Very new to this so bare with. If I were to make a DC Motor shaft with cogs and gears circuit, how would I know the required ampage of my power unit (im thinking, battery AA holder). And are there any pre cautions I should take to prevent damage or potential fire hazard? I roughly know about diodes and resistors.

To summarise:
DC AA battery holder with ON/OFF switch to run into a DC Motor Shaft that would have Cogs rotate (preferably very slowly).

Thanks

 

Welcome to AAC!
You need to read the datasheet for the motor to see what current it draws. Adding cogs/gears won't alter that much. An AA alkaline battery is unlikely to present a fire hazard, but a lithium battery has to be charged and discharged correctly to avoid a fire/explosion risk.

 

Run the motor and measure the current.
Stall the motor and measure the current.
Now you have your two extreme current requirements.

 

Cogs and gears that reduce the final output rotation (RPM) make it easier for a motor to run the setup. It won't increase the torque very much. By that I mean by a very small amount. If you go the opposite way and build for higher RPM then the motor is going to have to run much harder, meaning more current.

I just bought a cement mixer. It has a very small motor. Much smaller than I expected. It also has a gear reduction drive system that turns the drum as a common RPM for mixers. They could have gone with an even smaller motor with higher RPM's and more gearing, but at that point you're trading off the amount of current for the work you're doing. The last cement mixer I used had a motor and pulley. The larger pulley reduced the speed of the mixer. Then there was the tiny gear that spun the large diameter drum. In the end it was all the same thing. Large motor, few gears for a set RPM or smaller motor with more gearing for the same (approximate) RPM.

 

DC Motor Shaft that would have Cogs rotate (preferably very slowly).

Unless you are talking about a DC gear motor, the motor on it's own won't turn slowly. Small hobby size motors turn in the 6,000 to 10,000 RPM range on their own. If you need it to turn slower from the output shaft you need to go to what is called a gear motor, one that has a gear box built into it. Something like this -
https://www.bananarobotics.com/shop...MBN21mldkQJwRCyCQjrjbATYywgGCvX4aAiIJEALw_wcB