Daisy progress with rigid blades seemed to go a step backwards on the practical side today.
We did however get the data from high wind today… Sorely lacking from a previous try.
@Ollie has managed to populate new areas on his charts, extending neat curves.
Plenty carbon rod and tube parts progressed into fragments today.
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The video below shows the lift from the rotors. When they stop spinning they descend to the ground, while the lifting kite continues to fly.
Beside this I wonder if an accordion style technique could allow to bring the rotors closer for takeoff and landing then to expand them during the operation.
The rotors descend in this video because I pull the back line down.
So I was wrong. Thanks for the precision.
Like an autogyro parachute, the turbine should provide some lift? Have you calculated its theoretical lift or have you tried to measure it?
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Today’s progress is printing out new fuselage prototypes to fit hexagonal tubes instead of bending them into a circle.
I will get around to some new force and operation explanation material as posted on twitter soon. Along with 1000000 other competing urgent jobs.
It’s not an easy thing bringing a new tech to market when cashless.
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I’d put understanding that at in the top 5. It allows you to quickly evaluate different ideas and optimize things. Your system relies on tension after all. You and Oliver (and Christof) spent a little time on this already, surely you’ve put out some content on this already? Or if you haven’t you might be able to give some ballpark estimates?
Thanks for quoting me correctly Tallak. I should clarify: in reasonable, workable windspeeds, especially just for experimentation where you are there, you can get away with no overspeed protection. But if the winds pick up higher than expected, you are in trouble! The problem is, the cubic relation between windspeed and power output. A few more MPH changes from productive to destructive. This means you are balancing on a knife-edge between the most productive winds and destructive winds. So you mostly experiment in light or medium winds.
When you want to release a model that should be expected to run unattended and last for years, overspeed protection of some type is way more important than peak power output, since a machine rendered nonfunctional delivers zero power. Even 10 Watts is better than zero. For example this downsized (due to a crash) Sky Serpent
machine has no automatic overspeed protection, since it’s just experimental, and I can choose not to run it in very strong winds, but it does have a brake. Nice but not foolproof. Often such a brake will be overcome by a truly strong wind. The next step is an exploding machine, a burned-out generator, etc.
Still have to see which component weak spot overspeed will kill first on the current Daisy.
Was 5o’clock trailing edge bending the tube in the first rigid model… fixed with inner tip to centre alignment line in the next.
The fact it goes into even more tension is interesting but … to be prepared for bigger systems needing overspeed protection…
Yaw control using lift kite steering or backline side recovery for a TRPT / Daisy seems valid so far
But it will be a cumbersome operation to land a rotor this way in high wind and dependant on the lifter keeping flying well.
Hinging the blade pitch around TRPT connection will likely be fragile. Could maybe be based on polygon tension but looks heavy.
Active bridle reconfiguration solutions are all sorts of bother. But work in kite sports.
A compliant span folding wing hmmmm maybe.
A local weather warning activated turbine dropper … recover to base down the lift line… maybe.
Or just make a system so insanely cheap it doesn’t matter… but don’t litter.
I think the bigger you scale, the less you can rely on a lifter kite to supply the tension, and the less you can rely on centrifugal force. If you solely rely only on a lifter kite for tension, I think you’d need rigid elements out to your blades to resist the tension from your torque tube (and there’s limits on how big you can make those), otherwise there would be nothing to resist that. You’d still have the centrifugal force, but you’d like to lower weight and speed, and increase radius, which all reduce centrifugal force. The lifter kite can help with elevation angle.
I think you’re already relying on centrifugal force and lift from the blades to supply tension but you haven’t calculated/measured them?
I’m beginning to get a little more interested in this idea. If I were to try this though, I’d try to eliminate all rigid elements except for the blades and, as a start, have a single blade rotate around a lifter line. Something like that was posted before, but that could have been better executed.
Maybe I’m saying obvious or wrong things.
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Yes you’re right. Daisy will have to rely less on lift kites above the turbine in larger models.
Once flying the lift kite is mostly used for aligning the turbine downwind and adds a bit of tension to the torque lines. Most of the tension in the torque lines comes from the rotary blades.
The turbine requires very little lift as it acts like an autogyro. I launch when there’s over 50N tension in the lift line… That’s tiny.
So as long as other AWES developers keep developing and scaling single line lift type kites (soft or rigid)… There’s a long way to scale.
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I’m not planning to rely on centrifugal force for scaling. That could make launch very hard…
The turbine blades have a slight bank angle already (outer tip closer to the ground station)
This promotes aerodynamic expansion. Too much can however lead to heavy drag on the lower blades.
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Eliminating rigid apart from the blades also makes launch hard… However, there will be ways to significantly reduce the mass to swept area once flying by expanding a given rig in the air.
Damit.
Bust the tube sockets on 2x fuselages at launch today. Suspected twisting of the rods could lead to too much hexagonal deformation… But had had an OK practice lifting …
Time to adjust/adapt tubes with an anti turn mechanism… Bodge a bolt, flatten a strip…
Damit
Swear swear swear
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Today’s test went a lot better… Well OK not a huge lot better … but at least it got up safely, spun up well and made some power … Just didn’t go quite high enough for long enough. The lift kite line tension was as I suspected before launch (doh) a bit too low… I need to stop testing from my croft where the wind is too turbulent, and there’s not much room to go higher.
Well it was a nice way to spend some home isolation time & on my birthday too… woo hoo not quite the party I had been planning 12 years ago (I had a 33.333yrs party with records , was planning a 45revs party too)
Videos on the way. They don’t need to be long ones.
At least the 6 blade configuration flew well for a while. Made a nice noise too. (subjective and minimally relevant)
The fuselages seem more fragile with the straight tube inserts instead of sitting over a hoop. Makes sense.
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So if you want the full greusome detail of the whole test (all ~30 sec (not months))
It’ll be loaded here soon…
Quite a few lessons I really aught to have sorted by now.
Must fly higher for better wind.
Strengthen the fuselage connectors.
Start using lift controllers.
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Perhaps replace the lifter with more lifters on the same line to get more tension? Seems lile the rotational part of the rig is running well. Like the look of the hexagonal part of the shaft
Im not an expert in show kites (you might want to speak with one): Large show kites use a smaller pilot kite to stabilize the larger kite. I see that your pilot kite is «hunting» the ground due to low winds. A smaller kite with a longer tether would not have the issue to the same extent. Even the same kite with a much longer tether would probably not do this. Hope this helps… seems like too much time wasted in a crash. Even if crashes are to be expected, we want them to be as far as possible between.
Yeah I could have learned more from this rig. But fast iterations pay off too.
Yes flying higher would be better… But I told air traffic control I’d be <30m AGL. I’m in an ATCZ.
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