AH-6Z "littlebird" scale FPV build.

[zeeflyboy]

Hi guys...

I haven't been posting this here since the section isn't so active, but I've found myself pointing several guys to the build thread I have been running on FPVlab... so I have decided to post it here as well since there might be some interest in it.

This build has been going on for a few months already so there is a lot to catch up on... and things have evolved since the start. I'm going to try and post only the more relevant stuff here but please bear with me while I catch up. There may also be some odd out of place replies where I've written replies to people in the main build thread but have missed it and not deleted it from here, so sorry about that lol.

Anyhoo... here we go


Before you try and google it, the Z is for Zeeflyboy lol, this will be a build inspired by the AH-6 but takes from several different types and will have a few creative inputs of my own... so not an exact scale model, but a Zeeflyboy special edition if you will.

One thing that irritates me about the Euro is that I have to be quite selective about where I fly it due to take off/landing considerations so the solution to that is clearly a VTOL. I briefly considered the Osprey but decided against it for a few reasons.... A scale cockpit stuck in a quad ain't gonna do it for me either, so that leaves Heli's! The only thing that I've found tricky in my experience is hovering with a head tracking camera. Even with an external frame of reference it can be a tiring and wobbly experience... I have plans for this however, Skookum's soon to be released GPS unit that should bring some very helpful abilities to the table along with the natural stability of a heli this size.

So while the Eurofighter still isn't entirely finished in terms of exterior polish it is flying and functionally complete, thus I need something new to sink my teeth into... And this time I'm being a bit more ambitious and hope to end up with a more impressive model. The euro is fun to fly and was a great build to do, but this is going to be better! I have yet to see a scale FPV heli (perhaps I'm the only one stupid enough to try?) so who knows, maybe it'll even be a FPV first.

I chose the Littlebird in the end because I always thought it looked awesome when decked out with weapons, and the design affords absolutely fantastic forwards visibility from the cockpit, something that is lacking in most other attack variant heli's. I already have a 500 sized Cobra, and while it would be great to turn into FPV it's just a bit too small to work with and the visibility is comparatively poor from the cockpit. The only problem is that the kit comes with slightly tinted windows - I may have to pull my own clear ones.

So a brief outline of the project goals then:

- Build a semi-scale 12S powered 600 size AH-6 heli
- Fully featured scale cockpit with working rudder pedals, cyclic and collective
- Active glass cockpit display perhaps with live feed on one screen from FLIR, and cockpit illumination.
- Pan/tilt mounted cockpit camera, no OSD but audio alerts (voltage, mah, signal loss etc) active
- FLIR-esque B&W low light exterior camera with IR illumination, HUD style OSD and auto iris lens
- Remote operated camera switch to change between views
- External navigation lighting to allow LoS orientation in low light
- GPS position hold/atti mode and RTH courtesy of the as yet unreleased SK720 GPS unit
- Dual vTX diversity using Immersion RC 5.8ghz vTXs and 5800DUO (modified for dual channels).
- And finally, once again, to have a model that is visually and physically pleasing to fly LoS as well as FPV

My lovely, lovely girlfriend has been kind enough to buy me the MD500D scale fuselage from Century for my birthday (so I'm not allowed it until my birthday in late September lol), while the equally lovely parents got me an HK600GT to go in it and a few other bits and bobs. My cockpit kit just arrived though and hence this is where my build begins.... I'm afraid to say that once again this will be slow and painful, but this time not simply due to the work required.. Also the expense! It's going to be a complex build with lots of kit and it's going to make the euro seem cheap I fear. It's too much for me to stomach all at once so I'll be parting out the purchases over the course of a few months (and hopefully santa might bring me yet more bits for christmas!) With a bit of luck I'm aiming for a flight in the new year just after Christmas but we shall see...

So, here begins the journey... This is the present from the girlfriend which is currently being held in customs (for a week thus far... sigh. Hopefully it arrives before my birthday!)





And now I want to make it look like something roughly resembling my own interpretation of this, but with something more like the glass cockpit from an AH-6i:







My first goal is to build the cockpit, followed by the fuselage and finally the mechanics will come later and be extensively test flown separately before finally being introduced to the fuselage.

Hopefully Sassy Sander is going to give me at least 10 channels to play with, and it'll be assigned something like this, though exact details depend upon how the skookum GPS needs to be operated... Given what I've been told about how the GPS operates I can lock the gains as usual with the skookum, thus removing the need for a gain channel. I can then use a 3 position switch to determine choice of GPS mode.

