The whole point of this discussion which includes comments by other former tram drivers as well as myself, is that for whatever reasons, the W8s are far less reliable in service than the ‘old junk’ they displaced. Very rarely was one disabled in the street.

While the City Circle line I believe is not part of the ludicrous 0PR system of fines and bonuses for performance, one photograph showed an E class stuck behind a broken W8 and this would be incurring fines for the company.

There are other faults with upgraded trams that can occur. The story of the tram which didn’t like going around the City Circle in one direction suggests that there was a door interlock glitch on one side of the tram. The need to disable a tram if a door was not closed fully is a complication not considered important for over 100 years but seems essential today. Do the W8s have a door override switch? The Zs, As and Bs did although I think it has been removed from the reach of the driver these days.

These engineers seem to think of the most complicated and convoluted ways of overcoming problems, almost certainly partly because they have never been tram drivers. The more complicated, the more things that can go wrong.

In the 1990s there was a number of car ahead collisions by Ws caused by the brake system running out air because the compressor failed to start when the pressure dropped. Sloppy maintenance in the depot could well have been a factor.

A cheap, simple and effective solution would have been to fit an air pressure sensitive switch in the air system which rang a buzzer, even the next stop buzzer, continuously whenever the tram was turned on and the air pressure was below about 45 PSI. No driver will ignore a buzzer running continuously, will soon see that the air pressure is getting low, and act accordingly..

Did they adopt that simple approach? Of course not. They completely rebuilt the air system so that they would be like modern trams with the brakes being spring applied, and released by the air.

Next thing we know, trams are crashing and drivers claiming the brakes didn’t work. But as soon as the brakes were tested, everything was normal and the driver was demoted or otherwise disciplined.

Eventually the truth came out. Some of this new equipment involved the air passing through rather small apertures. But all the Ws were 40 or a lot more years older. The brake pipes were full of gunk and rust and other stuff which was floating about and spasmodically blocking these little holes, stopping the brakes from working. But another application just as likely blew the gunk away and the brakes were normal. Too bad for the drivers who were disciplined unnecessarily.

What is causing these apparently frequent failures of W8s may never be learned by us but the final result is that there certainly needs to be improvements made to their reliability, not just simply patching them up and hoping they last another couple of days.

Regards,

On 22 Dec 2018, at 6:36 am, Matthew Geier matthew@...> wrote:

> On Fri, 21 Dec 2018 at 22:06, Tram Gunzle tramgunzle@...> wrote:

> The big differences between W-type trams breaking down now and then are (1) when a tram fitted with all this new, whiz-bang technology breaks-down, it is usually totalled: unable to move by itself

Which indicates that only fitted one traction converter for the 4 motors.

If that converter faults - they lose all 4 motors. That's an engineering call that some one has made and it was probably purely a cost 'optimisation'. I'd have put two indepenant converters, one for each bogie. Lose one, the other gets you home.

The 'modern' tram i'm familar with has 4 seperate converters that drive motors in pairs. Pairs of converters are together in a pod and share a control computer (in the pod with the converters).

An entire converter pod could be swapped in an hour or so. The computer is all modular and card swaps take minutes. A master controler swap takes about 10 minutes or less.

All the other systems are duplicated or have battery backup. About the only thing that would prevent a 'limp home' is a flipped pantograpgh.

Singe point of failure is a design issue. There were plenty of single point failure modes built into the old trams too.

> - the older cars could (except in rare circumstances) still limp out of the way;


So can many new cars, as they have duplicated or redunant systems.

> (2) the older cars were REPAIRED - the newer ones have the defective 'Black Box' removed and THROWN AWAY, to be replaced by a new 'Black Box'.

And are back on the road in hours instead of days or weeks.

The 'black box' is then sent to an appropiate place for repair or replacement.

How long did it take to replace burned fingures on a master controller ? - how long does it take to swap a PC5 ?, a line breaker, compressor governers..
Our of those I would expect only the breakers and governer contactors would be a less than a days work.

And we have seem what happens if you don't look after those 'traditional' control components properly. (Memphis trolley fires)

Really the only thing 'different' between new and old is the complexity has moved from a mass of wires and contactors into a box of electronics that uses software to do all the complex stuff, often resulting in significant simplifaction of the actual hardware that does the work. And that the electronic box of tricks is modular and easly removed. So the tram is repaired by module swap and sent on it's way. The faulty module is then repaired by specalists in a specalist workshop instead of insitu in less than ideal conditions.