Crossing rivers without bridges

EarthOS Autarky Lab
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A tuin is “a type of hand-powered aerial lift traditional to the Himalaya” (Wikipedia), used to cross rivers in a small gondola. The problem with the old design is that “many people have lost fingers while operating tuins, and there also is the danger of falling out of a trolley while crossing a river” (source).

@anu has seen problems with the use of tuins in the mountainous Karnali region in Nepal, in the Kalikot and Mugu districts there. Children have to use tuins for commuting to school, resulting in many having swollen arms, and a substantial number of deaths. So she wants to organize a solution there, and we thought to make it an Edgeryders project and write funding applications for it.

Content

1. Existing design improvements for tuins

2. Our designs for better river crossings

1. Existing design improvements for tuins

1.1. VillageTechSolutions (VTS) wire bridges

An improved design that prevents injuries and falling out, but still have only one cable, so no redundancy. See the details.

1.2. PracticalAction tuin design

As detailed on Appropedia, the PracticalAction tuin design is much safer and simpler to use. They have seats and sidebars against falling out. Efficiency is doubled by reducing friction with ball bearings etc., and there is no danger of injury. The two-cable system has a better balance and allows a bigger load.

At this stage, the tuins were safer and easier than traditional ones during operation, but still needed improvements. The problem was that the safer gondola is also heavier and could not be pulled from across the river if the distance was larger than 100 m. Means, when the gondola is on the opposite side and one wants to pull it to ones own side to enter it. So a sag control cable and hauling cable was added, solving this issue. (source)

2. Our designs for better river crossings

2.1. First design

To be fundable as an innovation project, we should include some innovation :slight_smile: So our first design proposal is derived from the PracticalAction tuin design, with the following modifications:

  1. Chains instead of steel cables. With the two chains made from galvanized steel or better stainless steel, maintenance requirements should be low to non-existing. Also they provide traction for the traction pulley system introduced below. Also, chains can be repaired by exchanging broken pieces and welding the chain together again, and the type and strength of chain should be chosen so that this is possible.

  2. Stationery cycle. This is the main innovation: the gondola is powered by pedaling, which is much more comfortable and powerful than pulling a cable manually, allowing higher loads. One to four seats of the gondola would be equipped with a set of bicycle pedals. Each set powers the traction pulley immediately overhead using a bicycle chain. For transmission, the pulley interlocks with the chain links to provide traction. A standard 3-gear bicycle planetary gearbox is used to switch gears while being maintenance free. The bicycle chain transmission to the pulley is enclosed to be low-maintenance as well. There has to be a way to switch direction, which has not yet been thought through.

  3. Balancer arm. The gondola would be suspended from a central point so that it will keep nearly upright even in case of one chain rupture. Nobody should fall out if that happens.

  4. No sag control cable. Chains allow higher tension / less sag, so a sag control cable is probably not needed, simplifying the construction.

2.2. Second design

Similar to the previous, but the overhead lines can be regular steel cables. In addition, there is a light chain running at floor level through the gondola, and this is where the traction pulleys are mounted. The advantage is that this geometry avoids the need for lengthy chain transmission from floor level to the overhead cables.

2.3. Third design

A loop or even network of bicycles running on horizontal aerial ropeways, as detailed here:

The advantage of this approach is that very large gaps (up to 1.5 or 2 km) can be bridged. It would also be a perfect tourist attraction alongside :slight_smile: The remaining problem is that these sky bikes can only transport approx. 200 kg of load in one gondola, so no yaks, donkeys etc…

2.4. Fourth design

This design is more similar to a suspension bridge, wile the ones above are more like a suspended bridge. So here, we have two suspension chains made from 1.5 - 2 m long “chain” elements (20-40 mm rebar with welded eyelet ends), connected with bolts, with vertical thin steel wires connected to each bolt and carrying a metal profile to which the gondola is connected. This way, the gondola travels in a straight line (mostly, depending on the load) and it needs very little force to move it. Moving it can be done manually with a hauling cable, or again with a stationery bicycle. Since the force to move the gondola is low, it will even be possible to transport cattle this way.

The profiles used for this can be square profile (with a slot cut to its bottom), T profile, double-T profile or L profile. The cheapest will be L profile. With all these profiles, the gondola can be connected in an interlocked way so that it cannot disconnect itself. Square profile (say 50 × 25 mm) can also be used when using rollers on top and bottom that have elevated sides, and when connecting these profiles with bolted-on curved parts so that they are effectively suspended from their center, not from a side (which would make them tilt when attaching the gondola). Square profile (without making a cut to the bottom) seems best as it can take the most load for a given amount of material. It can be suspended every 50 cm by hooking 3 or 5 wire ropes to each chain element connector above them. This way, the profile will not come under heavy load, making it sufficient to use square profile that is bent and welded together from sheet metal in DIY fashion.

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Karnali District of Nepal is very underdeveloped. Many people mostly children are very affected by tuin transportation. I discuss about it with @matthias. I liked the proposed ideas. The seats and sidebars will be much safer and help children from swollen arms. I am still thinking how can we make it more safer.

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Hmm you are right, even the improved version is not that safe, and needs to be properly maintained to keep being safe and functional.

So maybe we should try to go for wire bridges instead? As I understand it, the only reason tuins are still used is simply the cost. They are cheaper than complete wire bridges for foot passengers, which are also very widespread in Nepal (about 3000 of them I think).

So it may be better to explore low-cost ways for bringing wire bridges to Karnali. We could frame this as OpenVillage challenge … because for proper self-supply one needs footpaths and bridges to the OpenVillage houses. (No full streets though, instead one day there will be robotic little vehicles going on these footpaths, without a driver … .)

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Wire Bridges will be best options. Had you seen one in Kathmandu? Some paces in Kathmandu also have wire Bridges. (Not very safe but safer than others, I think). Building a wire bridge is definitely what i think will be better but people are often uncertain with the weights, As district like Karnali, lots of things are exported from Capital (Potter Service). We have to set a limit for the bridge for weights as well. How can we begin? We need to have a solid plan and then we can go on developing the concept.

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While sorting through ideas an initiatives, I came across this one again. We have so many ideas, but how do we make them happen? :slight_smile: Let’s at least settle on the right solution here, and then explore development and funding for it.

If that’s the problem with wire bridges, a nice solution would be to have a weight indicator at the ends of the bridge, which measures the tension of the main steel cables and shows it on a display. The display would indicate if it’s ok for one more person or animal to go on the bridge, or not.

A robust mechanical solution with a mechanical display could be good, but might also be much more expensive due to the need of measuring high tensions mechanically. An electronic solution (with photovoltaics for power) would be much cheaper, as it could measure tension indirectly, for example via oscillation (similarly to a guitar string: higher pitch means higher tension). Since the bridge can still be used when the load meter breaks, I think this would be the better solution.

Such an electronic load meter (if it really solves an issue with wire bridges) could be a marketable product because it can be added to the many existing wire bridges in Nepal and other countries. We would develop it as an open source project, and it can be produced by a small company (for example one starting inside an OpenVillage house). This way might even open a way of funding wire bridges in Nepal: we’d partner with an NGO specializing in wire bridges, developing the open source load meter device for them in exchange for getting (say) five wire bridges built in Karnali.

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For the sake of completeness, here’s another thing somebody invented to let school kids safely cross rivers: “water bicycles”.

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Again for the sake of completeness, I recently found this document, which instructs in great detail how to build foot passenger suspension bridges with a length up to 50 m:

(I also included it into my Autarky Library collection of works, at ID 10).

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