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4OfaKind
02-28-2007, 03:04 PM
What would be the pros and cons of hydraulic steering on a road race car? I know they are used on off road vehicles and boats. Though the reason for marine use is odvious to me, the benefits of off road use escape me.

Other than less feedback, what other problems arise in hydraulic steering? The extremely quick ratio should be a plus, since it only takes one full turn to go lock-to-lock.

What are you guys thoughts?

Mal

KWIKND
02-28-2007, 04:53 PM
Loose Hyd..... loose steering :drive1:

Dan

David Pozzi
02-28-2007, 09:13 PM
Hydraulic steering is used extensively in farm equipment. The only disadvantage is lack of feel (low effort) somewhat jerky response, and a lack of staying on-center. What I mean by on-center is, the steering wheel will change where straight ahead is with time. Tractor systems compensate for this by having the unit self-center when a full lock turn is made.

Yelcamino
03-01-2007, 08:29 AM
The plus for off-road use (i.e. 4x4) is that when rock crawling with large x huge tires, the hydraulic steering makes it easier to turn the steering wheel when the tires are fighting against big obstacles. The more serious guys have full hydraulic setups while the weekend warriors will have hydraulic assisted setups on top of their manual or power steering systems. Off the top of my head I can't think of any real advantage on a street car.

6'9"Witha69
03-01-2007, 08:36 AM
There are some european cars which have(had?) this. There is really no advantage that I can see. The negatives though are that I am not comfortable without a linkage connecting me to the wheels (ie BMWs). Also, I have to imagine that there could be more load on the pump to operate which will mean more power loss. That is just my thought and I have no info to support it.

Randy67
03-01-2007, 09:11 AM
Pros of hydraulic steering: 1. independent front and rear wheel steering :woot:
2. allows for axle articulation
Cons: Loose hydraulic pressure = no steering at all.
2. Not DOT or street legal.

Alot of the off-road guys us it because of the extreme axle articulation, a mechanical steering linkage would interfere or just wouldn't work. The hydraulics allow for articulation without affecting the steering. See the attached picture for extreme articulation, although the truck still has mechanical steering.

4OfaKind
03-01-2007, 09:47 AM
Loose Hyd..... loose steering :drive1:

Dan

Yeah Dan and others,

I did not consider the fact that a leak or break would eliminate steering completely :hand: :scared: :drive2:. That is con enough not to use it as evidenced by its DOT ban. The low speeds of off-road use and the open spaces of marine use kinda negate this.

Cool, thanks guys I learned something new about 4x4s.

Mal

4OfaKind
03-01-2007, 09:50 AM
Hydraulic steering is used extensively in farm equipment. The only disadvantage is lack of feel (low effort) somewhat jerky response, and a lack of staying on-center. What I mean by on-center is, the steering wheel will change where straight ahead is with time. Tractor systems compensate for this by having the unit self-center when a full lock turn is made.

That is an interesting fact also David. There does not appear to be any benefit to road racing use.

Mal

David Pozzi
03-03-2007, 07:57 PM
Eventually cars will have electric steering systems from what I've read. They already have electronic throttles and electric steering assist, and when steering is fully electronically controlled, RH or LH drive cars will be much easier to make and the lack of a steering column will make the interior more quiet.

terryr
03-24-2007, 07:33 PM
Mercedes supposedly has a system ready to go, but it illegal almost anywhere in the world. There has to be a mechanical connection.

4x4s tap the PS steering box to drive a double acting cylinder, but the stock steering is still in place.

The Rook
02-19-2008, 06:39 PM
I come here to read and relax after another hard day of work and someone has to bring up electric steering!?!?!!? WTF I spend 10-12 hours a day on that and now I have to deal with it here....Thanks David!

Anyway, true electric steering is still a little ways out there due to all of the safety issues involved and the lack of a true mechanical connection from the wheel to the wheels scares a lot of people. Ever see a car "snow plow" the front tires while doing 45mph.....scary fun.

aosborn
02-07-2009, 03:54 PM
I have considered hydraulic steering in a street rod for some time, though it would have to be for more of a show car initally. The idea appealed to me for several reasons...

1. You could locate the steering wheel anywhere in the passenger compartment. Center of the front seat would be interesting. No steering column to clutter up the dash area.
2. Steering feel could be taylored with adjustments in preassure and flow.
3. To overcome the loss of steering if the pump stops, I was considering using an accumulator so you would at least be able to get off the road. Kind of like the vacuum brake booster gives you a couple of applications of the brakes with assist after the engine stops.
4. Mount the rams outboard near the control arm pivots to eliminate all the traditional linkage or steering rack, and to easily adjust for eliminating bump and roll steer.
5. With the reliability of common hydraulic pumps, hydraulic cylinders and hoses, I really didn't see a major reliability issue.

It is on my list of projects if I ever get bored...

Andy

David Pozzi
02-07-2009, 11:03 PM
Some of the farm tractor steering units can still steer when the engine quits. They aren't easy to steer, but they steer. The head unit attached to the steering wheel has pistons that push fluid to the front ram, but they are heavy and all iron, weigh more than a saginaw box and pump. The later systems stay centered better but they all "drift".

Norm Peterson
02-12-2009, 05:31 AM
2. Steering feel could be taylored with adjustments in preassure and flow.What you get is simulated feel, which you can use to add some effort but which won't tell you what's happening down at the contact patches. I understand that this may be a complete non-issue for many or even most drivers in normal daily driving. But I think it would play rather poorly at autocross, open-tracking, or even hard street cornering, as ultimately a simulated "feel" will tell lies to you.

Electrically it might be possible to introduce or reproduce the vibrations that come through as feedback, though that sounds like an awfully complex way of going about getting what a purely mechanical system gives you directly.



4. Mount the rams outboard near the control arm pivots to eliminate all the traditional linkage or steering rack, and to easily adjust for eliminating bump and roll steer.Fluid is at least minutely compressible, and hydraulic lines will expand under pressure, so there will be some additional steer effects comparable to the compliance steer that already exists. I see a pretty complex mapping of bumpsteer vs steer vs bump/roll being necessary, as varying the ram lengths to make the steering happen will change the bumpsteer effect.


Maybe The Rook will chime in with a few thoughts.


Norm