Drive Sizing 101

[Paul Copioli]

So, the emergence of Dr. Joe back to these forums inspired me to look into all of his and my old posts in the technical forum. I have noticed that I have not done my part on the instruction and guidance in these forums as I used to. With that in mind for the entire design season I will be posting these little educational lessons based on the actual design and analysis that 217 is doing this year.

Now, I will not be sharing all of the information and assumptions that we are using as I think that is part of the lesson. I promise that after several others post with what they think are the proper assumptions and analysis steps, I will share more detail.

First lesson: Drive sizing for an arm that lifts a 150ish pound robot

Objective: Lift our robot at the end of the match in less than 5 seconds.

Assumptions:
1. Robot Weight (W) is 150 lbs
2. Center of Gravity (CG) is approximately in the middle of the robot
3. Robot is a long body (37" from front to rear)

Final Decisions:

1. Use 1 Fisher-Price (F-P) motor as that is the highest power motor available to use after the motors were allocated of other tasks (Using all 5 CIMs and one other F-P).

2. Final gear ratio from the F-P to the arm joint is about 1500:1


The question has two parts:

1. Why did we select 1500:1?

2. What type of lift are we using (scissor, rotational arm, winch, etc)?

Again, I will share all of our calculations and thought process after some discussion in this thread.

Have fun,

Paul