Rope-drive transmission

HORIZONTAL CABLE DRIVE.pdf (64.9 KB)
When turbines are oriented to face the wind it occurred to me that a pulley transfer to cable drive is possible without the need of bevel gears, universal joints, or right angle belt drives. The concept is shown in the attached drawing. The generator drive wheel on the ground is horizontal and we require idler pulleys close to the drive wheel since the sag of the cable would result in premature wear on the cable due to rubbing on the walls of the pulley, especially on the low tension side. Since cable drive is most efficient at high speed, we require a larsger pulley at the turbines and a smaller pulley at the generator. To keep the cable lines parallel we require an additional idler pulley. Unlike the Kitewinder system, which has a floating generator, the horizontal generator can be permanently fixed to the ground. Changes in wind direction can be accommodated by rotating the idler pulleys in a circle around the generator pulley.

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I think that on the current topic the rope drive transmission designs mainly a transfer of type @Kitewinder’ and variants. However other configurations of rope drives are evoked on Another laddermill concept and on What is possible with Payne's patent US3987987 figure 5? - #85 by Windy_Skies . I quote again the sketch below, that describes a ground-based rope drive pulled by at least one kite flying quite crosswind:

. This rope drive could work like NTS’ straight rail (video below) while being simpler and more transformable.

On the video above the kite flies by figure-eight while the cart moves slowly with high torque, probably tailwind. If the kite flies quite crosswind and on a side and pulls directly the cart, said cart could go faster with a lesser torque, and the kite could fly forth and back. The same could be applied for a ground-based rope drive in crosswind position. So the kite move could be like a kite surf (video below), with a tack at each end of the trajectory:

Hi Doug, the rope drive transmission works for the only one marketed AWES (kiwee). Although I take into consideration that you are talking about a ground-based wind turbine where such a transmission is not needed except to lighten the whole, I do not see a better means of transmission for an AWES: continuous power, almost unlimited range, good output.

Hi Pierre: Yeah I was referring to tower-mounted turbines. It’s hard to be the only wind person in a discussion group like this. In a regular wind turbine group, most people would already know that. Here, any simple well-understood fact becomes a head-scratcher or reason for an argument.
Interesting they promote a tower-mounted turbine by saying they got rid of the f*** tower or whatever it was. All kind of goofy.
Yes I agree kitewinder is a different case. What I commented on was a standard tower-mounted configuration where they use a belt drive to increase RPM at the generator. Belts, pulleys, and chain drives are often tried, and never seem to work out. The most probable outcome might be a burned-out generator(?). I remember being warned against a chain drive and trying it anyway. Like experienced people tried to tell me, it was noisy and got rusty real fast. At high speeds there is a lot of centrifugal force at a small pulley. I can’t remember all the problems, but I would advise against a chain drive. It’s one of those things that sounds great but just turns out to be impractical. I think I still have that chain-drive machine around here somewhere…
I also saw a pretty-nice-looking industrial-scale home turbine somewhere in Texas a few years ago with an industrial-grade belt drive of some type. Multiple parallel belts if memory serves. Looked pretty nice in the pictures. I thought it might turn out to be the first belt-drive turbine to catch on. Well like most small wind companies, they never went anywhere as far as I know. Probably just one more press-release-prototype breakthrough. Wind energy innovation looks so deceptively simple, but ends up as basically a pile of dead bodies.

[quote=“dougselsam, post:65, topic:366”]
configuration where they use a belt drive to increase RPM at the generator. Belts, pulleys, and chain drives are often tried, and never seem to work out. The most probable outcome might be a burned-out generator(?).

If we develop an industrial version of Kitewinder, with a rope drive groundgen system, we must employ an alternate method to prevent overspeed conditions. When the tension in the tether (rope drive) exceeds a certain value then the system is retracted to prevent generator burnout or damage to the turbines. No other overspeed control is necessary.