Ch1: Aileron
Ch2: Elevator
Ch3: Throttle
Ch4: Rudder
Ch5: Pitch
Ch6: GPS mode
Ch7: Pan
Ch8: Tilt
Ch9: Camera switch
Ch10: Either landing light on/off or fun stuff eg "firing" miniguns

And hopefully by the time this project is done, I'll be able to have RSSI from the EZUHF rx without losing a channel in the ppm stream.

As always, I am 100% open to all suggestions and inputs. You guys improved my last build greatly with your comments, criticisms, suggestions and general support... Couldn't do it without you guys! Apologies once again for the somewhat verbose first post, so without further delay let's do this thang....

[zeeflyboy]

So to kick things off, I've built the basic structure for the cockpit... bit of a brain exercise as there were no instructions!







And here you can see I'm sizing it up for a 1.8" screen. I think it'll fit okay but I may have to do some custom work on the upper frame just to make it work.





Lots of space inside to put all the electronic goodies which is nice! I need as much weight as possible upfront.

this is the screen I'll be using for the live feed



of course it'll need to be separated from the driver board, and I anticipate some UHF noise from that ribbon cable - It'll be positioned well away from the EZUHF and I may look into some shielding too.

[zeeflyboy]

And finally for now, the pilots need somewhere to sit of course! Where better than this cushioned seat I ask you....




And safety first of course, so seatbelts have been added (will trim to length later when I've seated the pilot/passenger)

[zeeflyboy]

So this is my idea for cyclic.... it allows everything to be contained within the seat which should be nice and tidy.

I carefully cut a slot up the bottom shaft of the stick, and then cut a piece of plywood to place in between. This gives it a flat extension.

I then took some aluminium tube and drilled an axle hole through before then slotting the end... finally I cut a piece of carbon to size and use as an axle.






This whole assembly will then be mounted to the seat, with the tube free to rotate. One servo will be attached to the seat, linked to the underside of the tube and operate aileron, the other will be attached to the tube itself and have a small linkage wire connecting to the flat piece on the control stick and operate elevator.

Should look pretty good I think once the front cover is made up and the tube painted black.

[zeeflyboy]

So, just quickly stuck a single seat on to get an idea for how this is going to work. Looks good!








I have managed to find some 10" figures on ebay.co.uk called "HM armed forces" which come with proper clothing and weapons etc. The 12" figures are a bit too big and 10" equates to somewhere between 1:7 and 1:8 scale, so should suit this build nicely. Obviously one of the poor bastards is going to be decapitated and turned into a cyborg with a camera for a head, but oh well... you win some you lose some.

Here's my passenger



And my pilot (I may change him into the same camo as the passenger, bought a spare set just in case)



I imagine they'll need some significant lightening up, but we'll see when they get here.

[zeeflyboy]

I've screwed down the seats (about 60mm apart - enough to allow the front of the t-rex 600 frame between them if necessary) and fitted the cyclic controls, minus servos and linkages for now.

Looks pretty good I think (imaging it all painted), and puts the cyclic stick into a good position. At least collective will be easy - I'll just attach the lever directly to a servo arm and install the servo in the side of the seat.

[zeeflyboy]

The idea is that by night the cockpit will be illuminated by green LEDs in the roof, and some very limited forward visibility on the ground afforded by the 1W landing light/surrounding lighting... when actually flying at night the plan would be to switch to the "FLIR" view as though you were putting on your NV goggles. I have in my mind the image of spooling up with the cockpit view looking around, then switching to FLIR mode and away you go....

The "FLIR" will be permanently in black and white to simulate a different kind of view, and will be the only camera with OSD... the cockpit camera will be "pure" with no OSD display, but audio alerts will still come through the audio channel (eg low fuel etc). I may set up some simple LED warning/mode lights too.

The basic wiring for the video system goes something like this:

"FLIR" camera goes direct to OSD, then from OSD (maybe through a video splitter... might not be needed) to the cockpit display and to a two way video switch. The cockpit camera goes directly to this switch. The switch then feeds a video splitter which splits whichever video stream is selected (ch9 will select) between two imrc 5.8ghz vTXs operating on separate video channels.

simple huh? lol...

