Page 47 - Vauxhall 20-60 H.P. (R Type) Chassis Shop Manual

VAUXHALL 20-60 SHOP MANUAL

GROUP V

BRAKES, FOUR WHEEL

DESIGN AND METHOD OF OPERATION

( See Figure 8 )

SECTION The four wheel brakes are mechanically operated. Each brake is operated
250 by a separate cable coupled to a central brake compensating mechanism.

The pressure applied to the pedal ‘A’ is transmitted through a rod ‘B’ to a
lever ‘C’ mounted on the tube ‘D’. This latter tube fits over part of another
tube ‘E’ carried in roller bearings and to the centre of which is pinned the
tube ‘D’. The stiffness of the tube ‘E’ is so arranged that it springs a small
amount when the brake is applied and so affords a sufficient degree of
compensation between the brakes on either side of the chassis. On each end
of the shaft ‘E’ is a lever ‘F’, from which is suspended a swinging link ‘G’,
called the compensating lever, the purpose of which is to fix the ratio in which
the total braking effort is divided between front and rear. As the front and
rear cables move in opposite directions, the forward movement of the lever
‘F’ causes the compensating lever to swing until both sets of brake shoes are
just rubbing the drums, after which it acts as an ordinary lever.

The front brake shoes are operated by a wedge ‘H’ working between rollers
which, in turn, transmit the pressure to the ends of the shoes ‘J’ by means
of spherical-ended struts. The shoe supports swivel on knife edges in place
of the usual plain bearings, as the plain bearing is only satisfactory so long

as it is kept well lubricated and free from all grit, conditions very difficult
to fulfil in the brake gear of a car. The hardened steel knife edge, on the
other hand, requires no lubrication and its efficiency is unaffected by dirt,
thus mitigating the troubles due to seized brake gear and at the same time
considerably reducing friction. Similar principles have been applied to the
rear brakes, although the method of operation is different. The shoes are
expanded by a lever ‘K’ working on a knife edged thrust block ‘L’ carried
in the top of the leading shoe and re-acting on the trailing shoe through a
spherically ended strut ‘M’.

The only point in the whole of the footbrake gear which requires lubrication
is the pedal bearing, a grease nipple for which is fitted in the offside of the
frame opposite the pedal shaft.

FOOT BRAKE PEDAL — TO REMOVE

SECTION – Remove the pin connecting the thrust rod to the lower lever of the brake
251 pedal. Remove the three hexagon headed set screws which hold the pedal

shaft bracket to the inside of the frame. The pedal assembled to the shaft
can then be removed. Remove the split pin and plain washer from the end
of the shaft, which can then be withdrawn from the pedal bearing.
Page 43.