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Yeah all the beginners or not-even-quite-beginner-yet internet beard-strokers always say that. Always have. Most small-wind systems are on guyed towers, like that “no-tower” camping turbine. Most of these guyed towers can be tilted up and down, using a truck and/or winch of some type. It is usually a pretty significant operation to tilt a tower up or down, since the winch must be operated with care, then the guy wire must be connected with hardware once tilted up. I guess this could all be automated, but the problem then becomes tilting it up and down in a strong wind which nobody wants to do, and also which guy wire to reel in or out would depend on the wind direction in a strong wind. The next problem with the idea of taking a system down when winds get too strong is your most productive times are during strong winds. Such a system would be constantly adjusting with every gust. You want your turbine to keep running in strong winds to make the power, and have it automatically reduce wind response during gusts and surges.
“Oh look the wind is too strong, let’s reel 'er in! – No wait, it’s dying down, let 'er back out! Hold it - another gust - reel 'er back in! - no wait a minute, it’s slowing down again, reel it back out…”
In actuality, nobody wants to reel a turbine up or down when it’s even moderately windy. Preferably it is done in the early morning on a 100% calm day. This “just take down the turbine when it gets too windy” theme is a very repetitive on-paper response from people who have never run an actual system. Same thing the guys running the last forum used to say. But it’s hard to reel in a kite just when it gets too windy to even fly it. The thing about wind energy is, what sounds great on paper is often impractical in real life. Not saying what you suggest is impossible, but it is probably not the simple slam-dunk one would imagine from just musing about it in general terms. As the saying goes, “the devil is in the details”. If you had what you thought was a good way to do this, then you;d have to build it and try it, and stuff would go wrong and you’d have to fix it. Be prepared for years of adjustments, with many burned-out generators, many structural failures, possible exploding turbines etc. Mother nature is not kind to wind energy systems of any type.

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Winds at altitude are more consistent and there is less chance of turbulence. Obviously the system will be designed with a large safety factor on tether forces. How about installing extension springs in the trailing bridles so that the angle of attack is reduced during high winds? This will reduce tether tension.

When the tension in the tether (rope drive) exceeds a certain value then the system is retracted to prevent generator burnout or damage to the turbines. No other overspeed control is necessary.

I agree with you Pierre. Rope drive transmission favors higher velocity cable speeds since cable size and weight can be reduced. Multiple small diameter turbines will rotate faster and we can combine this with differential pulley sizes so that the generator pulley will be rotating faster. Perhaps we can consider 2 blade turbines with an optimal tip speed ratio of 9-10 to further increase cable speed.

One can deduce a very good power coefficient of about 0.3 or 0.4 according to wind speed (comparable to that of a small conventional turbine) from data on Can you share your experience with your lifters? - #15 by Kitewinder and on Kiwee One – Kitewinder :

It delivers up to 100 W of continuous power at 25 km/h wind speed and can work up to 100 km/h.

Perhaps we should consider other architectures than a simple juxtaposition of small rope driven turbines possibly replacing (always stationary) flygen turbines.

One of the first proposed AWE systems described and illustrated was my original buoyant aerial tramway in the 1970’s, (with a watered-down version cleverly named “laddermill” by Ockels perhaps a decade ago). Seems a little strange that nobody has ever even tried to build one to this day.
Was this the first consideration of a “rope-drive” AWE configuration?
Anyway, I quickly moved on to “SuperTurbine™ by the early 1980’s as being perhaps more 'efficient”(?) and/or more easily achievable, simpler, and possibly more reliable. I remember running it by my Fluid Mechanics professor at U.C Irvine in I think 1981 or '82, with an illustration, after being taught how to derive the Betz coefficient from scratch, just to show that while the Betz coefficient was of course valid, there was nevertheless a workaround to produce more power from a turbine of a given diameter, using more rotors, comprising “a single moving part”… Never quite got a response. Seemed that the only consideration was whatever was in the official curriculum.

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Rope-drive transmissions do not seem to have been a success for conventional wind turbines. Yet they would allow the generator to be on the ground. But the necessary tension would be detrimental to the structure. On the contrary, AWES themselves generate the required tension for the rope-drive transmission to be effective, through the lifting kite or whatever, also through the thrust on the turbine aloft at a lesser level. Right?

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In terms of rope drive I found a type of belt I don’t think I’s considered before
and warning - this may just be problematically heavy but

seems interesting

There was discussion previously about how to drive a band around in tension by using the large radius of a TRPT loop as the gear to drive a curtain blinds style beaded belt
This belt changes the power transmission of Tensile Rotary Power Transmission to be perpendicular to the rotor axis, (down and downwind a bit) towards a generator nearly underneath the rotor on the ground

probably the roman blinds beaded belt is just as good or better

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Interesting. In the brochure:

Q1: endless rope available?
A: No, Synchromesh rope is for linear motion only, not for rotational motion.

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