Anna Noyd-Dryver Wrote in message:
Marland wrote: bob wrote: Graeme Wall wrote: On 08/02/2019 10:58, Bevan Price wrote: On 08/02/19 4:14, Recliner wrote: The DfT remains consistent in its dislike of OHLE https://www.thetimes.co.uk/article/battery-powered-trams-to-beat-congestion-pzz3p9jk3?shareToken=d7efc8230f20d995b8ea4bff5daae 175 As usual, the incompetent DfT only thinks about short term costs of initial construction, not the long term running / operating costs. Batteries have a finite life. You can recharge them, but they eventually deteriorate, hold less charge, and have to be replaced - and they are not cheap to replace. Moreover, you use additional energy to convey the weight of the batteries on every journey, instead of getting energy from fixed overhead wires to move a vehicle that is lighter due to the absence of batteries. And before anyone suggests fuel cells, they also have finite lives, and to function, they often rely on the presence of rare, expensive, precious metals (platinum, palladium, rhodium, etc.) Though once you've done the difficult bit of the infrastructure, actually getting the tracks in the road, adding OLE later is a much simpler engineering task. It is provided you’ve done the work to properly isolate the track return current to prevent electrolytic corrosion problems. If not, it probably means ripping the whole lot up again. Or use twin conductors like a trolley bus. There was a short section In Greenwich when the Royal Observatory was still located there where stray current even from normal track would have affected some instrumentation. They were rare though and I don’t immediately recall another UK installation. Having gone to the trouble of avoiding overhead returning a few years later and putting up twice as much would hardly be popular. That would necessitate use of trolley poles, where pantographs are thecurrent standard fitment for new tramways. I suppose you could have twin pantographs as fitted for 3-phase on certainmountain railways, though you might get polarity issues on single tracksections, plus I suspect the OLE then needs to be aligned more accurately,thus making it more intrusive. Anna Noyd-Dryver

On the other hand... What's wrong with trolley poles? They seem pretty reliable even in inclement weather*. On a tram, where the poles wouldn't even have to deal with the vehicle moving all over the road to overtake etc., I don't see any reason why they should be particularly problematic.

Interestingly (to me...), Bucuresti city council has just (within the last week) put out a tender for new trolleybuses (100 vehicles), the spec for which says every vehicle must be capable of 20km of autonomy (i.e. battery power) to allow for flexibility to extend the end of routes. (The existing, somewhat aging, fleet already has limited autonomy required to get round an OHL problem or some other traffic issue.)

http://www.economica.net/mobile/prim...la_164481.html


Normally I'd dismiss this along with most Buc city hall plans as "never going to happen", but since a fleet of new buses is currently being rolled out more or less on time and with relatively limited drama (a few whinges about drivers turning the heating up too high or not at all, that's about it) hope springs eternal... I guess in summer we'll learn if the air conditioning is as unreliable or ineffective as the old Mercedes fleet, but they're being made in Turkey (by Otokar) so I suppose we can hope they know how to manage hot climates...



* A couple of weeks ago we had a weekend of freezing rain - the type that comes down as liquid but instantly freezes on contact with anything - which genuinely covered /everything/ from trees to pavements in a layer of pure clear ice about a centimetre thick. The fireworks from every passing trolleybus were really quite impressive (even if actually attempting to walk to a bus stop was to take your life in your hands.)

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