Restoration - page 6
Princes Risborough North Signal Box
2021 - 2022
Even
though
early
Spring
saw
the
final
throes
of
lock-down
restrictions
easing
following
the
Covid-
19
pandemic,
our
team
still
tried
to
work
outside
in
the
fresh
air
as
much
as
possible.
We
started
building
the
wooden
platform
and
upper
works
on
the
bracket
signal
behind
the
signal
box
although
it
will be a while yet before we can attach the actual red signal arms.
In
late
spring
we
set
about
the
internal
electrical
wiring
needed
for
the
block
shelf
instruments
and
lever
plungers.
The
plungers
are
required
so
the
signaller
can
release
the
electrical
locks
which
act
in
addition
to
the
mechanical
locking.
Even
a
1905
built
signal
box
needs to adhere to 21st century safety requirements!
We
created
the
new
illuminated
diagram
of
our
track
layout
in
the
Princes
Risborough
area
and
fitted
the
indicator lights. The siding from points 113 will be put in place during 2023.
The
next
thing
to
do
was
run
cabling
between
the
electrical
relays
housed
inside
the
signal
box,
outside
to
lineside
cabinets
which
in
turn
have
wires
connecting
to
the
actual
rails
of
the
track.
These
'track
circuits'
detect
the
presence
(or
more
accurately,
the
absence*)
of
a
train
and
activate
(again
more
accurately,
de-
activate*) the relays which control the lever locks.
*The
safety
systems
employed
by
all
railways
are
designed
to
'fail
safe'.
That
means
if
something
goes
wrong
with
any
piece
of
equipment,
it
will
never
allow
an
unsafe
indication
or
action.
A
simple
example
is
if
a
signal
wire
breaks
-
the
arm will revert to danger, by a combination of weights and gravity.
A
purpose
built
testing
panel
was
constructed
inside
the
box
from
an
old
office
telephone
exchange
switch
panel
to
simulate
the
external
connections
and
track
circuits
thus
allowing
us
to
be
confident
of
the
wiring
integrity prior to the final more stringent testing at time of commissioning.
With
an
eye
to
the
future,
we
experimented
with
setting
up
a
'Block
Bell
over
Internet'
(BBoI)
system
whereby
our
signaller
at
Risborough
can
communicate
with
the
signal
box
in
the
box
at
Chinnor,
and
vice-versa.
Although
we
do
not
use
this
as
a
'safety
critical'
method
of
notifying
train
movements,
it
does
add
to
the
authentic
sights
and
sounds
inside
the
signal
box
as
well
as
providing
training
for
our
signallers,
ready
for
when we can connect the two signal boxes via trackside wires.
We
made
more
additions
and
enhancements
to
the
mechanisms
on
the
locking
frame
which
is
housed
directly
under
the
upstairs
operating
floor.
Throughout
the
year
we
continued
with
seemingly
endless
task
of
repainting
the
window
sashes,
replacing
more
newly
discovered
timber
rot.
We
identified
the
few
remaining
areas
of
brickwork
that
urgently
needed
re-pointing
and
used
the
correct
lime
mortar
mix
to
deal with those.
All
in
all
it
was
another
year
of
preparing
the
station
end
of
the
box
for
its
imminent
role
as
the
working
Princes Risborough
Middle
Box.
