AH-6Z Littlebird Night-Ops build project

[Zeeflyboy]

So as promised the ImmersionRC guy popped round today and picked up my gear. We had a good chat about stuff over lunch lol... if we can't figure out what's up with the current setup he had some other ideas about supporting 16 channels natively with some firmware changes.

So that's good, one way or another this'll get sorted out.

So while Anthony is off trouble shooting/devising new and clever ways to give me what I need, I do have things to be getting on with.

One such thing was a quick redesign of the battery boxes. You can see I incorporated some holes on the underside - the primary reason for this was to provide an easy way to push out the battery from inside the box... I also built in a "collar" for the front straps. This means the box simply cannot shift forwards or backwards as the strap is locked inside this collar.






For cosmetic reasons I also printed out a thin black cover that simply lies on top of the battery and gets held down by the strap. Stealth batts.

in case anyone is wondering what the red tape is - that's simply my way of denoting pairs of batteries - one will be red tape, the next blue etc etc.

[Zeeflyboy]

So look what was just sitting in my postbox when I got home... YEAH BOY! Thanks so much to the guy that sold it to me at such a ridiculous price (you know who you are buddy!)






In other news, Anthony from ImmersionRC has been awesome too... he picked up the gear to check it all out on his oscilloscopes, and he decided that this project needed a native 16 channel solution and as such he's been coding away some new firmware for me... it's not entirely finished yet and I'll leave it to him or Sander to expand on the details as they see fit, but basically since my Taranis is capable of producing 16 channels this gives me the full 16 channels the need for a channel wizard anymore. It's eeeeven more clever than just a simple 16ch ppm stream as the 4 additional channels (13-16) while being fully proportional and full resolution will have a slightly lower refresh rate (eg they will only update position once every 2 frames for example). This adds a little latency obviously but it's irrelevant given their non-primary flight control functions... the advantage is the data rate stays lower and the sensitivity higher as a result.

So, good news! I just need to install the Ace One and Anthony to finish coding up this firmware update, then I can begin some test flights of the new systems.

[Zeeflyboy]

So I couldn't wait to get going on the Ace One install...

Happily the shelf I made for the EzUHF rx during flight testing is a perfect fit for the main controller. Losing this space when installed in the fuselage is no problem as the Rx sits further back in the fuselage itself... during flight testing I'll just have to strap the EzUHF Rx underneath. This position also means I can reach back inside the fuselage to plug in a USB cable to program the unit (since my lovely Naza hatch can't be used anymore :( )

I needed the main controller raised slightly so the servo connections could clear the rear brace, and it occurred to me I could make the riser into a wire router as well. Since I was re-wiring I also changed the wires to all be colour coded - makes matching channels to Naza ports much easier. The IMU fits nicely where the old Naza-H was.










So next up I need to make up some servo extensions and break open the frames (hopefully for the last time!) to install them properly and plug them into the main controller. The only mod I will need to do to the Ace One is cut the GPS cable and use a thin profile 4 pin locking connector so I can pass the cable through the GPS mount in the fuselage (the canbus port is too big to fit).

[Zeeflyboy]

I have just been playing around inside my heli and thought this made for a cool picture to share.

Just added - you can see the 3D printed tail servo wire guides that prevent the tail servo wire from going anywhere it shouldn't (like into the gears for example!), and the small servo wire tidy at the end of the IMU shelf that keeps the Cyclic servo wires away from the ESC.

Also nicely shows the combined elevator pitch arm/anti rotation mechanism and all the interior gubbins.

[Zeeflyboy]

Got a message from Anthony last night and he has finished the 16ch firmware. Channels 1-12 are as normal, and 13-16 are at 1/4 rate. This means they only update their position once every 4 frames - so given a 38ms 16 channel frame from the taranis for example, that would mean an update every 0.152 seconds - perfectly acceptable for light switches etc... so depending on whether you hit the switch just before a refresh or just after, the delay would be between 0.038 and 0.152 seconds before the action was updated. The advantage of doing this is that it only adds 2 bytes to the RF frame, which is negligible.

He is dropping the kit back today so I will get to have a play.... Assuming it works as intended it should be very straightforward. Just set muxed PPM to one of the output pins on the RX and then channels 12-16 on the remaining pins. Channels 1-7 get broken out on the mechanics by the 8 channel decoder while channels 1,2,4,6-11 get broken out by the 12 channel decoder in the cockpit.

