I've sometimes wondered why modern tramcar makers don't make double deckers.


Probably for the same reasons that here in the UK double deck buses
are also in decline.

Bus operators are increasingly turning to longer modern low floor
(floor lowering) single deck buses for their ease of access (mother
and baby), greater safety, better passenger supervision and disabled
friendly features compared to double deckers.

Also in these days of integrated transport consideration of things
like luggage (airport buses) is often required.

There is also no longer the need to accommodate smokers.

But what really swings it for the modern single decker bus is the
extent to which actual seat capacity, falling short of double decker
capacity, can usually be measured in single figures.

Plus, we don't think trams anymore, we think light rail and that means
trains not trams and, as others here have pointed out, that raises the
issue of connecting vehicles together.

I believe Manchester Metro operates some services with six car trains
(with all the ease of access that implies) and it's that kind of
thinking that has brought about the renaissance of the street tramway
into the modern light railway with both on street and off street
running.

On Tue, 20 Dec 2011 15:34:07 +0000
Graeme Wall wrote:
On 20/12/2011 14:59, d wrote:
On Tue, 20 Dec 2011 14:38:07 +0000
Graeme wrote:
Have the universal joint at floor level with the upper deck instead of at
floor level with the lower deck. Fairly simple.


For a given value of simple. Means the buffing loads will be rather
higher than is usual for rail vehicles which will have major
implications for the design of the trams.

Whats a "buffing load"?


What the buffers/couplings have to cope with.

Why would they have a higher loading simply because the joint is positioned
6 foot higher?

B2003

wrote in message

On Tue, 20 Dec 2011 15:34:07 +0000
Graeme Wall wrote:
On 20/12/2011 14:59, d wrote:
On Tue, 20 Dec 2011 14:38:07 +0000
Graeme wrote:
Have the universal joint at floor level with the upper deck
instead of at floor level with the lower deck. Fairly simple.


For a given value of simple. Means the buffing loads will be
rather higher than is usual for rail vehicles which will have major
implications for the design of the trams.

Whats a "buffing load"?


What the buffers/couplings have to cope with.

Why would they have a higher loading simply because the joint is
positioned 6 foot higher?

Higher moment.

On 20/12/2011 15:41, d wrote:
On Tue, 20 Dec 2011 15:34:07 +0000
Graeme wrote:
On 20/12/2011 14:59, d wrote:
On Tue, 20 Dec 2011 14:38:07 +0000
Graeme wrote:
Have the universal joint at floor level with the upper deck instead of at
floor level with the lower deck. Fairly simple.


For a given value of simple. Means the buffing loads will be rather
higher than is usual for rail vehicles which will have major
implications for the design of the trams.

Whats a "buffing load"?


What the buffers/couplings have to cope with.

Why would they have a higher loading simply because the joint is positioned
6 foot higher?


Sorry, I meant the application of the loads would be at a higher level,
not that they would be greater in magnitude.


--
Graeme Wall
This account not read, substitute trains for rail.
Railway Miscellany at http://www.greywall.demon.co.uk/rail

On Dec 20, 3:48*pm, bob wrote:

Articulations and double deck vehicles are generally not compatible.
In all of the variations of double deck railway carriages I have
encountered, none has gangway connections on both levels.

No, though SBB's double deck IC stock has the gangway well above the
(traditional screw) coupling, probably about a metre or so.

Neil

"allantracy" wrote in message
...

I've sometimes wondered why modern tramcar makers don't make double
deckers.


Probably for the same reasons that here in the UK double deck buses
are also in decline.

Bus operators are increasingly turning to longer modern low floor
(floor lowering) single deck buses for their ease of access (mother
and baby), greater safety, better passenger supervision and disabled
friendly features compared to double deckers.

Also in these days of integrated transport consideration of things
like luggage (airport buses) is often required.

There is also no longer the need to accommodate smokers.

But what really swings it for the modern single decker bus is the
extent to which actual seat capacity, falling short of double decker
capacity, can usually be measured in single figures.

Plus, we don't think trams anymore, we think light rail and that means
trains not trams and, as others here have pointed out, that raises the
issue of connecting vehicles together.

