This one should be easy if you have any of the current crop of Kickstarter VTOL airframes, of course I will award less points so you might not win.
The task is simple.... (not)
Auto take off
Autonomous hover for at least 1 minute after take off
Transition to winged flight and fly no higher than 120m
Then circle radius 80m for as long as you can. (This makes the circle 500m a turn)
This of course points to the current delivery drone mania. To get noticed by Amazon try for greater than 24km about the distance their machine can deliver (apparently)
We will make this a six month contest as its hard. On the plus side its building time in the Northern Hemisphere.
For extra points some sort of silly cargo that makes me smile. Super bonus points added for an autonomous vertical landing as well. (All landings to be vertical)
If you can make a multirotor fly that far then all well and good, but I will be looking for the least amount of power used in event of a draw.
The longest distance wins.
Good luck, I look forward to May 2nd 2016 and the fruit of your labors.
Glittering prizes TBA
Let the pointing out of my Swiss cheese thinking commence...
Comments
For those you want to try a QuadPlane for this challenge, some docs here:
http://plane.ardupilot.com/wiki/quadplane-support/
I all, we are thinking about an entry, fortunately that there's still some time left, it is going to be hard.
See you soon
Yes, thanks Rob. Just can't bring myself to get into bigger R/C heli's, but you may change my mind. I flew CH-46's, which get's rid of that nasty tail rotor. Makes me want to create a tandem rotor BBot variant. Never enough time. Great info on the ESC's. We will need to compare.
And thanks again to Gary for picking VTOL for this T3. It's apparent that people have some cool ideas. I can't wait to see more data when they start flying. We have managed to try a few different designs but never get enough time to test them well before we are on to the next project.
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Rob
Great comparisons as usual!
But I'm wondering how your quad would perform if you would add a pusher prop and motor to the rear for forward flight. I'm guessing some 20-30% better. Even better if you add some little wings...;-)
I'm hoping to post some VTOL flights over Christmas when I get some hobby time.
The new helicopter designs don't have that many small parts. Check out the Goblin 380 design. Elegance in Simplicity. It doesn't even have adjustable swash links. Just molded single piece. There are exactly two adjustable links on the entire thing. Now, imagine that thing with no tail drivetrain. ;) Helicopters can be very simple. They just don't get much development work anymore because they are old. Everybody wants to work on the new hotness. ;)
Check out the HobbyWing XRotor ESC's. They are the most efficient ESC's on the market. I was already a big fan of HobbyWing because of their quality and reliability. I didn't know there was really any efficiency difference between ESC's, but then I stumbled upon this:
http://www.rcgroups.com/forums/showthread.php?t=2492809
I have promoted their use to other people, and everybody who has used them has been happy. That includes some people with very large multirotors who have struggled with some "high end" ESC's.
Always interested in the details Rob. Very interesting data. We are also running KDE's. A bit of a mix right now until we settle on a good power setup. Right now it looks like BBCopter will work best with the 475kv and 14in props at 6s. Should handle 10 pounds without real issues. Just got a flight report back from one of our partners and they got 22 minutes out of that setup at 11.5 pounds running a 10,000 6s. But again mostly hover work. What we do not know is if the "fuselage" of the BoxBotix has any real benefits for forward flight in terms of drag reduction. Easy to compute the wetted area of our design but might be a bit hard to compare to a more traditional quad frame. I guess the proof may be in the pudding as they say. My guess is we may need to spin closer to 24in props to get anything close to a the kind of times you are getting with a trad heli. The irony is, I am an old helicopter pilot, and I have no interest in building and maintaining a heli. Too many small parts for me.
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Ok, just did a back to back test of the two machines. That's the1530g Tarot 660 quadcopter with 15" props, and 2 4S 8000mAH Multistar 10C batteries, with NO payload. And, the 1680g Protos 500, with a 200g camera, and the exact same batteries. Both machines flew the exact same mission at the exact same 15 m/s speed. Here's the trick though. There was a light wind, about 15-20km/h blowing. You can really see the effect of this on the quadcopter. Each graph contains 4 laps, and you can see the large power increase on the quadcopter flying the upwind legs. The helicopter was much less affected. If the wind was even higher, the difference would be even worse. In fact, the quadcopter was using 100% throttle on the upwind legs. The helicopter was also using 100% throttle, but... not really. I run minimum rotor speed, which can be increased when needed. Last week I flew the same flight plan in 40 km/h winds without problem. The helicopter allows the easy ability to tailor the flight power to the requirements. In fact one thing I'd like to add soon is automatic variable rotor speed according to requirement.
