Re: Re: Getting a vintage tram system going in Melbourne
IS Edit
Monday, December 10, 2001 10:27 AM
Hi Peter.
A lot of people think that magnetic track brakes are necessarily rough.
Not so.
Most of them think that because most trams are set up so that you have to be
using a lot of brake pedal for them to come on.
In San Francisco we had 70 1100 series trams (ex-St Louis 1700s. You saw
that wonderful model of Greg's. One of them.) that had a dash switch which
you could use independent of the dynamic brakes. The switch was variable,
the harder you pressed the more track brake you got.
That independent control was good on night runs in the fog where we were
going up and down steep grades. You could use the track brakes and just
"spot" the car with the dynamics. That way you didn't get flat wheels. Our
sanders were stuffed so that was the best way. Of course that is hard on the
track. It wears the head down. It's a bit like sanding it.
But it taught me that track brakes are not rough per se. They never come on
(or shouldn't) for a normal service stop. They are there for emergencies
when you jam the brake pedal to the floor.
On the Muni Railway 1100s, if you went to the floor on the brake pedal, the
sander came on, the repeater gong sounded, the track brake came on and the
doors went into kind of a neutral so you could pull them open if you had to.
I don't know what the Z, A and B class cars do.
Cheers,
Bob Murphy
----- Original Message -----
From: "demondriver44" <[email protected]>
To: <[email protected]>
Sent: Monday, December 10, 2001 8:49 PM
Subject: [TramsDownUnder] Re: Getting a vintage tram system going in
Melbourne
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:
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A lot of people think that magnetic track brakes are necessarily rough.
Not so.
Most of them think that because most trams are set up so that you have to be
using a lot of brake pedal for them to come on.
In San Francisco we had 70 1100 series trams (ex-St Louis 1700s. You saw
that wonderful model of Greg's. One of them.) that had a dash switch which
you could use independent of the dynamic brakes. The switch was variable,
the harder you pressed the more track brake you got.
That independent control was good on night runs in the fog where we were
going up and down steep grades. You could use the track brakes and just
"spot" the car with the dynamics. That way you didn't get flat wheels. Our
sanders were stuffed so that was the best way. Of course that is hard on the
track. It wears the head down. It's a bit like sanding it.
But it taught me that track brakes are not rough per se. They never come on
(or shouldn't) for a normal service stop. They are there for emergencies
when you jam the brake pedal to the floor.
On the Muni Railway 1100s, if you went to the floor on the brake pedal, the
sander came on, the repeater gong sounded, the track brake came on and the
doors went into kind of a neutral so you could pull them open if you had to.
I don't know what the Z, A and B class cars do.
Cheers,
Bob Murphy
----- Original Message -----
From: "demondriver44" <[email protected]>
To: <[email protected]>
Sent: Monday, December 10, 2001 8:49 PM
Subject: [TramsDownUnder] 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 Wsstopping 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:
toActually, 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
itcatch 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
4must cost 4 traffic lights a trip on most lines, sometimes more. That's
cableminutes 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
thecars) or electromagnetic is that it increases the contact area and that
increased area is made up of a higher friction coefficient surface (in
thecase of a pine block track brake a la cable trams, they can get slick in
effectively.wet when they absorb water so then need sand under them to work
first toThey 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
MelbourneAt 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
modernagree that, a W driven properly can stop in the same distance as a
as acar by using 4th emergency, remembering, a W does'nt travel as fast
lessmodern car either but, in our type of operation, high speed is of
Kildaspeedimportance than scheduled speed.
Agreed, given the relative closeness of tram stops in Melbourne, highisn't really an issue, except maybe on the light rail on the ex St
wouldandPort Melbourne train lines. Acceleration would be more important I
tramhave thought, and even then not really again due to the spacing of
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