Lever frames
This
a lever frame is a development of the Scalefour Society's design which
has been available from the Society Public e-shop for several years.
This "Mk II" design is fully compatible with the previous frame but
incorporates a number of features as follows:-
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The facility
to add mechanical interlocking, (available as a
separate etch) without modification
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Integral
lever handles with the option of replacing these by
a turned steel alternative
·
Easier and
more accurate assembly as a pre-requisite for the
locking
·
The ability
to build “long” frames easily and accurately
whilst retaining the ability to remove a block of five levers from the
middle
of a longer frame
·
The ability
to easily remove an individual lever from a block
of five without dis-assembling the whole frame
·
A separate
bracket for mounting microswitches at the rear of
the levers making it possible to replace an individual failed switch
without
major surgery to the frame.
·
A stronger
catch box design which is also more accurate in
locating the levers at the ends of their travel.
Levers frames are supplied in units of 5 levers and the
modular
design allows frames of any multiple of 5 levers to be easily built-up
and moreover, to be easily disassembled for maintenance.
The design was developed from the Scalefour Society "SHAG" lever frame
which has been on sale for a number of years.
A five-lever fret, including catch-handle springs,
costs approx. £33 and they are available to Scalefour
Society members
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10-lever frame being assembled with the optional locking
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Download Assembly guide
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Download Drilling Template for mounting base (Since
this must be printed "Actual size", please download and print from your
own machine - don't use your web browser's PDF printer)
Right-click and choose "Download" in your browser. If your browser does
not allow this, open the link then click on the "Download" icon in the
upper RH corner of the pdf viewer.
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Mechanical interlocking
Designed specifically to fit the above lever frame modules,
the locking is based on the Great Western Railway's five bar vertical
tappet locking - a very compact and efficient design - but for reasons
of practically, has four, rather than 5, bridles per tray. There
are 8 trays and hence the basic design can accommodate up to 32 locking
bridles. An extension kit is available to extended this of 64 bridles
for very long lever frames, but the basic kits have been used to
successfully lock a frame of 70 levers
The locking embodies a number of design features as follows:
• The interlocking can be fitted and removed from the
lever frame at any time to allow for fault finding and correction. This
also means that the lever frame and locking table can be built
separately and assembled after all testing is complete. To this end,
the design of a suitable assembly jig is suggested in the assembly
guide.
• The Tappets may be easily removed at any time for
maintenance, adjustment, etc and this allows the Bridles – both front
and back – also to be removed should this be necessary. Although it is
hardly an easy job, this does mean that subsequent modifications to the
layout can be accommodated without scrapping and rebuilding the frame.
• The design provides the capability to create all
the mechanisms used on the prototype including releases, deadlocks,
conditional locks, sequential locks, loose nibs, butts etc.
Locking Etches for 5 levers costs approx. £37 and they are available to Scalefour
Society members
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Download Locking Assembly guide |
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