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Jan Steinman


Great article! I have one nit:

"… power can be transformed into velocity and vice versa" should be "force can be transformed into velocity and vice versa."

Power in would, of course, always be equal to power out, less losses associated with transformation.

Kris De Decker


Thanks Jan, corrected.

Alan Harper


Love this--but I can't imagine that the higher speeds would be very quiet. A rope whipping around a pulley at 60 mph would make a fearsome sound, and I can't imagine wanting to be anywhere near a higher speed system.

Ray Van Dune


Two comments:
An interesting American application was the short transmission of power at the Folsom, California dam on the American river. This system coupled a turbine to an electrical generator at a slightly higher elevation within the powerhouse and it used multiple wraps of a continuous hemp rope! I saw it many years ago and the rope seemed to be about 3-4 inches (100mm) in diameter. The generator "ran away" and burned out sometime in the early 1900's but its melted remains and the drive rope are still on display. IIRC it looked like the rope spiraled around two winch-like drums more than 10 times.

Another more modern example are the kite systems being used to assist in propelling cargo vessels. These are parasail type kites many meters across and they are stored furled in a vertical tube at the bow when not in use. Last I heard automatic deployment and retraction was being perfected. Strangely, the kites deliver more pull if flown in a continuous vertical figure-8 pattern rather than simply staying in one place. Software controlling the multiple control lines accomplishes this continuous up-down and side to side swooping.

Jason Olshefsky


It took me a while to decipher your statement, "With AC, the losses are about 3% over a distance of 1,000 km [9]. This means that, today, the table for electricity would show the same efficiency throughout the column."

I think it would be clearer to say, "With AC, the losses are about 3% over a distance of 1,000 km [9]. Since all the distances in the table are far shorter than that, calculated today, the table for electricity would have the highest value in the column repeated throughout."

Kris De Decker


Thank you, Jason. Eventually I decided to delete the statement altogether. It is not essential and, indeed, confusing.



What another amazing article !
I wish i could have learned that in school !
We had a "technology" class that should have been "history of technology" and the program would have been this whole internet site.

I learn a whole new side of our history and how our world did come together reading your brilliant synthesis.

Keep on the good work !

Ronald Pottol


Of course, what is the efficieny of mechanical>AC>mechanical? 90%+? There is a reason we don't see these systems any more.

For a cool operating relic, however, check out San Francisco's Cable Cars (they have a nice museum), same tech, pulls them over miles. Or a ski lift.

Kris De Decker


@ Ronald:

For a transfer of about 100 hp, the combined energy losses in a modern electric motor and generator are about 15%, which makes the double energy conversion 85% efficient. More powerful motors are generally more efficient, less powerful motors are less efficient.

This was all mentioned in the article.

Whether or not this efficiency loss is acceptable, depends on how much energy you have available, and how much energy you need. You don't seem to realize that these systems have disappeared at the same time that we got access to large amounts of cheap energy.

San Franscisco's cable car is far from the only cable car in the world still operating. Quite some new lines have been built, others have been modernized. I would not call it a relic.

Aerial ropeways (such as ski lifts) are indeed a related technology -- again, read the article. And it becomes interesting when you combine them, so that you get free transportation or free power transmission. It has been done, recently. See: http://www.lowtechmagazine.com/2011/01/aerial-ropeways-automatic-cargo-transport.html



Very interesting! I wonder if it would be possible to make a miniature version of this at home, with a wind turbine? The problem is, I'm not sure what I could power with it, since all the stuff that I use is either electrical (like my computer) or designed specifically to run off of electricity (like a coffee grinder). Seems like you really need something like a millworks to take advantage of this.

Kris De Decker


You need a windmill, not a wind turbine. And you need other machines, basically the kind of machines that were in use before the advent of electricity. For most of the machines that run on electricity, you have an alternative that can work on mechanical energy (electronics are the main exception since they don't run on mechanical energy). It can be hard to find these alternatives, but they exist, or can be made. You can find more ideas in the articles on pedal powered machines:





So if I'm understanding this correctly- the only difference between this and a belt is that a belt is held on by elastic tension, whereas this hangs loose and uses the weight of the rope to grip the pulleys. Is that correct? And is that why it needs to be at least 15 m long to work (to have enough weight to grip the pulleys)?



A very interesting article.

The factory in Neuthal, Switzerland can be visited and the water turbine together with the transmission will be operated for demonstration.

Picture 2 and 3 says Schaffhausen, Germany which should be Switzerland.

Actually DC is more efficient to transmit power over long distances. New build power transmission, especially underwater lines are high voltage direct current (HVDC). The point is that DC cannot transformed. Until mid of 20th century a motor generator had to be used to transform DC, While AC could be transformed with a transformer without moving parts. So AC could be transformed to a higher voltage. As the power is the product of voltage and current if we double the voltage we have only half the current. The losses are the current squared multiplied by the cable resistance. So doubling the voltage will lead to a quarter of cable losses. Thats why AC won over DC.

Today a continuous moving cable would have to be protected for safety reasons. Electrical installations are very save today. And cables can be easily laid in cable trays. Also electric motors are very efficient and easy to control especially with todays power electronics. Also electricity why can
be used to run our computers, light our rooms and many things more. while a mechanical transmission only can drive rotary machines at a constant speed. Today even if we have a mechanical transmission electricity would still be needed. Doubling the infrastructure would not be worth it.
Todays its all about safety and automated control. Those old transmissions didn't have a emergency stop. Many workers lost an arm because it was caught into a driving belt, Worse id a ladies hair got entangled. To change speed of the machine the belt had to be moved from one pulley to another while the whole machinery was running. see picture 3 to get an idea. Making mechanical transmission safe would be possible but never could compete with off the shelf electrical parts.

