Need Help With First Build

[GreenSkyy87]

It seems I am overloaded with information and could use some guidance.

I really like the Dragonfly PentaCopter and plan on taking this on as my first build. I may be jumping right into the deep end here, but I'm sure with the help of the community I can pull it off. I plan on using the naze32 board, but that is about as far as the electronic list goes.

I am just starting to try and understand the ratings on motors, and am having a tough time understanding how everything works together. I plan on making this an AP ship eventually, but would like to overpower it as much as I reasonably can. Because why not fly a PentaCopter like a race quad? And when it comes to matching ESCs with motors, props, and batteries, I'm just at a loss.

Can someone out there help me get started? I've started browsing Hobby King to source the parts, and it just becomes all that much more overwhelming.

 

[pressalltheknobs]

personally I would just start with this..

https://store.flitetest.com/power-pack-d-dragonfly-pentacopter/

Once you have to working you will have a better understanding of how things work and what you want to be different.

 

[GreenSkyy87]

I was considering going that route, however I want to fly 4s. I would really like to know the specs of Eric's tricopter in the tough tilt episode as that is the exact performance I am looking for. They briefly mention the motors my referencing another build, but I can't seem to find any more specs than that or find an episode on the build mentioned.

 

[GreenSkyy87]

So I dug a little bit deeper and found the motors that Eric had on his tricopter. Link below.

http://www.quadrocopter.com/QuadroPower-Motor-QC-3328_p_392.html

A little bit over budget from where I want to be, but now I have a starting point at least and what I came up with is linked below.

http://rctimer.com/product-509.html
http://rctimer.com/product-1324.html
http://www.hobbyking.com/hobbyking/...ropellers_11X4_7_LH_and_RH_Rotation_Pair.html

Basically I would be running 750kv motors, 40A escs, and 11X4.7 props. I found an alternative motor, but it is pushing my budget. However I do seem to find a lot of people talking about Sunny Sky products. Is there going to be any advantage to this motor vs the one linked above?

http://www.buddyrc.com/sunnysky-v2814-11-700kv-ii-brushless-motor.html

12 X 4 props may be an option too. Not sure if I am headed in the right direction here or not. Also, will a 6v BEC for the receiver be necessary?

 

[Crazyjoker77]

Your really oversizing those motors for your intended setup and this is not a good thing. Everything about power system design is a balancing act.

There are 3 main things that affect how much power you are going to have. Props(size and pitch), voltage, and rpm (kv).

For example comparing your rctimer 3536 and the SS 2814 Both with 4s and 11" props are roughly gonna make the same thrust(the RCT motors will be slightly higher because of the extra 50kv) but you will be carrying around alot of extra weight that you arent taking advantage of as both motors are gonna pull roughly the same amount of current (amperes) because you are spinning the same prop at the same speed and voltage. Now the 3536 would be able to run a bigger prop compared to the 2814.

Basically you want to choose a motor that is going to withstand the current that the load(prop) is going to apply and going any bigger is actually a disadvantage.

A good analogy I've been told is that lets say you have one bottle of pop now you can pour it into a cup or a bathtub. Sure the bathtub has the potential to hold more but all you have is one little bottle so why wouldnt you choose the cup? Now if you had a barrel of liquid the glass wouldnt be able to hold it all so you would have to use the bathtub.

The same goes with the ESCs if you motor/prop combo is only capable of pulling 25A a 30A esc is all you will ever need.

Ideally if your looking to spin a 11" prop at 750KV on 14.4 volts you should be looking for a motor ~300watts. even that is probably bigger than you would need as multirotor never goes full throttle for long periods of time so you could go with say a 250watt motor and still be safe.

Another thing thats pretty important to consider is your battery capacity.


I use alot of Sunnysky motors and have nothing bad to say about them other than there are alot of fakes being sold so make sure to buy from a reputable place and not ebay/aliexpress.

My suggestion for you would to run SS 2212 980kv with 9" props and a 3500-4000mAH 4s Battery. It will give you more power than your current plan, be lighter, and because of the smaller props alow you to make a smaller (and lighter more agile frame) 30A escs would be all you need but it doesnt hurt to much to oversize the ESC a bit.

 

[Crazyjoker77]

...

 

[Crazyjoker77]

Oh and you WILL need a 5V Bec(not 6v) if you use those ESCs as they are "opto" which means they do not have a BEC or find a ESC that has a Bec built in. Also because its a tri/penta you will need a bit higher amperage bec because it has to power the servo as well as the flight control and reciever.

 

[GreenSkyy87]

I did finally figure out the ESC thing, and I am looking to go in this direction with those.

http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=52338

Plus, after more research, I did find that the SimonK firmware seems to be the way to go for multirotors.