So just to complete the picture from the post above, here is the other side of the frame... as you can see I have braided the servo lines to reduce RFI and where there are servo extensions I have heatshrunk the connection to prevent them coming loose from vibration





and here she is all ready and waiting (complete with 2kg ballast for CG and fuselage weight simulation, and temporary tail support rods since the tail is normally supported by the fuselage). Once I get the transmitter back I can go through the Ace One setup and see if I've installed it all correctly. If no problems arise she'll then be ready for her Ace One testing program!

[Zeeflyboy]

did some setup earlier on 1.48 and everything was working (12 channels).

Installed 1.49 (16 channel) just now and that all works - I can control 16 channels just fine... But the Ace One won't power up the servos.

Plug in a Jeti rx and it powers up fine. Plug back in the EzUHF, nada.

BUT, all channels report fine in the Ace One software monitor...

Brain exploding.

EDIT - won't initialise with the longer 16ch frame rate. Put it to 12ch and it comes to life. Humph.

[Zeeflyboy]

This is a problem... DJI seem to have arbitrarily set it to not initialise with a longer frame rate than XXms despite the fact that it can see the channels just fine and reports them in the monitor.

There are only 2 solutions I can see to this...

- Either run 2 rx's (which means more antennas and wiring and space). One rx outputs a 12ch ppm stream which works with the ace one, while the second outputs the auxiliary channels.

- Option 2 is completely custom ppm decoder hardware for the mechanics that will double the pwm output frame rates by playing the same frame twice... That would make the Ace One see a frame rate of 17ms rather than 34ms and hopefully keep it happy.

One step forward, 10 steps back...

I'm going to play with it at 12 channels for now - at least that lets me get some flight testing done with the Ace One.

EDIT - a third option just came to mind. Limit the muxed ppm to 12ch which seems to work fine and leave the auxiliary channels (13-16) only outputting on the servo pins, not in the muxed stream.

Don't know if that is technically feasible. Something to discuss with Anthony!

[Zeeflyboy]

So I was discussing with Anders about the possibility of using the Channel wizard as this custom decoder and he mentioned that it already has a fixed PWM output refresh rate of 50Hz.... So Ka'ching I thought - that will solve the problem.

However it also occured to me that perhaps the 12 channel decoder also sets it's own refresh rate while the 8ch is dependant on the incoming PPM frame. I pulled the 12ch decoder out of the eurofighter cockpit and just hooked it up to test. It works! Ace one initialises as it should when using this decoder - it must have a fixed PWM refresh rate.

So I now have a fully functional 16 channel native EzUHF solution. Need to do some testing just to make sure it's all behaving but wow that's great news... I was getting a bit annoyed with the setbacks.

[Zeeflyboy]

So unfortunately the world is ending. Been nothing but rain and storms all day... back to work tomorrow with long days all week as well. No flight testing any time soon :(

However I did mount my new ppm decoder (minus front cover just at the moment) and I came up with this temporary EzUHF mount for the test flights.

[Zeeflyboy]

Guys you know how I'm never happy with anything?

I'm finally happy with something :)

While working on my heli it fell on its side and bent one of the feathering shafts of my head. I disassembled it and found the feathering shaft is not an obvious replacement... I will be contacting the guy to ask how to replace and for a replacement part but in the mean time I've been quietly grumbling about the space taken up by the swash follower and the non mechanical phased head anyway.

So we are now on our *counts fingers* 1,2,3, 4th head. But this head is a Zeeflyboy Hybrid Special edition and I'm finally happy lol.

So to summarise:

Head 1 - smooth and looked a little like rotary porn but was very heavy, mechanically phased head but poor linkage design to achieve it (recently noticed a new v2 that loses this arm design)... some machining variances. Poor swash design meant there were some interactions between elevator and aileron (eg an aileron action would cause the swash to twist slightly, introducing some elevator).

Head 2 - light weight and well made, great design of phasing arm... swash was a bit oversized for the purpose and wrong colour (silver despite black head). Turns out the head was perhaps a bit too light weight as flight loads from my heavy copter seem to have tweaked the hub out of true.

