Re: Two Trolley-Poles (was [MELB] Trams with Trolley--Poles)

["Ernst Kers" <ernst.kers@planet.nl>]

"Jim Holland" <pghpcc@pacbell.net> wrote in message
3AF63F75.38DB@pacbell.net">news:3AF63F75.38DB@pacbell.net...
> > "McAndy B(tm) with cheese" <laurelb@dingoblue.net.au> wrote in message
>
> > Why have 2 poles on a tram? :)  Obviously there is some reason,
otherwise
> > they'd just use the same one, and turn as necessary :)
>
> Quite a few reasons why 2-trolley-poles are on a trolleycar.
>
> This is most common on double-ended equipment and it allows the car to
> change directions by a simple X-over on double track or just change ends
> on single track.
>
> But that also begs the question implied in McAndy's question - why not
> still use one pole and just swing it around.  As mentioned in other
> posts, this is what is done with shorter equipment, but when the
> trolleycar is 40-60-feet long, it is very difficult to get the trolley
> pole back on the wire when it is mounted in the center of the car and
> the trolley pole is only 14-feet long!
[some text deleted]
> Thus the longer
> double-ended cars use 2-trolley poles so they can operate effectively on
> overhead placed near the center line of a turn.
>
> --
> James B. Holland

There were other reasons for two trolley-poles. When it was prefered not to
use the rails as one of the current-poles, two trolley-poles could be used.
This happened in The Netherlands in De Bilt (between Utrecht and Zeist) to
avoid interference with the apparatus of the Meteorologic Institute and in
Porto (Portugal) on the bridge across the river Douro to prevent accelerated
damage to the bridge by oxidation.

--
Ernst Kers
The Tram of Porto
http://home.planet.nl/~ekers/