Power steering on a car is a form of torque amplifier: the driver applies X Nm (or ftLb) of torque, and the power steering adds Y torque - but maintaining the same angle of turn. But what's the approximate ratio of Y:X for the power steering on a typical domestic car? Is it e.g 10:1 ?
I had a go at measuring it - on my Toyota Auris. I used a handheld digital device (for weighing luggage), which conveniently records the maximum weight sensed in a measurement. I strapped it around the spoke of the steering wheel in a fixed location, just inside the rim, and made sure that I was always applying the force tangentially.
My measurements were all taken with the vehicle stationary (not while driving!) and with the car parked on gravel.
With the power steering on, turning the wheel seemed to take a force of anywhere between 5 and 20 N (so maybe 1-4 Nm torque). With the power steering off I got readings of between 15 and 25 N. Not great data, but it seems to suggest that the amplification from the power steering is of the order of 10:1. Though, I am not very confident in this result, and I have to say that my subjective impression was that it was greater than this
If anyone can provide a more specific figure based on manufacturer's design specs- for any domestic car - I would still appreciate it.