Tri(+2)Copter Dragonfly Style AKA In at the deep end!!

[LukeStyles]

Hello all!!!

I am rather new at the whole RC thing, and after playing about with one of my friends' 350 quadcopters, and a variety of prebuilt micro quads, I decided to build one myself. But a tricopterish contraption instead! I know this is a complicated 1st project to get started with.

This will be my first serious foray into the world of RC, a little ambitious I know...... I hope to have this built for AP and FPV (not racing, just fun & exploration), but want to get it off the ground before looking into the FPV side of things.

The problem is that my lack of RC specific DIY experience is holding me back. Thought this would be a good place to ask for advice, so excuse the long post!!!

I have spent a serious chunk of time designing and making a body out of wood, and the total bare frame weight is 320g. This consists of:

front booms 28cm long and 140deg apart; [#1 & #2]
2 middle booms sitting along the centre of gravity 23.5cm long & 90deg from the rear boom; [#3 & #4]
rear boom 30.5cm long with servo actuated tilt. [#5]

I plan on having motors #1, #2 and #5 mounted normally with the prop on the top side, but motors #3 & #4 will be mounted upsy downsy with the prop on the underside. As #3 and #4 will be mounted directly in line with the centre of gravity, they will just be there for additional lift/thrust and will output a percentage of the power #1 & #2 give.

Having some background knowledge in physics and engineering, I am confident in the construction & fabrication side of things, but I was hoping for any advice on the below parts list before I start buying nice shiny bits to play with!

Mainly the question is do you think this is a reasonable/workable setup for something that will weigh approx 1250g all in?

Motors: 5x Multistar Elite 2216-920kw
Props: 10x4.5... 9×5...undecided because all my previous quads came with specific sizes.
ESC: 5x Afro Slim 20A
Battery: Multistar High Capacity 3S 4000mAh
Flight Control: KK 2.1x of some description
Servo: BMS-385DMAX MG
Rx: Turnigy iA6 Receiver (to go with a TGY-i6 Tx)

Any ideas and help is muchly appreciated!!!

Thanks,
Luke

[guest325]

Looks interesting but I don';t see any arrangements for the yaw mechanism - any tricopter type model needs a servo operated yaw.
Have a look at the Flite test videos about their Dragonfly and all will become clear.
Good luck with your project!

[DarkButterfly]

Have a look at my pentacopter, its basically the same thing, 5 motors with tail servo, a double armed tricopter.

[LukeStyles]

DarrellW - Yup, the yaw mechanism is not mounted yet. Am awaiting delivery of the servo (as I';m 99% sure that the one ive ordered (BMS-385DMAX MG) will do). Am thinking of fabricating my own tilt along the lines of the tough tilt, but with needle bearings to reduce friction as I have a metric tonne of them lying around and nothing to use them with.
The FliteTest video is the one that got me interested in the dragonfly concept, its just im not so sure as to my choice of the other components.... Motor/ESC/Battery etc.

DarkButterfly - I did just see your pentacopter of doom!! it looks f*ing awesomely aweinspiring!!! Tis indeed along the same lines as what I';m attempting.... do you have a parts list i could have a gander at? and what kind of weight was it fully built?

[guest325]

You won';t regret getting into tricopter style aircraft, they are the best despite the possible lack of reliability of the yaw mechanism - this is by far outweighed by the performance!

[DarkButterfly]

Hi Luke,

My pentacopter weighs in at around 1.2Kg all up with battery.

I used the following parts

4x turnigy plush 18A ESC
1x turnigy plush 25A ESC
5x 1000Kv motors
1x Half metal servo analogue
KK2 FC, changed to a Pixhawk mini for GPS and autonomous functions
4 meters of LEDS
Custom 3D printed motor pods and yaw mech
Hitec minima Rx


The reason for the two different ESC';s is because that';s all I had in my parts box.

[LukeStyles]

DarrellW - Yeah, Ive heard lots of good things about tricopters, and its good to hear them again. Puts my mind at ease as Im already into the construction phase!!

