Thank you very much. Would you or anyon happen to know what happens when you hit the steering stop, as in a parking, what is the power/torque requirment then? I'm designing a crank pulley and the belt loads are one of my anlysis inputs.
The requirement would be almost zero, however the output might be close to maximum, depending on pump speed at maximum output, engine speed and pump drive ratio.
I think you need maximum pump output, not pump requirement.
Maximum load is likely to be when trying to steer past full lock or when doing very rapid steering action at higher engine speeds, such as slalom course racing.
The one car I had that was inclined to fail belts always failed when applying sudden correction for oversteer when cornering very aggressively in low gear at near red line rpm.
I won't mention brand names, but Greg will probably understand from the term 1988 EA. It may well be he who fixed the problem in later models.
Regards
eng-tips, by professional engineers for professional engineers
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Your best bet is to talk to a power steering manufacturer, or reverse engineer a current installation.
Roughly speaking the steering force in the tie rod can max out at around 1 ton for a large car, so you should be able to work out the torque from that, for a given rack and pump configuration.
The maximum force in normal use is seen when parking, when you spin the wheel round rapidly, with the car stationary, and in the worst case with the wheel against the kerb. Ouch.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
You can cause the belt to momentarily skid on almost any system if you turn the wheel right up to a steering stop. The pump will by-pass but there is a significant hydraulic shock before full by-pass occurs. No, you're not supposed to steer that way, but it does happen.
Many big trucks have steering boxes that by-pass at full lock.
