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Download scientific diagram | Moulton’s Hydragas suspension system [21] from publication: Recent developments in passive interconnected vehicle suspension . Find great deals on eBay for mgf hydragas suspension. Shop with confidence. Hydragas suspension (Moulton-Dunlop) the conical piston and the tapered displacer chamber skirt as the suspension deflects up and down when the wheels.

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English language Original Source http: A stiffness matrix was generated that included terms due to individual unit and interconnection effects.

Dynamic tests were performed at various sinusoidal amplitudes and frequencies to calculate the damping matrices. One unit was held at its datum position while the other was moved. The damping force vs. Three models were developed to predict forces transmitted through the units. The first was a linear model that showed reasonable accuracy over restricted frequency ranges.

The second model used bilinear spring and damping suspenwion, and was accurate for predicting force at both the front and rear units for frequencies from 1 to 10 Hz.

The third model treated the inertial and hydeagas effects by inserting a mass into the spring-damper system. The magnitude of the mass was estimated based on the areas of the damper force vs. The Hydragas System Designers have considered for decades the interconnection of the front and rear wheels as a means by which to reduce unpleasant pitch behaviour of small cars. In an interconnected, or “equalising” suspension, the front and rear wheels on each of the suspeneion and suspenson sides are interconnected, forming two independent systems wherein an input at one wheel will cause a force to be generated at the other.

A forward-travelling car will first encounter disturbances at the front wheels that tend to lift the front of the car in relation to hydtagas rear. Interconnection has striven to transmit some the upward vertical motion of the front wheel into a downward force exerted by the sprung mass on the rear wheel, through the rear suspension. Reducing the differential hyddragas front and rear suxpension on the car body induces more of a bounce mode of vibration than a pitching mode.

Pitching motion, which causes fore-and-aft movement of the occupants, is generally regarded as being more objectionable than bounce motion [1]. Smaller cars are particularly susceptible to being set into a pitching mode compared to large cars, and it is this “choppy” quality to which many people attribute the inferior ride of small cars.

The Hydragas suspension was developed by Dr. Alexander Moulton of Great Britain to improve the ride quality of small cars. The system uses nitrogen gas as the springing medium and hydraulic fluid pressure drop as the damping mechanism.

Hydrolastic – Wikipedia

Suspensioon damping fluid chambers of the front and rear wheels on each side of the car are connected via a hydraulic hose, such that an input at the front wheel pumps fluid through the pipe to the rear wheel. The increase in fluid pressure at the rear unit creates an upward force on the sprung mass, thus reducing the differential between suspension forces on the front and rear of the car body.

Figure 1 [2] depicts a later-generation Hydragas unit. Each unit contains both a gas spring and a damper spring Figure 1 – Hydragas Suspension Unit Cutaway [2] A butyl rubber separator, in concert with metal sealing rings and overlapping case pressings, seals the nitrogen gas from the fluid.

Hydragas Suspension Info

The lower diaphragm is composed of a sealing rubber layer atop a structural rubber layer. Upward vertical movement of the tapered aluminium piston increases the area of the diaphragm against which fluid pressure acts, and vice versa.

Sufficient pressure differential between the upper and lower chambers compresses either the bump or rebound compression block, increasing fluid hhdragas as a function of pressure difference. The Hydragas units used in the present research project were from the new Rover MGF sports car, and featured a smaller-volume gas chamber and a damper valve of different construction.

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The function of the compression blocks was performed by normally-closed metal leaf-spring flaps. Figure 2a [2] shows the general response of an interconnected Hydragas system to pitch-inducing motions in which the front wheel is lifted in relation to the car body, while the rear wheel is lowered.

The upward motion suspnesion the front wheel in pitch displaces fluid to the rear unit, causing the rear wheel to exert an upward force on the car body. Simultaneous upward front wheel and downward rear wheel motion not only positively displaces supsension also draws fluid from the front to the rear unit.

The stiffness, or resistance of the system to such wheel motions, is clearly lower than it would be were the interconnection removed. The variable-area pistons stabilize the pitch oscillations. After the wheel motion of Figure 2a occurs and pressure stabilizes in the system, the larger area of the front piston causes a higher downward force on the front wheel than does the fluid pressure acting on the smaller piston area of the rear unit.

The piston area variation thus produces a restoring moment about the pitch axis. Figure 2b [2] depicts response in pure bounce or roll in which both wheels suspesion one side of the car move the same distance in relation to the body. No flow occurs from one unit to the other, with flow occurring only between hydeagas upper and lower chambers of individual units through the damper valves.

The increase in piston area with higher bounce motions causes the resultant increase in fluid pressure to produce an increasingly higher downward restoring force on the wheels. The system thus has a progressive rate characteristic. The combination of higher fluid pressures and increasing piston areas give the system a higher stiffness in bounce and roll than in pitch, possibly obviating the need to fit a front anti-roll bar [2].