I believe Manchester Metro operates some services with six car trains
(with all the ease of access that implies) and it's that kind of
thinking that has brought about the renaissance of the street tramway
into the modern light railway with both on street and off street
running.

In the same way that at least one person here responded to my question by
referring to Felthams you've gone to the opposite extreme and simply
regurgitated current propaganda. Now, don't get me wrong, I am all in
favour of the resurgence of trams (all right LRVs if you will) in the UK.
That said I don't see why a modern double deck tram which can be articulated
(with difficulty as discussed above) and/or MUed (for pity's sake Mumbles
did that) is impossible.

Suppose you put together a vehicle that was as long as a NET LRV but on two
decks. The downstairs could have minimal seating but maximise space for
pushchairs, disabled access etc. Seating would be upstairs; best of both
worlds. Nothing to stop you MU ing 2 or more if you wanted to.

I think it's technically feasible. The real issue is whether it's
operationally feasible and there the issue relates to speed of access
to/from the upper deck. Well, maybe we need a bit of off the wall thinking
to solve that. How about dedicating one section to a ramped method of
going up/down?

And the word "tram"? It's not used because of connotations with noisy,
draughty, wooden seated, slow vehicles. An LRV is a tram by any other name.

On Tue, 20 Dec 2011 06:48:47 -0800 (PST), bob wrote:

Articulations and double deck vehicles are generally not compatible.
In all of the variations of double deck railway carriages I have
encountered, none has gangway connections on both levels. The tight
corners and ability to climb hills in an urban setting would make this
problem worse for trams than "big" trains.

Flat curves just need a bit that stays where it is as the outer bits rotate
around the curve. It's the gradients that cause the problems, with the
required connection being stretched or squeezed more and more the further
away it is from the ground.

The other issue is that
modern low floor trams use the roof to mount all kinds of equipment
like power electronics and air conditioners. With a double deck
arrangement, this would have to be accommodated somewhere else
(where?).

Where they are, in many cases, IWHT. Put the upper deck above them. It's
only the lower deck that has to be "low floor".

In article
,
bob wrote:

On Dec 20, 4:06*pm, wrote:

accommodating vertical curves on both floor levels simultaneously.
Without having a telescoping floor section vertical curves can not be
handled, and I would have worries about the safety implications for
passengers crossing the join as it stretches and contracts.

I've never heard of anyone being squashed inside a bendy bus because of it.

But on all bendy buses I have ever travelled on the transverse axis
about which vertical bending occurs passes through the floor, so that
as the bus bends in a vertical sense, the floor "folds" but does not
extend or contract in length. On a double decker, the floor that does
not contain the axis of rotation will experience an extension or
contraction of the floor as well as rotation. One of the floors will
therefore experience extension and contraction as well as rotation,
which is a whole lot less safe.

On all the corridor trains I've been on the floor in the gangways is
subject to extension or contraction as the couplings and/or buffers
react to stresses. Granted it's not to the same degree as you'd get
with a DD tram, but it's not an entirely novel problem.

Sam

On Dec 20, 6:01*pm, Sam Wilson wrote:

On all the corridor trains I've been on the floor in the gangways is
subject to extension or contraction as the couplings and/or buffers
react to stresses. *Granted it's not to the same degree as you'd get
with a DD tram, but it's not an entirely novel problem.

I'm pretty sure Stagecoach has or had some double-decker articulated
coaches with through connections at both levels. I think they were
used on Megabus duties.

Neil

On 20/12/2011 17:13, Neil Williams wrote:
On Dec 20, 6:01 pm, Sam wrote:

On all the corridor trains I've been on the floor in the gangways is
subject to extension or contraction as the couplings and/or buffers
react to stresses. Granted it's not to the same degree as you'd get
with a DD tram, but it's not an entirely novel problem.

I'm pretty sure Stagecoach has or had some double-decker articulated
coaches with through connections at both levels. I think they were
used on Megabus duties.


Couldn't find any pictures of a Stagecoach or Megabus articulated double
decker but I did find this:

http://www.sfu.ca/person/dearmond/phono/London.tbus2049b.jpg


--
Graeme Wall
This account not read, substitute trains for rail.
Railway Miscellany at http://www.greywall.demon.co.uk/rail