Hexa Belt F550 Build Thread

[jperkosk]

Hehehe, and this is the medium FOV, Andy. In narrow FOV (85°) the fisheye is almost completely gone, that's why I'm so pi$$ed they don't want to make these settings available for other resolutions than 1080p

This was shot with H3 in the role of a hatcam, 1080p, narrow FOV (85°), 30fps, when I adjusted it with my phone too high :

[ame]http://www.youtube.com/watch?v=pmQhauVHbm4[/ame]

My conclusion so far is that the higher frame rate is of benefit when you're shooting the medium-to-fast moving object, so it would be nice to shoot your heli at least at 60fps from the hatcam. H3 can do 1080p@60fps, but the resulting clips are frighteningly large; I would much prefer to shoot with 720p@60fps, and I'm tempted to try 720p@120fps, but with 720p I'm limited to fisheye (170°) FOV setting. They practically force you to use 1080p.

Now all this said, H3BE gives you 1080p@30fps & 1080p@60fps with 3-step FOV adjustment, so if the size of the clip doesn't scare you it very well could make the best hatcam in existence at this time. I'll shoot 1080p@60fps this weekend and post the results, so you can compare. Still, with 720p I could do 120fps if it weren't for FOV

When you send the camera up, the high frame rate shouldn't be that critical, but the FOV is. You're shooting the scenery that isn't moving as long as your platform is decently stabilized, but you're quite far away, so the fisheye becomes prominent. Less fisheye means more zoom which also means more difficult to stabilize the image, so the FOV adjustment for me is most critical up there. H2 gives me 1080p@30fps with 3-step FOV adjustment, so it probably won't be improved much by replacing it with H3, but I have to modify the gimbal for H3 to test this claim, so it won't happen this weekend.

[jperkosk]

Changed the motors and props on the hexa last Thursday, and had a hairy moment while taking one of the props out



Maybe I had it overtightened? Also, I had to grab the propeller to loosen the nut, but it didn't feel all that much of a force . Anyway, the new motors are a bit slower and much bigger, and there was no issue with the screws reaching too deep (I checked ), so I took all the extra washers out and just Locktited the screws into the motor housing:



The test flight yesterday morning showed all kinds of interesting results. First, I almost crashed trying to takeoff in manual mode:

[ame]http://www.youtube.com/watch?v=QE39GIBVSIA[/ame]

Then I realized I couldn't remember if I ever took off or even flown in manual mode before It was always either in stabilized or GPS locked mode, I think. I actually don't think you can fly FPV in manual mode, well maybe you can, but it takes a lot of practice, there is a limited feedback when you're flying watching the screen. So I realized I never adjusted any gains on the Naza, everything seemed to work decently with the default values. Except for manual mode, of course . Looking into the manual I found they recommend much higher gains for F550, so I'll do that first before I fly again. Did two flights in about 20kph wind and except for takeoff didn't find anything out of ordinary. Looking at the video later, it's a different story:

[ame]http://www.youtube.com/watch?v=fscgnvuGmX0[/ame]

There is a periodic vibration which I don't really know where it's coming from, of which I had some before but much less, so now I think it maybe gain-related: when the wind knocks the hexa out of it's stable position it compensates, response is too slow, and so it oscillates for a few seconds before setting down. What do you think?
If I'm right the gain tuning should do the trick.

On the bright note the calculated flight time has increased from 9:00min to 11:30min, and both the ESCs and the motors are ice cold . Can't wait for the 12" props to show up, the calculator says 12-13min flight time!

[Tomstoy2]

Yep, it's a gain thing.
Gains can be a funny thing. First you're going to want a pretty calm day to set them up.
Easiest way is you can set up a knob for gain adjustment.
It's just like setting up a tail gyro, go until is shakes, then back off.
When hovering, knock the stick and see how the reaction is. Increase to your liking.
Later, go in assistant and see where you are at and set the basic for that, with the knobs at neutral.

Then, in the wind, see how it behaves, and adjust with your knobs again.
Go into assistant again and see where you are at.

Assigning knobs requires you to not use the gimbal, ( I believe, as mine ist comes off of port F1 and F2.