Society suspemsion Automotive Engineers. Other Interconnected Suspension References 1. Council of the I Mech. Anyway, for all you Moulton fans out there here’s an article on the great man that I have cheekily culled from the pages of “MiniWorld. Hydrabas, at this time Ford’s state of the art small car was the angular Anglia; Ford’s answer to the Suspensoin Minor and only 11 years late.

He gave us some insights into the development of the Car of the 20th Century – and his opinion on the BMW Mini of the 21st century. After the Second World War I was determined to move my family firm — Spencer-Moulton based at Bradford on Avon — from the manufacture of rubber suspension for railway coaches, and into suspensikn suspension.


I had heard of Alec Issigonis by reputation and we met socially before we worked together. He was given a free hand to do what he liked, more or less. It had been driven over miles on the pave at MIRA, an unimaginably tough test that the standard car would not have been able to withstand. Issigonis was determined that he should have interconnected fluid and rubber suspension on his Alvis. Interconnecting front and rear suspension units with fluid in pipes meant that the pitch mode was separated from bounce and roll.

As a result, the car moved smoothly over a bump in the road, giving a much higher quality ride. Lord was determined to make a range of new and innovative cars, and he plucked Alec Issigonis back from Alvis to design them. The Suez crisis occurred in and petrol rationing meant that tiny bubble cars, mostly of German manufacture and including some BMW-Isetta models, began to flood the roads.

Lord wanted to sweep them away and so Issigonis got the order to build the smallest of his new cars first, a proper miniature four-seater.

BMC took a shareholding and paid all the costs of development. This left me free to work on the things I wanted to do. I had previously designed the rubber cone suspension system — it was a specially shaped rubber and metal unit that gave a smoothly rising spring rate. This meant that, when the car cornered or went over a bump the suspension stiffened up as it was deflected. When practically undeflected ie: We fitted this system to the original Mini of They had total authority from Lord: The whole of the Midlands was committed to the new project.


OK, there were some small problems, such as the floorpan sealing, but when you think of all the technical innovation in that one small vehicle, it was amazingly right, and look how little fundamental change it then needed in the following 40 yearsl The next suspension innovation for the Mini was the Hydrolastic system introduced to the saloon models in They were filled with a water and antifreeze mixture and interconnected front to rear via pipes under the car.

This gave the car a rising and falling motion rather than the sudden pitching of the rubber cone system. Alex Moulton takes up the story once more The Morris was introduced in with the first Hydrolastic installation. It was a great success, and Ford in particular were very upset by it. Dunlop and Moulton Developments took some time to make a unit small enough to fit in a Mini, but it was done by the early s. The whole Mini racing thing was started by John Cooper. We never thought about racing during the design phase; we were worried about safety, particularly when the car was overloaded with lots of students aboard or such like.

In this later version of the interconnection principle, the rubber cone was replaced by using a gas under pressure. Hydragas was introduced with the unloved Austin Allegro in the s and is still in use on roads today fitted to the MGF. Hydragas was never fitted to a production Mini, but Alex Moulton has some fascinating prototypes in his stable: We were able to take a short trip in both of these cars, and the sophistication of ride and handling has to be experienced to be believed.

We then worked with Rover on the Minky 2, a one-off based on extended Mini sheetmetal that was essentially a test rig for a potential suspension set-up for their new car.

However, there was a major personnel change at board level. Bernd Pischetsrieder, with whom I had had encouraging discussions left and the decision was taken that the new Mini should be wholly conventional in its suspension.

The original] Mini was the best-packaged car of all time this is an example of how not to do it.

The crash protection has been taken too far. I mean, what do suspdnsion want Princess Diana was killed in a two-tonne Mercedes: With the original Mini, we set out to prevent any accidents by having excellent handling, not by cushioning people from the consequences of their own folly The old Mini was the absolute apogee of this philosophy of built-in safety via the handling —people avoided accidents by driving around them. His conclusion was basically that he would not want to drive it on anything other than dead-smooth tarmac.

I can do no better than to paraphrase his published thoughts: I suggest that these duspension will have the Issigonis layout supension transverse engine and front wheel drive. Their suspension could comprise fore and aft fluid interconnection to separate pitch from bounce and roll. These cars could have uncompromised damping which, with the wheel at each corner layout.

Past and Future — Institution of Mechanical Engineers. Automobile Division, Amazingly. He gave us some insights into the development of the Car of the 20th Century – and his opinion on the BMW Mini of the 21st century After the Second World War I was determined to move my family firm — Spencer-Moulton based at Bradford on Avon — from the manufacture of rubber suspension for railway coaches, and into automotive suspension.