Hydrolastic
Encyclopedia
Hydrolastic is a type of space-efficient automotive suspension system used in many car
s produced by British Motor Corporation
(BMC) and its successor companies.
Invented by famous British rubber engineer Alex Moulton
, and first used on the 1962 BMC
project ADO16
under designer Alec Issigonis
(of Mini
fame), later to be launched as the Morris 1100.
Although the official recipe contains triethanolamine phosphate and sodium mercaptobenzothiazole, many home mechanics refill the system without these two ingredients, and uses only alcohol (methylated spirits) and concentrated glycol antifreeze in a 50/50 ratio.
Each displacer unit contains a rubber spring, and damping is achieved by the displaced fluid passing through rubber valves. The displaced fluid passes to the displacer of the paired wheel, thus providing a dynamic interaction between front and rear wheels. When a front wheel encounters a bump fluid is transferred to the corresponding rear displacer then lowers the rear wheel, hence lifting the rear, minimising pitch associated with the bump. Naturally the reverse occurs when it is a rear wheel that encounters a bump. This effect is particularly good on small cars as small wheelbase vehicles are more affected by pitching than long wheelbase vehicles.
or subframe
replacement. Even welding the sub-frame to repair rust damage typically required the system to be drained. The only way to re-pressurize was to pay a properly equipped mechanic, usually at a BMC dealer. Inevitably the charge for this service was higher than many cared to pay.
of the Citroën DS
motivated Issigonis and Moulton, who were at the time of the launch of the DS working on a rubber and fluid suspension system themselves. Pressnell also suggests that the complexity of the Citroën system encouraged Moulton to develop a much simpler system.
In a magazine interview for 'CAR' magazine in the late 1980s, Dr Moulton stated that he and Issigonis had also studied the Citroën 2CV
in the 1950s, which featured fore/aft interconnected steel springs. They particularly wished to address the comical lack of roll stiffness of that car with the system that they were designing.
s produced by British Leyland and its successor companies.
Invented by British automotive engineer Alex Moulton
, Hydragas is an evolution of the previous Hydrolastic system. It was first introduced in 1973 in the Austin Allegro
and was later fitted to the 1975 Princess
and its successor, the 1982 Austin Ambassador
. Both systems attempt to address the ride-handling compromise of car suspension by interconnecting the suspension of the front and rear of the car in some way. Hydragas attempted to perform the same function and advantages as the hydropneumatic system developed by Citroën
, but without its attendant complexity.
The heart of the system are the displacer units, which are pressurised spheres containing nitrogen gas. These replace the conventional steel springs of a regular suspension design. The means for pressurising the gas in the displacers is done by pre-pressurising a hydraulic fluid, and then connecting the displacer to its neighbour on the other axle. This is unlike the Citroën system, which uses hydraulic fluid continuously pressurised by an engine-driven pump and regulated by a central pressure vessel.
Despite early problems (the Allegro version of Hydragas was found seriously wanting), it was gradually developed into an effective and efficient alternative to steel springs on later BL/Rover Group models such as the Austin Metro and MGF
.
The Austin Maxi
was the only in production car to feature both systems.. The Maxi featured 1100 designed Hydrolastic Units with the regulator valve fitted with the interconnection pipe. However in 1978 production of Hydrolastic bottles at Dunlop came to an end and BL modified the Leyland Princess
Hydrogas bottles to fit.
This involved fitting a new front subframe design,with a larger diameter horizontal chamber in the subframe.
Cars using the Hydragas suspension system:
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
s produced by British Motor Corporation
British Motor Corporation
The British Motor Corporation, or commonly known as BMC was a vehicle manufacturer from United Kingdom, formed by the merger of the Austin Motor Company and the Nuffield Organisation in 1952...
(BMC) and its successor companies.
