[For a contrast cousin: RRKs]
I find Charles Max Fry clearly teaching AWECS torque
tube as one of his taught options; so torque transmission from kited
systems went into public domain for AWECS at least a couple of decades ago,
if not sooner via basic torque-tube transmission of torque..., even the
torque of a shaft of a generator driven by prime movers of various
sorts....something used in 1800s.
Click image for full Fry instruction:
Jan. 2, 2011 M2801 Many years ago, BF Goodrich developed a rubber tube "torsion bar". If you pump a rubber hose with air pressure, torsional strength increases. It may be possible for a very long, lightweight, fiber-reinforced tube that is pressurized with air to point skyward . . . . with multiple propellers attached to it. Pressurizing an inflatable structure does increase its structural rigidity and torsional strength.
Harry [ ]
March 16, 2010 at M1340
While twisting line is one way to transmit energy, there are clear practical limitations. Hockles, kinks, loops, & bird cages are common partial failure modes. Sampson Rope, a technology leader in DyneemaŽ ship hawsers, asserts on its website that "high twist levels adversely affect the residual strength & should be avoided".
Twisting line concentrates stress on a just a few fibers,
which fail progressively. Then there is the fact that twisted line
pulls with great mechanical advantage, the basis for a "Spanish windlass",
so an AWE kite or aerostat must pull against very powerful downforce or
the line promptly supercoils into a twisted wad. These
problems can be somewhat mitigated by thicker heavier line but this severely
limits scaling potential compared to simply pulling or pumping a thinner
less abused line.
Still, for a small novelty AWE demo, a kite
tether based on a "rubber-band motor" or the Thessalian witch's jynx
(spinning disk string toy) [[Jinx ?]] will do fun micropower. An
advantage is high rpm. There are old posts touching on this
March 16, 2010 at M1341
I pulled together some numbers for the weight of loop
transmission vs electric conductors, and the loop looks like a clear winner.
If somebody wants to have a particular tether material or voltage compared,
let me know, or I'll go with 400 V and 1,000' of transmission, with solid
aluminum conductors, vs Spectra line.
I'd be happy to
compare numbers for the best hardware folks want to specify, from the shelf
March 21, 2010 "I would point out that the "DNA" helix (twisting rope ladder) without compressible strength would also tend to pull the machine down from the sky, however it may be that upward/downwind thrust would always be greater." Doug Selsam
PS: "P.S. I might point out that "the twist method" is the ONLY method actually used in millions of real wind turbines today. In reality, it's not just "A method", It's "THE method". In fact it is so common and taken for granted that I don't know if anyone has seen the need to name it before! :)" Doug Selsam
March 21, 2010 "There are being considered some wide multi-sub-tether schemes with three-rung-per-station segment with axial segmental struts to give compression strength when occasionally needed; smart tethering may well play a part that communicates with lifting bodies and generator or pump load-taking. JpF
March 17, 2010
While I applaud the micro independent individual set up, I do envision larger applications. The time is nigh, the weather is breaking and the fun begins; I do hope for a breakthrough on the tether front: some inside the box, some outside the circle and others off planet thinking will help us there.
Can you make a numeric list of what's available in the young
art of tethers, then maybe we can explore each from there, DaveS? All
March 17, 2010
Some actual achievements of torsional tether in AWE in its water analogue are several.
Airborne turbines driving short flexible torsion tethers can be understood:
March 17, 2010
The gyro with the counter-rotating rotors is an interesting concept . . . there is a tail-less helicopter known as a "Manx" that uses concentric counter-rotating rotors . . . like the radio controlled toy.
Piasecki built a helicopter with inter-meshing, counter-rotating rotors . . . that concept allow for gigantic rotors and it also allows for each drive-shaft to drive a flexible torque-tube or twist-drive mechanism that could carry power to ground-level alternators.
Doug Selsam holding generator receiving torque from pilot-kited series of
In ten AWECS scales (microAWE to free-flight) what are the potentials of aloft twisting of tethers in order to have tether untwisting drive ground generators? What are the challenges? The theoretical limits of effective energy generation from such a method category?
In early 2009 such twist method was listed in a methods collection for AWE online (now seated in AWE Sector). It might be easy to quit the quest with fears of torsional-knotting-tangle failures. However, a comprehensive analysis of the category may be worthy of attention.