So, to get back to gimbal control you can either, set basic thru assistant in between and then plug the gimbal servos back in , or get a seperate gimbal controller . Hoverfly gimbal controller works pretty damn good.

Some people like being able to tune the gains for the wind conditions manually with the knobs. And, let's face it, gimbal stabilization is not DJI's strong point.

Me, I just use the happy medium approach.
I'm waiting for the new brushless direct motor drive gimbals to come out and prove themselves. They have their own seperate control.
Once I get one then I'll go with the knob gains.

Just remember it's another thing you must add to your preflight checklist as these knobs do get kicked around when transporting or placing in a box. You don't want to take off without checking where the knobs are positioned!

Yeah, manual is a bitch, requires LOTS of expo to fly! I've done that myself a few times.
Hell, I got like 35% expo just for attitude and gps flying!

[jperkosk]

Thanks, Tom. I'll bump us the settings to wherever the new version of the manual suggests. No point of setting the gains to pots on the Tx, I can't see this vibrations. Maybe if I'd have flown closer (to my forearm? ). Only by looking at the video can I see those shudders, actually thinking about it they show up on FPV screen as well, so maybe there is a point to it after all? Don't have any separate gimbal controller, so I'll go the PC route first. I'll stick some decent expo in the Tx, I don't think I have any at all

[Tomstoy2]

Expo deffinately! In manual, which we camera flyers never use, you need even more than 30-40%, more like 60%!

You got damn lucky with that prop, buddy! Naza won't fly worth a crap with only 5 props. You were damn lucky you didn't throw it in the air! That's what brought me down in the pumpkins.
Now you know why I said to just throw them DJI props out.

As far as vib's goes;

1. Prop balancing is critical, both blade and hub. Don't dothe tape thing. If you throw a tape your filming session can be ruined. A real bummer if you made a long drive just to get some footage, like a nude beach.

2. If your new motors have tape label applied to the barrel remove them and clean the barrel good.
The motors themselves can be pretty well balanced at the factory but then they apply the tape throwing off the balance.

Engraving the barrel for the logo is worse! Now you have to balance!
It's time consumming as hell but a good phone app and some good tape will do the trick.
A well balanced motor has a cerain sound, it just sings! Nothing like a happy motor!

[jperkosk]

Well, increased the Naza gains as recommended in the manual for F550 and did the stability test by moving the cyclic sharply and letting it go: can't ask for a better response, really. Filmed the takeoff with the H3 hatcam 1080p@60fps, narrow FOV, stability tests @ 0:08 & 0:37:

[ame]http://youtu.be/EShHDJetBR4[/ame]

Looking at full FPV clip (H2 1080p@30fps, medium FOV) from the same flight you can see the same tests @ 0:16 & 0:45

[ame]http://youtu.be/ccapznYtxBg[/ame]

Now it's clear that the gains are set well enough. The shuddering got reduced, but still is annoyingly persistent, there is no doubt in my mind now that it's the props. No more putting off the balancing now, will have to get it done before next flight

On the bright side I'm beginning to fly further away and using FPV monitor more and more Went out about 200m on this flight and couple of times I had to hit GPS lock and look around to find my hexa in the sky. The flight time is adjusted to 10min now and there is still about 1:30min reserve in the battery. Can't wait for the 12" props to show up, the calculations show possible further 1:30 increase of the flight time.

[sutty]

Don't balance the props, as it will be wasted effort, balance the new 12" ones when they come.

From the ground the gain reaction looked terrific. Very fast and reactive. From the FPV, I don't know what is showing up as vibration. Probably just being shaken, as a result of wind, and then the lightning fast corrections due to your optimised gain. Can't think it is the props, as there are moments in between when I could see clrearly. Not saying it won't benefit from the props, but if it were them how could there be those moments of clarity?

Does it not come down to being able to mount the camera in a manner that can dampen the vibes? Or perhaps the speed and gain seetings for the gimbal as well?

All seems ever so tricky. Especially for you in your perma windy environment.

I look forward to further developments and reports.

