1. Serif Mark II Proposal
Paso Robles High School Engineering Department

2. We Have an Idea
Build an arm that:
● mimics human motion
● is controlled by
human motion
● is programmable

3. Welcome to the Drawing
Board
● Designed in Autodesk
Inventor
● Functioning elbow joint
● Improvements easily
applied

4. Forearm

5. Upper-Arm

6. ● Motor rotates
● Rotates gear fixed on axel
● Moves forearm up/down
Designing the Elbow

7. We (Could) Have the
Power

8. Building Something New
● Prototype for ball and
socket joint
● Omni-Wheels
● Can be robotic

9. Intro
Gear ratios use different sizes and
types of gears to change the speed and
torque.

10. Speed
With the same input speed
● Gears with more teeth (bigger) rotates proportionally slower because it takes more
teeth/rotation
● Gears with less teeth (smaller)rotates proportionally faster because it takes less
teeth/rotation
Therefore
● Speed in*Teeth in=Speed out*Teeth out or
● Speed in*(Teeth in/Teeth out)=Speed out or
● Speed in/(Teeth out/Teeth in)=Speed out or
● Speed in/Gear reduction=Speed out
(“Teeth out/Teeth in” is gear reduction)

11. Torque
Torque=Force*Distance so Torque in=Force in*Distance in or
Force in=Torque
in/Distance in
Force in is exerted on the gear out teeth so
Torque out=Force in*Distance out or
Torque out=(Torque in/Distance in)*Distance out or
Torque out =Torque in*(Distance out/Distance in) or
Torque out =Torque in*(Teeth out/Teeth in) or
Torque out =Torque in*Gear reduction
(distance is radius)
(radius is proportional to teeth)

12. Torque Pics

13. More

14. What is a motor?
A machine, especially one powered by electricity or internal combustion, that
supplies motive power to a vehicle or a device with moving parts.

15. How do electric motors work?

16. Motor Strength
● Motor strength comes from the motor’s rotation speed and
torque
● Depending on operating voltage, the stall torque can either be
25.5 kg x cm or 31.6kg x cm
● What this shows is how much weight a motor can hold when
it isn’t rotating

17. Our Motors
● The motor we selected has the strongest stall
torque within our budget.
● The resolution will help the arm mimic actions
precisely
● The motors will be light enough to attach to
the arm without weighing it down

18. Introducing the Omni Wheel
● Rotate like normal wheels
● Smaller wheels roll
perpendicular to rotational
axis
● Two degrees of freedom

19. It’s Alive!
This is the prototype
of a ball and socket
joint

20. The Advantages
● More degrees of freedom with less joints
● Can rotate a ball
● Robotic

21. Cy’s Creative Corner
Imagine if our
elbows were ball
and socket joints
similar to a
shoulder...

22. Real World Applications
Manufacturing would be more efficient if they had less moving joints.