Multirotor, multicopter and quadcopter discussion - The Drone thread

RomanNose said:
10 mins, some guy managed to do a 50 minute hover though. Battery capacity is improving day by day.
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Cool. I was only half considering bodging a quad, due to the complexity of it, but reading n3m1s1s' post has explained more than an hours reading!

i am going to use a dt700 motor so i need to know its maximum amp draw at "WOT" with any given prop from this info i can pick an esc and from that info i can estimate what lipo i need to power it so i go on the website and look for everything i have added ** to, so....
Spec.
**Required Voltage: 11.1v**
Suggested Battery Capacity: 1300mAh +
**Suggested Prop: 10x4.7, 11x3.8 or 11x4.7**
**Max current draw: 13A (with 11x4.7 prop)**
**Max thrust: 900g+**
No Load Current: 1.2A
Shaft: 4M (perfectly suited to Towerpor/GWS SF Slow Fly props)
Weight: 78g
Diameter: 41mm
Overall length: 77mm
Kv: 700rpm/v

this tells us we will draw 13amps with an 11/47 slow fly prop and it will give us 900+ grams of thrust so we now know we need a esc that can handle 15amps continually and 18amps in short bursts which is more than the motor and props max draw we want less amp draw than the motors max so we pick a 10 inch prop instead of 11 inch we want help in slowing down motors on a windy day as it will give us a crisper response to throttle changes so we pick a 10/6 prop (which will give us 700+ grams of thrust and draw 11 to 12amps at WOT) for good solid control in wind but if we fly where there is less wind we can make the craft more stable by picking a lower pitch prop like a 10/45 which will spin faster than a 10/6 prop but due to extra head speed should produce similar amounts of lift as the 10/6

so we have a motor and prop that we will say draws 12amps and gives us 700grams of thrust we also have a 15/18amp esc but how heavy can we make the quad??

700x 4 = 2800 or max thrust from all for motors in a quad
2800/ 2 = 1400 or max weight of quad if we want it to lift off by time we get to half throttle i,e 50% we want lift off or better yet we want to be hovering
so all of a sudden we know everything needs to be under 1400grams to lift off at 50% throttle making a quad in that weight class is very easy as my maths has left plenty of overheads in the power train as it stands and all my builds have been under 1.5kg with cameras

so next we overestimate weight of electronics
dt700's 80grams x 4 = 320grams
4x 18a esc = 120grams
FC = 60grams
RX 20grams
servo extension wires = 50grams
power harness wire and plugs 130grams
700grams which leaves 700grams for lipo frame and camera/fpv equipment NOW WE CAN PICK THE PERFECT LIPO

for tri times by 3 instead of 4
for hex times by 6 instead of 4
for octo times by 8 instead of 4

you get the picture right?
**************************************

Li Po SELECTION

the most important thing right here is motor/prop spec i,e
**Max current draw: 13A (with 11x4.7 prop)**
to add a good safety margin and make maths simple we will round that up to 15a
15x4 = 60 so we need a lipo that can give 60amps all day long but how do we find it amongst all those other lipos?

simple

we look at the C rating and times that by the mah so...
we need a 3000mah 20c pack eh? did i jump ahead of you? how do i get those numbers?
simple we halve the digits then times the remainder so 3000mah is 4 digits reduced to 1st 2 digits is 30 20c is 2 digits reduced to 1st digit is 2
30x2 = 60amps divided by 4 = 15amps all day looong

but hang on? actual amp draw was 13amps right? what lipo would that be?