Cheers

Sutty

[jperkosk]

I think it's the props. What clued me in was comparing ground with on-board video, I think I'm becoming better at video analysis by now The stability gain is almost perfectly balanced, fast but not overshooting. Camera gimbal stabilization is far from perfect, but it's actually quite a bit slower than the flight controller response and looks over-dampened, so it won't cause any resonance.

Since the hexa has to give continuous cyclic corrections to fly straight (just like a heli), and it does it by slowing down and speeding up the motors, I think at least one of the props is out of balance and passing through resonant frequency during the cyclic corrections, hence periodic "shudders" not visible to naked eye in flight.

What I'll do for now instead of balancing is select the best balanced props from the lot (I have 4 sets of these props) and then re-test. Once the 12" come in I'll test these and when I decide which are the keepers (it'll be either 11" or 12") I'll just order a couple sets of decent CF equivalents.

[sutty]

Fair enough, good thought about the different possible resonance as they change speed for the corrections.

Why are the 12" ones taking so long? Slow boat from China?

On an different note, lovely day, so like you Jerry I just played hooky from work and took the 450 out. As the packs went on I was getting so confident with piro manoeuvres that I thought, this is great, for the next pack I will go and get my hat cam, and share with the guys. Guess what happened on the pack whilst I was thinking that.

Oh well, very minor, hit TH, then saved it, but had insufficient headspeed left, and autoed into the field quite quickly. Straightend the blades out, bent the long links straight by eye, checked all the gears, quick spin up to check the mainshaft, and up and away to test it. Horrible tracking, but flew for a minute anyway to check it for performance otherwise. Not the safest way to test, but there you are, it's just a 450.

Anyway, otherwise okay, no servo gears broken, etc, but go figure, one of those sodding blade grip balls, the long ones, is bent in the grip again. Can't tell you how many grips I have bust up in crahses. Amazing that one of those can bend, the grip itself, but not bend the mainshaft, the feathering shaft, or break the servo gears. Might buy the DFC and see if it is any better, if I can't repair the bent one. Trying to repair them usually results in them breaking, but I have an idea about how to do it on this particular occasion, so we'll see. DFC is definitely on the cards, but only when I need new for sure.

Sadly though, no hat cam, so I can't share my piro improvement. Serves me right for thinking it as I flew. Like taking a fish smoker fly fishing with you.


Cheers

Sutty

[Tomstoy2]

Hmm, ok, I watched the whole thing. Not bad there, Jerry, really. You lost orentation when you went over the road though, didn't you? Looked like it as when you rotated 180 to face you it is still moving backwards. Got the ol' knees knocking, didn't it?

You got a few things going on;

1. Most of the jello is due to the way the camera is mounted on the gimbal. If you are using the housing and the GP mount for it, loose it. Just mount the camera to the gimbal, loose the housing.
If you look at how my camera is mounted I have it sitting on a pad of ear plugs laying on there side. The ear plugs ore secured to the gimbal plate using double sided servo tape.
Believe it or not, ear plugs on there side is the best vibration absorber for a GP out there. Lots, and I mean lots of people swear by them. My own tests have sold me on them, too.
Just strap the camera tight down onto the ear plugs.

2, Is the gimbal 'linkage' driven from the servos? If it is, and it looks like it probably is in the vids, then you can further reduce the jello by putting a rubber band across each axis of the gimbal to keep the servo lash in the gears loaded. The lash is a real killer.
Looks funky, but it works well.

3. Balance the props. As I've said, sand the inside, (bottom side), of the heavy blade to balance, the put the prop vertical and sand the heavy side of the hub. Once complete the blade will hold position on the balancer no matter its attitude.

Anything after that is induced by the motors.

Speaking of which, if you are only using 2 bolts to secure the motors to the mounts, use 4, and use washers to spread the load. This is important. If you need to drill holes in the mount to accomodate 4 bolts, do it.
Using 2 bolts induces vibrations into the arms a hell of a lot easier than 4 bolts.

Where is your throttle positioned in hover? It should be mid stick.
What is important here, and many people end up missing this step initially, is when calibrating the radio in the assistant program they forget to have the throttle set in mid position, green, before writing.
If you did this correctly, and you hover below mid position on the stick, then you are over proped for the weight. Over mid position you are under prop'd.
12's might give you more flight time, but will cause problems with the controller if you can't hover at mid stick. It will cause you to constantly adjust throttle position.

