On 08/02/2019 15:08, Robin wrote:
On 08/02/2019 10:58, Bevan Price wrote:
On 08/02/19 4:14, Recliner wrote:
The DfT remains consistent in its dislike of OHLE

https://www.thetimes.co.uk/article/battery-powered-trams-to-beat-congestion-pzz3p9jk3?shareToken=d7efc8230f20d995b8ea4bff5daae 175




As usual, the incompetent DfT only thinks about short term costs of
initial construction, not the long term running / operating costs.

Batteries have a finite life. You can recharge them, but they
eventually deteriorate, hold less charge, and have to be replaced -
and they are not cheap to replace.

Moreover, you use additional energy to convey the weight of the
batteries on every journey, instead of getting energy from fixed
overhead wires to move a vehicle that is lighter due to the absence of
batteries.

And before anyone suggests fuel cells, they also have finite lives,
and to function, they often rely on the presence of rare, expensive,
precious metals (platinum, palladium, rhodium, etc.)


All of those factors would be included in the appraisal of costs and
benefits of competing options - bus, battery tram, OHLE etc - over the
the life of the project.

You would think that they ought to do that, but on past history, does
anyone here trust the civil service to get anything right ????


I recognise however that many proponents of trams argue that that is the
wrong approach, and that conventional overhead powered trams ought to be
chosen even if they will cost more for the same quantifiable benefits,
because they are just better.

Anna Noyd-Dryver Wrote in message:
Marland wrote: bob wrote: Graeme Wall wrote: On 08/02/2019 10:58, Bevan Price wrote: On 08/02/19 4:14, Recliner wrote: The DfT remains consistent in its dislike of OHLE https://www.thetimes.co.uk/article/battery-powered-trams-to-beat-congestion-pzz3p9jk3?shareToken=d7efc8230f20d995b8ea4bff5daae 175 As usual, the incompetent DfT only thinks about short term costs of initial construction, not the long term running / operating costs. Batteries have a finite life. You can recharge them, but they eventually deteriorate, hold less charge, and have to be replaced - and they are not cheap to replace. Moreover, you use additional energy to convey the weight of the batteries on every journey, instead of getting energy from fixed overhead wires to move a vehicle that is lighter due to the absence of batteries. And before anyone suggests fuel cells, they also have finite lives, and to function, they often rely on the presence of rare, expensive, precious metals (platinum, palladium, rhodium, etc.) Though once you've done the difficult bit of the infrastructure, actually getting the tracks in the road, adding OLE later is a much simpler engineering task. It is provided you’ve done the work to properly isolate the track return current to prevent electrolytic corrosion problems. If not, it probably means ripping the whole lot up again. Or use twin conductors like a trolley bus. There was a short section In Greenwich when the Royal Observatory was still located there where stray current even from normal track would have affected some instrumentation. They were rare though and I don’t immediately recall another UK installation. Having gone to the trouble of avoiding overhead returning a few years later and putting up twice as much would hardly be popular. That would necessitate use of trolley poles, where pantographs are thecurrent standard fitment for new tramways. I suppose you could have twin pantographs as fitted for 3-phase on certainmountain railways, though you might get polarity issues on single tracksections, plus I suspect the OLE then needs to be aligned more accurately,thus making it more intrusive. Anna Noyd-Dryver

On the other hand... What's wrong with trolley poles? They seem pretty reliable even in inclement weather*. On a tram, where the poles wouldn't even have to deal with the vehicle moving all over the road to overtake etc., I don't see any reason why they should be particularly problematic.

Interestingly (to me...), Bucuresti city council has just (within the last week) put out a tender for new trolleybuses (100 vehicles), the spec for which says every vehicle must be capable of 20km of autonomy (i.e. battery power) to allow for flexibility to extend the end of routes. (The existing, somewhat aging, fleet already has limited autonomy required to get round an OHL problem or some other traffic issue.)

http://www.economica.net/mobile/prim...la_164481.html


Normally I'd dismiss this along with most Buc city hall plans as "never going to happen", but since a fleet of new buses is currently being rolled out more or less on time and with relatively limited drama (a few whinges about drivers turning the heating up too high or not at all, that's about it) hope springs eternal... I guess in summer we'll learn if the air conditioning is as unreliable or ineffective as the old Mercedes fleet, but they're being made in Turkey (by Otokar) so I suppose we can hope they know how to manage hot climates...