Spiraling kites, looping kites, in-tether rotors, helicity gobblers, spinning kites, barrel-rolling kites, off-end-reel let-outs, rotating tails-twist piped to main tether, etc. can put extra twist in kite-held or aerostat-held tethers. If twist is deliberately designed to enter into an AWECS tether with deliberate intention of mining that tether twist for doing ground work, then what are the possibilities for practical execution? What materials at what scale? Niche uses?
Hold off comparing energy gains against other methods while this twist category is mastered to its limits and well analyzed and described. For some, this will be an interesting challenge; some may make a life's business from the category; others may see this quest as a dilution or distraction from what they may see as more profitable methods. But it might be neat to have the method well described for all.
Instead of installing a relieving swivel, consider installing a relieving-working-mining generator. What is the physical theoretical Betz-like limit for this category? Where will be the failures and how smart might be a tether to handle the challenges? Twist limiters? Calm-section smart reactions? Best materials? Controls? Life of the tether? Heat? Structure of best tether per use? Open-mesh tethers? Aerodynamically-working tethers? Full-Magnus-effect rotating tethers? Bladed tethers? Large-diameter airy lifting rotating tethers? Twist thresholds? Flexible drive shafts. Long torsion tubes doubling as system tether? High-tension cables? Encased pre-stressed tether? Smart anti-buckling tether? Open-mesh torsion case? Darrieus flying flex-shaft doubling as tether?
Yes, Dave Lang is invited to this tether-in-focus party, as well as all others. Top scientific analysis and practical experience are invited to the Tether-Twist Quest (TTQ). Who will do the twist? Why? Where? When? At what scale? Free aloft ended? Double-end-anchoring? Wide-collector of multiple tethers of one system? World-records in this method? Not to forget that in an extreme sense conventional turbines are do the twist with a "tether" that is frequently a hard and rigid direct driveshaft to a generator. And consider how a multi-part tether system is doing a large twist in the KiteGen carousel arrangement with a sub-tether doing a twisting!
On wide separated multi-strand tether complexes with open center and stack wings, have smart controls to fly segments in order to keep macro tether complex turning in all of its parts at the same rate. This has not been modeled yet. CoopIP JpF
Some attending links:
Your favorite links for the
TTQ project party are invited:
|Flexible Rotary Torque Transmission Cable|
|Tethers anchored at both ends:|
Definitions of hockles on the Web:
Keywords towards this topic:
Tether, tether types, tether material, tether structure, fiber-based tethers, flexible drive shaft tethers, ladder-like tethers, multi-tether tether complexes, high-tension, low-tension, torque, loops, hockles, kinks, tangles, bird cages, rigidity, tension meter, twist measuring, torque measuring, untwisting, sudden relaxation, high modulus polyethylene (HMPE) synthetic ropes, retirement criteria of synthetic fiber ropes, abrasion, tensile fatigue, shock loading, drum compression, twist, concept: building kite to fit a given bridle, shear, shear stress, strain, torsion, torque, rotation, tension, torsion equation, open-mesh shafts, flying open-mesh shaft, tether set, Hockling,
Following list is clipped from Simple determination of the maximum axial and torsional energy dissipation in large diameter spiral strands with extensive references
Note: OCR errors
may be found in this Reference List extracted from the full text article.
ACM has opted to expose the complete List rather than only correct and linked
 Raoof M. Interwire contact forces and the static, hysteretic and fatigue properties of multi-layer structural strands. PhD thesis, London University, 1983.
 Hruska, F.H., Calculation of stresses in wire ropes. Wire Wire Products. v26 i9. 766-767.
 Hruska, F.H., Radial forces in wire ropes. Wire Wire Products. v27 i5. 459-463.
 Hruska, F.H., Tangential forces in wire ropes. Wire Wire Products. v28 i5. 455-460.
 Knapp, R.H., Derivation of a new stiffness matrix for helically armoured cables considering tension and torsion. Int J Numerical Meth Eng. v14. 515-529.
 Lanteigne, J., Theoretical estimation of the response of helically armoured cables to tension, torsion and bending. J Appl Mech, ASME. v52 iJune. 423-432.
 Hobbs, R.E. and Nabijou, S., Changes in wire curvature as a wire rope is bent over a sheave. J Strain Anal. v30 i4. 271-281.
