help needed regarding steering servo

[brainwave06]

Hi!
I am doing my final year project of a autonomous robotic car. Its size is 3.3feet by 5 feet and its weight is approx. 60kg. My mechanical assembly is almost complete. Its a four wheel vehicle with rear wheel drive and front wheels for steering. But I have a problem regarding steering servo.

Plz help me how to find the torque requirement for steering and which servo is best for me. Also tell me, is one servo enough or should I go for two servos?

Plz do reply its very urgent coz the completion date is 4th April, 2009.

Thanks in advance.

[ArcMan]

The torque required of your steering servo depends on many factors besides the size and weight of your car - wheels used, terrain, mechanical design of the linkage, required steering speed, etc.  For a 60 kg car, it will have to be quite large - bigger than a typical hobby servo.  Probably a large DC gearmotor with encoder feedback and a separate servo controller board.  Without knowing all the parameters mentioned above, my gut tells me you will need something like a wheelchair motor or similar size.