There is one more test to do with prop size after you get it to hover at mid stick, and that is forward flight.
If it hovers at mid stick but looses altitude in forward flight then you probably either need to change to more pitch or possibly bigger prop. Always try more pitch first.

If you are sold on 12's but it hovers under mid stick, then you will need more payload to counter act, such as dual batterys.

Now on to fpv. Addicting, isn't it? I just love it.
What kind of vtx do you have? I'm just assuming you are running 5.8ghz? Sorry, I just don't remember.
If so then basically there are 2 different types made by different manufacturers. Boscam owns the frequency for the 8 channel starting on chanel 1 at 5705mhz.
Immerson starts on channel 1 at 5865mhz. Fatshark is an Immerson system.
Nothing wrong with either one, both work with the same result, ntsc or pal. It's just a personal preference thing, you just can't mix and match.
What I would like to see is a picture of you set-up, please.

When you were out there, how did your monitor behave? Any snow?
What is the mw of you vtx?
You really don't need much. What is important here is 2 things.
1. placement
2. antenna

Placement is why I would like to see a picture.

Antenna design is extremely important. The best all around antenna to use is a cloverleaf antenna on the vtx and a skewer planer on the reciever, like this;

http://www.readymaderc.com/store/ind...oducts_id=1255

There are other manufacturers of these, some even cheaper, but IBCrazy balances theirs, pretty important. Hell, you can even make them yourself if you really want to.
They will give you great reception, are not directional and great range.
I'm using a 200mw vtx and these antennas I have been out 1/2 mile with it and no loss of signal.

If you are using the rubber ducky antenna, loose it. No sence inducing an accident when you can easily aviod one with a simple upgrade.
Just remember, you will need an adapter with the antenna. Read the link, it has a link to the adapter.

I know it's a lot to take in right now, and that you probably just want to concentrate on one thing at a time, nothing wrong with that. Just want to throw all this out there to you to think about so when you do get to that point you have a good base of knowledge to work with.
Remember, I've been there and done that, paid for it along the way. Knowledge is power.

And finally, heres a clip of a friend of mine who has fast turned into an fpv guru;

[ame]http://www.youtube.com/watch?feature=player_embedded&v=l8lfDFBWiQg[/ame]

[sutty]

Interesting clips there Tom. Two things that I found interesting, firstly he looked at the ground more than I thought he would, as opposed to more forward, and secondly, how difficult it was to judge the height, especially when over the water, and there was nothing but a smooth surface to see. Can he adjust his camera position or is this what he wanted? I'm thinking that if you were fyling for real, you would probably look forward most of the time, and glance down periodically, but maybe you need something different for this application.

Good stuff though, he was really zipping along.

Cheers

Sutty

[Tomstoy2]

He's flying a TBS Discovery, a dedicated fpv designed quad.
As you can see in the pic, the GP is just strapped onto the frame, no gimbal to keep it level, so when you go into ff the nose sits down. That's why the camera is always looking down.

He pushes 60 miles per hour in forward flight! Plus, he's flying very close to the ground and going miles out for distance.
He's got a vid of flying on the Colorado river in California where he's so low he actually skips it along the river and off of sand bars!

He started out at the same time I did, but he flys daily. He's tried about everything out there and as a result his knowledge is now priceless!!!

He flys vtx on 2.4ghz and uses uhf for the radio. 2.4 is exceptional at range and can burn thru small hills.
He also flys Zephyres, (flying wings), and has vids of it going over the ocean out in the double digits for miles!!!

Now he's gotten into camera ships and is shooting vids professionally.

If Jack ever thought I needed help, this guy would have made Jack think I was just small potatoes!

[sutty]

Right, that's interesting. I'm didn't expect 2.4GHz to be good for penetration and range. I thought short waves were more easily blocked. I thought that's why they used long wave for really long distance comms. My wireless router won't even make it to the living room, lol. Seriously though, I have to have a repeater in my house, and it is only 25m long.

I can see the pleasure from zipping along at a lick like that, but I'm sure I would like being able to see where I was going more. Sounds like he knows his stuff though.