I also did decide to go with some variant of SS motor afer more research as well. Everyone that has used them has nothing but good things to say about them.

As far as motors are concerned, I am even more confused now than I was before after reading your comments. I thought lower kv = lower rpm and more torque which would turn into more efficiency and more lifting power. I may have misinterpreted the information in my research. I am guessing more thrust does not necessarily equal more speed?

 

[Crazyjoker77]

No you are correct that a lower kv motor with a larger prop will be more effecient han a faster smaller prop making the same thrust. I only suggested the 980kv w/ 9" props as its a tried and true properly sized setup and because I got the impression you were looking for more performance than a long distance/duration rig due to your comments about using it as a racing quad. Although the effeciecy between those two setups would be close just because your using such grossly oversized motors/udersized props. Not only that you usually end up with a heavier craft in order to accomadate the larger props and the extra weight offten offsets the extra effeciency you gained from the larger props.

Like I said everything is a tradeoff larger slower props will be more effecient but its at the cost of throttle response and agility.

To take that a step further a lower pitch prop(say 11x3) will be more effecient hovering where as a more aggressive pitch prop(11x6) will get better effeciency while flying forward.

A smaller, higher pitched prop will have a higher top speed than a large slower prop at the same thrust but again at the cost of flight time due to the loss of effeciency.


If you dead set on running 11 or 12" props on 4S a good sized motor from the SS lineup would be the SS X3108 720KV.

Basically if you want a quad that is gonna keep up with the mini racers your gonna have a short flight time. If you want a long flight time your not gonna have much forward speed and agility. Its all a balancing act and a quadcopter that can do it all wont do anything particulary good. If there was a perfect power setup everyone would be running the same thing but unfortunatly the powe system has to be tailored to its inteded use and compromises will have to be made.

 

[GreenSkyy87]

I think I understand now. Thrust does not necessarily translate into agility, speed, and climb with large props and torque. And I am not going to be able to be fast and agile and expect to have any battery life.

Since I already have a 200qx, I may as well leave the agility flying to that as a camera ship at this time interests me more at this time.

If I were starting a fresh dragonfly build, what would it take to get around 12 - 15 minute flight times and the ability to lift extra gear down the road? (Camera, FPV, etc) It would be neat to have something that comes close to the speed of the 200qx, but that takes a back seat to lifting power and battery life. I would like to still have something that is fun to fly line of sight without any camera gear as well but it does not have to handle like a race quad by any means. I'd basically like to have a finished product that is different from the norm and has a great presence in the air and on the ground.

 

[Crazyjoker77]

there are still alot of variables that need to be known (especially the weight) to say for sure what flight times your going to get. As well I don't have a pentacopter so its hard to say how the extra 2 motors are going to affect your flight times.

15" props ~450kv motors on 4s will give you awesome flight times but will end up with a slow craft(relatively speaking) thats more affected by wind
12" props on 720KV motors is a good compromise between speed and flight time.
9" props at 980kv is gonna be a rocket with short flight times.

All those combos are going to give you ample capacity(even just on a tri) to lift a gimbal+action cam, fpv system and just keep upping the battery size (mAh) till you get your desired flight times.

All my fpv rigs run 3s packs just because so many accesories are only rated for 12v. It really cuts down on the complexity(and usually price) of the builds. A 3s system can be just as effecient as a 4s with a properly spec'd power system.

I use the afro 30A ESCs quite a bit. They have been very good to me. Although I do make sure on my tri's that the rear servo is fed from a seperate ESC from the ones that are powering the FC and RX. (i use corona 919 and 939 digital MG servos). That being said they are not the best ESC available but certainly are a very good bang for your buck and its nice they have a BEC built in, work without having to be flashed, and are always in stock.

Since you initially wanted something similiar to eric's tricopter the SS X3108 720kv on 12" props is probably your best bet. It will still have a higher top speed than your little 200qx just probably wont accelerate as fast or be able to turn and stop as tight.

I would stay away from most of the Hobbyking un-branded Carbon fiber props. I've bought a bunch of 10 and 11" ones. They were all decently balanced but the hole was drilled off center and caused rediculous vibrations. Short of a lathe there was no saving them. I would suggest looking at RC timer for cheap(er) carbon props.

I love my Naze32 boards but wont use them on a tri(im assuming penta is the same since it uses the tri Firmware) Just seems the stock Tricopter firmware isnt quite there yet but if your set on using it you can definatly make it work. Although for a camera ship it is nice having the GPS options and would recommend the apm/pixhawk platform. It is what I run on my camera rigs and tri copters.