Just tried a collective pitch heli...

[DennyR]

Thanks Rob but actually I only have access to a CNC lathe so I use my old tool making skills to make those pre production parts. I reckon I can file it to within .001" .

As far as any electronics are concerned I tend to use no more than is needed. Here is a good enough reason for that thinking.

As soon as I read about the first FOD with the S800 I set up a test rig to strap it down to a workmate portable bench. I very soon found that I was able to induce the FOD with constant mode changes in and out of GPS and Atti modes. So I new where the problem was a very long time before DJI found it. So the reason that I totally avoided any problems when all around me were crashing was because I (and my students that bought S800's as a package of equipment and training) used a different flight program. We started up in GPS and then switched to atti. before take-off. No other autonomous modes were ever used. 250+ trouble free flights including a few commercial assignments. The S800 when it was dialed-in was nice to fly and a very capable package. Will it do what this TDR can do? Never. Sorry about that! You can argue about it til the cows come home but the laws of Physics always win.

When Skookum announced they were getting into GPS I lost interest until I can see 2 months of trouble free use. All this delayed release has me worried. I think DJI have learned a valuable lesson and they said that the whole GPS algorithm has been rewritten. I will try Naza H without GPS and when I can do the same tests I may use the GPS but there is no substitute for having the right man on the sticks. The GPS you see in that picture is for the Gimbal system. Mini V-Bar stabi is the stabilizer of choice for just about everyone who puts 3 D helis through the hardest test of all. I'm sure DJI want a share of that market as well but it's gonna be one strike and your out. so I guess they will be on their toes this time around.

 

[R_Lefebvre]

Was the FOD ever traced down to flying in GPS mode? Was it shown that it never happened in Atti? Honest question, I don't know.

I understand your aversion to higher flight modes. Obviously more complexity brings with it more room for error. Still, I hope for better. The higher flight modes bring possibility of more capability, no matter who is on the sticks.

 

[DucktileMedia]

Denny, you just went up a notch in my book. That puts you at notch 1. Kidding. But good reading. You're getting me all SRH hot and bothered !

 

[DennyR]

Yuri
At the end of the day it all comes down to what you are comfortable doing. As cameras get better and smaller they place less demand on the platform used to carry them. MR's have had far more development in recent years and helis have stagnated because they were quite good at what they did even with a flybar. As SR dev. starts to become more intense again I think they will move ahead once more as the emphasis becomes geared to efficiency. The more electronic components you have the more heat you create and that energy has to come from somewhere, every component has some degree of loss and is a potential failure point, the more rotors you have the less aerodynamic efficiency you have.

Statistically the reliability issue is no contest. SR's win hands down. We have a Vario Gas Turbine machine here that has been flying for about 8 years now.

I was totally happy that the much modified S800's I built were fantastic from a user point of view and I am sure there are others out there that are working very well.

As payloads and endurance requirements get higher then the efficiency curve reaches a point where adding more battery capacity becomes a law of diminishing returns unless the swept area of the blades increases in direct proportion. The only answer is to use a more efficient platform. With that platform comes better stability, speed through the air and reliability.

As the attention switches to better SR controllers I think the MR fad will start to fade away IMHO

There will always be a market for small Toys and fun machines but for the serious AP market the penny must surly start to drop.

I'm sure this is not music to Barts ears but I was not comfortable with entering the WHY comp. as I would have had to avoid or lie about some of the immutable laws of flight.

 

[mitmit]

http://www.helicommand.com/index.php?option=com_content&view=article&id=53&Itemid=60&lang=en

If all else fails you could try one of these.

If your doing this professionally then cost is not an issue.

have one set HCP GPS for sale BTW. half of HC price

cheers

 

[R_Lefebvre]

Denny, I agree with you to a certain point.

