How can a hydraulic steering be replaces the modern power steering system

[varun atri]

Hi every one,
i am a mechanical engineer working on a project hydraulic steering . i want to know that in power steering systems it has been used. but the thing is as far i know that the modern power steering system uses a hydraulic cylinder in addition to the rack and pinion arrangement.

i want to know that i am removing that pinion and rack system and want to make the steering system completely working on hydraulics . could it be possible and what will be the modifications i have to make it to the system to make it working. Also does the load will affect the hydraulic system more as i have considered the frictional losses and many other power losses.

A +VE CRITISM IS ACCEPTED FROM THE EXPERTS OF THE FIELD AND ANY OTHER IDEAS AND MODIFICATION IS WELCOMED.

"ONLY ENGINEERS KNOWS HOW THINGS CAN BE CREATED AND DESTROYED"

 

[6Stang7]

May I ask why you're set on having a pure hydraulic steering system?

 

[serbring]

Hi every one,
i am a mechanical engineer working on a project hydraulic steering . i want to know that in power steering systems it has been used. but the thing is as far i know that the modern power steering system uses a hydraulic cylinder in addition to the rack and pinion arrangement.

i want to know that i am removing that pinion and rack system and want to make the steering system completely working on hydraulics . could it be possible and what will be the modifications i have to make it to the system to make it working. Also does the load will affect the hydraulic system more as i have considered the frictional losses and many other power losses.

A +VE CRITISM IS ACCEPTED FROM THE EXPERTS OF THE FIELD AND ANY OTHER IDEAS AND MODIFICATION IS WELCOMED.

"ONLY ENGINEERS KNOWS HOW THINGS CAN BE CREATED AND DESTROYED"

Hi,

a pure hydraulic steering system already exists since 70s. It is used on tractors.
Search on google hydrostatic steering system or hydroguide, you would find a lot of information

 

[Ranger Mike]

A bit of history is in order. Automobile and truck steering was strictly mechanical for years. The hydraulic assisted power steering was an expensive Option. As more woman began driving in the 1950s and 60s ( originally the task was solely male dominated ( early 1900s) and more and more of the purchasing public began selecting the automatic transmission and air conditioning, the auto manufacturers began packaging the more popular car models with “ standard options” a true oxymoron. Certain features were sold at attractive prices to give the purchasing public incentive to buy the car off the lot and avoid custom manufacturing of each automobile. This reduced delivery time and even more importantly, decreased time of customer order to payment. Cheap credit and option to finance the car purchase were also refined by the automobile manufacturers.
Anyway, it is pretty common to buy a car with automatic transmission, power steering and air conditioning now.
Todays power steering is not pure hydraulic but a hybrid with electric power steering pump and slave cylinder rack and pinion.
Why electric..ease of installation during assembly..no long drive belts, pulleys, tensioners, to install, reduced warranty as you eliminate squeaky belts, parasitic drag on the power plant, It pretty much goes back to lowest cost to install AND Maintain over the warrant period.

 

[russ_watters]

You wouldn't want to eliminate the rack and pinion completely because it serves as a back-up system in case of power (engine) failure.

 

[Ranger Mike]

as usual Russ..most excellent point...as a safety feature all automoblies have steering ability even when engine is turned off..

 

[serbring]

You wouldn't want to eliminate the rack and pinion completely because it serves as a back-up system in case of power (engine) failure.

that's wrong. On farm tractors it's used a pure hydrostatic system and in this case, the rotating valve is used as a pump. To reduce the steering wheel effort, it is used systems with two gerotor,i.e. valves: a big valve and a small ones.

here it is explained a bit.

http://www.pirate4x4.com/tech/billavista/PR-Hydro_Steering/index2.html

 

[russ_watters]

A farm tractor is not a car. Farm tractors spend most of their lives going perfectly straight at 1mph (so no risk of a crash) and often (big ones) have wheels too large and buried in dirt to turn easily by hand.

 

[serbring]

A farm tractor is not a car. Farm tractors spend most of their lives going perfectly straight at 1mph (so no risk of a crash) and often (big ones) have wheels too large and buried in dirt to turn easily by hand.

Unfortunately the tractor usage in completely changed in the last 20 years. Tractors with more than 100 kW are used for more than 50% of their life on road and they run 65km/h.
Anyway the EU regulation doesn't permit to install pure hydraulic steering systems on cars.

 

[Lsos]

I imagine it would be a terrible experience driving a car with purely hydraulic steering, as it would remove most of the feedback the driver gets and further disconnect him from the machine.

 

[serbring]

I imagine it would be a terrible experience driving a car with purely hydraulic steering, as it would remove most of the feedback the driver gets and further disconnect him from the machine.

The feeling while tractor driving is completely different than while car driving. In fact a high speed tractor has a mechnical steering with hydraulic assistance. As example there are hydrostatic steering system that you have to rotate the steering wheel after having run a curve because it doesn't allineate by itself.

If you are interested in, take a look at the following paper, it is well explained it.
http://elibrary.asabe.org/azdez.asp?JID=3&AID=36248&CID=t2011&v=54&i=1&T=1&redirType=

 

[Mech_Engineer]

Full hydraulic steering conversions are already available for 4x4's, take for example here here:

http://www.pscmotorsports.com/motorsport-specific-products/offroad/full-hydraulic-steering

Hydraulic steering has the advantage of being very strong, which is a big plus on off-road vehicles with big tires driving on big rocks, but they have drawbacks too. They don't have any "on-center feel", little road feeback, are difficult or impossible to use without the engine running, require complex hydraulic setups including fluid coolers, etc etc.

As it is modern cars are going away from hydraulic altogether in favor of straight electric for power steering assist. A full hydraulic setup is a step backwards in terms of road manners rather than a step forward.