Anyhoo...

I've decided I'll just build my own upper cockpit section. I've ordered some 1.6mm fibreglass sheet to that effect... makes fitting the screens much easier and gives me more control over the appearance.

I knocked up this mock up of the dash, all to scale and correct. If you look carefully you can probably see faint red lines around the right screen - these denote the entire module and viewable area dimensions respectively of the 2" display. As you can see I'm cutting down the size slightly by making the hole smaller so I will be able to make it match the 1.8" photo viewer screen, which will be displaying radar images or navigation displays etc etc.

It's just a rough idea of what I'll need to build (all in 3D of course, not a flat print out), but what do you think? The first photo compares it to the dash that comes with the kit.

[zeeflyboy]

Right, I decided to try and be clever.... always dangerous.

I have downloaded some free 3D modelling software and am currently constructing the fascia panel. The idea is then to get it 3D printed by shapeways in the ultra fine detail stuff. I have never even played with 3D software before, let alone made a 3D model and had it printed.

Anyone want to point out a flaw in my plan? Here's a little screen shot of where I'm at (it's taken me quite a while lol, I'm getting the hang of it though!)

[zeeflyboy]

So I was reading up on my material of choice, and the specs say a minimum detail size of 0.1mm for embossed/engraved detail - so lets put that to the test I suppose! Some of these finer details are 0.2mm deep (eg the arrows on the buttons).

Anyway, pretty happy with what I've got so far. I might have to wait to get detailed screen dimensions before ordering though so I can make a specially sized pocket to seat each module in in the back.

What do you think?

[zeeflyboy]

So Just had the pleasure of paying the courier a butt load of cash for import duties but look what he brought me! Of course I had to open it to "check everything was there", but now I'm not allowed to have it until my Birthday... Arggghhh!

Quality looks pretty awesome actually, it's going to be a good base to start from. The cockpit is not a direct fit annoyingly enough despite being designed for it, I have already "massaged" some edges to make it fit better but it'll take some work to make it perfect. Regardless, I can't really start playing until I'm allowed to have the fuselage lol.

It's a good size, not too big so as to be difficult to handle but lots and lots of space inside for equipment, I've put a 20cm rule in one of the pics, and the most ubiquitous item known to man - the iPhone - in another, for scale... there's a cavernous area below the floor as well which will be able to hide some kit.









The bad news is, I'm definitely going to have to pull my own canopy... the good news is the vacuum forming rig I'm going to have to build to do it will also let me pull one for my eurofighter. Every cloud has a silver lining and all that!

[zeeflyboy]

I tweaked the design again - I've cut more material out in places on the back so managed to save about $4-5 while keeping all the walls sufficiently thick for strength. I also added a 3mm hole and detail panel for a low voltage warning LED.

Think it's good to go now, just need to see if it passes the manual checks when I try to order.

btw guys, when you click across to the next image on the link you can manipulate the 3D view with your mouse

http://www.shapeways.com/model/700775


here's a couple of shots (just missing some fixing screw details from the final)








I also had a quick look at how the cockpit fits, I think I've got some ideas for how to mount it better and make it look spot on. Now I have to put the Fuselage away though for another 12 days , at least I now know what I'm working with though.

Edit - just took the plunge and ordered my final one in the link using frosted ultra detail.... a cool €46 delivered in that material but (if it works) I think it'll be worth it since it's such a visible and fundamental part. Hope it passes all the checks it has to before it gets printed!

[zeeflyboy]

Just got my all important figures! the hyper observant may notice they are sat on top of an HK600GT box too....

[zeeflyboy]

Here's some of the electronics I've amassed so far:

-Scorpion HKIII 4035-450 Motor... POWER!!!! Peak power of 4200 Watts to be precise... This thing is designed for 700 size helis but although this is a 600 build it is going to be a heavy bird - it certainly doesn't hurt to have the power available to get out of trouble. This will require some modifications to the frames to get it to fit as it's simply too big. The kv of 450 is spot on though - with a 12T pinion it should allow around 12-1300rpm at around 90% throttle which should be about right for the 5 blade head and semi-symmetrical blades.

- Futaba BLS451 servos for cyclic... I've used these before in my 600 Pro before I went to a high voltage arrangement. Beautifully smooth servos with plenty of power and importantly reliable!

- Futaba BLS251 servo for tail... again, great heli tail servo. Does the job on 3D monsters, so should have no issues here.

