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

["Alan Reekie (delete 'nospam.' to reply)" <alan.reekie@ping.nospam.be>]

David McLoughlin a Êcrit dans le message
<368833E3.148B@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?
>
Yes, many lines in Brussels (STIB/MIVB) have single-ended operation
with trams using single-arm pantographs (eg T2000 cars on route 91).
AFAIK there are no problems in running in either direction alternately.
But of course pans *do* come to a sticky end from time to time,
usually because they get snagged on some bit of overhead line that
is out of place (remember the 'knitting' is not absolutely fixed, and can
sway quite a lot under dynamic forces). I think that the constraints on
positioning under pans should be significantly stricter than under
trolley-pole operation.

-- Alan Reekie (in Brussels)