Twinstar II FPV build log - RC Groups
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Dec 02, 2010, 12:41 PM
O <- this a ground loop
Build Log

Twinstar II FPV build log

UPDATE: I'm adding updates as comments - I'll prune it down later and throw it into the original post once complete so be sure to check the comments - thanks - 2010/12/29

Short and to the point build log here.
Initial post may have small errors as I'm not in my work room to check on exact spec or am typing from a phone.
Will correct any later.

Flight platform & propulsion
Multiplex Twinstar II
7x4 push & pull (reverse rotation on one motor)
Turnigy 2826 1650kv Outer runner x 2
Turnigy 18A ESC/BEC x 2

Power System
Flight power: A123 2300mAh 3 cell
Avionics & Electronics power: 11v 1000mAH
BEC 5v/3A

FPV setup
KX171 NTSC 12v (IntelligentFlight build)
2.4GHz 10mW/5v & 40mW/5v OEM TX
2.4GHz RX (add spec)
PUP3 12v DC to DC stepup converter 12v/300mA output

Piloting and Control Setup
Futaba 10CAP modded to mode 2
Futaba 72MHz TP-FSM TX module (removable)
Corona Dual Conversion 72MHz 8CH RD8P1 modded with RSSI & PPM buffered output
HXT900 servos

OSD & Autonomous Systems (planned)
DragonOSD+ v2
Locosys GPS module
Ardu IMU v2 (flat)
Last edited by devfor; Dec 28, 2010 at 12:25 PM.
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Dec 03, 2010, 11:17 AM
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On with the build...

On with the build...
A lot of this work was done last year but got put off due to other commitments.
Currently focused on getting this done.

Servo mounting

Don't like the idea of hot glueing everything in place.
Added to the fact that the HXT900 servos are smaller than the Twinstars II servo bays I decided to pad out the servo bays to give them a more mechanically secure fit.

Last edited by devfor; Dec 03, 2010 at 11:34 AM.
Dec 03, 2010, 11:40 AM
O <- this a ground loop

FPV setup

Didn't want to hack the original nose.
Don't have a pan and tilt urge just now.

So I opted to make a nose piece that would hold a fixed attitude camera dedicated to FPV piloting (as opposed to 'FPV tourism').
The camera is placed forward enough to keep the nose out of frame.
The angle of the camera casing counteracts the slight upward angling of the nose piece giving me a view that is pretty much straight forward.
You can't see it but there is a small red xxxxx xxxxx module mounted underneath the camera
Hope to have fun in foggy dusk/dawns

Last edited by devfor; Dec 03, 2010 at 12:11 PM.
Dec 08, 2010, 09:24 PM
Registered User
rdbell's Avatar
This is awesome.
Dec 08, 2010, 09:51 PM
SENTRY 62's Avatar
So when are you going to sell me that nose pod? Just a complete pod that I can shape and cut for my camera? I'd love one of those for my TS2.
Dec 09, 2010, 04:50 PM
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Thanks rdbell

Hey Sentry,

The solid layers make for quite a heavy part.
Of course we're only talking a few more grams but...

I've actually got an idea for a skinned version.
Allow for better cooling, maintenance and what have you.

Waiting on a few more parts from HK till the next installment.
Dec 09, 2010, 08:07 PM
SENTRY 62's Avatar
Well when you perfect it I'll take one - just say when and cash in hand.
Dec 11, 2010, 07:53 AM
O <- this a ground loop

Propulsion Testing

Propulsion Testing

Tested the Turnigy 2826 1650kv Outer runner with a 7x4 prop this morning.
I chose a higher kv because I'll be using a 3S (9.9v) LiFePo4

Fully charged battery left to 'relax' overnight.

Peak values as follows
  • 128.2 W (bang on what I had hoped for)
  • 13.22 A (Turnigy 18A ESC is happy)
  • 9.58 V (lowest voltage under load at end of 5 second test)
Haven't measure RPM or thrust yet.
I need to build a safe enough rig.

I just built a thrust test rig and got 430gm at 115 W.
I'll test again on a fresh charge later (hoping for 128W) and see what the thrust is.

In theory, half throttle (13Amps total drawn by 2 motors at 6.5A ea.)
should give me 17mins of flight time.
What with gliding and coasting, expect to get closer to 20 minutes.

As a foot note - if you were using LiPo instead of LiFePo4, for the same 7x4 prop
your motor would be
1100kv for a 4S LiPo
1400kv for a 3S Lipo
in theory...
Last edited by devfor; Dec 12, 2010 at 07:51 AM.
Dec 28, 2010, 11:23 AM
O <- this a ground loop

Been busy with other stuff... as one does

So here's an update

Wanted to go SMT with the OpAmp but couldn't as the Vmax was too low at 5.5v (and a diode will only give me 6.2v) so I did this.

Battery and Current Sensor Adapters

Roll your own folks...

ESC & Motors all Soldered

Placed thin metal washer between motor and mounting plate on left side to correct the offset as i will be running one prop counter-clockwise.
Used plastic washers for the hex bolts to bight into. Will threadlock if need be after first flight.

Unfortunately the timing is off on the ESCs
One kicks in at 1.25ms the other at 1.45ms
I guess I buy one more...
Oh and one of the motors feels 'smooth' while the other feels 'klunky' (klunky is German for 'clunky' or 'dodge' like a cabbage)
So I guess I buy one more of them as well...
Last edited by devfor; Dec 28, 2010 at 01:23 PM.
Dec 28, 2010, 12:13 PM
O <- this a ground loop

The Only Reason

I'm not airborne yet

This is multiple choice
1) I ordered a Donkey and they sent me 16AWG Black Silicon Wire
2) I ordered Black and Red 16AWG Silicon wire but they sent me a Donkey
3) I ordered Black and Red 16AWG Silicon wire but they sent me 16AWG Black and 18AWG Red

Here is the hint
Jan 11, 2011, 06:45 AM
O <- this a ground loop
Started a swarm that might interest Twinstar II owners

The swarm is done - thanks to those who contributed.
I hope you got what you wanted
I grabbed 2 new motors (spares if you will) and an extra ESC in the hope the timing will be better.

I was only able to get two swarm items in the basket but I ended up offloading about $200


Last edited by devfor; Jan 13, 2011 at 11:04 AM.
Jan 16, 2011, 06:55 AM
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I've held out for a long time - but its time to start hacking

Cutting/Melting the foam for wiring

To allow for wiring I decided to hotwire the foam.
I don't like the idea of cutting with a straight knife as it will leave potential tear/crack points for the foam to tear under stress.
Nice melted curves should distribute any stresses better... in theory.

Jetboil + copper wire + chopsticks

Jan 16, 2011, 07:00 AM
O <- this a ground loop

The black foam Japanese shoe thingy

You're probably wondering what that little Japanese shoe or "Geta" is doing in there.

Well at this time of the year in Japan its traditional...
Ok, not its not.

Its not a geta - its actually a level caddy upon which one day the IMU will sit.
With the DOSD close by...

Jan 16, 2011, 07:09 AM
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Houston we have video...

Mini Base Station

Not much to say... it works.
Haven't range tested yet - will post back when done.

This is pre FPV, nothing to do with this set up...
Probably knocked this up around 2002 or 2003
900 something MHz and very low power
Got a good few hundred meters in a residential area
The RX is in a box somewhere - it wasn't PLL - just direct voltage driven tuning.
If the antenna looks a bit wonky its because I hand drilled everything

Jul 12, 2011, 12:56 AM
So many UMs, so little money.
Did you ever get this in the air?


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