But one thing you have to keep in mind is that, in theory, an MR rotor with proper taper and twist could be more efficient than a SR rotor. The problem right now is that, frankly, we have crap selection for propellers on MR. Just about all of us are using propellers made for a small, slow flying airplane, these props are not designed with this purpose in mind, and they're really not very good. If we could ever get past this deficiency, then we might have a better result.

Another important thing to know however, is that there's this issue with a MR will be more efficient with bigger propellers. However, bigger propellers have more inertia, and thus are slower to respond. This hurts stability.

I do agree with in that I believe the current fascination with lifting a Red Epic with a MR of today's technology is, well it's fairly well insane. But that doesn't mean it will *always* be this way.

 

[DennyR]

Denny, I agree with you to a certain point.

But one thing you have to keep in mind is that, in theory, an MR rotor with proper taper and twist could be more efficient than a SR rotor. The problem right now is that, frankly, we have crap selection for propellers on MR. Just about all of us are using propellers made for a small, slow flying airplane, these props are not designed with this purpose in mind, and they're really not very good. If we could ever get past this deficiency, then we might have a better result.

Another important thing to know however, is that there's this issue with a MR will be more efficient with bigger propellers. However, bigger propellers have more inertia, and thus are slower to respond. This hurts stability.

I do agree with in that I believe the current fascination with lifting a Red Epic with a MR of today's technology is, well it's fairly well insane. But that doesn't mean it will *always* be this way.

Rob lets forget for a moment about the electrical disadvantages and talk just about the aerodynamics. It is cast in stone that the most efficient way to convert energy into static thrust is to use the largest swept area that produces a static thrust that is as close to the operating velocity as you can get whilst absorbing the available power. As we have virtually no airspeed in the hover the theoretical optimum is an infinite dia. If we were traveling in an upwards direction at 100 mph then we would need a thrust velocity that is just slightly higher than that value. But again using as much dia as the available power will allow. Airliners choose an eflux dia that corresponds to the cruise speed and jet fighters use smaller ones albeit that they also have greater thrust velocity. Pylon racing aircraft use small dia props with very high pitch angles. Stol aircraft have large props' with low pitch angles.
It is very unlikely that significant gains will take place with MR's because they already use quite efficient slow flight props. Stability drops off as dia goes up. I spent a lot of time researching every conceivable blade design and found the cross over between stability and efficiency to be quite close to some of the currently available props. I don't think you should hold your breath for that revolution as it is not going to happen.
Helis on the other hand have fallen behind as the demand for 3D capability has increased. So-called asymmetric blades that are commercially available are in fact only semi symmetric profiles. The lower trailing edge of the blade should not curve upwards as this is a big drag generator, the clark Y flat bottom section is better but if you want to get the same efficiency that I have then you need something like that which the Apache uses, it has a reflex curve at the back. And yes it also has more pitch at the root.

I believe that guy who flew an electric heli for 1 hour 45 mins used a flat bottomed wood rotor.

OK so swept area for swept area on any given overall size of model, you cannot fit the same area into 4,6,or even 8 propellors without making the model bigger. You don't even have to believe the theory just strap the same battery to both types as seen the difference for yourself.

 

[Stacky]

Cameras are getting lighter and the quality isnt being hurt. The need to carry a camera the size of a Red Epic wont be a problem in 5 years time. The SLR mechanism is going to become redundant as well. Electronic shutters and the lag when using is no longer a problem and the speed of LCD displays mean that we are very close to no longer needing the slr mechanism. The trend is there in the NEX series of cameras and Nikon and Canon following the Sony lead. Improving battery technology will help the issue of multirotor flight times.
The biggest danger right now is people spending money on gear that is behind the 8 ball within 6 months of purchase and not being able to earn enough from it to have justified the cost. I went through this with the switch from film to Digital in the 90's.

I started out messing with RC Helicopters but the single biggest issue I had was safety, the bigger blades needed to lift a camera scared me. Even something the size of a 500 rc heli bothered me. Blades that size are deadly at the speed they spin at.

