On 20/12/2011 13:22, Neil Williams wrote:
On Dec 20, 2:04 pm, Graeme wrote:

Not insoluble but possibly expensive.

It presumably depends on the size of the curves. SBB IC2000 stock has
upper level gangways only.


I doubt whether SBB IC2000 stock has to cope with curves, both
horizontally and vertically that, say, Sheffield trams have to negotiate.


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

On 20/12/2011 13:49, d wrote:
On Tue, 20 Dec 2011 13:04:23 +0000
Graeme wrote:
On 20/12/2011 13:02, Graham Harrison wrote:

"Basil wrote in message
...
On 2011\12\20 08:57, Graham Harrison wrote:
I can't find a tram related newsgroup.

I've sometimes wondered why modern tramcar makers don't make double
deckers. Yes, modern artics swallow lots of people quickly but they also
take up a lot of space. A double deck artic (with connections at both
levels)

How would the upper floor connection cope with vertical curves?

That's an engineering detail (he said having no idea what the answer is!).

Not insoluble but possibly expensive.

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.

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

On Dec 20, 2:00*pm, "Graham Harrison"
wrote:
A double deck tram has by nature about

the capacity of a double deck bus, so given the choice the operator
opts for the bus which is more flexible and cheaper.

You're limiting your thinking. * In effect I'm asking why you can't take a
modern multi section single deck tram and build a double deck version.

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. 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?).

Robin

On Dec 20, 8:57*am, "Graham Harrison"
wrote:

Yes, modern artics swallow

Laden or unladen?

On Dec 20, 2:49*pm, wrote:
On Tue, 20 Dec 2011 13:04:23 +0000





Graeme Wall wrote:
On 20/12/2011 13:02, Graham Harrison wrote:

"Basil Jet" wrote in message
.. .
On 2011\12\20 08:57, Graham Harrison wrote:
I can't find a tram related newsgroup.

I've sometimes wondered why modern tramcar makers don't make double
deckers. Yes, modern artics swallow lots of people quickly but they also
take up a lot of space. A double deck artic (with connections at both
levels)

How would the upper floor connection cope with vertical curves?

That's an engineering detail (he said having no idea what the answer is!).

Not insoluble but possibly expensive.

Have the universal joint at floor level with the upper deck instead of at
floor level with the lower deck. Fairly simple.

But that would just shift the problem from the upper deck floor
aticulation to the lower deck floor articulation. The problem is
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.

There's also the issue of where to put all the kit that sits on the
roof of a modern low floor tram (that in the days of high floor trams
might have been under the floor).

Robin

On Tue, 20 Dec 2011 14:38:07 +0000
Graeme Wall 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"?

B2003

On Tue, 20 Dec 2011 06:56:00 -0800 (PST)
bob wrote:
Have the universal joint at floor level with the upper deck instead of at
floor level with the lower deck. Fairly simple.

But that would just shift the problem from the upper deck floor
aticulation to the lower deck floor articulation. The problem is

Not really , both floors would articulate the same amount but it would
be less that the upper floor would do it if the joint was in the usual place.

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.

B2003

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.

On Tue, 20 Dec 2011 07:23:40 -0800 (PST)
bob wrote:
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.

I'm sure people would get used to it just like they've got used to the ends of
escalator. But if its really an issue you could simply wall off the seperate
compartments of the tram.

B2003

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.

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