- Gryphon 7075 LMT BEC.... The beating heart of my system - this will power almost everything! Input Voltage Range : 11V ~ 75.6V (3~18 Cells), Output voltage Range : 5.2V, 6.0V, 6.8V, 7.4V, 8.4V, Output current (Peak) : 20A, (Cont) : 10A.... also note a small nimh buffer pack. In the event of BEC failure this pack will supply power for long enough to get down safely.

- Skookum SK-720... The brain! one of the best FBL units I've ever used - one also resides on my 600 Pro - and soon to get the all important GPS module which is really the enabling technology that made me even consider doing this project.





So that has managed to tick off a lot of the boxes of things left to buy. I also have the cameras on the way which should be waiting for me when I get back to geneva with any luck, already have an IMRC 5.8ghz vTX going spare to put into the project and have ordered a video switch and few other bits and bobs from flytron... so whats left to get in terms of magic boxes?

Slightly depressingly - SK-720 GPS module (when it comes out!), a second imrc 5.8ghz vtx, imrc 5800 duo, EZUHF diversity rx, SPS 120A magnetic switch, some PPM decoders, maybe some splitters, and one of these magic ppm-max type doohickeys. My 600 Pro will be donating it's YGE 90A HV ESC (another very high end ESC) and in return will be treated to an upgrade after christmas.

I've been giving some thought to redundancy on this build, since it will effectively be a flying bank account (not to mention big and scary with a lawn mower on top).

Camera/video signal wise we have two cameras already, and each can be supplied by the main BEC voltage stepped up to 12v by two separate stepups... in the event of failure of the BEC the nimh will still be supplying power so they will stay live as will all the control electronics... the IMRC vtx's can perhaps run from 1 of the 6S packs and will obviously have redundancy built right in - if one fails the second will hopefully still be transmitting and the imrc duo will simply switch to the one that's still working.

Electronically, as previously mentioned, we have the BEC backed up by a buffer pack that will take over in event of failure. During normal use the buffer pack remains topped up by the BEC so will always be charged and ready to kick in. Flight pack current usage and voltage will be monitored by the eLogger and displayed in the FLIR view, with audio alerts that will also be heard when flying with the interior cockpit cam view. As an extra precaution, the gyphon has an adjustable low voltage alarm that uses an LED - this will be routed to the cockpit dash and when the voltage starts getting low there will be a flashing LED warning displayed in view of the camera.

Signal wise we already have a diversity rx... in the event of total signal loss however the failsafes can be set in such a way that the GPS unit takes over and flys the heli either into a position hold mode, or into a return home mode where it will fly back and hover 10m above the starting point.

To cover unusual electronic failures we have the RTH function on a switch which will bring the heli back as long as it is still able to fly.

So while there are of course still hundreds of ways in which strange and unfortunate things could bring the heli down, that only really leaves ESC failure as my big concern. I'm happy to autorotate a normal pod and boom, but FPV AND scale with low headspeed/5 blade head I think this scenario is destined for doom. Perhaps the crash can be controlled though... I can always practise FPV autorotations in Phoenix RC now at least! To this end however, she is getting a very nice YGE 90 HV ESC which hopefully will not put me into this undesirable situation!

[zeeflyboy]

Wow... just wow.

Look what came today! This is just even better than I had hoped for - the detail is insanely good... If I had known it was going to come out this well I might have tried for even more details lol. Remember those arrows on the screen buttons for example are only raised 0.2mm above the button (hopefully just enough for me to be able to paint them white)! Dimensions are spot on too so it looks like I managed to pull this one off - I'm one happy chappy! Just need to paint it now.

[zeeflyboy]

And here is Juan having a test fit...

He's still looking fairly happy because he doesn't know that he's in for some major surgery over the next few days. The arms and legs aren't free moving enough, and the legs have too limited upward travel so they will be hacked apart and modified... ultimately the poor chap is going to be decapitated too. To add insult to injury (and I suppose, injury to injury) he'll finally have a screw inserted up his posterior... life can be cruel.

[zeeflyboy]

just disassembled a 1.8" photo viewer... quick test fit to see how it's looking! I checked looking through my FPV camera and I don't get any screen flicker, so that's good. The lipo will be replaced with a 3.3v power supply.

[zeeflyboy]

So, been working a lot lately = not too much time...