DarkButterfly - That is MASSIVELY useful thanks for that. Think I should be set to order the right parts now! Have also been keeping pics and a track of the build, so once its done will be putting them all up as one big post for anyone who wants to see

[Ynot6]

i don';t personaly rate multistar motors. i had some on a 250 and they were horrid, unbalanced little things. i replaced them with emax 1804s, which are very smooth. i also  have emax 2213s on my Y6 and my new part built 340H quad. just my 10 bob';s worth. BTW emax are a good price, they won';t hurt your wallet. 

[DarkButterfly]

How is this project coming along, any updates?

[LukeStyles]

I';ve kinda got carried away......

Oooooops!

https://drive.google.com/folder/d/0BxUcyR4AnrtbejF3UEdTN1UyMWs

All I';m waiting on now is battery, tx & rx hehehe! :P

PS. literally typin up the mistakes ive made along the way now.

[LukeStyles]

Right, here goes. Firstly i watched pretty much every video going on youtube....

Secondly, I had a go on my friends 250 fpv racer....

Duck.... On.... Water!!!!

Yet nothing around looked interesting or particularly useful in my price range, and nothing that I really liked the look of. Figured that if I can build other things, why not this?

Years later, I saw a craft I liked the characteristics of, and after painstaking months (with maths I hadn';t used since year 7 physics, and calculators/MacGyvering ability I hadn';t seen since university) it became modified into my current design. So for approx £180ish (so far) and with a total build time of 175hrs i have......

"The Hornet"
[attach=2]
Named so, due to how much
of a pain in the arse the
steps after the build phase
are over are gonna be!

https://drive.google.com/folderview?id=0BxUcyR4AnrtbejF3UEdTN1UyMWs&usp=sharing

Its beefy, easy to make and replace, and with the lifting assistance from the additional motors mounted along the centre of gravity. Hopefully it';ll be quite agile and powerful.

Non expensive too as long as not too much electrical damage is taken.

Dimensions:
1 & 2 (front tricopter) - 28cm long [12mm x 32mm]
3 & 4 are one 58cm long piece as above
5 (rear tricopter) 28.5cm long

Mounted them as follows. 140 degrees between the front two. 20 degrees between the next ones which is the single piece boom which is right angle to the rear and centre mounted. 4mm machine screws with nuts that are DEFINITELY not going to vibrate off, but that can be undone with a breaker bar when required . 4mm wood board for the body plates measuring 8.5cm x 12.5cm square.

Neat and tidy blueprints will be done and available when they get done.

Choosing the electrics was a painful task... ended up with:

1045 props, so EMAX 2213 935kv x5 to go with them.
20A EMAX BLHeli esc';s, KK2.1HC, a UBEC for clean power to an FPV unit (at some point, not gonna waste money just yet!).

After much more random wire/plugs/bits/mounts/nuts/bolts/glues/epoxies & zipties later ive got something on my hands.

Still waiting on delivery of tx/rx & battery so am at that very annoying almost (after weeks more tuning) there point.

This is the brief version, was going to post the build diary but decided to err on the side of caution due to language used and probable forum rules violations/offence being caused if made public!!!! hehehe........  :evil

[LukeStyles]

Sorry about the quiet front recently, weird shift patterns in work 

This';ll be the last update before first tuning test flight... and when I say flight, I mean probably no more than a cm off the ground in the back garden. Taking this one slow cos of my noob status! Plus the fact all I have are the bare numbers and haven';t even programmed the FC yet or started any tuning at all. Nervous is not the word....

