Great Western Double-Twist lever
frame
from 1870 onwards, the Great Western built their own lever frames, all though they still bought from contractors when demand necessitated it. They were constructed at their Reading signal works.
Early frames were if the Single- and Double-Twist type, this referring to the means of driving the locking from the lever.
All examples featured a raised tread pattern on the floor plates, and a few also had and angled portion (as seen here) to assist grip. This example is also interesting in that the central bank of levers (spares by this date) sit at a different angle to the rest of the frame.
This example is at Sarnau, more details of which can be found in the Photo Gallery.
Great Western
5-bar Vertical Tappet frame
The above type of lever frame gradually morphed into the type seen here, introduced around 1926 and manufactured at Reading right through to 1966.
This type features tappet locking driven by a cam from the lever to reduce the locking movement.
This example is at Ystrad Mynach South, more details of which can be found in the Photo Gallery. Similar examples are illustrated at Exeter Riverside and Newtown.
This view shows the cam plates beneath floor level on a Great
western 5-bar Vertical Tappet frame at Minehead. The cam plates are operated
directly by the levers, their shape caustin a two-movement process to be
applied to the numbered lock bars which travel vertically downwards into the
locking tray.
Photo by Kevin Weston.
And here is a good view of part of the locking tray.
The lock bars have notches cut in them for the tappets to engage upon. The
tappets are attached to bars which slide horizontally according to which levers
have been pulled, and engae in these notches to preven other levers (that would
set a conflicting route) being operated.
Each section of the locking tray holds five bars (three above and two behind) - hence the term 5-bar tappet locking. Nine such sections can be seen in this view.
Photo by Kevin Weston.