So, bicopters... Method to madness? - Page 5 - RC Groups
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Dec 05, 2012, 05:20 AM
Registered User
Freakazoid's Avatar
There, hows that.

The avatar one is getting a bit cliche, so im trying to sniff out some other hoverpods.
This is the buzzard, from the game called Borderlands
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Dec 05, 2012, 05:23 AM
um.. yeah, I can make that fly
Carlos230023's Avatar
Awesome! I guess you could do a reverse tricopter :P. With swept forward nacells instead of swept back. And the battery right at the back. It could be done.

Dec 05, 2012, 05:32 AM
Registered User
Freakazoid's Avatar
Bicopter would be more fun though. But the cabin juts out too far with nothing behind it to make that happen.

I have been thinking about maybe surrounding the props with a slab of EPP foam,
and putting some kind of silver surfer smack in the middle of it though.

But I suspect it ll look all funny with 2 big ol' holes in whats supposed to be a sleek silver board,
not to mention the implications on flying it "sideways".
Dec 05, 2012, 06:33 AM
um.. yeah, I can make that fly
Carlos230023's Avatar
Simple. Just swap alierons and elevator control over on your Tx so they use each others axis on the joystick :P. lets see if we can get the concept to work first, before we get fancy with design lol. I may do a smaller proof of concept (and firmware on the KK2.0) before I assemble a 2600 watt beast with a 12,000mah 6s2p lipo on board :P.

Dec 05, 2012, 06:54 AM
Registered User
Freakazoid's Avatar
I will be trying out a sideways flight, but I think the awkwardly leaning weight will want to break out easily.
The controller might be able to just deal with it though, but only one way to find out.
My design will be a uniform little square pack, and have swivel mount blocks to go OAT or FAAT,
it will basically a backpack with velcro on both ends, stick it to anything and see if it flies.

Would be neat if it could deal with flying sideways, because this guy comes to mind.

Take a dremel to this guy and you're golden:
Dec 05, 2012, 08:59 AM
um.. yeah, I can make that fly
Carlos230023's Avatar
Lol, well I can see no reason why moving the forward flight axis through 90 deg would make any difference at all. Just keep your COG centred and fly straight, It'll make banking much faster as compared to a chinook design.

Dec 05, 2012, 09:07 AM
Registered User
Freakazoid's Avatar
Well normally motor speed is responsible for roll control, turning it 90' would put that job on motor pivoting.
OAT would go out the window with this I think? Or atleast, it would act a little funky?

I do suppose it would negate the need for a tail fin though, wouldn't it?
Since it wont be dolphining when motorspeed is in charge of pitching the craft, it would behave like a normal quad in that respect.

Somuch fun things to experiment with, man I wish hobbyking would hurry.
Dec 05, 2012, 09:11 AM
um.. yeah, I can make that fly
Carlos230023's Avatar
well you probably wouldn't need OAT if normal forward flight was done from prop to prop, as opposed to going between the props.

Dec 05, 2012, 04:36 PM
1400 watt RW Zephyr
matwelli's Avatar
regarding flying sideways, i did not have any problem at all, if anything it is more stable than forward flight , havent tried an oblique setup tho.....

have got my tilt mechs done, all out of PLA plastic, some 16 gram 2.2 kg servos and 750 kv RCT motors, the linkage is temporary to check the alignment, will be a clevis arangement

regarding thrust to weight, when your pack gets down to 20% left, the available thrus has dropped to 77% of a charged pack (square law), for me 1.4:1 thrust ratio is to close to the limt, esp as you need left over capacity for manuvering, its ok in calm/indors, but when you need to fight the wind you will very soon run out of headroom

2:1 thrust, in my setups is quite common, but the motors are working hard (you will be at 75% throttle for 50% thrust) and in very slow moving air, so they get warm

3:1 thrust is where i like to be, motors are running cool, and efficient, heaps of reserve for low battery and wind , 57% throttle is 33% power
Dec 05, 2012, 04:52 PM
Newbie but coming on fast
KYChopper's Avatar
Originally Posted by Freakazoid
Heheh sorry, I should have been a little more clear about that.
Its surprisingly hard to explain with just words, so have a look at this video instead:

See how the motor axles point outwards when sweeping forward, and vice versa?
The pivotpoints on which the motorpods sway, are not parallel to the fuselage.
This is apparently called an oblique tilt rotor system, and im trying to figure out the advantages of it.
This looks more like a Marine Osprey than what I would consider a bi-copter.
Dec 05, 2012, 05:23 PM
Registered User
Freakazoid's Avatar
I was running off the top of my head with the figures on my setup, seems ive overshot a few things.
Ive had a closer look at things and heres my rundown of the stuff ive got planned.
43 gram motors, 21 gram ESCs, 14 gram servos, 10 gram FC board, 2 gram receiver, 2 gram battery monitor.
That tallies up to about 170 grams worth of gear with just the battery and the frame itself missing.
I'll be guessing on the frame weight but since its just 2 tricopter tails nailed together im guessing maybe 100 grams?
A 2200mAh pack might be a bit big but thats what ive got. So 187 grams.
That means an all up flying weight of roughly 485 grams leaving some slack for mounting and wires.

The motors are KDA20-26M ones, roughly 560gr thrust on 12 amps on 9x4.5 props.
I plan on using some Threebladed 8x4 props so I guess that ll boil down to roughly the same.

So 485gr takeoff weight, 1120 grams lift capacity. 2.3:1 ratio at takeoff, and 1.6:1 at landing.
Bit tight, and I suppose using 1800 packs would give me 2.4:1 to 1.7:1, but it should still be reasonable I hope.

Ive found a bunch of RCtimer 2822-14 motors laying around in my drawer, maybe ill use these instead.
830 grams of thrust each, pulling about 150 watts, thats an OK kinda trade I think?
1660gr thrust, means 3.42:1 at liftoff, 2.3:1 at landing, so plenty of grunt.
My calculator says over 15 minutes of flighttime, that cant be right can it?
Last edited by Freakazoid; Dec 05, 2012 at 05:35 PM.
Dec 05, 2012, 05:36 PM
1400 watt RW Zephyr
matwelli's Avatar
those timer 2822-14 are great motors. that's what I always use. they Also perform well on 4s
Dec 05, 2012, 06:02 PM
Registered User
Freakazoid's Avatar
Yeah they seem quite a lot more worth it pound for pound. An average near 3:1 is pretty good.
I can even bring it down a lot more if I fly it on 1300mAh packs, still 10 minutes of flight according to my calculator.
I think ill oil up a pair of these orange powerhouses and have a go at it.
The KDA ones are only good enough on a quad I suppose.
Dec 05, 2012, 06:25 PM
um.. yeah, I can make that fly
Carlos230023's Avatar
:P. I did say 1.4/1 is the bare minimum for anything under 2Kg. It would be an uncomfortable craft to fly, especially outside with a depleted pack. As you say, ideally you want 2 or 3 / 1 power to weight. Without my DSLR my bicopter will technically have a 5/1 ratio. But the camera and gimbal bring it to an estimated 3.5/1.

Did you get your PLA parts 3D printed? I've got the Up! Plus 3D printer, I plan to use ABS as its a little stronger than the PLA for the structural parts, but I intend to use PLA for the nacelle covers (as its translucent I also plan to load it with LED's :P).

Dec 05, 2012, 07:04 PM
1400 watt RW Zephyr
matwelli's Avatar
I brought a 3D printer (reprappro huxley) backin august and managed to get it all built and working a coulple of weeks ago

would like to use ABS, but still learning to model parts and playing around with printing so PLA is easier/cheaper to work with it seem strong enough as long as you build in plenty of structure, built an upright for my boys 1/18 scale truck and so far its taking the abuse

those nacelle will look sweet

so, im building a weight-over-prop (WOP ?) , Carlos you are doing OAT ? and Freakazoid Pendulum ?

will be interesting to see how it all works out im quite keen to put a surfboard on top of mine !

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