AH-6Z Littlebird Night-Ops build project

[Zeeflyboy]

So first up, I have to give a big shout out to Ian Davidson. He took a break from (not) flying Hello Kitty to turn me out some pieces on the lathe - He's made me the spacers I needed for the head and also some small bushings that I'll explain when they get here.





So next instalment in the ground station build - I needed to modify the DVR. Due to space constraints I can't use the plugs at the bottom and I also wanted a simple push button record/stop record which involved doing some wiring anyway.

Here's the DVR stripped out of the box and wired directly - Thankfully Foxtech have a document showing all the pin outs which makes life easier - I have soldered video in, video out, start/stop record and power.







So I then cut a big hole in the side of the case for the wires to exit, put it back together and printed out a gasket for the wires... I also printed out a mount to secure it to the top plate... could't find any m3 grub screws so have just gone with a normal screw until I find them.

[Zeeflyboy]

It's a new week, and with the first post comes the first repair/replacements to the AH-6....

This funky little tail arrived today. I've spent a bit of time on it getting it to move smoothly and also getting sufficient pitch, but mostly done now... This as mentioned has the advantage of being pretty scale, and also happens to weigh about 30g less than the tail it replaces - thats quite significant when it's mass hanging all the way out on the tail and should help with CG.






What will be really interesting is whether or not the tail has more power as a result of this staggered blade formation... time will tell.

[Zeeflyboy]

So, All has been quiet on the western front lately. Still waiting for the postman to bring me some essentials but I've now hit some further delays too.

First up, the tail blades I received were a bit weird - one set was fine but the other set had a mismatch between blades - one was a real matt colour and the other was a more glossy black which matched the other pair. Unfortunately it's not just cosmetic as the matter blade is also lighter - they don't balance.... I will have to order a new set and return these in the mean time.

On a related noted, I bumped up one size in blade - I ordered the 105mm rather than the 95mm.... quite by accident in actual fact, I thought I was running 105's already. I decided this was quite a happy accident on the order and I'll stick with 105's for now - it should give quite a bit more tail power to counter the high torque and low rpm (just look at how much larger the blade is overall!).




In other news I've been dissecting my new tail and I'm not 100% happy with the design. The biggest faux-pas is that they have designed it so the m4 screw takes all the shear load at the base of the grip. Putting shear loads against a thread is a recipe for disaster, especially loads that are constantly cycling. This is a stress fracture and blade separation waiting to happen - those of you familiar with T-rex 700's may remember when they threw tails in relative abundance - same design flaw at work... To add to my distaste, the grips are only using 2 small radial bearings with no thrust bearing, and the bearings have some play. Nail in the coffin is that due to the design, blade spacers are required too. If you look carefully in the below pic you'll see the black spacers I printed up on my printer.

Here you can see how the screw goes directly into the shoulder that the inner bearing sits against - all shear forces are directed at the thread here:






so what to do... I happen to have some beautifully engineered german grips going spare from my crashed tail. These have dual beefy high quality radial bearings, and a thrust bearing at the end. There is a small weight penalty for this of around 2g per grip, but this is somewhat offset by the fact the original grip requires blade spacers.

the two grips, german on the right and unknown origin on the left:




As you can see in the below pic, the german tail was designed with steel tail shafts so that all shear load is focused on a solid shaft rather than a threaded section - this is the way it should be done....




So I needed a part to make these two different tails come together. That is where good old Ian Davidson steps up once again with his lathe! Hip hip...

This is the part I designed for him to make:




It replaces the aluminium shaft you can see in the pics and acts as a feathering shaft for the german grips. The downside is that due to this being steel it should weigh about 7.5g per shaft for a total of 15g... aluminium would be substantially lighter but I'm just not sure I'm comfortable with it being strong enough at 4mm. I've done some sums and overall the whole tail mech (hub, grip, shafts, slider) ends up at about the same weight as the original german tail. So while I don't really gain any weight overall I do lose out on the savings I thought I initially had with this new tail. Such is life.