Invented by famous British rubber engineer Alex Moulton
Alex Moulton
Dr. Alexander Eric Moulton CBE is an English engineer and inventor, specialising in suspension design.Moulton is the great-grandson of the rubber pioneer Stephen Moulton, the founder of the family business George Spencer Moulton & Co...
, and first used on the 1962 BMC
British Motor Corporation
The British Motor Corporation, or commonly known as BMC was a vehicle manufacturer from United Kingdom, formed by the merger of the Austin Motor Company and the Nuffield Organisation in 1952...
project ADO16
BMC ADO16
ADO16 is the codename for the development of what became the Morris 1100, a small family car built by the British Motor Corporation and, later, British Leyland...
under designer Alec Issigonis
Alec Issigonis
Sir Alexander Arnold Constantine Issigonis, CBE, FRS was a Greek-British designer of cars, now remembered chiefly for the groundbreaking and influential development of the Mini, launched by the British Motor Corporation in 1959.- Early life:Issigonis was born into the Greek community of Smyrna ...
(of Mini
Mini
The Mini is a small car that was made by the British Motor Corporation and its successors from 1959 until 2000. The original is considered a British icon of the 1960s, and its space-saving front-wheel-drive layout influenced a generation of car-makers...
fame), later to be launched as the Morris 1100.
Description
The system replaces the separate springs and dampers of a conventional suspension system with integrated, space efficient, fluid filled, displacer units, which are interconnected between the front and rear wheels on each side of the vehicle. The official recipe for genuine BMC/MG Rover fluid is as follows:- 49% alcohol
- 49% distilled water
- 1% triethanolamine phosphate
- 1% sodium mercaptobenzothiazole
Although the official recipe contains triethanolamine phosphate and sodium mercaptobenzothiazole, many home mechanics refill the system without these two ingredients, and uses only alcohol (methylated spirits) and concentrated glycol antifreeze in a 50/50 ratio.
Each displacer unit contains a rubber spring, and damping is achieved by the displaced fluid passing through rubber valves. The displaced fluid passes to the displacer of the paired wheel, thus providing a dynamic interaction between front and rear wheels. When a front wheel encounters a bump fluid is transferred to the corresponding rear displacer then lowers the rear wheel, hence lifting the rear, minimising pitch associated with the bump. Naturally the reverse occurs when it is a rear wheel that encounters a bump. This effect is particularly good on small cars as small wheelbase vehicles are more affected by pitching than long wheelbase vehicles.
Servicing difficulties
The system was not popular with home mechanics, as it had to be re-pressurized after a chassisChassis
A chassis consists of an internal framework that supports a man-made object. It is analogous to an animal's skeleton. An example of a chassis is the underpart of a motor vehicle, consisting of the frame with the wheels and machinery.- Vehicles :In the case of vehicles, the term chassis means the...
or subframe
Subframe
A subframe is a structural component of a vehicle, such as an automobile or an aircraft, that uses a discrete, separate structure within a larger body-on-frame or unit body to carry certain components, such as the engine, drivetrain, or suspension. The subframe is bolted and/or welded to the vehicle...
replacement. Even welding the sub-frame to repair rust damage typically required the system to be drained. The only way to re-pressurize was to pay a properly equipped mechanic, usually at a BMC dealer. Inevitably the charge for this service was higher than many cared to pay.
Influences
Jon Pressnell suggests in his book that the hydropneumatic suspensionHydropneumatic suspension
Hydropneumatic suspension is a type of automotive suspension system, invented by Citroën, and fitted to Citroën cars, as well as being used under licence by other car manufacturers, notably Rolls-Royce, and Peugeot. It was also used on Berliet trucks and is since recently used on Mercedes-Benz...
of the Citroën DS
Citroën DS
The Citroën DS is an executive car produced by the French manufacturer Citroën between 1955 and 1975. Styled by Italian sculptor and industrial designer Flaminio Bertoni and the French aeronautical engineer André Lefèbvre, the DS was known for its aerodynamic futuristic body design and innovative...
motivated Issigonis and Moulton, who were at the time of the launch of the DS working on a rubber and fluid suspension system themselves. Pressnell also suggests that the complexity of the Citroën system encouraged Moulton to develop a much simpler system.