Head 3 - Extremely nicely made, a great head all in all. Swash follower design means there is a limit to how low the head can be taken and requires electronic phasing. Never tried it before bending the feathering shaft, but will repair and save for another project or sell. Swash is light weight and built to a very high standard with no interaction errors or slop.

So now we get to head 4...

I bought this just to see how I liked it, and I did indeed like it very much. It comes with a fiendishly clever swash that uses the arms at the bottom for mechanical phasing but has three remaining problems - it is still a poor design in terms of interactions since the swash-servo links are not in line with the axis of rotation around the main shaft, and it weighs just a gnat's whisker short of a metric ton (190g compared to the 39g of my german made swash). Lastly the design is a bit too clever for the level of execution and this introduces a little unwanted slop. I must admit I fitted it and it did look pretty boss though.

here is the uber swash:




So what to do?

The answer of course was to combine the best bits to build one super head that I could finally be happy with.

So I started with the swash from my german head. It's by far the lightest and highest quality, and also has the swash to arm balls closest in to the centre giving the highest resolution possible on aileron/elevator movements.

I then looked at adding the great mechanical phasing arms of the second head. Unfortunately due to the different design geometries this wasn't a direct fit... well it could have been but I would have had a few degrees of phasing error that would need to be programmed out and that was something I was trying to avoid. What was needed was some careful measuring, a longer blade grip screw and a spacer to move the arm into the correct position to produce a perfectly mechanically phased head.

I ended up creating this prototype spacer and printing it out - 4.5mm long including the 0.5mm lip which keeps the bearing of the grip arm moving smoothly even when tightened up. While this does work fine it was mostly for design verification and I will probably look for someone with a lathe to make me the spacer out of aluminium for the final version (speaking of which anyone got a lathe and want some beer tokens?).




And finally of course I added the latest head and put it all together for my special sauce head... End result is a beefy strong head with no swash follower required and perfect mechanical phasing with no unwanted interactions between elevator and aileron visible at all, no slop and good values on the aileron and elevator mixes due to the high resolution. Zee = Chuffed.








There is also a lot of space on the shaft now to lower the head, so I'll need to cut and drill another main shaft - No rush for that though as it changes very little other than cosmetics so it can wait. I will probably also add the head button from my german head but at the moment I'm enjoying the beefy industrial look.

[wgt40w]

This should lead on to the question:

Why don't you 'market' your best-of-the-best head ?

[Zeeflyboy]

Simple answer, because it's not worth my time lol.

Plus the head that donated the pitch arms is quite an elusive head in its own right, spares are non existent as far as I can tell. The only way to get your hands on the arms is to buy the entire head. That means I would have to get custom arms made up, the cost just isn't feasible.

However, it means I have a truly unique head at least!

[Zeeflyboy]

So mechanics test flight is scheduled for tomorrow. Weather is looking co-operative and flight packs are charged, Ace One is set up... I just spent a little time finishing my Taranis setup too so here's a quick tour. The two toggles at either side for guns/missiles will be replaced by push button switches - just waiting for some SPDT pushbuttons to arrive from china.


I like how it gives you a quick rundown of the current modes and selections when you switch it on - much easier than looking at the switches and trying to remember what position they should be in. Generally I've aimed for a setup that requires all switches in the full up/back position on start, but it's nice to have audio confirmation.


Taranis Voice setup for AH-6


So all being well, hopefully I can complete both the first manual test flight required by the Ace One manual, and some auto modes testing plus general tuning. I'm not sure whether my friend will be available to film it so there might not be any video this time, but I hope it won't be hugely different to the test flight I already posted many months ago lol. Need to get back to work on the fuselage and cockpit, all being well tomorrow I hope to fit the two together soon.

[Ratty]

Good luck for the test flight, hope all goes well and works as expected.

[DaveyLC]

The copter is looking EPIC! :D

But damn I so hate the Taranis... <CLICK> <blurgh-blurgh-throttle-blurgh> <CLACK> <flight-mode-blurgh-blurgh-active> <PLANG> <camera-view-blarrrgggh>

Its like a posh American talking type-writer trying to speak with a half a banana in its mouth! Everything about it just screams cheap Chinese components... I can't believe you are going to trust it to fly your life's work?  :o

:laugh: