Front
wheel drive was unique
and
fluid suspension unheard of
in
1965.
This
is the system already made famous by the Morris 1100 and Mini De Luxe.
This
miraculous fluid suspension is the simplest yet most effective suspension
system ever devised. No moving parts to repair or maintain. Gives cushioned
riding comfort, free from bumps, bounce, pitch, lean and sway.
Gives
miraculous roadholding, even on the most tortuous tracks. BMC
Australia's advertising statement.
Here
is what BMC engineers had to say about both.
As
for the 'east-west' engìne layout, the theoretical attractions of
driving the front wheels from a front-located engine transmission unit
are:
1
. The
engine and transmission occupy a space so restricted by the need for wheel
clearance on full lock that it is of limited value for the alternate carriage
of luggage.
2. For
a given length of car the cubic content of the rear luggage boot is considerably
enhanced, as there need be no intrusion from a rear axle beam. The absence
of this also provides space beneath the rear seats.
3. As
there is no intrusion by the clutch housing, gearbox or propeller shaft,
the floor can be set a ground clearance level and, from this, good headroom
given within low overall height.
4. The
reduced height improves maximum speed by diminishing frontal area, and
this enhances stability by lowering the centre of gravity and lessening
roll angles.
5. On
straight roads directional stability is improved by the forward position
of the centre of gravity in relation to the centre of wind pressure.
6. On
corners maintained power through the tyres promotes the understeer condition
best suited to the technique of normal drivers but, in an emergency, shutting
the throttle will bring the car back sharply onto a closer radius - that
is, to its own side of the road.
7. In
extreme conditions of ice or snow, the car will follow the direction in
which the front wheels are steered, even in conditions of wheel spin,
provided any adhesion remains.
8. By
comparison with front engine and rear driven cars, adhesion on the driven
wheels is improved in that they carry considerably more than half the
laden weight.
There
are four major reasons why Alec lssigonis did not hesitate to apply his
ADO 15 (Mini) philosophy to the ADO 17 (1800). In all the years and millions
of miles experienced since the first ADO 15 Mini took to the road in August
1959, it has been proven that:
l. An
all direct drive from the crankshaft to the final drive does not bring
with it objectionable noise, even when big mileages have been reached.
2. No
disadvantages attend a common casing and a common lubricant for the crankshaft,
the gearshaft, and the final drive.
3. The
use of Moulton elastic inner universal joints gives a sweet, cushioned
drive with absolute reliability.
4. The
employment of Birfield constant velocity joints (built under Rzeppa and
Cull patents) confines reaction transmitted to the steering wheel to that
arising from the self straightening properties of the tyres, and permits
an angle of lock which provides an acceptable turning circle.
Simplicity
is the keynote of the Hydrolastic suspension, as no glands or wearing
parts are used anywhere. The hydraulic system is hermetically sealed during
assembly of the ADO 17 and needs no further maintenance. Seasonal temperature
changes in any one territory do not affect the trim height to any considerable
extent, but provision is made for trim adjustment under global extremes
of temperature. As is now well known, fluid is the medium used within
the Hydrolastic unit to transfer the weight of the car to the main springs
and also act as the main damping medium. The design is such that no glands
are needed to prevent escape of fluid. lndeed, if glands were used, it
might have been necessary to incorporate a motor-driven pump, and very
complex levelling devices to control this pump's action. There are essentially
three parts in the Hydrolastic unit:
1. The
hydraulically actuated rubber spring, which resembles an inverted cone
spring but has the bonded area of the pressed-steel inner cones less than
that of the rolled-steel outer canister. Under hydraulic pressure the
spring deforms axially, and has the desirable rising rate characteristic.
Attached to the top of the inner cone is a flexible rubber hose allowing
for movement of the spring, and uniting it with ½" diameter
Bundy tubing which is, of course, the inter-connecting piping.
2. The
damper assembly, positioned between the hydraulic spring and the displacer,
comprises simply of two rubber flap valves, one either side of the pressed-steel
port plate which is pierced by four identical ports, each flap covering
two ports. The upper flap damps the bump movement, and the lower the rebound.
These flaps are prevented from rotating by steel clips; there is a permanently
open bleed hole.