In a magazine interview for 'CAR' magazine in the late 1980s, Dr Moulton stated that he and Issigonis had also studied the Citroën 2CV
Citroën 2CV
The Citroën 2CV |tax horsepower]]”) was an economy car produced by the French automaker Citroën between 1948 and 1990. It was technologically advanced and innovative, but with uncompromisingly utilitarian unconventional looks, and deceptively simple Bauhaus inspired bodywork, that belied the sheer...
in the 1950s, which featured fore/aft interconnected steel springs. They particularly wished to address the comical lack of roll stiffness of that car with the system that they were designing.
Hydragas
Hydragas is a type of automotive suspension system used in many carAutomobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
s produced by British Leyland and its successor companies.
Invented by British automotive engineer Alex Moulton
Alex Moulton
Dr. Alexander Eric Moulton CBE is an English engineer and inventor, specialising in suspension design.Moulton is the great-grandson of the rubber pioneer Stephen Moulton, the founder of the family business George Spencer Moulton & Co...
, Hydragas is an evolution of the previous Hydrolastic system. It was first introduced in 1973 in the Austin Allegro
Austin Allegro
The Austin Allegro is a small family car manufactured by British Leyland under the Austin name from 1973 until 1983. The same vehicle was built in Italy by Innocenti between 1974 and 1975 and sold as the Innocenti Regent...
and was later fitted to the 1975 Princess
Leyland Princess
The Princess is a family car that was produced in the United Kingdom by British Leyland from 1975 until 1981. The car inherited a front-wheel drive / transverse engine configuration from its predecessor, the BMC ADO17 range...
and its successor, the 1982 Austin Ambassador
Austin Ambassador
The Austin Ambassador was a medium-to-large hatchback car model introduced by British Leyland in 1982. The vehicle was a heavily updated version of the Princess, an ageing model that had lacked a hatchback...
. Both systems attempt to address the ride-handling compromise of car suspension by interconnecting the suspension of the front and rear of the car in some way. Hydragas attempted to perform the same function and advantages as the hydropneumatic system developed by Citroën
Citroën
Citroën is a major French automobile manufacturer, part of the PSA Peugeot Citroën group.Founded in 1919 by French industrialist André-Gustave Citroën , Citroën was the first mass-production car company outside the USA and pioneered the modern concept of creating a sales and services network that...
, but without its attendant complexity.
The heart of the system are the displacer units, which are pressurised spheres containing nitrogen gas. These replace the conventional steel springs of a regular suspension design. The means for pressurising the gas in the displacers is done by pre-pressurising a hydraulic fluid, and then connecting the displacer to its neighbour on the other axle. This is unlike the Citroën system, which uses hydraulic fluid continuously pressurised by an engine-driven pump and regulated by a central pressure vessel.
Despite early problems (the Allegro version of Hydragas was found seriously wanting), it was gradually developed into an effective and efficient alternative to steel springs on later BL/Rover Group models such as the Austin Metro and MGF
MG F
The MG F and later the MG TF are mid-engined, rear wheel drive roadster cars produced from 1995 onwards. The MG F was the first all-new car to bear the MG marque since the MG MGB, produced from 1962 to 1980...
.
The Austin Maxi
Austin Maxi
The Austin Maxi was a medium sized 5-door hatchback car from British Leyland for the 1970s. It was the first British five speed five-door hatchback.-History:...
was the only in production car to feature both systems.. The Maxi featured 1100 designed Hydrolastic Units with the regulator valve fitted with the interconnection pipe. However in 1978 production of Hydrolastic bottles at Dunlop came to an end and BL modified the Leyland Princess
Leyland Princess
The Princess is a family car that was produced in the United Kingdom by British Leyland from 1975 until 1981. The car inherited a front-wheel drive / transverse engine configuration from its predecessor, the BMC ADO17 range...
