The Birkenhead Bridge in Port Adelaide had two lifting "drawbridge" spans
to allow large vessels to pass. Trolley bus wires across the bridge simply
sagged downward towards the road when the bridge spans were opened.
This proposed tram bridge for Docklands appears to be similar except that
the illustration shows only one lifting. "drawbridge span. Tram overhead
wires could sag when the bridge was opened in a similar manner to the
Birkenhead Bridge.
http://www.theage.com.au/victoria/the-epitome-of-ugliness-designs-emerge-for
-docklands-tram-bridge-over-yarra-river-20140715-zt7ra.html
The vessels shown in the illustration of the Docklands bridge appear low
enough to pass under a non lifting bridge. If clearance was marginal, the
approaches could simply be 'ramped' upward to allow greater headway beneath
a non lifting span.
Sydney's Glebe Island Bridge and Gladesville Bridge on the Ryde tram line
had swing spans similar to the old Jervois Bridge in Port Adelaide. The tram
overhead wires were anchored to 'portal' structures which were aligned
close together when the spans were closed for tram and road traffic. Flat
inverted 'pans' for the trolley wires were fixed below the portal structures
and came into alignment when the span was closed.
When the Ryde line was still in operation as far as Gladesville. I enjoyed a
90 degree return trip in the Gladesville Bridge control cabin. The cabin
contained several tram controllers for the several functions of the swing
span, including sliding rails and boom gates. Also in the control cabin
was a ten lever 'slide' type frame from which the road and tram signals as
well as marine colour light signals were controlled.
Attached is a picture looking south from the control cabin, also a picture
of the Sydney ferry Karingal. a favorite ferry of the late Geoff Johnson,
about to pass through the bridge on a "Head of the Rivers" tourist cruise.
Pictures of both the Glebe Island and Gladesville bridges appeared on pages
71 & 72 of "Tramways of Sydney" by the late David Keenan.
Noel Reed.
_____
From:TramsDownUnder@... [mailto:TramsDownUnder@yahoogroups.com]
Sent: Tuesday, 15 July 2014 6:08 PM
To:TramsDownUnder@...
Subject: Re: [TramsDownUnder] New Tram Bridge for Docklands
Just imagine - a drawbridge with wires !
As something that's never been done before the difficulties are obviously
insurmountable...
Beyond satire. Ignorance these days is displayed like a badge of honour.
Meanwhile, in Sydney we have a disused swing-span opening bridge (old Glebe
Island bridge) ideally suited for trams and bicycles that the government
would prefer not to exist, so is allowing the usual demolition by neglect.
Tony G
On 15 Jul 2014, at 5:42 pm, 'Mike Alexander'mike@...
[TramsDownUnder] TramsDownUnder@...> wrote:
http://www.theage.com.au/victoria/the-epitome-of-ugliness-designs-emerge-for
-docklands-tram-bridge-over-yarra-river-20140715-zt7ra.html
The twittersphere has already identified three lifting tram bridges in
addition to the train one that "Engineering expert Martin Baggott" knows
about:
http://en.wikipedia.org/wiki/File:Galata_Bridge_767.jpg
http://waronthemotorist.wordpress.com/2011/10/11/hogesluisbrug/
http://bit.ly/We8R41
The collective wisdom of this group must surely know of many more.