Page 17 GCR Class 8B
Page 17 GCR Class 8B
Complete the other slide bar parts as above and file to correct profile. They should be 1 mm wide and at the deepest point 1.2
mm.
Insert a pair of slide bars into each side of the frames and check they locate correctly and not too tightly into the cylinder head
rectangular slots with a small protrusion at the front. Ensure that they fit between the Slide Bar Supports (22,23).
Do not solder up at this stage, first the crossheads must be assembled and then tested for a smooth sliding fit! It is likely that a
small adjustment with a file will be needed to the slide bar supports to achieve the desired 4.66 mm spacing all along the slide
bars.
Crossheads
Note
An alternative to the crosshead assembly provided is the Markits Double Slide bar and Crosshead (M4CRHDSns). However, while
this looks very nice it is not deep enough between the slide bars, which means that the locating holes in the cylinder heads must
be adjusted very slightly inwards. The upper and lower slots of the cross heads must be slightly widened to suit the slide bars.
The Crossheads provided are built up in layers. There are two outer layers (one of them partly half etched to show the profile),
two inner layers one of which is half etched and two inside layers which are shaped to allow the Connecting Rods to partially
rotate. All of these should be used unless you are confident of great accuracy in which case the half etch layer may be left out.
Remove the two sets of
Cross Head parts (171-184)
from the fret and align each set locating them in place with a steel pin or
something else suitable through the centre into several layers of balsa or other hardwood. If using hardwood such as Ramin
then drill a hole as deep as possible to suit the steel pin. In preference use a higher melting point solder than normal and use
lots of heat. This will allow the parts to be re-aligned should they
move.
Solder these layers together. Do not pick this up too soon, it will
have got very hot!
Trim and file to finish, the top and bottom edges should be filed
down to less than the depth of the slide bars. Do a test fit to
make sure these slide easily.
In the end of the cross heads drill a small hole 1.6 mm to accept
the cross head rod which is 1/16” brass rod of length 25 mm.
Solder this in place ensuring that the cross head is securely
clamped. Do a test fit to ensure it slides easily into the cylinder
tubing.
Check the measurements for the sliding faces on the crossheads
- this should be 4.67 mm for the supplied version (equivalent to
1’ 2”). For the corresponding slide bars the distance between
them is 4.8 mm. Ensure this is the case, filing and trimming as
needed. This will make a nice close fit without being too tight - a
little oil helps here.
7. Cross Heads
Cross Head Rear (171)
Cross Head Overlay (173
Cross Head Top Overlay (183)
Cross Head Inner Layers A
Cross Head Inner Layers B
6. Slide Bar Measurements
Содержание Robinson GCR Class 8B Atlantic LNER C4
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