  1 ___       ___ 2
            \  /
3 _____||_____ 4
             ||
             ||
           6 |
           5 |

1 - CW   - P: 43    R: -85 Th: 100 Y: 10  Type: ESC
2 - CCW - P: 43    R: 85  Th: 100 Y: -10 Type: ESC
3 - CW   - P: 9      R: -99 Th: 100 Y: 10  Type: ESC
4 - CCW - P: 9      R: 99  Th: 100 Y: -10 Type: ESC
5 - CCW - P: -100 R: 0    Th: 100 Y: 0    Type: ESC
6 -            Y: 100   Offset: ~50%           Type: Servo

LITERALLY all i need to is to go and get a 12V adapter for the lipo charger brick ';cos the only one I have is for the Xbox and I reeeeeeealy don';t want to destroy it!! I almost got desperate looking around the house 

Chiselled out some of the middle from each side of the arms, so the profile resembles an I-Beam. Reduced the weight down from 1600g-ish to 1453g!!!! Plus its also a bit stiffer... 

Final paint job and permanent fixings done now, after a build time of around 450 hours this is the finished article.

Renamed as the YT59 Hornet.

59.1cm "wing" tip to tip
35cm "fuselage" length
all up weight: ~1453g

Motors: 5x EMAX 2213 935kv - 98.4W max mechanical power
Props: 10x4.5 - approx 8g/w thrust, approx 1kg cargo cap?
ESC: 5x EMAX BlHeli 20A - should only have to cope with 25A burst (i hope!)
Battery: 3S 4000mAh 30c LiPoly -  wishing for a +10min flight time
Flight Control: KK 2.1HC
Servo: BMS-385DMAX MG
Rx: Walkera RX701
Tx: Devo 7E (gonna do the diode mod when I get better at flying )

Double checked all connections electronic and otherwise. Plus all of the mechanical and engineering points that I could think of and everything looks good to go.

[above comments made using a cheapo multimeter, knowledge from my early days and advice from ecalc.ch ITS AWESOME!!!]

Also, a couple of build questions that I think I';ve done correctly but would like confirmation.

One thing I am struggling with is finding the correct props to use on the upside down motors... I have figured out (after much frustrated brain racking) which direction of self tightening prop mounts to use on them; but have had to modify some props to fit them so they are facing the right way.

Have been told I need to get pusher props but cant find any for multirotors?.... took me an EON to balance the hubs again after milling them out to fit. Took the joyful use of some resin, nicely wax moulded from the prop mounts themselves! If it helps i think they are 6mm prop mounts with a cut-offs on 2 opposite sides?..... because the motors are upside down the cut offs are wanting to go into the top of the prop hubs. will this happen on all props?...

Fits like a charm but a b*tch to do and get balanced! 4 hours per prop is a bit OTT!!

I have done the battery through a 6 way splitter into 5x ESC channels and 1x UBEC. UBEC power out goes to receiver side power bus on KK2.1. The RX701 receiver then gets power from this bus.... Is this workable? Havnt been able to charge lipo';s (safely) yet so havnt had the chance to do anything but bench test. Now everything is permanently connected I';m having paranoid visions!!!

Criticisms, comments, hints and tips appreciated

[guest325]

On a Tricopter type aircraft you don';t have to have reverse rotation props, they fly quit happily with single rotation.  It does give the FC a bit more to do but works fine!
Can';t wait to see the maiden flight ::)
Just an afterthought,  have you upgraded the firmware on the kk2.1x?
It will fly considerably better on Steveis firmware!

[LukeStyles]

Had the maiden, but my phone died so only got the first 30s of sliding on the floor powering up The rotors however make a lovely sound, at about 20% throttle there is this quiet "thwap thwap thwap" oscillation made because of the differing motor speeds on the crossover sections. May be a problem to come, but sounds AWESOME!!!

Shortly after this I had a brief 10s in the air, after a bit of a slow oscillation (wobble caused by p-gain too high I think, didn';t have much time to tell) turns out I have completely stripped the crappy plastic gear in the BMS-385DMAX MG. In general though, didn';t go as bad as I thought it would!!! 

By the way, MG! couldn';t tell the first time i opened it cos of all the si grease, but turns out that it is 3mg 1pg so biting the bullet and going for a Turnigy TGY-390DMH instead....

Specs out as 5.4kg / .11sec / 22.5g so is a nice part to have access to anyway useful to have the ability to actuate things reliably! And has full metal gears