John wrote:
In article , John Rowland
writes
®i©ardo wrote:
Boltar wrote:
On 19 Jun, 22:32, wrote:
Street - Blackfriars area. AFIAA, only 33s and 73s are allowed
through the Thameslink tunnels and beyond as far as Kentish Town.

Whats the reason for the restriction , is it loading gauge or
gradiants or something else entirely?

Height of the tunnels?

ISTR it's carriage length, because of the sharp curve around St
Pancras.


If I recall right, there were only certain class 31s allowed to haul
the trains through hotel curve to Kings Cross for a similar reason.

Aren't the Thameslink carriages curved in at each end to go around St
Pancras?

On 21 Jun, 05:18, "John Rowland"
wrote:
John wrote:
In article , John Rowland
writes
®i©ardo wrote:
Boltar wrote:
On 19 Jun, 22:32, wrote:
Street - Blackfriars area. AFIAA, only 33s and 73s are allowed
through the Thameslink tunnels and beyond as far as Kentish Town.

Whats the reason for the restriction , is it loading gauge or
gradiants or something else entirely?

Height of the tunnels?

ISTR it's carriage length, because of the sharp curve around St
Pancras.

If I recall right, there were only certain class 31s allowed to haul
the trains through hotel curve to Kings Cross for a similar reason.

Aren't the Thameslink carriages curved in at each end to go around St
Pancras?

Surely the clearances arn't *that* tight? Besides , didn't they
extensively rebuild that part of the tunnel in the last few years?
Perhaps they improved the clearances while they were at it and these
restrictions no longer apply.

B2003

On 20 Jun, 14:15, Boltar wrote:
On 20 Jun, 12:28, David Cantrell wrote:

With these things taking all kinds of unusual routes, how do they cope
with the need for the driver to have route knowledge? Keep changing
drivers all over the place?

Perhaps theres some low maximum speed and train weight below which a
driver can drive any route because he'll be able to pull up before he
reaches any red signal after first seeing it?

B2003

Conductors?

"Surely the clearances arn't *that* tight? Besides , didn't they
extensively rebuild that part of the tunnel in the last few years?
Perhaps they improved the clearances while they were at it and these
restrictions no longer apply. "

Whilst work may have happened on the southern end of the new
Thameslink station box at St Pancras, where the track is relatively
straight, I am not aware of any work on the reverse curves (the Hotel
Curves) between KX Thameslink and the new station box. These are, I
believe, the main constriant to the route clearances.

BTW how do you improve clearances in a brick tunnel under a builidng,?

OC

In article . com,
(Old Central) wrote:

"Surely the clearances arn't *that* tight? Besides , didn't they
extensively rebuild that part of the tunnel in the last few years?
Perhaps they improved the clearances while they were at it and these
restrictions no longer apply. "

Whilst work may have happened on the southern end of the new
Thameslink station box at St Pancras, where the track is relatively
straight, I am not aware of any work on the reverse curves (the
Hotel Curves) between KX Thameslink and the new station box. These
are, I believe, the main constriant to the route clearances.

I think it's Midland Curve. Hotel Curve is the GN connection now
abandoned. IIRC the main constraints were in the GN rather than the
Midland tunnels.

BTW how do you improve clearances in a brick tunnel under a
builidng,?

With difficulty?

--
Colin Rosenstiel

Doh! Of course it is not the Hotel Curves. The constraints in the
Midland tunnels are significant.

With even more difficulty I suspect if there is a Grade 1 listed
structure on top.

OC

On Thu, Jun 21, 2007 at 05:18:05AM +0100, John Rowland wrote:

Aren't the Thameslink carriages curved in at each end

No more than countless similar carriages on the rest of the network.

to go around St Pancras?

Umm, on a curve, it's the *middle* of the carriage that comes closest to
the tunnel walls, not the ends.

--
David Cantrell | Cake Smuggler Extraordinaire

I caught myself pulling grey hairs out of my beard.
I'm definitely not going grey, but I am going vain.

In article .com,
(Old Central) wrote:

Doh! Of course it is not the Hotel Curves. The constraints in the
Midland tunnels are significant.

With even more difficulty I suspect if there is a Grade 1 listed
structure on top.

The Midland Curve tunnel is double track and nothing like as bad as the
King's Cross Hotel Curve and York Curve tunnels were.

--
Colin Rosenstiel

David Cantrell wrote:

Umm, on a curve, it's the *middle* of the carriage that comes closest
to the tunnel walls, not the ends.

Depends on the direction of the curve.

Centre and end throws exist depending on relative lengths of
wheelbase, overhang, etc.

AFAIUI most stock is designed to balance the effects of these throws.

Note that on a tight radius the passing clearance between vehicles
will be a function of both throws.

OC