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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 their shorter wheelbases are more affected by pitching.
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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
290:
Hydragas bottles to fit. This involved fitting a new front subframe design, with a larger diameter horizontal chamber in the subframe. MGF was the last vehicle platform to use this design. The
Hydragas system was dropped in favour of conventional suspension by Rover when BTR AVS sought to increase
178:
The design of the displacer units, and the way in which they are mounted means that as the suspension is compressed, the (roughly spherical) displacer deforms, and hence presents a larger area to the mounting plates. The pressure in the system is thus acting over a larger area, and hence applying
171:
However, the key improvement over conventional suspension is that the front/rear interconnection allows the vehicle to be stiffer in roll than in pitch. Hence it is possible to design a compliant suspension - giving a comfortable ride - without suffering a penalty in terms of excessive roll when
182:
Cars with
Hydrolastic suspension do, however, have a marked tendency to squat under acceleration, and to dive under braking (and for the rear end to sag under heavy loads). This requires clever design of the suspension components to minimise these forces, and to maximise the rising rate
446:
Later 'New Series' Moulton bicycles are fitted with rear suspensions systems marketed as 'Hydrolastic'. These are, in essence, miniaturised versions of the displacers used on
Hydrolastic-equipped cars being a rubber cone spring with an internal fluid chamber to provide damping.
270:. The Metro originally featured independent Hydragas units, with no fore/aft interconnection (the pipework was deleted on cost grounds, against the advice of Moulton). While the Metro was praised for its handling, and offered a significant improvement in ride quality over the
285:
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
253:
The heart of the system is 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
199:
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 Citroƫn system encouraged Moulton to develop a much simpler system.
172:
cornering. In roll, there is no transference of fluid from the displacers, and hence its internal pressure rises. The only "give" in the suspension occurs because of the inherent flexibility of the rubber springs. These are naturally stiff.
242:. 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
258:, and then connecting the displacer to its neighbour on the other axle. This is unlike the Citroƫn system, which uses hydraulic fluid continuously pressurised by an engine-driven pump and regulated by a central pressure vessel.
179:
additional force. This gives the suspension a sharply rising rate even in pitch, so that there is a strong tendency to return to equilibrium. Without this rising rate there would be no effective pitch resistance at all.
261:
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
163:
The system replaces the separate springs and dampers of a conventional suspension system with fluid filled displacer units which are interconnected between the front and rear wheels on each side of the vehicle.
230:, Hydragas is an evolution of the previous Hydrolastic system. Manufactured under licence by BTR AVS under the Dunlop brand at the historic Holbrook Lane site. It was first introduced in 1973 in the
207:
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.
175:
In pitch, as described above, fluid is displaced front to rear, and hence the pressure in the system stays effectively the same, and thus the suspension is much more compliant.
274:, it was criticised for its tendency to pitch and bounce on uneven roads - precisely the characteristics the interconnection was intended to remove. The revised
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466:- 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.
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the price of the units substantially. After servicing the spares market for some years a buyer was found and the production line was sold.
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In a magazine interview for 'CAR' magazine in the late 1980s, Dr
Moulton stated that he and Issigonis had also studied the
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Morris / Austin / Wolseley / MG 1100 / 1300, Riley
Kestrel / 1300 & Vanden Plas Princess 1100 / 1300
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Moulton fitted his bicycles with rubber suspension units similar to those used on the original Mini.
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had its suspension interconnected and went on to receive plaudits for the quality of its ride.
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is a type of space-efficient automotive suspension system used in many
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Huffaker
Indianapolis cars 1964-1969 "MG Liquid Suspension Special"
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Hydragas is a type of automotive suspension system used in many
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Austin / Morris 1800 / 2200 & Wolseley 18/85 / Six
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Austin / Morris Mini & Wolseley Hornet / Riley Elf
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49:. Unsourced material may be challenged and removed.
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8:
388:Austin Allegro & Vanden Plas 1500 / 1750
191:Jon Pressnell suggests in his book that the
435:company to build his innovative design for
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394:Austin / Morris / Wolseley 18ā22, Princess
413:(not interconnected front to rear) &
109:Learn how and when to remove this message
250:, but without its attendant complexity.
