Anna Noyd-Dryver wrote:
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.



That would necessitate use of trolley poles, where pantographs are the
current standard fitment for new tramways.

I suppose you could have twin pantographs as fitted for 3-phase on certain
mountain railways, though you might get polarity issues on single track
sections, plus I suspect the OLE then needs to be aligned more accurately,
thus making it more intrusive.


What polarity issues would that be? Trolley buses frequently moved poles
over to the opposite set to get around an obstruction or damaged section.
DC traction motors as used in trams ,trolleys and trains have the the field
windings made from coils and are not polarity sensitive, its only on small
DC motors with permanent magnets like on model trains etc that reversing
the polarity will make the motor rotate in a different direction.

Though in the unlikely event of such an installation happening would trams
still be using DC motors nowadays?
Or like most trains electronic gubbins that can be fed all sorts of things
then send it to a AC 3phase motors.


GH