Even with improved flight controllers coming in for RC Helis I wont head back down that path, I dont care if they are getting far easier to fly I wont head back that way because of the fact that a set of blades a meter across spinning at 2000rpm is too dangerous for me to consider. The biggest cause of my crashes has been by a massive distance my own mistakes. The possibility of me hurting someone with one of those bigger blades is something I dont want to consider. I dont see the multi rotor boom at present being just a fad.

 

[DucktileMedia]

The answer to all our problems. Sorry I know I posted this before but it gives me a woody every time. All this tech talk aside, when the Gh3 comes out, I will be happy. I plan on making my helis smaller, not larger. As cameras get better in smaller/lighter packages we will have the benefit of making more streamlined helis that will be easier to travel with and have less wind footprint. Maybe someone will come out with a hack for the Zenmuse so it doesnt need a woochang to control it. Or better yet, someone like Photohigher will actually start selling the Hero.

 

[DennyR]

The Schiebel actually killed an operator recently. But the technology behind it seems reasonably sound as there was talk of a jamming scenario from the opposing side.

@ stacky I do believe that the first consideration is not whether a 710mm blade is more dangerous than a Okto turning 16 inch blades at a near critical limit of electrical failure as both scenarios are capable of fatal injury. It is all about the possibility against probability of a failure occurring in the first place. The SR wins every time on reliability.

I think someone could do a great job of turning the whole kudos and philosophy on it's head by taking a Walkers 500 and strapping a gopro three on the front and turning in some awesome footage.

I recently started doing some aerial HDR for night aerial stills... Awesome!
For those who don't know what HDR (High Dynamic Range) is all about then this is the basics. When you shoot a still image you actually take three images The first is over exposed by 2 stops and the second has no compensation. The third is under exposed by 2 stops. These three images are then processed in one of several software programs to produce a image that has a staggering dynamic range. The human eye can see a range equal to 14 EV's but your camera can see only about 8-9. the final result is spectacular.

How can you take three images without any movement? With a Zen of course....

Probably the only time I use a GPS lock. FWIW

 

[R_Lefebvre]

Rob lets forget for a moment about the electrical disadvantages and talk just about the aerodynamics. It is cast in stone that the most efficient way to convert energy into static thrust is to use the largest swept area that produces a static thrust that is as close to the operating velocity as you can get whilst absorbing the available power. As we have virtually no airspeed in the hover the theoretical optimum is an infinite dia. If we were traveling in an upwards direction at 100 mph then we would need a thrust velocity that is just slightly higher than that value. But again using as much dia as the available power will allow. Airliners choose an eflux dia that corresponds to the cruise speed and jet fighters use smaller ones albeit that they also have greater thrust velocity. Pylon racing aircraft use small dia props with very high pitch angles. Stol aircraft have large props' with low pitch angles.
It is very unlikely that significant gains will take place with MR's because they already use quite efficient slow flight props. Stability drops off as dia goes up. I spent a lot of time researching every conceivable blade design and found the cross over between stability and efficiency to be quite close to some of the currently available props. I don't think you should hold your breath for that revolution as it is not going to happen.
Helis on the other hand have fallen behind as the demand for 3D capability has increased. So-called asymmetric blades that are commercially available are in fact only semi symmetric profiles. The lower trailing edge of the blade should not curve upwards as this is a big drag generator, the clark Y flat bottom section is better but if you want to get the same efficiency that I have then you need something like that which the Apache uses, it has a reflex curve at the back. And yes it also has more pitch at the root.

I believe that guy who flew an electric heli for 1 hour 45 mins used a flat bottomed wood rotor.

OK so swept area for swept area on any given overall size of model, you cannot fit the same area into 4,6,or even 8 propellors without making the model bigger. You don't even have to believe the theory just strap the same battery to both types as seen the difference for yourself.

