Tried to think of that too... ended up with 2 solutions, both super awkward, if possible nonethless. They involved amazingly messy set of ropes and four large water tanks rolling up (empty) and down (full of water) 45 degree tracks... came to estimate that it's about as efficient as buliding the new copy of Giza Pyramids in low tech methods... with natural hill of that shape it might be more feasible... but all in all even wooden bow-springs seem a better idea... as they seem to be able to store several tens of times of their weight in energy. And with proper design no need for any bearings, and "product life cycle" could be made very ecologically low cost... still not sure whether it's just more efficinet to use the wood for CO Gasification (or CH4, even ?), which can be done as high precision low tech stuff... utilize the produced heat (heating, clay owens, generators), burn the resulting CO for heating/generators, feed the resulting CO2 to plant cultivations (preferably greenhouse ones... or to ground level of open air ones... at least
some would then go to feeding the plants)... and ashes to plant nutrients (or if charcoal is produced, then the ashes from that... and ground charcoal powder to Tiera Preo Do Indios technique for turning sandland into farmable soil while tying C to it for long time... for mycofarming and myco-orchards and myco forestry... or just myco remediation in case of polluted land.)
But anyhoo, I'll be doing a proper diagram of the proposed "Tensioner" thing when I can find time for it. One from which it is actually possible to decipher what I tried to depict. Never ever again publishing cryptic rushed sketches which just cause more confusion.
