The cables may have to be Kevlar, or something exotic. I'm not sure that steel could cope.
It would be interesting to see the fag packet calculations.
In my early career, I was involved in the development of Kevlar with DuPontwhen it was a military secret. There was also Twaron developed by Akzo at the same time. A bit like NyLon earlier where 2 organisations developed the same material in different places at the same time. I worked with both DuPont and Akzo.
My work involved replacing high tensile steel wire ropes used in long haul conveyor system (the co I worked for held the world distance record of 52Km for a single flight conveyor system in Australia, my first project as part of the world's 1st billion dollar mega project). The requirement was to reduce electrical power required to haul ever longer distances in ever more remote regions where power infrastructure was limited, hence the need to reduce system mass and frictional losses.
The obvious choice was para aramid (Kevlar/Twaron) due to the weight/tensile strength ratio compared to HTS. Another option was Dyneema, a variant of NyLon, but due to moisture absorption was discounted.
Unfortunately I failed with para aramid due to intertersal abrasion ie the fibres destroyed each other when dynamic loading was applied, in simple terms.
However from failure we learn. I then developed a hybrid cable product that was branded Triton under my employer at the time, later being made under licence for us by Bridon as Tiger. This was a central fibre core, with an extruded polyester (Hytrel) cover. Each of the outer 6 steel wire strands were then sheaved in a trapezoidal wedge extruded using a rotating die, the clever bit and a first. The wedge would form the helix of the outer strands. Mathematically a wire cable/rope shouldn't work. By effectively creating a pre formed helix for closing the final rope/cable and having smooth surfaces friction was reduced.
That work was decried by Professors of Engineering at several universities as defying the laws of physics, not the first nor last time in my career did I do such things. We then sold the rights to Bridon, who then in concert with me developed a product for cable stayed bridges. The 1st being the dartford Crossing where the wire profile, almost a flattened figure of 8 was drawn adding zinc for corrosion protection, then extruded with a polyester sheaf before being closed for the final ropes/cables.
The failure mode of para aramid is how bullet proof vests, personal armour are made. DuPont asked us to continue working with them in that arena. The CEO explained it wasn't part of his core business. DuPont gave him a cheque for £24m to cover our failed development costs. Fantastic time working in a true industrial conglomerate where failure was accepted and some amazing things were done.
Fantastic memories to take into retirement at the end of the month after 49 years in the wonderful world of Engineering.
Been a long time since, but the technique is probably further developed to use in bridges.
), one of my favorite companies.
