On Wed, 19 Sep 2007, Barry Salter wrote:

Primary reason being that if the HSE thought that safety was their
primary purpose, they'd make LU install them at all the other deep level
stations, which'd cost a fortune...Doubly so when/if the stock is
replaced if the doors don't line up with the PEDs.

I had an idea about this. I was trying to think of a way to put PEDs on NR
platforms, where trains with pretty much any door geometry can turn up.

What i came up with is a setup where there are two rails along the
platform edge, and corresponding ones on the ceiling. You then have doors
about the width of a train door (half the width of a two-leaf door)
mounted on wheels on the rails, so they can slide sideways, with motors to
make them do it (and photocells reading a position code painted on the
platform). You put the doors on the rails in alternation: door one is on
rail A, two on rail B, door three is on rail A, etc. Like this:

1111 3333 5555 7777 9999
0000 2222 4444 6666 8888

Now, every one of these doors has enough space to slide sideways (in
either direction) by one width, exposing an empty space behind it
(provided another door hasn't slid into that space). So, when a train
pulls in, you just need to figure out which of the platform doors are
covering doorways, and slide them out of the way:

DOOR
1111 3333 5555 7777 9999
0000 2222 4444- 6666 8888

Becomes:

DOOR
1111 3333 5555 7777 9999
0000 2222 44446666 8888

Double door:

BIGDOOR
1111 -3333 5555 7777 9999
0000 2222 4444- 6666 8888

Becomes:

BIGDOOR!
11113333 5555 7777 9999
0000 2222 44446666 8888

At this point, Bob is your uncle.

This works as long as the train's doors aren't too close together; there
has to be a door's width between doors for it to work.

DOOR DOOR
1111 3333 5555 7777 9999
0000 2222 4444- 6666- 8888

DOOR DOOR
1111 3333 5555 7777 9999
0000 2222 4444 66668888

And:

BIGDOOR! BIGDOOR!
1111 -3333 5555 -7777 9999
0000 2222 4444- 6666 8888-

BIGDOOR! BIGDOOR!
11113333 55557777 9999
0000 2222 44446666 8888

How good's that?

You need to make the platform doors very slightly wider than the holes
between them to eliminate cracks between layers of doors; this apparent
impossibility can be accomplished by making the edges of the doors
inflated bumpers, which squash flat when doors press together. This also
makes things a bit safer when passengers' hands get caught between the
platform-facing doors.

Looking at those diagrams, i think each row of doors only has to be able
to move in one direction; that means you could dispense with motors and
photocells and use a lot of hydraulic pistons, which would be more
reliable. The motors give you more flexibility for dealing with funny door
layouts, though.

Train doors do have to be roughly constant width for this to work. And in
phase with the platform door array. Although if the density of the doors
isn't at the limit of what the system can handle, doors being out of phase
can be worked around.

Must drink less coffee.

tom

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3118110161 Pies

"Tom Anderson" wrote in message
h.li...
On Wed, 19 Sep 2007, Barry Salter wrote:

Primary reason being that if the HSE thought that safety was their
primary purpose, they'd make LU install them at all the other deep level
stations, which'd cost a fortune...Doubly so when/if the stock is
replaced if the doors don't line up with the PEDs.

I had an idea about this. I was trying to think of a way to put PEDs on NR
platforms, where trains with pretty much any door geometry can turn up.


I'm just visualising that on the three platforms at Eastleigh - there's
seventy two sets of doors needed for the 12.450s... but at least their doors
are evenly spaced down the train. Then the 10.444 needs four permutations,
cos the doors are'nt the same position on all the coaches...

Yep I'm sure it'll be a goer, just need to get the DfT thinking about it...

Paul

http://shortlink.co.uk/nqu

Nice Picture of the new platform at T5 here.