Hydrogas bottles to fit.
This involved fitting a new front subframe design,with a larger diameter horizontal chamber in the subframe.
Cars
Cars using the Hydrolastic suspension system:- BMC 1100BMC ADO16ADO16 is the codename for the development of what became the Morris 1100, a small family car built by the British Motor Corporation and, later, British Leyland...
- MiniMiniThe Mini is a small car that was made by the British Motor Corporation and its successors from 1959 until 2000. The original is considered a British icon of the 1960s, and its space-saving front-wheel-drive layout influenced a generation of car-makers...
(from 1964 to 1971) - Austin America (from 1968 to 1971)
- Austin 1800Austin 1800BMC ADO17 was the model code used by the British Motor Corporation for a range of cars produced from September 1964 to 1975 and sold initially under its Austin marque as the Austin 1800. The car was also sold as the Morris 1800 and Wolseley 18/85, and later as the Austin 2200, Morris 2200 and...
- Austin MaxiAustin MaxiThe Austin Maxi was a medium sized 5-door hatchback car from British Leyland for the 1970s. It was the first British five speed five-door hatchback.-History:...
(Until March 1978) - Austin 3-LitreAustin 3-LitreThe Austin 3-Litre was a British saloon car introduced by British Leyland at the London Motor Show in 1967. However, it subsequently became apparent that BMC were not geared up to producing the car: few or none seem to have been sold that year, but by July 1968 it was reported that the cars had...
- MG 1100 (from 1962 to 1968)
- Morris 1500
- Huffaker Indianapolis cars 1964-1969 "MG Liquid Suspension Special"
- Wolseley Hornet Wolseley HornetWolseley Hornet was the name of two different British vehicles produce under the Wolseley Motor Company nameplate.* Wolseley Hornet , lightweight saloon car produced in the 1930s....
- Riley Elf
- Riley Kestrel
- Wolseley 1100
- Wolseley Six
Cars using the Hydragas suspension system:
- Austin AmbassadorAustin AmbassadorThe Austin Ambassador was a medium-to-large hatchback car model introduced by British Leyland in 1982. The vehicle was a heavily updated version of the Princess, an ageing model that had lacked a hatchback...
- PrincessLeyland PrincessThe Princess is a family car that was produced in the United Kingdom by British Leyland from 1975 until 1981. The car inherited a front-wheel drive / transverse engine configuration from its predecessor, the BMC ADO17 range...
- Austin AllegroAustin AllegroThe Austin Allegro is a small family car manufactured by British Leyland under the Austin name from 1973 until 1983. The same vehicle was built in Italy by Innocenti between 1974 and 1975 and sold as the Innocenti Regent...
- Austin MaxiAustin MaxiThe Austin Maxi was a medium sized 5-door hatchback car from British Leyland for the 1970s. It was the first British five speed five-door hatchback.-History:...
(From March 1978 onwards) - Austin Metro
- Rover MetroRover MetroThe Metro is a supermini car that was produced by the Austin Rover Group division of British Leyland and its successors. It was launched in 1980 as the Austin miniMetro. It was intended to complement the Mini, and was developed under the codename LC8....
- Rover 100Rover 100The name Rover 100 may refer to one of two different British motor vehicles:* Rover P4 100; produced by The Rover Co. Ltd. from 1960-62* Rover Metro, at various times also known as the Austin Mini Metro and Rover 100, amongst other names; produced by Austin Rover Group and MG Rover Group from...
- MGFMG FThe MG F and later the MG TF are mid-engined, rear wheel drive roadster cars produced from 1995 onwards. The MG F was the first all-new car to bear the MG marque since the MG MGB, produced from 1962 to 1980...
External links
- The Hydragas Register - a website helping owners of hydragas and hydrolastic cars to find a garage or individual who can carry out a pump up service in their area.