226:Invented by British automotive engineer
476:
511:. Automobile Engineer. September 1962
7:
135:Invented by British rubber engineer
47:adding citations to reliable sources
487:. Open University Worldwide. 2004.
132:(BMC) and its successor companies.
991:Automotive suspension technologies
681:Continuously variable transmission
352:Austin / Morris Kimberley / Tasman
14:
431:In 1962 Alex Moulton founded the
234:and was later fitted to the 1975
996:Automotive technology tradenames
960:
959:
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302:
23:
34:needs additional citations for
523:Citroƫn DS: The Complete Story
318:Innocenti IM3 / IM3S / I4 / I5
151:, later to be launched as the
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716:Automated manual transmission
485:Creativity and Concept Design
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223:and its successor companies.
139:, and first used on the 1962
238:and its successor, the 1982
16:Automotive suspension system
791:Semi-automatic transmission
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628:Internal combustion engine
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927:Hybrid vehicle drivetrain
816:Transmission control unit
756:Limited-slip differential
721:Electrorheological clutch
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406:(from March 1978 onwards)
193:hydropneumatic suspension
130:British Motor Corporation
706:Dual-clutch transmission
325:Austin Apache / Victoria
676:Constant-velocity joint
509:āHydrolastic Springingā
507:Moulton, Alex. (1962).
656:Automatic transmission
521:Jon Pressnell (1999).
525:. The Crowood Press.
457:The Hydragas Register
761:Locking differential
696:Direct-shift gearbox
437:small wheel bicycles
246:system developed by
43:improve this article
786:Preselector gearbox
766:Manual transmission
341:(from 1964 to 1971)
332:Morris 1500 / Nomad
932:Electric generator
837:Wheel hub assembly
462:2008-01-29 at the
381:suspension system:
361:(until March 1978)
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411:Austin / MG Metro
398:Austin Ambassador
240:Austin Ambassador
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54:Find sources:
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32:This article
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874:Racing slick
811:Transfer box
781:Park-by-wire
776:Parking pawl
691:Differential
666:Direct-drive
648:Transmission
638:Steam engine
583:Part of the
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409:ADO88 / LC8
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159:Description
137:Alex Moulton
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41:Please help
36:verification
33:
852:Alloy wheel
711:Drive wheel
701:Drive shaft
661:Chain drive
404:Austin Maxi
359:Austin Maxi
303:Hydrolastic
283:Austin Maxi
276:Rover Metro
205:Citroƫn 2CV
153:Morris 1100
122:Hydrolastic
980:Categories
937:Alternator
585:Automobile
574:Powertrain
197:Citroƫn DS
187:Influences
69:newspapers
806:Transaxle
771:Manumatic
741:Gearshift
613:Fuel cell
99:June 2018
965:Category
904:Tubeless
889:Run-flat
869:Off-road
686:Coupling
608:Electric
460:Archived
427:Bicycles
379:Hydragas
288:Princess
236:Princess
211:Hydragas
143:project
354:(AU/NZ)
334:(AU/NZ)
327:(ZA/ES)
248:Citroƫn
195:of the
83:scholar
955:Portal
915:Hybrid
879:Radial
857:Hubcap
671:Clutch
618:Hybrid
587:series
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402:ADO14
396:&
392:ADO71
386:ADO67
364:ADO61
357:ADO14
350:ADO17
344:ADO17
337:ADO15
330:ADO16
323:ADO16
316:ADO16
310:ADO16
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842:Wheel
746:Giubo
471:Notes
441:tyres
145:ADO16
90:JSTOR
76:books
894:Snow
884:Rain
864:Tire
527:ISBN
489:ISBN
320:(IT)
295:Cars
281:The
272:Mini
266:and
217:cars
126:cars
62:news
847:Rim
420:MGF
268:MGF
141:BMC
45:by
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87:Ā·
80:Ā·
73:Ā·
66:Ā·
39:.
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