Hydrosteer
Encyclopedia
Hydrosteer was the name given by Hydrosteer Limited of Luton, England, (later Cam Gears Ltd) to its automotive power steering
system of the 1960s and early 1970s. Based on a cam and peg system, it was characterised by its fully integrated design and variable steering ratio
. Introduced in 1960, it was fitted to several, mainly British, luxury automobiles of the era. Frequently described by road testers as too light and lacking in road feel, it was largely supplanted by other systems in the 1970s, notably the Marles Varamatic
.
The 1960s Hydrosteer system should not be confused with Hydrosteer Pty Ltd, an Australian company established in 1981 as a provider of heavy truck steering technology in that country.
Facel Vega II (optional)
Humber Super Snipe Series V (optional)
Humber Imperial
Rover P5 3-Litre Mark 1a (optional)
Rover P5 3-Litre Mark 2 Saloon and Coupe
Rover P5 3-Litre Mark 3 Saloon and Coupe
Rover P5B 3.5-Litre Saloon and Coupe
Vanden Plas Princess 4-Litre
Wolseley 6/110 (optional)
Tha cam track is not a regular helix but varies in pitch angle and depth. The variation in steering ratio between straight ahead and full lock results from the variance in pitch angle of the track. The more the steering wheel is turned, the lower the steering ratio becomes. In the Rover P5B, for example, the ratio of the power steering unit was 16:1 at the straight ahead and 11.3:1 at full lock.
The effect of the variable ratio is to give very light and relaxed steering at the straight ahead, with increased reaction when cornering. The system was designed to be fail-safe, so that the driver should still be able to steer in the event of a failure of the power system.
Whilst advanced for its time, the Hydrosteer system did have certain drawbacks, in common with all variable ratio steering systems. It was more complicated and expensive than a constant ratio power assisted system. It could also catch drivers out when they attempted to correct for understeer
or oversteer, the non-linear response of the steering working against the driver in such circumstances.
The Hydrosteer system was also criticised for feeling far too light under most circumstances. A particularly scathing article appeared in Car magazine
in January 1968 stating “Not even an octagenarian with Parkinson’s disease could possibly run such a risk [of losing control of the car due to sneezing] with the rival Rover [Hydrosteer] system, which is also progressive but with a complete absence of feel. This is power steering in the true American sense; we find it difficult to call to mind any virtues that anyone could claim for it apart from the obvious observation that parking would probably be impossible for a woman or an old man without some sort of assistance; on the other hand, we can think of every reason why it should be changed for something more sophisticated …”.
Indeed, use of the Hydrosteer system in cars effectively died out with the generation of 1960s models to which it was fitted. For example, the Rover P6B 3500S
that followed the Rover P5B used the Marles Varamatic
variable ratio system, which was slightly heavier in most circumstances and arguably had more road feel, although that system too failed to survive much beyond the 1970s.
Power steering
Power steering helps drivers steer vehicles by augmenting steering effort of the steering wheel.Hydraulic or electric actuators add controlled energy to the steering mechanism, so the driver needs to provide only modest effort regardless of conditions. Power steering helps considerably when a...
system of the 1960s and early 1970s. Based on a cam and peg system, it was characterised by its fully integrated design and variable steering ratio
Steering ratio
Steering ratio refers to the ratio between the turn of the steering wheel or handlebars and the turn of the wheels .The steering ratio, is the amount of degrees you have to turn the steering wheel, for the wheels to turn an amount of degrees.In motorcycles and bicycles, the steering ratio is...
. Introduced in 1960, it was fitted to several, mainly British, luxury automobiles of the era. Frequently described by road testers as too light and lacking in road feel, it was largely supplanted by other systems in the 1970s, notably the Marles Varamatic
Marles Varamatic
Marles Varamatic is the trademark name of an automotive power steering system of the 1960s and 70s, which was characterised by its variable steering ratio. It was developed in 1961 by the Adwest Engineering Co Ltd of Reading, England, in conjunction with the Bendix Corporation...
.
The 1960s Hydrosteer system should not be confused with Hydrosteer Pty Ltd, an Australian company established in 1981 as a provider of heavy truck steering technology in that country.
Adoption
The Hydrosteer power steering system was fitted to the following vehicles:Facel Vega II (optional)
Humber Super Snipe Series V (optional)
Humber Super Snipe
The Humber Super Snipe was a car produced by the British-based Humber car company, part of the Rootes Group, from 1938 to 1967.-Pre-war Super Snipe:...
Humber Imperial
Humber Super Snipe
The Humber Super Snipe was a car produced by the British-based Humber car company, part of the Rootes Group, from 1938 to 1967.-Pre-war Super Snipe:...
Rover P5 3-Litre Mark 1a (optional)
Rover P5
The Mark II version of the P5 was introduced in 1962. It featured more power from the same 3.0 L engine and an improved suspension, while dropping the glass wind deflectors from the top of the window openings which also, on the front doors, now featured "quarterlight" windows .The most...
