Power Steering

[patrick66]

Appologies for the vagueness of this question but I would be grateful if someone could settle an arguement relating to using full lock on a car with powersteering.
Could anybody let me know whether using full steering lock on a car with power steering has any detrimental effect on your powersteering. A friend of mine claims you should never use full lock and should stop just before you get to full lock otherwise you wear out something relating to the powersteering. Again appolgies for the vagueness of this question but it would be good to hear from someone who could shoot this theory down or support it.

Thanks

 

[wotan]

It is not considered good practise to turn the steering to full lock when stationary, you may be putting the seals under un-necessary strain/ pressure.

Wotan

 

[patrick66]

Thanks Wotan. Is it ok though whilst moving?

 

[wotan]

Thanks Wotan. Is it ok though whilst moving?

Well to put full lock on when moving it would depend on your speed. and the amount of room you have available.
If you want to put full lock on while stationary, drive the car on to two heavy duty polythene sacks (builders rubbish sacks) you can then turn the steering with far less strain.

Wotan

 

[^neo^]

I'd say your friend is talking rubbish

 

[Avocet]

Full lock is no different to any other position on the steering rack...

BUT, (with a hydraulically-assisted syetem), when you get to full lock, if you then increase the effort you apply to the wheel, you will put more strain on the system. You can often hear this as you turn the steering wheel. As the load increases, you'll hear the note of the power steering pump change. As you get to full lock, if you carry on trying to turn the wheel, you'll hear the pump working harder - some of them even whine a bit. The pump has a pressure limiting valve inside it, however, that's suppose to prevent it generating any more pressure than the rack can handle.

The rack has a seal at each end of the piston and one in the middle. When the steering wheel is at rest, the pressure in each "side" of the system is the same. As you turn the wheel, a valve opens on each side of the rack - one letting high pressure fluid in from the pump and the other letting it out to the reservoir, so there is a net force pushing the rack in the direction you want it to go.

"Twirling" the steering wheel round quickly (as one might do in a three-point turn) and suddenly hitting the lock stop gives the system quite a bit "spike" of hydraulic pressure which I don't imagine the seals in the rack will "enjoy"!
I think the "bottom line" is that from a general "mechanical empathy" point of view, there's no denying that it puts extra strain on the system. That said, a well-designed system ought to be able to cope with it.

Note that there are (increasingly) purely electrical assistance systems that use an electrical actuator on the steering column these days. I don't know how those work, but they don't have any hydraulic parts in them!

 

[wotan]

Avocet wrote:
Note that there are (increasingly) purely electrical assistance systems that use an electrical actuator on the steering column these days. I don't know how those work, but they don't have any hydraulic parts in them!

Personally I would steer clear of them (pun intended) sounds similar to Airbus's fly by wire.

 

[Avocet]

Ah, but they said that about hydraulic brakes in the 1930s!

 

[wotan]

Yes and flashing indicators, in lieu of semaphore arms.