On 10 Feb, 19:57, Tom Anderson wrote:

And a question: why do there not appear to be any sleepers in the old
engraving?

Because it's mixed gauge track, standard 4' 8.5" standard and 7' 0.25"
Great Western Broad Gauge. The GWR originally laid their rails on
longitudinal baulks of timber, with timber transoms and metal tie-bars
at intervals to hold them to the correct gauge. This form of track
construction is sometimes still used; I saw it in Paddington Station a
few years ago, and it's also sometimes used on bridges, possibly to
reduce the weight.

There's a picture of the mixed gauge trackwork at Didcot at the bottom
of this page:

http://www.didcotrailwaycentre.org.u...ormation.shtml

You can clearly see the construction of the trackwork. I did some of
the work on this track, about twenty years ago now.

On Sat, 10 Feb 2007 wrote:

On 10 Feb, 19:57, Tom Anderson wrote:

And a question: why do there not appear to be any sleepers in the old
engraving?

Because it's mixed gauge track, standard 4' 8.5" standard and 7' 0.25"
Great Western Broad Gauge. The GWR originally laid their rails on
longitudinal baulks of timber, with timber transoms and metal tie-bars
at intervals to hold them to the correct gauge.

Well i never. Thanks!

This form of track construction is sometimes still used; I saw it in
Paddington Station a few years ago, and it's also sometimes used on
bridges, possibly to reduce the weight.

Makes sense. What's the advantage of conventional construction over this,
then?

There's a picture of the mixed gauge trackwork at Didcot at the bottom
of this page:

http://www.didcotrailwaycentre.org.u...ormation.shtml

You can clearly see the construction of the trackwork. I did some of
the work on this track, about twenty years ago now.

Good job. Looks devilishly complicated. Don't suppose anyone ever made a
section of interlaced mixed-gauge track, did they?

tom

--
hypnopomp rapist

In message , Tom
Anderson writes
Makes sense. What's the advantage of conventional construction over
this, then?
The railway as laid down by Brunel wasn't level but sagged between
pillars down into the earth to prevent movement. Frequent sleepers
stop this and hold the gauge correctly.
--
Clive.

Clive Coleman. wrote:
In message , Tom
Anderson writes
Makes sense. What's the advantage of conventional construction over
this, then?
The railway as laid down by Brunel wasn't level but sagged between
pillars down into the earth to prevent movement. Frequent sleepers
stop this and hold the gauge correctly.

Interesting. Was this true of all Brunel's broad gauge lines? That
would have meant that high(ish) speeds on broad gauge wouldn't have been
compatible with the comfort (and possibly the safety) of passengers. Do
you know if Brunel realised that later?
--
Richard J.
(to e-mail me, swap uk and yon in address)

Richard J. wrote:
Clive Coleman. wrote:
In message , Tom
Anderson writes
Makes sense. What's the advantage of conventional construction
over this, then?
The railway as laid down by Brunel wasn't level but sagged between
pillars down into the earth to prevent movement. Frequent
sleepers stop this and hold the gauge correctly.

Interesting. Was this true of all Brunel's broad gauge lines? That
would have meant that high(ish) speeds on broad gauge wouldn't have
been compatible with the comfort (and possibly the safety) of
passengers. Do you know if Brunel realised that later?

Apparently he did. I've just realised that Brunel died (in 1859) four
years before the Met opened, so it's probably wrong to attach credit or
blame to him for the Met's tracks. I then discovered that there is
evidence that Brunel himself had modified the track design some years
previously:

"To rectify the shortcomings of the track, Brunel adopted the expedient
of cutting through the piles which supported the track-work, allowing
the track assembly to be supported by the ground, then re-packing with
ballast as necessary. When this work was done the track behaved as had
first been expected."
(from "The Broad Gauge Story" at
http://lionels.orpheusweb.co.uk/Rail...dG/BGHist.html )

--
Richard J.
(to e-mail me, swap uk and yon in address)

In message , Richard J.
writes
Interesting. Was this true of all Brunel's broad gauge lines? That
would have meant that high(ish) speeds on broad gauge wouldn't have
been compatible with the comfort (and possibly the safety) of
passengers. Do you know if Brunel realised that later?
I think it was discovered quite early on and most of the broad gauge
were converted to sleeper type track, on broad gauge.
--
Clive.

Clive Coleman:
I think it was discovered quite early on and most of the broad gauge
were converted to sleeper type track, on broad gauge.

No, it was just that they stopped having vertical piles. If the GWR
hadn't retained its longitudinal sleepers, they would have had a much
easier time when they finally abandoned the broad gauge in 1892.
As it was, they had to cut all the cross-transoms to allow one rail
*and* its longitudinal sleeper to be moved inward.
--
Mark Brader, Toronto | "This man must be very ignorant, for he answers
| every question he is asked." -- Voltaire

My text in this article is in the public domain.