Re: Re: Getting a vintage tram system going in Melbourne
IS Edit
Monday, December 10, 2001 7:39 AM
Actually, acceleration is quite important so you can get out into the
intersection before the light turns red.
Unfortunately the "W"s that have been half-assed converted for one man
operation have several problems in getting away from tram stops in time to
catch traffic lights.
One is the extra weight of the ticketing machine which, with its
counterweight, has appreciably slowed the rate of acceleration.
The other is the door interlock. W class trams used to have their doors
opening as they came into the stop and their doors closing as they
accelerated away from their tram stops. They can't do that anymore and it
must cost 4 traffic lights a trip on most lines, sometimes more. That's 4
minutes per trip, each way...
Centre entrance cars are not ideal for OMO.
As for the notion that a W class tram can stop as fast as a modern tram.
Physically impossible.
Even with sand down, the friction coefficient of steel on steel and the
limited contact area between wheels and rail limit maximum rate of
deceleration.
The main advantage of a track brake, whether it be mechanical (like cable
cars) or electromagnetic is that it increases the contact area and that
increased area is made up of a higher friction coefficient surface (in the
case of a pine block track brake a la cable trams, they can get slick in the
wet when they absorb water so then need sand under them to work effectively.
They actually can cause the wheels to skid because they take some of the
tram's weight off them.).
Bob Murphy
----- Original Message -----
From: "Michael Walker" <[email protected]>
To: <[email protected]>
Sent: Monday, December 10, 2001 5:16 PM
Subject: Re: [TramsDownUnder] Re: Getting a vintage tram system going in
Melbourne
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intersection before the light turns red.
Unfortunately the "W"s that have been half-assed converted for one man
operation have several problems in getting away from tram stops in time to
catch traffic lights.
One is the extra weight of the ticketing machine which, with its
counterweight, has appreciably slowed the rate of acceleration.
The other is the door interlock. W class trams used to have their doors
opening as they came into the stop and their doors closing as they
accelerated away from their tram stops. They can't do that anymore and it
must cost 4 traffic lights a trip on most lines, sometimes more. That's 4
minutes per trip, each way...
Centre entrance cars are not ideal for OMO.
As for the notion that a W class tram can stop as fast as a modern tram.
Physically impossible.
Even with sand down, the friction coefficient of steel on steel and the
limited contact area between wheels and rail limit maximum rate of
deceleration.
The main advantage of a track brake, whether it be mechanical (like cable
cars) or electromagnetic is that it increases the contact area and that
increased area is made up of a higher friction coefficient surface (in the
case of a pine block track brake a la cable trams, they can get slick in the
wet when they absorb water so then need sand under them to work effectively.
They actually can cause the wheels to skid because they take some of the
tram's weight off them.).
Bob Murphy
----- Original Message -----
From: "Michael Walker" <[email protected]>
To: <[email protected]>
Sent: Monday, December 10, 2001 5:16 PM
Subject: Re: [TramsDownUnder] Re: Getting a vintage tram system going in
Melbourne
At 04:21 PM 10/12/2001 +1100, you wrote:speedHi Peter,
As for the green cars having track brakes as well, yes! I am the first to
agree that, a W driven properly can stop in the same distance as a modern
car by using 4th emergency, remembering, a W does'nt travel as fast as a
modern car either but, in our type of operation, high speed is of less
importance than scheduled speed.
Agreed, given the relative closeness of tram stops in Melbourne, high
isn't really an issue, except maybe on the light rail on the ex St Kildaand
Port Melbourne train lines. Acceleration would be more important I wouldstops.
have thought, and even then not really again due to the spacing of tram
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