* A couple of weeks ago we had a weekend of freezing rain - the type that comes down as liquid but instantly freezes on contact with anything - which genuinely covered /everything/ from trees to pavements in a layer of pure clear ice about a centimetre thick. The fireworks from every passing trolleybus were really quite impressive (even if actually attempting to walk to a bus stop was to take your life in your hands.)

--

Anna Noyd-Dryver wrote:
Marland wrote:
bob wrote:
Graeme Wall wrote:
On 08/02/2019 10:58, Bevan Price wrote:
On 08/02/19 4:14, Recliner wrote:
The DfT remains consistent in its dislike of OHLE

https://www.thetimes.co.uk/article/battery-powered-trams-to-beat-congestion-pzz3p9jk3?shareToken=d7efc8230f20d995b8ea4bff5daae 175





As usual, the incompetent DfT only thinks about short term costs of
initial construction, not the long term running / operating costs.

Batteries have a finite life. You can recharge them, but they eventually
deteriorate, hold less charge, and have to be replaced - and they are
not cheap to replace.

Moreover, you use additional energy to convey the weight of the
batteries on every journey, instead of getting energy from fixed
overhead wires to move a vehicle that is lighter due to the absence of
batteries.

And before anyone suggests fuel cells, they also have finite lives, and
to function, they often rely on the presence of rare, expensive,
precious metals (platinum, palladium, rhodium, etc.)


Though once you've done the difficult bit of the infrastructure,
actually getting the tracks in the road, adding OLE later is a much
simpler engineering task.

It is provided you’ve done the work to properly isolate the track return
current to prevent electrolytic corrosion problems. If not, it probably
means ripping the whole lot up again.


Or use twin conductors like a trolley bus.



That would necessitate use of trolley poles, where pantographs are the
current standard fitment for new tramways.

I suppose you could have twin pantographs as fitted for 3-phase on certain
mountain railways, though you might get polarity issues on single track
sections, plus I suspect the OLE then needs to be aligned more accurately,
thus making it more intrusive.


What polarity issues would that be? Trolley buses frequently moved poles
over to the opposite set to get around an obstruction or damaged section.
DC traction motors as used in trams ,trolleys and trains have the the field
windings made from coils and are not polarity sensitive, its only on small
DC motors with permanent magnets like on model trains etc that reversing
the polarity will make the motor rotate in a different direction.

Though in the unlikely event of such an installation happening would trams
still be using DC motors nowadays?
Or like most trains electronic gubbins that can be fed all sorts of things
then send it to a AC 3phase motors.


GH

On 08/02/2019 17:52, Bevan Price wrote:
On 08/02/2019 15:08, Robin wrote:
On 08/02/2019 10:58, Bevan Price wrote:
On 08/02/19 4:14, Recliner wrote:
The DfT remains consistent in its dislike of OHLE

https://www.thetimes.co.uk/article/battery-powered-trams-to-beat-congestion-pzz3p9jk3?shareToken=d7efc8230f20d995b8ea4bff5daae 175




As usual, the incompetent DfT only thinks about short term costs of
initial construction, not the long term running / operating costs.

Batteries have a finite life. You can recharge them, but they
eventually deteriorate, hold less charge, and have to be replaced -
and they are not cheap to replace.

Moreover, you use additional energy to convey the weight of the
batteries on every journey, instead of getting energy from fixed
overhead wires to move a vehicle that is lighter due to the absence
of batteries.

And before anyone suggests fuel cells, they also have finite lives,
and to function, they often rely on the presence of rare, expensive,
precious metals (platinum, palladium, rhodium, etc.)


All of those factors would be included in the appraisal of costs and
benefits of competing options - bus, battery tram, OHLE etc - over the
the life of the project.

You would think that they ought to do that, but on past history, does
anyone here trust the civil service to get anything right ????


It may surprise you to know that Ministers can and do take decisions
against the advice of their civil servants. And that the influence of
the Civil Service declined from the 1970s. An awful lot of decisions
are made by Ministers with their special advisers and external interests.

And investment appraisals aren't secret. It's open to anyone to
challenge them and/or offer their own. The methodology is simple enough
- and published in the Treasury's "Green Book".

In any event, I'm unclear how civil servants are to blame for things
such as the Leeds Supertram (cancelled when costs were heading for
double the planned budget - and that before any serious construction
work). That inability on the part of promoters to estimate accurately
the cost and timetable of major infrastructure schemes seems to live on
with Cross rail - and isn't likely to help the "be big, be bold, it's
worth the extra investment" school.