2600mah 20c why? 26x2 = 52 / 4 =13amps now isnt that easy when you know how? now we can get the weights of the 2 above lipos and add that to our electronics list,

ummm the 3000mah lipo i picked is 239grams with wire so lets round that up to 250grams and add that to our electronics weight so far

700 grams + 250 grams = 950 grams that leaves 450grams for a frame and a camera/fpv gear

for the record the above combo will fly for 9mins at 1300grams and ALL components will be cold/cool to the touch which means no energy has been wasted as heat meaning we have a very efficient electronics combo
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Awesome :cool:
 
It looks like I have a dead speed controller or motor. I tried to take it off but one was spinning not as fast as the others so it flipped right over and broke one prop. It's great how little damage was done :D. They are all brand new, would be surprising if it was DOA.
Ahh I think I need to calibrate the speed controllers, doh! I have forgot about that.
 
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d_brennen said:
What does calibrating the speed controllers entail?
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Just turning the throttle on the transmitter to 100% while plugged into the receiver and then put it back to 0%. Fairly easy.
Here is a picture of the completed build. Going to tie it down in the garage tomorrow, to see if it flies okay without damaging it all.
t6XEfl.jpg
 
someones started a build thread for an expensive sounding octocopter on one of the other forums i use
http://www.rcheliaddict.co.uk/uavs-general/72864-octocopter-build.html
he goal - To build a heavy lift Octocopter capable of carrying a broadcast quality camera guided by GPS with a totally automated flight control and a flight time of no less than 10 minutes. The camera will be auto levelled and stabilised in flight using information from the flight gyros and accelerometers. The Octocopter will have two way telemetry to a ground station such that all sensors can be monitored during flight
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might be interesting to follow
 
Zomg it actually properly flies yaw is fixed now with a bit of left yaw trim. Don't know why it needs so much though. Hey ho, it sounds alright when flying and is controllable. Might enable auto leveling next :D.
 
My latest project- it's almost ready to fly, just needs a receiver and battery and that should be arriving this evening.

The frame is designed and machined by a guy in Poland for 55eu and the controller is based off the multiwii but custom designed by a group called KK. Should be a blast to fly - has around a 4-1 power to weight ratio.

Vid of one in action here: http://vimeo.com/18882815

418817_10150689905719882_622514881_11004900_2000968164_n.jpg
 
Awesom, I,might get a new frame that is stronger and lighter, still has an awful amount of power though with just a ratio of 1:3. Goodluck buy has some cheap fibreglass stuff. If it does break it will be harder to repair than my wooden frame though.
Had two flights last night, my god it is easy to control.
 
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SteveOBHave said:
My latest project- it's almost ready to fly, just needs a receiver and battery and that should be arriving this evening.

The frame is designed and machined by a guy in Poland for 55eu and the controller is based off the multiwii but custom designed by a group called KK. Should be a blast to fly - has around a 4-1 power to weight ratio.

Vid of one in action here: http://vimeo.com/18882815

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Nice. How much that set you back in total?
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Radiation said:
Is it possible to make smaller cheaper versions of these?
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Yes. You need smaller battery, low ampage speed controllers.
I am beginning to get basic control, keep tracking of orientation is damn difficult though. I am getting used to fly in gyro mode, level mode takes away a lot of the difficulty but you need to get the PIDs right first.
Ordered a bluetooth module for a tenner, going to be quite helpful. Also Easter holidays are soon, which means I can ram in a dozen flights a day.
 
I just use rcgroups, just get stuff off giantcod instead of hobbyking if you can.
I am really annoyed with European law about fpv, it means that 99.999% of all FPV pilots have to break the law. Why? because we are limited to a measly 25mw.
Where can we get 25mw equipment? The only company in the world is immersion RC and it is incredibly overpriced. It's just not worth the hassle and in all honesty it does not do any harm and ofcom don't have the equipment to tell between 10mw and 100mw.
I would say that a large %age of households already break the law with the use of wifi boosters which are sometimes around 1w and I have never heard of anyone care about that.
/Rant

I would say that if you are in the UK and are about to do FPV ( just like me), you will probably have to break the law but why would ofcom care if you are flying in a open field away from civilization on 5.8/2.4 ghz band which are just a "dump band" where anything goes.
 
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