Hello, I am building a 4 DOF robotic arm for a university project. As this is my first experience with robots, I need a bit of help with the selection of hardware.

The requirement for the joint at the base is as follows:

Speed: 3.33 rpm (this is the given requirement)

Torque: 133 Nm (calculated with simple statics)

Power output: 46.37 W (calculated with P = T x speed, please correct me if I am wrong)

I have found the following geared motor from Xajong, a Taiwan company:

Operating speed: 3200 rpm

Torque output: 0.21 Nm

Power output: 40W

My questions are as follows:

1. Am I right that I will need a gearing system with a ratio of approximately 1000 to step down the speed to 3.33 rpm?

2. By stepping down the speed with a gear, do I also step up the torque output by a factor of 1000?

3. Therefore, including efficiency of gear, am I getting 1000 x 0.21 x 0.9 = 189 Nm of torque output?

4. Since 189 Nm > 133 Nm, which is the amount if required, this motor should be good enough. However the power output is less than the amount required, and it contradicts the conclusion based on torque. This is when I get confused.

5. Lastly, any recommendation of a suitable motor for this case? Suggestions will be greatly appreciated. Motor should be as light as possible.

Helps will be greatly appreciated, since I am rather lost with what I should do as this is my first ever experience with building a robot.

Thank you!!