Q1.2) Do all brushless motors have hall effect sensors? Howabout the RC brushless motors that you can find on hobby RC sites?
No. There are three kinds of commutation: Sensorless, Hall sensors and high resolution encoders.
RC brushless motors use sensorless commutation. This means that the motor does not have any sensors in it. The controller uses a clever system that reads the induced voltage (back emf voltage) from the motor coils to get the position and speed information.
Sensorless commutation is not very accurate, but is good enough for RC car motors. If you need a very smooth and precise operation then a high resolution encoder must be used.
Q2.2) Could you show me a link where I could calculate position and velocity for the from the hall sensors signals for maxon motors or maybe other motors?
It is pretty much the same technique as with high resolution encoders. I couldn't find any good examples for hall sensors for now, but here is one application note that describes the overall control system:
https://www.electro-tech-online.com/custompdfs/2011/06/AN10661.pdf
https://www.electro-tech-online.com...larC4B1n2020BLDC2020Temel20C396zellikleri.pdf
Commutation using hall sensors or no sensors at all is called "block commutation". That might help you with google searches.
Commutation with high resolution encoder is called "sinusoidal commutation".
Q3.2) What if the both shafts had a gearhead each with the same gearhead ratio. Would that double the torque?
No, the torque comes from the rotor magnet attracting the stator coil. The shaft is just a metal rod through the rotor.. for a two-shaft motors they just make the metal rod longer so it comes out both ends.
Q5.2) Now when you mean high ratio gearhead, you talking about a gearhead with more than 4 stages? So something that would produce more torque, how does that relate to resolution?
Gear ratio means the ratio of speed reduction. With 0.5 ratio the motor turns 1 turn each time the output turns only 0.5 turns.
With higher gear ratio you get higher output torque and slower output speed. Slower speed means more accuracy for positioning tasks.
Q5.3) What kind of resolution am I looking at with a hall Sensor?
I know that with a magnetic encoder, you can get about 4096 positions per revolutions or even 16384 positions per revolution.
With hall sensors you get 6 positions per revolution.
There is a very good book from Maxon Motors called "The selection of high-precision microdrives". It is a must have:
https://www.maxonmotor.com/media_releases_The-design-of-high-precision-microdrives.html