Rover P5 3-Litre Mark 2 Saloon and Coupe
Rover P5
The Mark II version of the P5 was introduced in 1962. It featured more power from the same 3.0 L engine and an improved suspension, while dropping the glass wind deflectors from the top of the window openings which also, on the front doors, now featured "quarterlight" windows .The most...
Rover P5 3-Litre Mark 3 Saloon and Coupe
Rover P5
The Mark II version of the P5 was introduced in 1962. It featured more power from the same 3.0 L engine and an improved suspension, while dropping the glass wind deflectors from the top of the window openings which also, on the front doors, now featured "quarterlight" windows .The most...
Rover P5B 3.5-Litre Saloon and Coupe
Rover P5
The Mark II version of the P5 was introduced in 1962. It featured more power from the same 3.0 L engine and an improved suspension, while dropping the glass wind deflectors from the top of the window openings which also, on the front doors, now featured "quarterlight" windows .The most...
Vanden Plas Princess 4-Litre
Wolseley 6/110 (optional)
Operation
The Hydrosteer system was based on a conventional cam-and-peg mechanism, except that the cam is surrounded by the skirt of a piston within the body of the steering box. Hydraulic power from the power steering pump is transmitted directly from the piston to the peg carrier. A spool type hydraulic valve moves along the axis of the cam in response to steering wheel movement, causing oil pressure to be applied to one side or other of the piston according to the direction the steering wheel is turned.Tha cam track is not a regular helix but varies in pitch angle and depth. The variation in steering ratio between straight ahead and full lock results from the variance in pitch angle of the track. The more the steering wheel is turned, the lower the steering ratio becomes. In the Rover P5B, for example, the ratio of the power steering unit was 16:1 at the straight ahead and 11.3:1 at full lock.
The effect of the variable ratio is to give very light and relaxed steering at the straight ahead, with increased reaction when cornering. The system was designed to be fail-safe, so that the driver should still be able to steer in the event of a failure of the power system.
Benefits and drawbacks
The major benefit of the Hydrosteer system is reduction in the amount of steering effort required of the driver, particularly at low road speeds or when a lot of turning is involved. Also, the Hydrosteer system was fully integrated into the steering box with no external jacks, giving it an advantage over earlier systems with external jacks, which needed more space and were heavier.Whilst advanced for its time, the Hydrosteer system did have certain drawbacks, in common with all variable ratio steering systems. It was more complicated and expensive than a constant ratio power assisted system. It could also catch drivers out when they attempted to correct for understeer
Understeer
Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of a vehicle to steering. Simply put, oversteer is what occurs when a car turns by more than the amount commanded by the driver...
or oversteer, the non-linear response of the steering working against the driver in such circumstances.
The Hydrosteer system was also criticised for feeling far too light under most circumstances. A particularly scathing article appeared in Car magazine
Car Magazine
Car Magazine is a British automotive enthusiast magazine published monthly by Bauer Automotive. International editions are published by Bauer Automotive in Brazil, China, Greece, India, Mexico, the Middle East, Poland , Romania, Russia, South Africa , Spain, Thailand and Turkey...
in January 1968 stating “Not even an octagenarian with Parkinson’s disease could possibly run such a risk [of losing control of the car due to sneezing] with the rival Rover [Hydrosteer] system, which is also progressive but with a complete absence of feel. This is power steering in the true American sense; we find it difficult to call to mind any virtues that anyone could claim for it apart from the obvious observation that parking would probably be impossible for a woman or an old man without some sort of assistance; on the other hand, we can think of every reason why it should be changed for something more sophisticated …”.
Indeed, use of the Hydrosteer system in cars effectively died out with the generation of 1960s models to which it was fitted. For example, the Rover P6B 3500S
Rover P6
The first P6 used a 2.0 L engine designed specifically for the P6. Although it was announced towards the end of 1963, the car had been in "pilot production" since the beginning of the year, therefore deliveries were able to begin immediately. Original output was in the order of . At the...
that followed the Rover P5B used the Marles Varamatic
Marles Varamatic
Marles Varamatic is the trademark name of an automotive power steering system of the 1960s and 70s, which was characterised by its variable steering ratio. It was developed in 1961 by the Adwest Engineering Co Ltd of Reading, England, in conjunction with the Bendix Corporation...
variable ratio system, which was slightly heavier in most circumstances and arguably had more road feel, although that system too failed to survive much beyond the 1970s.
External links
- http://c.couvrat.free.fr/hydrosteer/hydrosteer02.pdf Automobile Engineer article on the Hydrosteer system, May 1960
- http://www.gracesguide.co.uk/images/8/82/Im19621003Mot-Hydrosteer.jpg Hydrosteer advertisement citing the system's use in the Rover P5