--
Robin
reply-to address is (intended to be) valid

Clank wrote:


On the other hand... What's wrong with trolley poles? They seem pretty
reliable even in inclement weather*. On a tram, where the poles wouldn't
even have to deal with the vehicle moving all over the road to overtake
etc., I don't see any reason why they should be particularly problematic.


More prone to dewirement, particularly as speed increases. Junction
'pointwork' more complicated and prone to failure. More maintenance
required too, I think. Need changing over at every terminus.


Anna Noyd-Dryver

Marland wrote:
Anna Noyd-Dryver wrote:
Marland wrote:
bob wrote:
Graeme Wall wrote:
On 08/02/2019 10:58, Bevan Price wrote:
On 08/02/19 4:14, Recliner wrote:
The DfT remains consistent in its dislike of OHLE

https://www.thetimes.co.uk/article/battery-powered-trams-to-beat-congestion-pzz3p9jk3?shareToken=d7efc8230f20d995b8ea4bff5daae 175





As usual, the incompetent DfT only thinks about short term costs of
initial construction, not the long term running / operating costs.

Batteries have a finite life. You can recharge them, but they eventually
deteriorate, hold less charge, and have to be replaced - and they are
not cheap to replace.

Moreover, you use additional energy to convey the weight of the
batteries on every journey, instead of getting energy from fixed
overhead wires to move a vehicle that is lighter due to the absence of
batteries.

And before anyone suggests fuel cells, they also have finite lives, and
to function, they often rely on the presence of rare, expensive,
precious metals (platinum, palladium, rhodium, etc.)


Though once you've done the difficult bit of the infrastructure,
actually getting the tracks in the road, adding OLE later is a much
simpler engineering task.

It is provided you’ve done the work to properly isolate the track return
current to prevent electrolytic corrosion problems. If not, it probably
means ripping the whole lot up again.


Or use twin conductors like a trolley bus.



That would necessitate use of trolley poles, where pantographs are the
current standard fitment for new tramways.

I suppose you could have twin pantographs as fitted for 3-phase on certain
mountain railways, though you might get polarity issues on single track
sections, plus I suspect the OLE then needs to be aligned more accurately,
thus making it more intrusive.


What polarity issues would that be? Trolley buses frequently moved poles
over to the opposite set to get around an obstruction or damaged section.
DC traction motors as used in trams ,trolleys and trains have the the field
windings made from coils and are not polarity sensitive, its only on small
DC motors with permanent magnets like on model trains etc that reversing
the polarity will make the motor rotate in a different direction.

Though in the unlikely event of such an installation happening would trams
still be using DC motors nowadays?
Or like most trains electronic gubbins that can be fed all sorts of things
then send it to a AC 3phase motors.


AIUI trolleybuses are designed with both the positive and negative traction
circuits fully isolated from the vehicle. Trams OTOH have the negative
side, ie rails, connected to to the vehicle underframe and body frame ie
everything is earthed. The two-wire tram would therefore need a
non-standard wiring loom etc.

I’d expect any new-build electric traction vehicle to be VVVF 3-phase
motors.


Anna Noyd-Dryver

Anna Noyd-Dryver Wrote in message:
Clank wrote: On the other hand... What's wrong with trolley poles? They seem pretty reliable even in inclement weather*. On a tram, where the poles wouldn't even have to deal with the vehicle moving all over the road to overtake etc., I don't see any reason why they should be particularly problematic. More prone to dewirement, particularly as speed increases. Junction'pointwork' more complicated and prone to failure. More maintenancerequired too, I think. Need changing over at every terminus. Anna Noyd-Dryver

With all due respect - and I use that in its extremely unusual totally sincere sense - are all those true, or are they just "received wisdom" used to back-justify the UK's resistance to trolleys (and indeed trams)?

The junction pointwork here is generally lightweight and simple, and even if it wasn't how much trouble would it be; an awful lot (crossovers etc.) can be done entirely passively, so given that a system like Croydon Tramlink would require all of about 3* sets of points how much overhead (no pun intended) do they really add?

On maintenance - trolleybuses are used in cities like Bucharest and L'viv which are not exactly famous for their exemplary standards of infrastructure maintenance, and seem to run completely reliably. L'viv in particular has streets that are literally falling apart with tram rails that are so loosely aquainted with the streets they run over, and so worn and damaged at every joint, that it's a miracle the trams don't fall off them - but keeping the OHL up for the trolleybuses seems to be no problem at all.




