1. Power Transmission Shaft
Irmydel Lugo
Victor Molina
Eladio Pereira

2. Purpose To design a shaft that transmits 40 HP of power.
It will be designed for infinite life.
Also, it will be as light as possible (mass minimized)

3. Applications Electric motors Turbines Automotive transmission
Manufacturing processes

4. Considerations
The torque acting on the shaft is fluctuating as the angular velocity changes.
The shaft will have cross sections of different diameters, which will make it more difficult to analyze dynamically.

5. Considerations
It was challenging to analyze all the four possible most critical sections and the effect of the fluctuating force on them.
The force is not changing sinusoidally, but it is decreasing exponentially as the angular velocity increases.

6. Force vs. RPM

7. Why is this Shaft Different?
The design is relatively large, but it can be made smaller or bigger and it will work in the same way, as long as the proportions of diameters is kept. That makes it unique.
This shaft will resist for an infinite life and at the same time it will be economical.

8. Principal Challenge
Our biggest challenge with this project was finding the forces that were acting on the shaft, because they fluctuate with the revolutions applied (from 100 rpm to 3000 rpm)

9. Challenges
Another challenge was designing for a light material, but at the same time resistant to fatigue and deflection and to have infinite life.
Finding a material to cover our requirements, but being economical at the same time.

10. Shaft

11. Shaft

12. Design Details
These calculations were made with 3000 RPM

13. Design Details
For the next step, we made a diagram show how the forces are applied at the point of the spur gear, we assumed the angle of attack for the teeth of the spur gear is 20º

14. Stresses
Section with diameter of 2 in:

15. Stresses
Section with diameter of 4.8 in:

16. Stresses
Section with diameter of 6 in:

17. Material Selection:
To minimize the mass we have to minimize the relation .

18. Material Selection:
Amongst the best materials to be used are aluminum alloys, titanium alloys and steel.
Also the ceramic and carbon fiber alloys, but due to the fact that the forces and stresses are so high, it is not recommendable to use them.
Aluminum 2024-T4 has the lowest ratio with 1.68
Beta Titanium Alloy has a relation of 2.70
1020 Steel has a relation of 2.85.

19. Deflection
The maximum deflection occurs at where a and b are the distances between the applied force and the supports, where b > a.

20. Deflection
At this point the maximum deflection is obtained by the following equation; where P is lb, I is in^4 and L is 28 in.

21. Deflection
We obtained the value of E for Al-2024 T-4 (E = KSI), ASI-1020 (E = KSI) and Ti-15Mo5Zr3Al (β titanium alloy) (E = KSI).

22. Calculating Safety Factor

23. Calculating Safety Factor

24. Calculating Safety Factor

25. Calculating Safety Factor
The safety factor was calculated by taking into consideration that we use infinite life as a goal of the design.
The highest safety factor was obtained by titanium, followed by steel and aluminum respectively.

26. Weakness of Our Shaft
There is no curvature between the sections of different diameters (no notch), so there are no stress concentrations to make the shaft more resistant to fatigue fracture.

27. Conclusions
We learned what materials we should have in mind when designing a shaft.
We also learned that the safety factor is different for each section of the component, so we should use the one of the most critical area. But we have to analyze all the possible critical sections, even if it is very exhausting.