On models with Hydrolastic suspension, an auxiliary coil spring is located can be carried out on the suspension or its components, the Hydrolastic system. Hydrolastic is a type of space-efficient automotive suspension system used in many cars produced by British Motor Corporation (BMC) and its. 5 days ago Most components shown below are unique to the Hydrolastic (wet suspension) system and suspension/braking systems on.

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A British sports car concept featuring the Bluebird cartridge exchange instant recharging system. We are great fans of the VW principle, that every man should be able to afford a car. In fact that was Hitler’s plan, where VW stands for “peoples car.

Porsche came up with a superbly simple design in the Beetlethat is unfortunately not suitable as an EV donor. The Metro above turned out to be just the ticket. The rules for the Cannonball ZEV International Runs are simple, you must use production vehicle running gear – the car must be road legal.

The ultimate prize is the Blue Bird World Cup. These cars used rubber cone and compressed gas suspension units with cross-axle liquid exchange known as Hydrolastic, or Hydragas suspension. When servicing suspension bearings and joints using the rubber cone hydrolastic and hydragas system s it is necessary to de-pressurize the fluid to effect replacements.

The UK team want their vehicle to be in tip-top condition so will be servicing the suspension roller bearings and spindles along with other brake and steering parts.

This is the basic suspension layout of the Metro, actually this is a picture Mini subframes. But they are very similar and of course the Metro was derived from the Mini design, an evolution rather than the Mini revolution. The Mini being the most popular car ever produced in the UK, with over 5, million cars sold worldwide.

The Rover Metro’s Hydragas suspension has sealed hydraulic displacers, one at each wheel connected on each side of the car by a reinforced plastic pipe. When a front wheel hits a bump, the upward force is transmitted to the fluid in the lower diaphragm. This in turn transmits the pressure to the gas in the upper diaphragm, which compresses to absorb the shock. At the same time, fluid is forced through the pipe to the rear unit. The result is that the floorpan stays level: At the same time, the redesigned geometry helps to prevent dive and lift on braking and acceleration, giving an impressively smooth, level ride.

Hydrolastic suspension has a rubber spring built into it – a sort of mini cone, when compared to the Mini dry cones, while hydragas uses a compressed gas spring. No rubber, which is sure to have made Dr Moulton cry. Both are suspension systems rather than just springs, in that they include a damping system to slow the action of the suspension. The operation of both systems is the same, operating in the same dimensional space. Thus, they are interchangeable. The main objective of using fluids, is to hydraulically link the front to the rear, to provide a more level ride.

The smoother the ride, the less energy the car will need to drive it along the tarmac. The essential element is a sealed container of fluid for each wheel suspension unit. Hence there are four sealed containers to replace coil springs for example.

These are then linked fore and aft; the left front linked to the left rear, along with the right front linked to the right rear. In this diagram the left unit is uncompressed and the right compressed. There are two containers for each unit as seen in the diagram above, stacked on top of each other, with the nitrogen gas spring above the fluid filled chamber below.

The lower chamber is linked hydraulically to the fluid chamber at the opposite end of the car. In order to flow to another unit, the fluid has to flow through a valve assembly between the two containers, and then through a long pipe to the other unit.

The idea is that if the front wheel hits a bump, the compression of the suspension pushes the fluid to the rear unit. The process is reversed when the rear wheel reaches the bump, again keeping the car level. This works for potholes as well as humps – useful today where the roads are so poorly maintained.


Thomas Telford would be appalled. The front hydragas unit is compressed by a bump, sending fluid to the rear which caused the swing arm to push down – so lifting the car by the same amount as the front wheel goes up – canceling out the bump. Some of you may have noticed the opportunity that such a system provides in terms of micro energy generation. This would not have occurred to Moulton or Issigonis, because of course their cars were petrol powered. Ours is electric with a battery store as a load leveler.

See the example micro generators at the foot of this page – all of which are too large for this application. It is the valve between the two containers that limits the rate at which any one suspension unit can compress or extend, and the diameter of the pipe that limits how quickly the transfer between either side’s front and rear units can occur, providing the damping within the system.

The next question is; what happens if both front and rear units are compressed at the same time, when they’d cancel each other out? The answer is that the top containers of each unit have a spring inside them – rubber on the hydrolastic system and gas in the hydragas units.

With the lower containers being squeezed by the suspension, and no way out of the upper containers as in escape to hydrolastlc other end of the car the fluid’s only choice is to compress the spring, giving pretty much the same suspension action as if the spring itself was being compressed directly.

Why doesn’t the fluid itself compress?

That is because of a basic hydrolwstic of physics that says a fluid in incompressible. Of course we don’t want it to compress, so it’s made up or water mostly with some anti-freeze and anti-corrosion agents added. Coloring is added to help show up leaks or contaminated fluid easily. The reason nitrogen gas is used, is because it is an “inert” gas – it is stable and does not react with most things, nor pressure or temperature.