 Owada S. Calculation of tensile and torsional stiffnesses of single lay cables. In: Proceedings of the 2nd Japan national congress for applied mechanics, 1952. p. 159-64.
 Machida, S. and Durelli, A.J., Response of a strand to axial and torsional displacements. J Mech Eng Sci. v15 i4. 241-251.
 Phillips, J.W. and Costello, G.A., Contact stresses in twisted wire cables. J Eng Mech Div, ASCE. v99 iEM2. 331-341.
 Velinsky, S.A., Anderson, G.L. and Costello, G.A., Wire rope with complex cross sections. J Eng Mech, ASCE. v110 i3. 380-391.
 LeClair, R.A., Axial response of multi-layered strands with compliant layers. J Eng Mech, ASCE. v117 i12. 2884-2903.
 Costello, G.A., Theory of wire ropes. 1997. 2nd ed. Springer-Verlag, New York.
 Ramsey, H., Analysis of interwire friction in multi-layered cables under uniform extension and twisting. Int J Mech Sci. v32 i8. 709-716.
 Jolicoeur, C. and Cardou, A., A semi-continuous mathematical model for bending of multi-layered wire strands. J Eng Mech, ASCE. v122 i7. 643-650.
 Hobbs, R.E. and Raoof, M., Interwire Slippage and fatigue prediction in stranded cables for TLP tethers. In: Chryssostomidis, C., Connor, J.J. (Eds.), Behaviour of offshore structures, vol. 2. M.I.T., Cambridge, MA, USA. pp. 77-99.
 Raoof, M. and Hobbs, R.E., Analysis of multi-layered structural strands. J Eng Mech, ASCE. v114 iJuly. 1166-1182.
 Hobbs, R.E. and Raoof, M., Hysteresis in bridge strand. Proc Inst Civil Eng, Part II. v77 iDecember. 445-464.
 Raoof, M. and Hobbs, R.E., Torsional stiffness and hysteresis in spiral strands. Proc Inst Civil Eng, Part II. v87 iDecember. 501-515.
 Raoof, M. and Hobbs, R.E., Torsion tests on large spiral strands. J Strain Anal. v23 i2. 97-104.
 Raoof, M. and Hobbs, R.E., The bending of spiral strand and armoured cables close to terminations. J Energy Resour Technol, ASME. v106 i3. 349-355.
 Raoof, M. and Huang, Y.P., Free bending characteristics of axially pre-loaded spiral strands. Proc Inst Civil Eng, Struct Build. v94 iNovember. 469-484.
 Raoof, M. and Davies, T.J., Determination of the bending stiffness for a spiral strand. J Strain Anal. v39 i1. 1-13.
 Raoof, M., Axial fatigue of multi-layered strands. J Eng Mech, ASCE. v116 i10. 2083-2099.
 Raoof, M., Design of spiral strands against axial fatigue. Int J Offshore Polar Eng. v9 i2. 149-157.
 Raoof, M., Free-bending fatigue life estimation for cables at points of fixity. J Eng Mech, ASCE. v118 i9. 1747-1764.
 Raoof, M., Design of steel cables against free bending fatigue at terminations. Struct Eng. v71 i10. 171-178.
 Raoof, M., Methods for analysing large spiral strands. J Strain Anal. v26 i3. 165-174.
 Raoof, M., Simple formulae for spiral strands and multi-strand ropes. Proc Inst Civil Eng, Part II. v89 iDecember. 527-542.
 Raoof, M. and Huang, Y.P., Simplified methods for analysing steel strands. Struct Eng. v70 i22. 390-397.
 Raoof, M. and Kraincanic, I., Simple derivation of the stiffness matrix for axial/torsional coupling of spiral strands. Comput Struct. v55 i4. 589-600.
 Raoof, M. and Kraincanic, I., Critical examination of various approaches used for analysing helical cables. J Strain Anal. v29 i1. 43-55.
 Raoof, M., The prediction of axial damping in spiral strands. J Strain Anal. v26 i4. 221-229.
 Davies, T. J., Static, dynamic and fatigue characteristics of helical cables. PhD thesis, Loughborough University, 2001.
 Raoof, M., Comparison between the performance of newly manufactured and well-used spiral strands. Proc Inst Civil Eng, Part II. v89 iMarch. 103-120.
 Eurocode 3: Part 1.11: Design of structures with tension components made of steel (prEN 1993-1-11:20xx3, September 2002).
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