It would be interesting to know the bore diameter of this tunnel, compared
with the metro tunnels, which have a walkway. It reminds of all that
palaver years ago about the metro tunnels being too small for double
deckers. So they're presumably smaller, yet they have a walkway?
Tony P
On Wednesday 6 December 2023 at 14:01:58 UTC+11 Tony Galloway wrote:
> The same problem would exist with single deck stock, even narrow stock
> like U sets.
>
> The double deck cars occupy virtually the same dynamic envelope as SD
> stock, the underfloor equipment filling the space that the lower deck
> occupies on DD stock.
>
> With a circular tunnel the only way you’d get a walkway in would be to
> make the entire bore larger.
>
> Tony
>
> On 6 Dec 2023, at 12:01, TP histor...@...> wrote:
>
> I'm getting the picture that the Airport Line tunnels were not built "on
> the cheap", but because they decided that the technology had progressed
> sufficiently to build future rail tunnels using TBMs which have the
> advantage of lining the tunnels as they go and, judging by the metro lines,
> seem to be quicker than using roadheaders etc, then having to line the
> tunnels. The downside for double deckers of course is their vertical
> dimension as you say. That may have contributed to not being able to have a
> walkway inside the tunnel as the metro does, but as was mentioned above,
> they might have decided that, if work was required inside the tunnel, they
> could reroute trains onto the Illawarra surface tracks. I wasn't involved
> in the project post-approval so I have no insight into what happened
> subsequently.
>
> Tony P
>
> On Wednesday 6 December 2023 at 09:36:11 UTC+11 Tony Galloway wrote:
>
>> It still has to meet standard structure/loading gauge clearances, but the
>> round tunnel shape, of which about 15-20% is taken up by the track bed,
>> means the tunnel walls are closer to the trains where the roof meets the
>> sides of the cars, and lower where the fish bellies of the double deckers
>> are close to the track.
>>
>> With this tightness there are no safe spaces for anyone on track where
>> two trains are passing.
>>
>> Tony
>>
>> On 5 Dec 2023, at 22:44, TP histor...@...> wrote:
>>
>> If the line was tunneled with TBMs, resulting in lined tubular tunnels
>> like the Sydney metro tunnels, I imagine that this would create a tighter
>> clearance for double deck trains. All previous Sydney railway tunnels had
>> vertical walls. Am I correct?
>>
>> Tony P
>>
>> On Tuesday, 5 December 2023 at 19:49:57 UTC+11 Tony Galloway wrote:
>>
>>> The type of tunnel construction precluded having refuges, and with the
>>> alternative route through Sydenham available, diversions were the easier
>>> option if anything failed in the tunnel.
>>>
>>> Apparently.
>>>
>>> Tony
>>>
>>> > On 5 Dec 2023, at 17:14, Matthew Geier mat...@...>
>>> wrote:
>>> >
>>> > On 5/12/23 16:59, Robert Taaffe wrote:
>>> >> When the airport line was designed it was intended that it would
>>> never be maintained under traffic, only at night or during possessions.
>>> >
>>> > So the assumption was that things would only break on schedule ?
>>> >
>>> > Actually given the state of some of the Sydney Citadis already, I
>>> think that thinking is being applied to them to.
>>> >
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>>>
>>>
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