Re: Pantographs (was Re: MBTA BREDA Light Rail Cars)

[David McLoughlin <davemcl@REMOVEiprolink.co.nz>]

Silas Warner wrote:

> There are usually two reasons why a locomotive might have two pantos.
> One is to bridge "dead spots" in an overhead wire, but this is not the
> usual reason.  The usual reason is that the pantos are designed for
> one-way operation, and cannot be asily reversed.  This was true of
> early Faiveley (one-arm) pantographs. which could only be operated with
> the "elbow" facing backward: a forward-facing wlbow would be forced up
> by the air rush of the panto's passage and might snag the wire.

Thank you Silas and also to James for answering my questions re
pantographs. While on the subject, can you answer another to do with the
section quoted above?

Melbourne in Australia is in the final stages of converting its large
tramway (streetcar) system from trolleypoles to pans. They are
single-arm pans, one to a tram. It seems there is a resulting problem
with pans breaking or bending over, causing major delays in services. 

There were a number of posts on this a couple of months back -- one
suggested maybe 10 pans a month were being wrecked from 300 trams so far
converted to pans in a fleet of 500.  I wondered then whether the cause
was the single-arm pan going out of shape when working in the reverse
direction  (Melbourne's trams are all double-ended as there are no
turning loops... at each end of each of the 30 lines, the trams shunt on
either a Y or an X to make their return journeys).

Most of the European trams which use single-arm pans are single-ended
trams which use loops to turn. 

Are there any cities where trams/streetcars are double-ended and use
single-arm pans that don't have this problem of pantograph-fouling?
There are the Media and Sharon Hill lines in Philadelphia (the S/S lines
in Philly still use poles!). AFAIK the new Sheffield system in England
uses shunts at each terminus for its double-ended cars. Any more?

I'll cross-post this back into aus.rail for the edification of the
Melbourne people from there who raised the problem originally.

David McLoughlin
Auckland New Zealand

I remember the Ice Age. It was what they claimed was happening to the
weather before they invented Global Warming.