3. The
displacer, which consists of the diaphragm with its separate impermeable
butyl liner, to contain fluid pressure: it has its outer 1/4" diameter
bead clamped between the rolled-over periphery of the port plate and the
flanged upper end of the skirt, and its inner 3/16 " diameter bead
buttoned on to the pressed-steel piston.
The
development of this diaphragm by Dunlop was a vital factor in the success
of the entire Hydrolastic system. lt is, in fact, a rubber moulding of
'diabolo' construction, reinforced with 424 nylon cords each 0.022 "
diameter, and it can withstand burst pressures of over 200 lbs per square
inch. The effective area of the diaphragm increases as the piston advances
into the tapered skirt, so that the load on the piston with a given hydraulic
pressure also increases: the rate due to this effect, whìch the Hall
christened the taper rate, contributes to the overall rate of the unit.
Finally, the complete Hydrolastic unit is formed by contracting the rubber
lined outer canister of the hydraulic spring around the displacer assembly.
This joint is capable of withstanding a static pressure of 1,500 lbs per
square inch. An essential feature of the Hydrolastic system to ensure
constancy of trim height is that of sizing the unit. This is done by machining
the top of the canister so that the overall height of the unit is held
to within ± 0.02" at a constant pressure of 200 lbs per square
inch, and a dead load of 2,000 lbs.
You
can see on examining any ADO 17, the Hydrolastic unit at each wheel carries
the vehicle weight through a suspension arm. This provides a leverage
of 3.95:1 at the front, and 4.4:1 at the rear. These different leverages
were chosen to accommodate the heavier front load of the ADO 17, at the
same time using common units front and rear. The complete Hydrolastic
unit weighs 9 lbs, of which 1.9 lbs is the weight of the rubber spring.
On the assembly line each side of the system is evacuated to an 80% vacuum
through a Schrader valve fitted into the front connection between the
hose and the inter-connecting pipe.
The
liquid, (there is no Moulton secret about this) ... is a solution of 49%
alcohol, 49% distilled water, 1% sodium mercaptobenzthiazole, which is
of constant viscosity, and has a freezing temperature of 31 degrees Celsius,
is then put in and pressured to 400 lbs per square inch, lifting the vehicle
on to its rebound stops. Pressure is held for 30 minutes and this eliminates
primary creep from the rubber spring; it is then reduced to the standard
figure (unladen) of 205 lbs per square inch.
Why
We Did the 1800.........
(Alec
lssigonis)
"I
am proud that in 1964 my team has been able to round off the front drive
family with the Austin 1800, which benefits from all the knowledge and
experience accumulated over the past years. We retain the east to west
layout with a new five bearing engine whích once again drives down
to four gears, transmitting power to the front wheel.
The
independently sprung wheels are placed as near as possible at the four
corners of the car. This contributes to accurate steering control and
high standards of road holding.
As
pioneers of bold projects in the past few years we have been most grateful
to the support that we have received from all kinds of people all over
the world. This new design consolidates our position in this field. We
believe that this new car will set new standards for performance, economy,
longevity, and comfortable travel for up to five people, their luggage,
and personal effects.
Planned
obsolescence is foreign to Austin thinking where engineering for economic
long life is, and always has been, a first principle. Many of Lord Austins
cars are still giving useful service with thírty years' life behind
them. Ten years from now the new Austin 1800 will still have an up-to-date
engineering specification."
|
Alec
lssigonis
Technical
Director
The British Motor Corporation Ltd |
 |
FRONT WHEEL DRIVE EAST WEST ENGINE
The
Monte Carlo Rally has proved the outstanding virtues of front wheel drive.
In
fact, the last five Montes have been won by cars with this unique feature,
in 1964, and again in 1965, the honours going to the BMC Mini Cooper 'S'.
These
hard-fought performances have demonstrated the vastly improved traction
and roadholding on all road surfaces.
The
Austin 1800 combines this valuable feature with the space saving virtues
of BMC's east-west engine design.
BMC
Australia's advertising statement.
These drawings, from the pen of Alec Issigonis, are arguably the best sketches for a family car ever produced.
His
bold concept of front wheel drive and fluid suspension, were unheard of
at the time.
Simple
in design from an engineering viewpoint, with many safety features built
in. These sketches epitomise the sheer brilliance of Alec Issigonis.
Original BMC 1800 drawings from the sketchbook of
Alec Issigonis