Denny, you are absolutely correct, that there is a cast in stone relationship between rotor disk area and efficiency. Or rather, the disk loading (area/mass) and efficiency. It's a very simple theory based on momentum theory. That is, the aircraft hovers by accelerating a mass of air downwards. The less disk loading, the lower the speed is. But you cannot ignore the actual efficiency of the rotor in question. Simply put, current typical RC Heli blades are not very efficient. They have a symmetrical profile that generates no lift at zero AoA, and they have no taper, or twist. Even the crappiest rotor used on an MR has taper and twist which helps it.

But in the final analysis, the swept area still rules. For example, my Octo with 12" blades has a disk area of 584,000mm2. My 600 heli has a swept area of 1,430,000mm2. And a 700 is 2,065,000mm2.

Even an Octo with 15" props is only 911,000mm2.

Another place where Helis rule is when actually moving. As induced velocity rises, the efficiency of a fixed-pitch prop falls off a cliff. Most people think that MR's have low top speeds because of airframe drag. This actually isn't the case. The issue is actually you've hit this brick wall due to induced velocity. Helicopters with variable pitch have a massive advantage here as they can move the point at which this cliff occurs.

I also agree that helicopter development has sort of stalled due to all this 3D silliness. But MR development isn't moving much faster. We don't have many good blades available. The fact that we still find it hard to beat an APC SF prop shows that. Not a knock against APC, they have always made very high performance props, ignoring scale looks, even back 10-20 years ago when I was flying them on airplanes. Though I still prefer an inefficient MA K-series on all my scale planes. So I'm part of the problem...

I will never agree that a MR is or always will be less efficient than a SRH. We'll have to agree to disagree on that point. An Octo can be designed to have very very low count of SPF. A heli will always be very high. Inspection or no, there's no getting around this simple fact. And I will never agree than a servo is "inspectable" or more reliable than a BLDC motor with a well-sized ESC. The only problem with MR reliability is the very low standards of engineering design put into them. Hexas, simply put are crap. Octos are good. Decas are where it's at but nobody is building those. And then we have the problem where everybody wants to "turn it up to 11". An Octo which can fly reliably with 5lbs payload is *capable* of lifting 10-15. So, that's what people do, they turn it up to 11, and fly with massive cameras. Now you're pushing the ESC too hard, and/or the motors too hard, and something fails. Either that, or they design too close to the ragged edge for the sake of efficiency, and have the same result.

I use both machines, but I use them to their strengths. If I simply want to lift something, not move around much, calm conditions, and I want simple and robust mechanics, I use the Octo. If I need speed, power, stability, manoeverability, range, duration... or there's some wind, the SRH is the way to go.

Economics also comes into play. Dollar for dollar, you're going to get more total reliability out of a MR. I can build a really nice Octo that is very reliable for the same price as a Hobby King 600. And the Octo will be much more reliable.

 

[R_Lefebvre]

Big weekend for me. I've finally got rate based control working really well on flybarless helis. Here's a test I did with my little HK450GT FBL. It's a joy to fly in dynamic fast forward flight now. It's very responsive but also very stable.

 

[Tahoe Ed]

Here ia the response I from DJI. "For mild 3D, you can switch modes and it will stab itself. But when you switch, make sure sticks are centered.
For Fierce 3D, must wait for a while then switch".

 

[R_Lefebvre]

Here ia the response I from DJI. "For mild 3D, you can switch modes and it will stab itself. But when you switch, make sure sticks are centered.
For Fierce 3D, must wait for a while then switch".

Ah, so the AHRS loses it during 3D. Not surprising, I have the same problem. I wonder how the other systems perform.

 

[DennyR]

The answer to all our problems. Sorry I know I posted this before but it gives me a woody every time. All this tech talk aside, when the Gh3 comes out, I will be happy. I plan on making my helis smaller, not larger. As cameras get better in smaller/lighter packages we will have the benefit of making more streamlined helis that will be easier to travel with and have less wind footprint. Maybe someone will come out with a hack for the Zenmuse so it doesnt need a woochang to control it. Or better yet, someone like Photohigher will actually start selling the Hero.