In other news I also completely stripped down my head for a thorough check... I ended up replacing the bearings in one grip as they weren't smooth but it's now all fine with the new bearings. The assembly guys were a bit trigger happy with the thread lock and getting it apart was not easy and involved copious use of a butane torch... the reason why I hand't yet ventured inside I was happy the thing was thread locked and safe, but it's just as well I did persist as the thrust bearings weren't even greased.

So I'm not going to put it back up in the air until I have the replacement for the new tail blades and the feathering shafts from Ian. By then all the other parts should have arrived anyway and we can go attack this once more. In the mean time I've got a few days off coming up so will probably try and motivate myself to do some fuselage work.

oh, and one other thing I did was to design a new boom clamp for the tail supports... I needed a bit more clearance on the Ace one plugs on the main controller so printed out this new clamp with lower support rails... I also of course designed it with a channel to allow the tail pushrod through. Not a big deal but previously it had to snake up and over the tail support rod. This was also a good chance to test my new E3D metal hot end I've installed on the printer - This has improved my print quality quite significantly - the clever design means only the bottom 2mm of plastic are molten meaning you have better control over the filament extrusion/retraction and less force is required. end result is better prints with less artefacts and stringing.

[Zeeflyboy]

things are slowly getting back together:

I fitted and wired up the two pushbuttons in place of the 3 pos switches on the taranis, happy to say they work perfectly.




I fitted my new tall landing gear to the mechanics (funnily enough this is actually about where the mechs sit when installed in the fuselage, just looks funny as hell without the actual fuselage! Anyway, this should give ample tail clearance during my testing which will make life easier:




And I printed up this central hub to make my training gear...






This is how the training gear will be installed - will just zip tie to the skids. These are pretty big - should mean that if the ACE one misbehaves again I can just dump it down without fear of a tip over.




The one problem is that the training gear and big landing gear add quite a bit of weight - with the 2kg needed to balance the mechanics it'll now be heavier than it will be in reality. I could put the nose weight further out but I think it's more trouble than it's worth.

So now I just need my replacement main gear, Ian's tail shafts and to sort out some odds and sods with the head.

[Zeeflyboy]

Got home to find the speakers I had ordered for the taranis arrived... forgot about those!

quick mod to do and WOW, massive improvement. She now sounds almost as smooth as my Jeti and even at half volume she's loud enough to be heard....

So here are the two speakers, stock on the right. The replacement is a much bigger speaker!




I printed up a little adaptor to mount the new speaker, from start of design to sitting on my print bed complete was about 15 minutes - not bad going lol.




Here you can see the stock speaker mount next to the oversized new speaker - hence why this adaptor was useful




Adaptor installed and secured with a little CA




And final install complete




I've been reading that some foam over the back improves the sound further, so when I find some suitable foam I'll put some in there too but for now I'm chuffed - huge improvement.

[Zeeflyboy]

Ian sent me a pic of the lovely steel tail feathering shafts he turned for me today (and a little main shaft topper in alu) - I think you'll agree that looks like a top job! He assures me they are as accurate as he can manage so we'll have to break out the old verniers and assign him a grade between A* and F when I get them.. lol. Cheers Ian!




In other news my new main shaft set arrived along with a new main gear... I decided to go with the DFC version as it's a shorter shaft and drops the head right down... this meant I had to ditch the top thrust bearing block and go with a normal one as the DFC shaft has a fixed retaining collar machined into it... not a big deal as this heli is designed to remain in positive G anyway and the thrust bearing at the bottom takes all the loading.

Three advantages of this approach - lower head for better look, and weight loss (lost about 18g with the shorter main shaft, no retaining collar and lighter bearing block). The disadvantage of this approach is that the main gear can't be spaced down anymore and the thick KDE gear just slightly slightly rubs on the top of the frame... I will need to do a little file work to give it some more clearance.





I also got around to fitting the spacers Ian turned for me to replace my printed ones - looks good in aluminium!




I also have a dirty confession - Just ordered myself a new plank. Until I finish the AH-6 it'll be LoS only but it'll likely become my next scale FPV project after that... I'm thinking full scale cockpit (see pic below) with independent cameras for the passenger/pilot with separate video links and full pan/tilt/roll head tracking for each... anyway it's a Sebart Pilatus PC-21.

