Does torque transfer over a network of tensioned hoops scale better (better power to weight) than over a solid shaft?

How to break the rings in a tensile torque transmission ring ladder set…

Best sim yet of the effects of line tension and lift to thrust ratio on ring compression and torque output


Ahhh had on some mistakes still… doh …classic types
yep the model was wrong… I’ve given a better try but still…
Hoop rotation sim compression angles straight uplooping.gh (77.2 KB)
definitely not quite solved on analysing the output…
tried uploading a wee vid but aparently too big.
Ahh crikey more mistakes…
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Oh at last… There were some right clanger mistakes…
Sometimes you just need to step away from the computer… take a walk and it becomes obvious…


The .gh file for anyone with grasshopper
Hoop rotation sim compression trig input checked output.gh (78.0 KB)
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Getting some initial scalability data out
Hoop rotation comparisons.gh (92.1 KB)

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Way back in the early days of AWES research… I’m sure there was a study which rightly pointed out that torque transmission over a rope (single line) was a very bad idea. Weight, compression, torsional rigidity, twisting etc being problems…

Q. Does anyone know what this study was? Where we can find it?..

Been looking for ages now.

The .gh model is now much more versatile and accurate.
Seems to like heating up my silicon though.

Hoop rotation all multi ring with weights.gh (403.4 KB)
Good to see the model has weight as more an issue higher up … physically not so great for implementation but realistic

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One further key point about rotary power over networked tethers… Line fairing is possible.
(@Ollie reminded me this week)
@Ollie has also developed significant analysis of the method which blows my tiny thinky capsule. It’s sooo sweet.

So line fairing is basically an aerodynamic sheath over your line. The cylindrical profile of a line has a very high drag coefficient ~1.2 whereas faired this drops to ~0.3 (correct?)

This AWES power transmission system is (uniquely?) suitable for fairing because the line lengths are so short, so no twisting is likely … and also because the line is always travelling in one direction.

I’ll have better scaling data (better model again) before the end of this week.

Could you explain why that is? I would expect a kite network to be easier to implement fairing for, as the lines might not be rotating…

The fairing will act as a vane, if it is free to move and orient itself correctly.
Manufacturing something light enough will be a challenge.

Hi @tallakt, yes sure,

So I was talking about the “shaft” part of a daisy kite here… hoop, 6 lines, hoop, 6 lines, hoop, 6 lines…
That’s as opposed to a lifting kite network…

Example of a rotary network

Example of a lifting network

Example of a lifting network used to support rotary networks

A rotary network is a continually rotating set of 6 tethers (Could be any number >2)
Already demonstrated is how the tethers don’t need to be going through a lot of air really fast… e.g. The lower tethers (near the ground) in the videos are spinning closer to the axis (Set on smaller radius hoops(hoops also closer together)) than the higher up tethers going around the big kite radius.

So on a rotary network, always going round clockwise from below… the lines will mostly be “seeing” apparent wind from their forward rotation motion + true wind vector … the true wind vector is likely a fair chunk less than the rotation motion. So a forward-facing fairing on the line will be mostly well aligned ± maybe up to 20deg.
The fairing can maybe be tuned to encourage line expansion radially away from the axis. This would consume energy… I think.

Fairing on a static lifting network would be harder as it has long lines and also has to face wind from any direction.

Any component moving over another component is prone to wear …multiplied by the frequency this would happen on a rotary part … Going to burn out rapidly. Do you see a need for a vane on the rotary part?
Have you seen the research on efficiency gains from fairing in AWES yet? Think it was in Storm Dunkers work.

That’s a weighty argument against it. Fairing fixed to line with rotating swivels would have less wear.

I don’t. But not all awes are rotary. Fairing easier for rotary.

Nope, anything online? It’s probably mentioned in the chapter on tether drag in the second awes book which I still haven’t read: https://link.springer.com/chapter/10.1007%2F978-981-10-1947-0_2

Damn… Due to sag / misalignment, the lines are contributing different amounts of torque … I’ll have to re construct the analysis and reporting part of my .gh to re-work for that…
Sim takes a lot of compute time. Gives me time to work on physical model between runs.



That’s not even ring compression on the PTO Oh FFS

A few more vids on this form finding and force finding
done in this order




Hoop rotation multi ring K2 loop v2 8 lines.gh (1.5 MB)
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What conclusions can be drawn from that?

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I conclude that I posted 3 videos and a .gh file
oh and a mahooosive kite monster will one day walk the earth eating humankind for pleasure.

Update, I’ve improved the speed of the model by adding 10 second data dams so that I’m not constantly updating the form finding model inputs. Result of the converged form finding state and force finding was quite similar to what was posted above… will be a bit more accurate.
I now have to run loads of these sims to get some hefty fancy looking data…
Hoop rotation multi ring K2 loop DAM v2 8 lines.gh (1.8 MB)

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A few more runs showing how higher L/d is much kinder to ring compression

A torsion transfer tube should get smaller with altitude from the first ring with kites on, right?
(Less torsion to transfer)

Once you’re at the altitude where you start adding torque… That’s up at the kite rings.
The kites you want to sweep through as much air as fast as possible. They’re going to tend toward wide.
However there is no reason not to continue the standard torque transfer ladder all the way up through your kite rings too. This also gives you more choice for stable spread bridling and control and recovery etc…


Quite what the optimal overall outline form is…? Some tapering off at the top may help as the increased turn rate will help build power into the stack whilst maintaining stability on the guiding main line (if you have one)

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Cant wait till you build the big one

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