Yuri that is not the answer. Maybe one of these, this one is waiting for a Naza-H to arrive. Oh yes I know. Quality German engineering spoilt by a chinese stabilizer. View attachment 7904View attachment 7905View attachment 7906 Then again a 3D purist would say what a waist of a good TDR. Ha Ha...

 

[DennyR]

Big weekend for me. I've finally got rate based control working really well on flybarless helis. Here's a test I did with my little HK450GT FBL. It's a joy to fly in dynamic fast forward flight now. It's very responsive but also very stable.

Rob That is looking really cool, I must try it when it's all done.

 

[R_Lefebvre]

Yes, the Schiebel is cool, but it's not that much cheaper or more practical than a full size heli.

Is that the heli you were telling us about Denny? Looks pretty good. The mass is nicely centralized on it. Good job. I don't quite understand, the boom supports in the front, you have both a spring, and some dampers? At least with the dampers you won't have as much sway as the standard boom mount systems. I never really understood why they do that. My heli doesn't do anything in the air that would require that type of damping, and then the sway they allow seems to cause a lot of problems?

I'd like to share more of my ideas what I'm working on but I've decided this is going to stay "closed source". But it's fairly radical. Much more radical than yours. Dunno if it will work...

Yes, I'm really really happy with how things are going on for SRH on helicopters now. I flew it last night in 20 km/h winds. It flew well, except it was "busy". Not difficult to control, but the wind was definitely affecting it. I think it was still more stable than my quad. I'm not really sure what to expect out of a 450 FBL in the wind, but I can't wait to try on my 600 FBL. I find the 450 FBL flies SO easy now in Stabilize mode. You can just cruise around like that, just have fun. I've never seen a 450 flying like that. Not sure if it's anything special. It's just all you see anymore is 3D.

I also finally fixed the slight tail waggle I always had.

I'm still not sure which is better for AP. FBL or FB. I think both have different advantages in different situations.

 

[DennyR]

Rob

This is the latest one that is a bit lighter. The extra dampers are used to stabilise the rails as the camera IMU (WKM) has to be quite stable. The Zen needs to integrate with a stand alone WKM IMU as neither the Naza-H or the WKH will work with it. The middle dampers are actually in tension against the spring damper/bump stop. The more attachment points the better I like it, even the DJI rubber donuts have a tie-wrapp through the center. In total there are four levels of damping. No matter how much you shake the rotor head the camera does not move, and that is with the electronics turned off.

I recently saw a video of a 710 size heli being flown with the same asymmetric blades that I use and it was doing nice slow graceful inverted 3D at only 1000 rpm head speed. This is an example of how blade technology is moving forward again.

Whereas the Mikado V-stabi is the controller of choice it is only a stabiliser and the Naza-H is a true position hold autopilot.

Also I have heard that the Naza M GPS is the same as the Naza-H NOT SO. Don't try it guys. Different part number.

 

[DennyR]

Ah, so the AHRS loses it during 3D. Not surprising, I have the same problem. I wonder how the other systems perform.

Actually Atti and GPS are not 3D modes (limit is 45deg.) only Manual can do 3D and autorotation. The switching is rather like using idle-up it just centers the mid. positions it would seem once you have it trimmed out in the hover. Nice bail out if you loose the plot far out.

 

[R_Lefebvre]

I understand that part already. That is exactly how Arducopter works. Theoretically you can do 3D in "Acro" mode which is basically just like any FBL controller. The problem is using it as a "bail out". The AHRS can lose the solution during these manoevers. So you do some 3D stuff, and then flight into "Stabilize" (Arducopter) or "Atti" (DJI) and let go of the sticks. Theoretically it should flip up but... if it doesn't know which way is down anymore, you're toast. So the statement from DJI that you must wait would indicate that it could be a problem.

I think the helicommand can bail-out well, but it has a thermopile so it never loses track of which way is up. I'm not sure about all the others.