Overall, it's pretty clear which machine will be able to cover a greater distance. The helicopter probably flying almost twice the distance if you were to add the same 200g load to the quadcopter.
Coby, not sure if you were looking for more details on my heli. This is a Protos 500 stretched to 465mm blades, so the rotor disk is about 1050mm. To those concerned about safety, I actually am going to try to assemble some junk parts I have into a minimum function chassis, and then fling a steak or chicken or something into the rotor. I'm very curious to see what happens too. My system operates with a greatly reduced rotor RPM, and the energy in the disk is probably less than 1/4 that of a standard helicopter of this size.
The empty weight of the frame is about 1680g, plus the 200g camera and batteries, it's about 3170g. The rotor disk is 0.86 m2.
By coincidence, I have a quadcopter that hovers for 45 minutes on the exact same batteries. It's empty weight is 1530g, and 15" props giving a cumulative disk area of 0.46m2. But note, the 45 minutes hovering is without the 200g camera, and it's not moving. I should put it up on the same mission and see how it does. I expect it will really start to suffer at speed. This machine is fairly well optimized with Hobbywing ESCs and KDE motors, and it's fairly lightly constructed (Tarot 650 quad frame). It folds up neatly, but takes up about the same amount of space as the helicopter does.
And this is the key differentiation here, and why I'm so bullish on helicopters for any application where you are required to actually *fly*. The helicopter required only about 25% more power to fly at 15 m/s than it did in a hover. And this helicopter is far from optimized. It is aerodynamically very dirty, I'm sure if it had a body, it could fly 20 m/s with the same power consumption. Also, mechanically, it's far from optimized, it uses a very draggy serpentine belt system and the motor is far too big. It's drawing 15A to hover on a motor specced at 60A continuous, so it's way down on the efficiency curve. I want to change the belt system and find a smaller motor.
Ah heck, I'm going to charge the batteries and go put it up, see what happens for comparison.
I did a bit of engineering work on the 18650 concept, and decided that they don't seem to be worth the effort and expense compared to the Multistar "10C" batteries (really, they are 2-5C, if you draw them at 10C, they puff). The thing about the 18650 Lion batteries, is that while they pack a lot of mAH into a given mass, they actually have a lower nominal operating voltage. About 3.4V/cell compared to 3.8V/cell for a LiPo. So when you actually calculate the Watt-Hours/KG, it's only about 20% higher than the 10C LiPos. Then when you consider how fragile the 18650's are, needing to be charged at only a 5-8 hour rate, and also factor in the cost, about 3-4 times that of the LiPos, it just doesn't seem worth it to me. They do make sense if you are trying to set a record, or if you just HAVE to have that extra flight time. But for most practical applications, it seems to make more sense to me to just use a good LiPo and return to change/charge more often. They are happy at a 1-hour charge rate, so you only need 2-4 sets to operate virtually non-stop. With the 18650's, you'd need 6-9 sets, to operate non-stop, so to equip a system for continuous operations, your battery cost could be 18 times higher than LiPo. Again, to gain only 20% longer flight time?
Furthermore, none of this seems to account for the nuance of the way the 18650's work. They have a much steeper discharge curve, starting full at 4.2V, but are intended to be taken down to about 2.4V, you have a 1.75 ratio of voltage from full to empty. Lipos are about 1.2. So when you consider the power system design, you need to plan for hovering thrust at 2.4V/cell, but then when fully charged at 4.2V, you will be throttled way back, operating at a low-efficiency point of the motors.
Rob,
Thanks for sharing details. For those who are wondering just how much more efficient a trad hell might be: We have a quad that is getting 45 minutes but that's mostly hover work. It also weighs 14 pounds and needs a 22,000 6s. Running 4 x 14in props for now but it's underpowered. Moving to three blade 15 and lower KV/bigger motors on the next build. Also keep in mind that we are sensitive to weight in our deign but it is built to be more of a farm implement than a potentially fragile ultra light build. I hope to have more detailed info in the next few months. Really want to see how far we can get for this T3.
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