A compressed gas spring gives a rising-rate performance, too, just like a rubber spring. It all looks so simple and it is, but it took a lot of working out how to produce a suspension system using rubber to begin with and fluid. Both systems are designed to be fit-and-forget parts or sealed units.

History has shown that they have a working life in the region of 15 years and more before leakage susspension corrosion become issues. They provide an excellent quality of ride without compromising handling, and, providing the damping is set up correctly, don’t “wallow” under cornering, braking and accelerating.

The continued development of hydragas eventually led to fully cross-linked systems joining both the left and right sides together to make the most of the benefits. Today, there are more modern systems that can outperform hydragas systems, but at greatly increased cost, and this level of performances was achieved over four decades ago, with relatively basic mechanical parts that lacked any kind of “active” or feedback control on them. Imagine how good they could be if they were active? We’ll stay with what works for now, because the design outperforms most production cars today.

There is no point re-inventing the wheel when there is more work to do on the EV drivetrain. During the war he had worked on engine design at the Bristol Aeroplane Company. In the late s, after the acquisition of the family business by the Avon Rubber Company, Moulton started up a new company, Moulton Developments Limited, to design the suspension system for British Motor Corporation’s new small car, the Mini, that was being designed by his friend Sir Alec Issigonis.


The combination of conical rubber springs and small wheels was one of the many innovative developments that allowed Issigonis to achieve the Mini’s small overall size. Alex Moulton with his most famous designs, the Moulton cycle with full rubber suspension and the Mini’s rubber cone suspension. Moulton also designed the Moulton Bicycleagain using rubber suspension and small wheels. Dr Moulton founded his own company, Moulton Developments Ltd, in and worked closely with the British Motor Corporation BMC for many years, developing automobile suspension systems.


Later, he was responsible for the Hydrogas system, which was developed for the Austin Allegro car and is still in use on the Rover series and the MGF. Alongside the development of suspension systems for cars, Dr Moulton designed his revolutionary Moulton Bicycle.

He explained that this was: We would agree with him. The Moulton bicycle was the original full- suspension bicycle, highly efficient and designed with superior performance and comfort in mind. These bikes are lighter, safer and more comfortable, yet still go faster than most as well! The Moulton Bicycle is now a design classic, which has continued to be developed over many years, spawning a massive following of devotees and a wide range of models and variants.

They worked together on rubber and hydrolastic suspension – to give the UK some huge motoring successes. Sadly, the UK is backward in thinking forward on most fronts, thus surrendering a technological lead for lack of investment – the inability to predict the future such at to cater for the future is a major UK failing; part of the stiff upper lip attitude that sends pioneers elsewhere.

Sir Alex was just under 6ft tall with large expressive hands. He hated all things big – big cars, big organisations, big houses – and loved to shock his listeners. Starting aroundhe raced a supercharged “Ulster” Austin Seven, later fitting it with a front axle of his own design, leading to employment at Austin. This greatly modified machine was replaced with a radical special completed inconstructed of plywood laminated in aluminium sheeting.

Hydrolastic – Wikipedia

The suspension was also of advanced design, with trailing arm front suspension attached to a steel cross-member, and swing axle rear, all with rubber springs made of catapult elastic. This car was remarkably light, weighing lb, of which the engine contributed lb.

By the time the chassis had been completed hard labour – it was all done by hand, no power toolsIssigonis had moved to Morris Motors Limited, but Austin supplied a “works” specification supercharged side-valve engine. Issigonis usually won, even when entered in the cc class if there was no cc category.

Most events entered were sprints, but he also raced at circuits. Alec Issigonis at the drawing suspeension. He was a practical engineer who had hand built a car in plywood and aluminium for some racing success, before he went on to work on rubber suspension and the Mini motor car.

By earlyprototypes were running, and by mid the project was given an official drawing office project number ADO15 so that the thousands of drawings required for production could be produced.

In later years, the car would become known simply as the Mini. Due to hysrolastic pressures, the interconnected suspension system that Issigonis had planned for the car was replaced by an equally novel, but cruder, rubber cone system designed by Alex Moulton. The Mini went on to become the best selling British car in history with a production suspensiin of 5. This ground-breaking design, with its front wheel drive, transverse engine, sump gearbox, zystem wheels, and phenomenal space efficiency, was still being manufactured in and has been the inspiration for almost all small front-wheel drive cars produced since the early s.

Many hydrolastic systems need an occasional top-up of hydrolasitc hydragas fluid to maintain the correct ride height, which in turn ensures the correct suspension characteristics.

Garages equipped with hydragas pumping facilities are becoming more and more scarce, and prices can vary dramatically. Manufacturer MG Part Number: A homemade evacuation and high-pressure system based on a bottle jack hydraulic pump. You’ll need a vacuum pump to complete the system. It was designed by Eric Crewdson in The maximum efficiency of an impulse hydrolzstic is achieved when the velocity of the runners at the center line of the nozzle is half the velocity of the incoming water.