Page 55
ROYAL ENFIELD 350cc and 500cc O.H.V. WORKSHOP MANUAL
nuts on the spindle. Tightening the nuts
should not have any effect on the ease with
which the spindle can be turned. If
tightening the nuts makes the spindle hard
to turn this may be taken as proof that the
bearings are bottoming in the recesses in the
hub barrel before they are solid against the
shoulders on the spindle. In this case the
bearing should be removed and a thin
packing shim fitted between the inner race
and the shoulder on the spindle.
9. Reassembly of Brake Shoes to Cover
Plate
Assemble the shoes with their return
springs on to the pivot pin and operating
cam, putting a smear of grease in the
grooves of the pivot pin and on the
operating faces of the cam. Now fit the
assembly into the cover plate, putting a
smear of grease on to the cylindrical
bearing surface of the operating cam and
secure with the pivot pin locknut and
washer. Fit the operating lever on its spline
in a position to suit the extent of wear on
the linings and secure with the nut and
washer. Note that the position of the
operating lever may have to be corrected
when adjusting the brake after refitting the
wheel. The range of adjustment can be
extended by moving this lever on to a
different spline. Limit of wear is reached
when the cam is turned through nearly 90°
with the brake hard on so that there is a
danger that the operating springs cannot
return the brake to the off position.
10. Floating Cam Housing
Note that the cam housing is intended to
be left free to float. The bolt holes in the
cam housing are slotted and the securing
pins are provided with double coil spring
washers beneath their heads to enable them
to be tightened sufficiently to prevent the
cam housing moving under the influence of
road shocks, while at the same time it can
be, and should be, left free enough to be
capable of being moved by hand in the
direction of the slots. The pins are secured
by locknuts which are centre punched as an
additional precaution.
The leading shoe (i.e. the one towards
the rear of the machine) has a servo action
which renders it more effective than the
trailing shoe. This servo action causes the
lining on the leading shoe to wear more
quickly than that on the trailing shoe and at
the same time tends to lift the leading shoe
off the cam and press the trailing shoe
harder on to the cam. With a fixed cam
housing the result is that the majority of the
cam pressure is applied to the less efficient
trailing shoe. By leaving the housing free to
float the cam can follow up the leading shoe
thus maintaining equal pressure between the
cam and the two shoes and so making full
use of the more efficient leading shoe.
Owing to the servo action the wear on the
leading shoe with a floating cam housing is
greater than that of the trailing shoe and in
time the limit of float of the cam housing
will be reached, after which the brake will
continue to function as a fixed cam brake
with some loss of efficiency. This can be
restored by removing the shoes and fitting
them in the opposite positions. Floating cam
brakes are self-centering and there is no
need to take any special precautions to see
that the two linings are of equal thickness,
or that the brake shoe assembly is centered
in the drum.
11. Refitting Brake Cover Plate
After assembling the brake shoe pivot
pin and operating cam into the cover plate
repack the hub bearings with grease. The
recommended greases are Castrolease
(Heavy), Mobilgrease (No. 4), Esso Grease,
Energrease C3 or Shell Retinax A. These
are all medium heavy lime soap or
aluminium soap greases. The use of H.M.P.
greases which have a soda soap base is not
recommended as these tend to be slightly
corrosive if any damp finds its way in to the
hubs.
Before fitting the distance washer and
felt washer make sure that the inside of the
brake drum is quite clean and free from oil
or grease, damp, etc. and replace the brake
cover plate assembly. Securely tighten the
cover plate nut.
12. Wheel Rims
The rim used on the 250 Clipper and
Model "S" is type WM1-19 in., internal
width 1.60 in. The rim used on the other
models is type WM2-19 in., internal width
1.580in.
The rim diameter after building is the
same in each case, i.e. 19.062 in., the
tolerances on the circumference of the rim
shoulders where the tyre fits being
59.930/59.870 in. The standard steel
measuring tape for checking rims is 5/16 in.
wide, .011 in. thick and its length is
59.964/59.904 in. All rims are pierced with
forty holes for spoke nipples.
Note that two makes of rim are used
"Dunlop" and "Palmer Jointless." These
differ in the positions of the pierced spoke
holes. The Dunlop rims have a group of
three holes on one side of the centre line,
then a single hole on the other side, a
further group of three and a single hole and
so on. Palmer rims have the holes
alternately spaced either side of the centre
line. Both rims are interchangeable and both
use the same length spokes but the method
of lacing the wheel is different (see
Subsection 14). Neither types of the wheel
rim are symmetrical and care must be
www.hitchcocksmotorcycles.com