However, a few small updates.

Firstly on the mechanical side of things:

I've been looking at mounting the mechanics in the fuselage, and I see some people just use plywood blocks to raise the mechanics up enough. The kit came with some stand-
offs, but these aren't in the right place for the T-rex 600 mechanics and hence why people do the plywood thing.

I thought I could attack this problem slightly differently so I have designed a mounting bracket that will go on top of the stand offs, and to which the mechanics will be attached. I'll be getting this machined out of aluminium.



and here you can see the stand-offs it'll attach to.




I'm also looking at pulling out all the linkages on the frame and running direct to swash servos... looks like it should work fine and it saves weight/removes slop and allows me to move the rear servo further in to clear the fuselage.... more to come on that later on.



And on the cockpit front:

I've been giving some thought to how to build a nice pan/tilt mechanism that can be stuffed inside a Torso... this is what I came up with. This will be printed out of the standard flexible and strong white plastic from shapeways for about €10.





The basic idea is this... the large piece on the right attaches to a round servo horn. You then insert a 10mm aluminium tube of whatever length is required into the hole. The piece at the back then mounts on to the top of this tube, and will be fitted with 3x6x2.5 flange bearings on either side for the tilt shaft. The piece on the left slots between the prongs and has a 3mm shaft inserted to keep it all together.

In the same way that I made a cut out in the tube for the cyclic elevator control, a cut will be made in this aluminium tube to allow a servo to be seated... this will then have a linkage running up along side the tube that attaches to the little tab at the back of the piece on the left and will operate tilt.

The whole lot then gets inserted into a hollowed out torso so that the top section comes out roughly where the neck would be, and the camera gets mounted to the top.


And finally, something actually real rather than 3D modelled... I just got done painting my dash. This is going to be a special ops heli so I wanted to go for something that looked like it had been beaten to within an inch of it's life... unfortunately my artistic talent is somewhat limited and this is the result






The two big emtpy slots will be filled with LCD screen obviously, while the top right will be an AHI and the other two will be black with green writing. They'll be printed on some backlit paper in the same way my eurofighter screens were and then lit from behind by LED backlight. The LF, O,H, and R holes will be filled by LEDs as mentioned before. The LF will be flashing red when voltage reaches a pre-determined level, then O will be green, H will be orange and R will be red... indicating the state of the GPS mode in which the heli is flying.

That's it for now I'm afraid, baby steps!

[zeeflyboy]

Here's a quick mock up of the dash with some screens photoshopped in...

[zeeflyboy]

So, it's my birthday and I'll play with my toys if I want to....

Got some little extra details for the boys, vests, knee pads and a better gun etc. Unfortunately I already broke the tip of the gun by dropping it... typical lol. I'll see if I can fix that. I had to do some cuts to the back of the seats in order to get them to clear the floor on the main body, and I also came up with a much better mounting system that consists of 3 very high tech lumps of plywood epoxied to the body onto which the cockpit can be mounted and screwed down. I think I'll add a middle support too as it does have a little flex as is.

Here you can see the rough seat cuts, plus note the position of the servo for collective stick movement.





Say hello to cyborg head. This is a small form factor Sony HAD II 600 tvl camera and will be replacing poor Juan's noggin.





Here's my dash with the auxilliary displays fitted - I first installed a little clear plastic then installed the backlit paper behind so you get the appearance of glass over the top when it picks up some reflections etc. I've pictured it here next to the dash that came with the kit for reference..





And finally the lads are chilling out for a test fit - really happy with the size of them, they look good I think. The doors on the fuselage will be cut away like the real version so you'll have a better view of the guys and visibility out the side will also be better for the camera.







My girlfriend just asked me how I'm going to paint it and I said I'll be buying an Airbrush for this one - she offered to buy it for me... what a girl!

[zeeflyboy]

I've spent today playing with solidworks again and I finally managed to make the skid lights I was trying to! The MD500 has a funny nav light location in the front of the skids, and some people just literally seem to bung an led on the end of the tube and call it a day. Not me however, I spend hours making this:



link is here http://www.shapeways.com/model/71624...a2fb49c1f95c88 and once again click next pic for a 3D view.

I designed them around these 5mm high flux LEDs, you can probably use your imagination to see how it goes together... If not the led sits in its square hole and then the cover goes over the top, wires run down into the skids through the centre channel.