Hacker/SebArt Pilatus PC-21

[Zeeflyboy]

So I got a little time today to install the tail shafts Ian sent me... they look great!

Just a reminder of what they look like:




Grips installed to check for fit:




And tail assembled:






So now not only do I have a hybrid head made from multiple different heads, I also have a hybrid tail lol. Haven't spun it up yet to check for vibes but from hand spinning it looks pretty smooth.

Thanks Ian!

Just a few small things left to do on the head and then the heli is all back together after the "incident of which we shall not speak".

[Zeeflyboy]

Been playing a bit today with scale suitable Pan/tilt/roll concepts in my head and I've come up with this little doohickey...

The basic idea is very similar the the Pan/Tilt but of course with added roll. It will use some tiny 2x5x2.5 bearings to keep everything tight and smooth... for an idea of scale the camera mount at the top is 20mm wide.

The idea will be to have 2 servos mounted side by side below, with control links going up to two hell swash style control balls. A y-tail mixer will take care of mixing, meaning that when you try to tilt (elevator to the y-tail mixer) both arms will move up or down together... try to roll (aileron to y-tail mixer) and one arm will move up and one move down).

Not sure yet whether this will make it into the AH-6, but certainly it will be a strong contender for the PC-21... anyway I'm going to order it from shapeways (my printer can't cope with this lol) and try it out for giggles.

[CAndrewGreen]

Hi,
Do you mind me asking what 3D printer are you using? I've been pretty much right through this thread and didn't see it mentioned, you seem to be making some quite tidy printed bits........
Regards
Andrew

[Zeeflyboy]

The really high quality stuff is from shapeways, the DIY stuff is using my makergear m2.

[wgt40w]

Has Juan gone home for the holidays ?

Are we now thinking and planning for the next project, rather than finishing off this one ?

Whatever, I'm suffering withdrawal symptons due to lack of more input.

Is there a support agency I can register with that offers help to people with these same personal problems ??

[Mudders]

+1  ;D ;D

[Zeeflyboy]

Lol

Just taking a frustration born break. Rebuild after the crash shows some excessive vibrations in the tail and head (mechanics run smooth as silk and straight as a die without head/tail attached).

Nothing that can't be fixed, but requires more time/money. Ace one rudder is also exhibiting strange behaviour - a constant slow drift to nose right which changes with gain. No way in the software to re-calibrate or otherwise assess the IMU. Have emailed DJI but no response yet.

So it's just on hold for a bit while I chill out and put it to the back of my mind for a bit!

In the mean time I have been distracting myself with this little project - a micro quad I've been designing the last week or so:

Still honing the design and optimising and will probably start building after christmas. So this is the current design, those of you who have seen the previous renders will notice the new motor mounts - these allowed me to drop some weight from the mount itself, plus lose 2 screws per mount for a total of 8 less screws and 16 less nuts (will now tap into the plastic directly).


Some design notes:

- Motors form a 200mm square (~8") and runs on 5" props.
- Frames cut from 1mm CF plate
- Arms 12mm x 10mm ID CF tube
- Mobius Mount on front
- Recessed FC mount in CG position (specifically designed for the new ET Vector)
- Booms feature small notches at either end to ensure alignment with a corresponding tab in the boom mounts and motor mounts











More info here: http://fpvlab.com/forums/showthread.php?23724-Developing-the-ZQ-M-quot-Vortex-quot-quad

[CurryKitten]

That's a lovely looking frame.  Be waiting with interest to see what choices you make in terms of motors, escs, number of cells to use etc etc.

You don't think the Vector is a little overkill for a mini-quad ?

[Zeeflyboy]

thanks

Yeah it's overkill, but it only weighs 50g including the current sensor and GPS (if I decide to use that too), so it's not totally ridiculous. What really appeals to me is that it is a flight controller and OSD in one, which simplifies things greatly on such a tiny frame while still allowing you to get the full experience.

I will certainly try it anyway, if I decide it's overkill I have a lot of other things to put the vector in lol.