Kris De Decker


@ Charlie: exactly

@ Matt, when you are talking about safety issues, you are referring to millwork, not rope drives. A rope drive would not be less safe than a ski lift. Nobody's arm or hair gets entangled in a ski lift.

I understand the advantages of electricity. But many things could be powered more efficiently without it. For a transfer of about 100 hp, the combined energy losses in a modern electric motor and generator are about 15%, which makes the double energy conversion 85% efficient. Whether or not this efficiency loss is acceptable, depends on how much energy you have available, and how much energy you need.

At this moment in history, there is no shortage of energy. This might change. Rope drives have disappeared at the same time that we got access to large amounts of cheap energy. Another reason why they might become useful again in the future is a shortage of copper to make electricity lines.

By the way, you can power a computer with a rope drive, if you use the rope to run a dynamo. From an efficiency viewpoint, this would be rather useless, but in the case of a copper shortage it could be done.


More comments at The Oil Drum: http://www.theoildrum.com/node/9885#comments_top



Kris you are right that energy is too cheap. I experienced it may time at work and enetgy is wasted in most indutrial plants. It is still common to run a pump at a fixed speed and then control the flow with a valve. At partial loads this is very inefficent, while its efficient at full load.
You dont need copper to transmit electricity. Actually the high voltage transmission lines are all made of aluminium. Copper is the second best conductor for a given wire diameter, silver is the best. But Aluminium has a much lower density than copper so per weight aluminium is better than copper. Steel is used a the back conductor of all electric railways. The steel rails carry the same amount of current like the wires. 3rd rail railways even use steel rail for feeding. As did some streetcars during austerity times So if there is a copper shortage we just can use aluminium or steel as conductor.We just need a larger diameter cable. Also in Some countries they still use 100V-120V for household. We could use 400V in houshold wich would reduce losses a lot.
Its possible to transfer mechanical to electrical to mechanical with an overal efficiency greater than 95%.
Electrical cables last much longer than a moving endless wire transmission. And routing is more restricted for a moving cable. So we could us the same steel cables to transmit electricity. As they are not moving they also need less tensile strength.
If you just need to have a point to point transmission then a mechanical transmission could make sense. Lets say a windmill powers a waterpump. The water could be pumped trough a membrane, thus we could provide reverse osmosis desalinated water to any coastal region. The desalinated water then stored in a reservoir.



Kites and rotary wind harvsting machines are among the applications for which rope drives seem a useful application. Are there any solutions for storing energy that is derived from such an unsteady source?
A storing device would enable conversions on demand into the energy forms best compatible with the currently most widespread systems. At the moment it's electricity.
I bet on transmission of energy and information via fibre optic cables in the future.

David OHara


Consider a tiny version of this drive system using carbon nano-tubes. One might construct a version of Maxwells Demon to harvest power directly from a hot gas.



Thanks for the great article.

How were the endless/continuous loops of wire produced ?

ie how were the ends joined ?

Were these joins the weak point in the chain ?



Regarding modern material applications to this construct: A Finnish company has apparently perfected a carbon fiber cable to be used for more advanced elevators - allowing for even higher buildings to be built (and that is another discussion) - but it seems that such cables which are lighter and stronger than steel cables, with significantly different resonance as well, could be used for this purpose at even longer distances than in past applications.

Kris De Decker


@ cumfy: the continuous loops of wire ware produced by "splicing". We showed this method in the article on ropes and knots: http://www.lowtechmagazine.com/2010/06/lost-knowledge-ropes-and-knots.html

@ michael: interesting. Maybe you know the name of the company?

Sanchan KAwashima


When the next post ???

Paul Holden


Birmingham (UK) airport used to have a magnetically levitated linear motor drive people mover to move people from the Birmingham international rail station (=depot) to the airport. This has now been "modernised" to a Doppelmayr rope drive system. There is hope for low tech progress !



Great article on rope drives. However, Schaffhausen is in Switzerland - not Germany! (I know, I live here) But I never heard about the rope drives. I will go down to the Rhine to see if there are any remnants of it.


Andy N


Would there be any benefit introducing an A/C version of this rope drive where the rope moves backwards and forwards. Presumably there would be comparable benefits to electricity like greater range of power transfer...?



@ Kris July 1 2013
RE:@ michael: interesting. Maybe you know the name of the company?Posted by: Kris De Decker | July 01, 2013 at 11:45 PM

Hi Kris, My apologies for missing this until now. The company is Kone. From an engineering pov, the advantages of the carbon fiber cable include much reduced weight which becomes prohibitive in vertical applications. The company explains the technicalities of such innovations on their website. Cheers. and thx for the many interesting articles. - M



Yes, it was interesting piece of technology, but I still did not see where we can use it today. Modern factories have machines controlled by electronics, even main motors can be controlled by PWM, which is efficient. Switching electricity on and of is safer than using of clutches and gearboxes.

to: Matt
Using 400V in household? Why not 600V (voltage of trams in Europe). It's mainly due safety reasons and due historical reasons. Can you imagine redesign of grid in Europe or in USA? Impossible no one will fund this. OK in many households in Europe you have 400V supply for three phase motors, but small devices rated in hundreds of Watts did not need it.



to: Matt
I'm here one more time, modern asynchronous generators around 20kW have efficiency around 93%, and if it runs as motor efficiency is around 93% too, smaller have smaller efficiency, around 83%, so efficiency of transmission by electricity could be between, 77%-86%, and if you have small plant with only like 8kW asynchronous generator, efficiency of transmission is only around 69%.

Yes electric wires can last longer, but for rope transmission is possible to use natural fibers and maybe with modern technology they can last longer. Transmission on long distances and with high power looks like nonsense but maybe it could connect small turbines (like 5kW) to one big generator with higher efficiency.

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