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| Long span between power poles |
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| soldar:
--- Quote from: Gyro on September 24, 2023, 12:26:05 pm ---This is not a record breaker, at a span of 3060ft,with towers of 487ft high and minimum height over the river of 250ft, but an interesting article from my mid 1930s "Wonders of World Engineering" book. The span was constructed over the river Thames at Dagenham (also the site of the Ford UK car factory) in 1932, during the construction of the UK National Grid. The article includes some photos of working practices of the time - for instance, the petrol driven winch sitting on baulks of wood near the top of the tower, working in white shirt, tie and braces and working at height with little protection. It's hard to see how much PPE was in use (other than a cloth cap!), particularly harnesses, unless they were tied on by their tool belts... --- End quote --- Thanks! Very interesting. |
| IanB:
--- Quote from: Gyro on September 24, 2023, 12:26:05 pm ---This is not a record breaker, at a span of 3060ft,with towers of 487ft high and minimum height over the river of 250ft, but an interesting article from my mid 1930s "Wonders of World Engineering" book. The span was constructed over the river Thames at Dagenham (also the site of the Ford UK car factory) in 1932, during the construction of the UK National Grid. --- End quote --- It's interesting that you posted that, since when this thread was first started I went looking for it. Unfortunately, I think it is not there anymore at that location. There seems to be a new crossing now, further downstream between Thurrock and Swanscombe. It can be seen at the link below: https://maps.app.goo.gl/KCzBb697UbxiPNsh8 |
| floobydust:
I worked in the utility industry and some powerline runs had problems with conductor gallop. Usually in flat areas, the plains with no trees to break the wind. You would get phase-phase arcing or shorts if the lines touched and welded, or just fatigue failures of the lines. The cable segments between poles has many mechanical resonances. Adding mechanical AC termination resistance like a Stockbridge damper or plastic spacers was done to stop it. |
| Gyro:
One thing that did strike me when I was re-reading the article before photographing it, (in page 3) was the conductor composition: --- Quote ---Each conductor is made up of ninety-one individual wires, The inner strands are of cadmium copper, to give conductivity, and the outer strands are of phosphor bronze, which is particularly suitable because of its resistance to corrosion and fatigue... ... No joints were permitted in the individual wires, and each strand was drawn from a single billet 2 feet long into a final length of some 6,400 feet [the combined distance between the strain towers and up and over the support towers]. Each of the complete conductors, after stranding, had a total weight of about 6 tons and it is believed that these conductors are the largest yet made in phosphor bronze. --- End quote --- They seem to have gone to extrodinary efforts and cost with these conductors, verging on unobtanium. If the crossing was indeed replaced with one downstream (rather than duplicated), the scrap value must have been rather lucrative (after a rather long unwrapping session)! I wonder what other long span conductors are made of, it seems unlikely that they would be of the same detail and composition. |
| soldar:
--- Quote from: IanB on September 24, 2023, 10:10:27 pm --- Unfortunately, I think it is not there anymore at that location. --- End quote --- I would think there's a good chance it was destroyed by that specialized German demolition team, the Luftwaffe. |
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