Cheers

Sutty

[Tomstoy2]

Hey Jerry, something else for you to consider doing. Like I haven't given you enough to think about.
I reciently took the gimbal servo power off of my flight controller and ran it thru a bec instead. Think about it.

[jperkosk]

So I got the 12" props in, balanced them, installed a second camera for FPV and roughly synchronized the tilt with that of GPH2, so they always look down the same.



I have also installed the cheap HK OSD with its own GPS module to put some flight data on the screen:





The results are interesting:

• The flight time has not increased as expected, it remains about 11.5min, I have my timer on 10min
• The hexa has become whisper-quiet, almost stealth
• The HK G-OSD data is near useless, and the GPS sensor takes 3-4 min to get the lock. Naza's GPS sensor locks-on in under 60sec consistently here. There is an open source firmware for HK G-OSD which reportedly improves things a lot, but now I'm missing $5 programming cable from HK
• The gains are now too high for 12" props, you can see the hexa overshooting in the stability tests. This was an issue yesterday with ~30kph gusts, had to drop down the hexa few times to stabilize the cyclic, it was bobbing out of control few times under funny gusts, you can see this effect in the video
• The resonant vibration is still there Tom, I have balanced the props only side-to-side on the balancer, didn't you say something about balancing the hub as well? How do you do it? Wouldn't it be too much to ask for some pics?

[ame]http://www.youtube.com/watch?v=HblzOxCVU9s[/ame]

And the bed for my baby:

[sutty]

I can see this is going to become a never ending quest to stop vibes. Don't see any earplugs yet? By the way, quick question, if the Naza knows all about your position, and orientation, why can't that output the data to an OSD feed?

Cheers

Sutty

[jperkosk]

Marketing. DJI has a $250 OSD module as an option for $1k WK-M controller, but nothing for $400 Naza. My HK G-OSD set was $40, and now I'm finding there is an open source code for it that makes it somewhat useful.
And no, no earplugs yet . I think I'll build the AeroXcraft landing gear and gimbal first, they've been sitting in the box since January. It's build in England, bound to be better than Chinese X468 I have on right now



Tom, I still need you to explain the "hub balancing" stuff.

[Tomstoy2]

Originally Posted by jperkosk

Marketing. DJI has a $250 OSD module as an option for $1k WK-M controller, but nothing for $400 Naza. My HK G-OSD set was $40, and now I'm finding there is an open source code for it that makes it somewhat useful.
And no, no earplugs yet . I think I'll build the AeroXcraft landing gear and gimbal first, they've been sitting in the box since January. It's build in England, bound to be better than Chinese X468 I have on right now



Tom, I still need you to explain the "hub balancing" stuff.

Balancing the hub is easy.

Once up have the blades perfectly balanced, stand the prop vertical on the balancer.
The heavy side of the hub will then fall.
Sand the heavy side until the prop will stay perfertly vertical.

That's all there is to it.

If a bad hub it too heavy that sanding is not enough, some people will add superglue to the light side of the hub.
Personally, I hate this idea and perfer to just scrap the prop.

Are you just using 2 bolts to secure your motors to the mounts? If so, use 4, to radically reduce resonance.

[jperkosk]

Confirming the use of 4 screws on each motor.
Still unclear about "standing the prop vertical on the balancer", could you post a photo please?

[Tomstoy2]

Sorry Jerry, I'm at work, screwing off. I can post one tomorrow, but I'll try to explain.

When balancing the blades, you do it with the prop horizontal to the ground, right?
When you have the blades perfectly balanced so the prop hold a true horizontal position, then you do the hub balance by putting the prop perpendicular to the ground, blades straight up and down.
With the prop in this position and blades balanced, if the hub is heavy on one side it will pull the blades off vertical on the balancer dragging the heavy part of the hub to the ground.
Sand the heavy side Of the hub, ( the hub space between the two prop halves ), until the blade will hold a vertical position.

After that, no matter which position of the clock you put the prop on the balancer it will hold it. Example, 45 degrees.

If you are still confused, I will get with you tomorrow when I'm home.

There are some good boobtube videos of how to balance a propeller.