Re: Getting a vintage tram system going in Melbourne

Murph,am not comparing Ws to Zs and after,just saying that I can't see Ws stopping any quicker than they can now,it all depends on keeping those wheels turning as you slow them down,adhesion is crucial otherwise it doesn't matter how good your brakes are,you must stop the car not the wheels.I know that you know all this I just thought you missed my point,I don't know anything about modern cars,I've never driven them.I think I only once flatted a W post Ferodo and that was just plain bad driving.There was one other exception,you sometimes got a car which almost always locked up one axle every application so you would get multiple flats on the same wheelset,it sounded horrible and was very irritating,you felt as if you were at fault although there was bugger-all you could do about it,never happened before Ferodos.Murph I take your point about track brakes it just seems to me that should be used very sparingly on account of the damage that can be done to standees,again I have no direct experience.Regards all, PBruce--- In TramsDownUnder@y..., "IS Edit" <isedit@g...> wrote:

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" <wk@c...>
To: <TramsDownUnder@y...>
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:

Hi 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

speed

isn't really an issue, except maybe on the light rail on the ex St Kilda

and

Port Melbourne train lines. Acceleration would be more important I would
have thought, and even then not really again due to the spacing of tram

stops.

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

-+-+

Don't be afraid to try something new.
Amateurs built the ark.
Professionals built the Titanic.




Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/