* Approximately, and I've not looked in detail, but pretty sure the central loop, and all the various sets of track points for the single line sections on the Wimbledon branch could be handled by passive trolley OHL with no points required - so the only places you need actual points in the OHL are Sandilands, Arena & Church Street.


--

"Bevan Price" wrote

Batteries have a finite life. You can recharge them, but they eventually
deteriorate, hold less charge, and have to be replaced - and they are
not cheap to replace.

Moreover, you use additional energy to convey the weight of the

Steam trams?

--
Mike D

Anna Noyd-Dryver wrote:
Marland wrote:
Anna Noyd-Dryver wrote:
Marland wrote:
bob wrote:
Graeme Wall wrote:
On 08/02/2019 10:58, Bevan Price wrote:
On 08/02/19 4:14, Recliner wrote:
The DfT remains consistent in its dislike of OHLE

https://www.thetimes.co.uk/article/battery-powered-trams-to-beat-congestion-pzz3p9jk3?shareToken=d7efc8230f20d995b8ea4bff5daae 175





As usual, the incompetent DfT only thinks about short term costs of
initial construction, not the long term running / operating costs.

Batteries have a finite life. You can recharge them, but they eventually
deteriorate, hold less charge, and have to be replaced - and they are
not cheap to replace.

Moreover, you use additional energy to convey the weight of the
batteries on every journey, instead of getting energy from fixed
overhead wires to move a vehicle that is lighter due to the absence of
batteries.

And before anyone suggests fuel cells, they also have finite lives, and
to function, they often rely on the presence of rare, expensive,
precious metals (platinum, palladium, rhodium, etc.)


Though once you've done the difficult bit of the infrastructure,
actually getting the tracks in the road, adding OLE later is a much
simpler engineering task.

It is provided you’ve done the work to properly isolate the track return
current to prevent electrolytic corrosion problems. If not, it probably
means ripping the whole lot up again.


Or use twin conductors like a trolley bus.



That would necessitate use of trolley poles, where pantographs are the
current standard fitment for new tramways.

I suppose you could have twin pantographs as fitted for 3-phase on certain
mountain railways, though you might get polarity issues on single track
sections, plus I suspect the OLE then needs to be aligned more accurately,
thus making it more intrusive.


What polarity issues would that be? Trolley buses frequently moved poles
over to the opposite set to get around an obstruction or damaged section.
DC traction motors as used in trams ,trolleys and trains have the the field
windings made from coils and are not polarity sensitive, its only on small
DC motors with permanent magnets like on model trains etc that reversing
the polarity will make the motor rotate in a different direction.

Though in the unlikely event of such an installation happening would trams
still be using DC motors nowadays?
Or like most trains electronic gubbins that can be fed all sorts of things
then send it to a AC 3phase motors.


AIUI trolleybuses are designed with both the positive and negative traction
circuits fully isolated from the vehicle. Trams OTOH have the negative
side, ie rails, connected to to the vehicle underframe and body frame ie
everything is earthed. The two-wire tram would therefore need a
non-standard wiring loom etc.

AFAIK modern trams have separate traction wiring for both polarities though
as you say they will eventually arrive at the same earth point, but there
would not be much complication if the the cable to that was connected to a
second pole and wire, just not at the same time , any idea how London’s
conduit trams were wired? The conduit supply was not electrical different
from a two wire supply except the wires have become protected live rails,
the track was not used as the return . It must have taken some good
planning on such a large system to ensure no tram could end up with the
plough turned around, and you have the added complication that after
dropping the ploughs and going to overhead on some routes then the chassis
and wheel return would then be used. Did those trams have a switch that had
to be operated to go from plough return or track?
I understand that some of the Underground’s battery locos can be switched
to third rail supply from the fourth
as there was a hope they could be hired out for engineering duties on the
National Rail 3rd rail network.
I don’t that ever came about though a pair once top and tailed a railtour
and Sarah Siddons the Met Loco was similarly modified for the tours it did
at one time to Portsmouth etc.

GH

On Sat, 9 Feb 2019 01:08:41 -0000, "Michael R N Dolbear"
wrote:


"Bevan Price" wrote

Batteries have a finite life. You can recharge them, but they eventually
deteriorate, hold less charge, and have to be replaced - and they are
not cheap to replace.

Moreover, you use additional energy to convey the weight of the

Steam trams?

Toby!