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

["Robin Payne" <rcp27@cam.ac.uk>]

> > There were other reasons for two trolley-poles. When it was prefered not
to
> > use the rails as one of the current-poles
>
> It seems that the original question was more:::::::
>
> **Why were there 2-trolley poles on trolleycars, one one each end.**
>
> Two trolley poles side by side is different.
>
> Cincinnati, like others, was worried about corroding the underground
> pipes.  There were a number of places that used positive and negative
> overhead.

For the same reason, the London Underground uses 3rd (+420V) and 4th (-210V)
electrics, and the tram conduits had 2 rails in them, though I'm not sure of
the voltages.

I did wonder the same thing about the trams in the London Transport musem.
The one that piqued my interest was a Feltham tramcar, which if you aren't
familiar with them, a good photo is at the bottom of
http://www.magma.ca/~dewi/trains/conduit/tracks.html (not my site).

As this makes clear, although the tram is a bogie vehicle, the poles are
mounted almost centrally and still extend beyond the ends.  At the museum
you can look down from above where you can see that the hubs of the two
poles are only a coupld of inches apart.  Why in such a case would you want
2 poles?

Robin