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ROYAL ENFIELD 350cc and 500cc O.H.V. WORKSHOP MANUAL
Front Fork
With Casquette and Aluminium Alloy Bottom Tubes
Used on Model G deluxe and 350 Clipper
1. Description
The telescopic fork consists of two legs each
of which comprises a main tube of chrome
molybdenum alloy steel tubing which is
screwed into the Casquette fork head at the
upper end and securely clamped to the fork
crown. Fitted over the lower end of the main
tube is the bottom tube made of high strength
aluminium alloy with an integral lug which
carries the wheel spindle. Fitted on the lower
end of the main tube is a steel bush which is a
close fit in the bore of the bottom tube. The
upper end of the bottom tube carries a bronze
bush which is a close fit over the outside
diameter of the main tube. The bush is secured
to the bottom tube by means of a threaded
housing which contains an oil seal. A stud
known as the "spring stud" is fitted in the lower
end of the bottom tube and a valve port is
secured to the lower end of the main tube. As
the fork operates oil is forced between the
spring stud and the bore of the valve port
forming a hydraulic damping system. A
compression spring is fitted inside the main tube
between the upper end of the spring stud and the
upper end of the main tube. The lower end of
the main tube and upper end of the bottom tube
are protected by a cover secured to the fork
crown.
A special fork is available for sidecar
machines. This has bottom tubes with extended
wheel lugs giving less trail and is fitted with
stronger springs and a steering damper.
2. Operation of the Fork
The fork provides a range of movement of 6
in. from the fully extended to the fully
compressed
position.
The
movement
is
controlled by the compression spring and by the
hydraulic damping system. The hydraulic
damping is light on the bump stroke and heavier
on the rebound stroke, thus damping out any
tendency to pitching or oscillation without
interfering unduly with the free movement of
the fork when the wheel encounters an obstacle.
The fork is filled with S.A.E. 20 to a point
above the lower end of the fork spring so that
the damper chamber "B" is always kept
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