They have complete tables that show you how thrust changes versus prop size and the voltage applied to it. Try to get familiar with those numbers
and take it from there. More cells allows for a larger prop, but also lets the motor rotate faster. Power is voltage * current, so if you increase power, 
current decreases.

Then you can start scouring cheaper alternatives, but weights can become prohibitive for those alternatives. 

More cells could mean more expensive ESC's. 2-4s are the usual ones for multirotors, but going 5s or 6s changes the budget quickly. It may also
have some consequences for how you measure voltage on a board (resistor bridges and such). 

You shouldn't load ESC or motor to its maximum current, the specs are typically from the lab and I see frequent reports of burnt ESC's or motors 
when they're taken close to the maximum (over 15 seconds). A safety margin of 80% is recommended, I usually go with 60%. 

Also if you fly in tropical areas like me, the ambient temperature becomes a significant issue to consider for motor cooling and how much power you  
can thus draw.

A very interesting site to get acquainted more with the multirotor dynamics is here:

http://www.ecalc.ch/xcoptercalc.htm?ecalc&lang=en

That allows you to insert some numbers from rotors and props you find and see how that affects your endurance, the current in the motor,
the motor temperature and so on. Because you're on a Y6 the efficiency of a 6 rotor is a little bit off because one prop works in a more turbulent 
column of air, so the exact numbers need some reinterpretation because of that.

Finally I flew before with plastic props, but they will bend significantly under heavy load, affecting vibration and efficiency. I'd go for carbon props to reduce
this prop flex which nowadays go pretty cheap. You have the Graupner kind and also foxtech or rctimer ones.

I'd scour the internet for heavy load octo's, hexas and quads and see what choices people have made in those areas and then use the xcoptercalc site
to see what ranges it's giving you in terms of payload, endurance and other specs.

Good luck!

Gerard

On Tue, Jul 30, 2013 at 9:47 AM, Alexander Biersack <address@hidden> wrote:

I was thinking of a copter with 6 rotors in a Y configuration, with 3 on top and 3 on the bottom.

To answer your questions: I was thinking of a heavy load and agile flight. This implies a short flight, and somewhat contradicts itself, but I want to see how agile I can still be with a lot of mass.

So I was thinking of strong engines with much torque, props with as much thrust as possible and fat energy supplies that burn up fast.

But I assume that the KroozSD/Apogeee question is independent of this, or is it?

Thanks for the quick reply Gerard.

On Tue, Jul 30, 2013 at 2:29 PM, Gerard Toonstra <address@hidden> wrote:

I've just done some research on multirotors for a long endurance project. The two most important choices you need to make:

1 Do you want to lift heavy weight (DSLR camera, > 1000g ), lift medium weight (point&shoot, 200-1000g) or lift very little weight (0-200g)?
2 Do you want agility and forward speed or fly a long time?

The first determines if you should go for an octo, hexa or quad. The second determines what your choice for props, motors, battery
and frame looks like. Obviously, lifting heavy weight means you reduce the total flight time, but there are some who lift 8-10kg for a
short time. Obviously this also has consequences for frame strength and weight.

On the other side of the spectrum you have quads that can stay in the air for 95 minutes, but get into an unsafe area regarding
torque and available throttle for extreme manoeuvers both due to motor overheating or overloading the battery. So they're docile flyers
and if not used correctly could set it on fire.


Then you have the entire area inbetween where a good idea about payload will guarantee the best fit. These are some basic requirements:
1. payload  (and how flexible it must be for future configurations).
2. endurance requirement (required time in the air).
3. agility and forward speed requirement (how fast it responds, how fast you can ascend and how fast you can go forward).
4. available budget

which give you a useful start for selection. Some of these are mutually exclusive, so compromises always have to be made.

Feel free to message me personally for more questions.

Rgds,

Gerard

On Tue, Jul 30, 2013 at 9:04 AM, Alexander Biersack <address@hidden> wrote:

Hi,

I would like to start into the multicopter world. And would like to get some hints as to where to start and what to buy.

I have seen the Apogee board, but could not find where to order them, they look very attractive to me. Or should I start with KroozSD? I am daring so I tend to take the risks with the Apogee, or shouldnt I?

The Apogee is also not listed in the feature mix table so I was wondering, is it too new? Still in development?

I am a newbee with a background in math, physics and programming. I have a little experience and understanding of electronics.

Hints and tips also as private messages as to what parts, ESCs, brushless engines, propellers, sources and shops are all welcome. 

Alex

_______________________________________________
Paparazzi-devel mailing list
address@hidden
https://lists.nongnu.org/mailman/listinfo/paparazzi-devel

_______________________________________________
Paparazzi-devel mailing list
address@hidden
https://lists.nongnu.org/mailman/listinfo/paparazzi-devel

_______________________________________________
Paparazzi-devel mailing list
address@hidden
https://lists.nongnu.org/mailman/listinfo/paparazzi-devel