[Greg Needel]

What type of motor should be used?

i would recommend a motor used in the automotive field (window motor, windshield washer, door) all are commonly available and cheap but powerful

How do I determine the required torque rating of the motor?
take the force (5lbs) at the point of most stress (45 deg) and
[[[[multiply the distance from the orgin * the sin(45deg) * the force (5lbs) ]]]this will give you the moment about the rotation of the motor which is the exact torque needed at that point. so get a motor that is at least that strong

Any external control electronics necessary?
not really you can do this with relays and limit switches. but if you need any external feedback of any sort (exact position, angle, torque, etc) you will need some external electronics and i would recommend a micro controller (oopic is a good one) easy to program and interface

How to vary the speed of the motor (vary speed of arm movement)?
in the simple circuit do this with resisters (less voltage=slower speed) but you loose torque that way so be careful. you can also do this with gearing but for your application a potentiometer(variable resister )would work fine



Any other considerations?
just plan it out before you build anything and remember we are here to help if you need it