1. 2.810 Car Suspensions James Penn 10/25/2010

2. Video 2008 2.810 Contest Second Round

3. Video 2008 2.810 Contest Final

4. Video 2008 Team C vs Speed Bump

5. Bump

8. No Suspension

9. Quarter Car Suspension Model

11. 2 nd Order Frequency Response

12. Quarter Car Suspension Model

13. Car and Unsprung Responses

14. Quarter Car Suspension Design Unsprung mass should be much less than sprung mass. Suspension should be just stiff enough to keep the unsprung response faster than the input.

15. m c =0.5kg, m us =0.02kg, k s =150N/m, v=3m/s

16. Adding Damping to damp oscillation of sprung mass by order of magnitude in one period logarithmic decrement

17. m c =0.5kg, m us =0.02kg, k s =150N/m, c s =5.9Ns/m, v=3m/s

18. Half Car Suspension Model

19. 2008 Team C, v=3.5m/s

20. 2008 Team C, v=4m/s

21. 2008 Team C

22. 2008 Team C Halfcar Model UnitValue mcmc kg1.3 IcIc kg.m 2 0.01 lflf m0.102 lrlr m0.127 k sf N/m2000 c sf N.s/m4 k sr N/m1600 c sr N.s/m2 m usf kg0.044 m usr kg0.6 k tf N/m6000 c tf N.s/m3.2 k tr N/m20000 c tr N.s/m6.4

23. Natural Frequencies Want low Want high

24. 2008 Team C Redesign UnitValue mcmc kg1.3 IcIc kg.m 2 0.01 lflf m0.102→0.127 lrlr m0.127→0.102 k sf N/m2000→800 c sf N.s/m4 k sr N/m1600→800 c sr N.s/m2 m usf kg0.044 m usr kg0.6→0.1 k tf N/m6000 c tf N.s/m3.2 k tr N/m20000 c tr N.s/m6.4

25. Natural Frequencies Want low Want high

26. 2008 Team C Redesign, v=3.5m/s

27. 2002 Team C (Record Holder)

28. 2002 Team C Halfcar Model UnitValue mcmc kg2.25 IcIc kg.m 2 0.02 lflf m.102 lrlr m k sf N/m∞ c sf N.s/mN/A k sr N/m∞ c sr N.s/mN/A m usf kgN/A m usr kgN/A k tf N/m6000 c tf N.s/m8 k tr N/m1200 c tr N.s/m10

29. 2002 Team C, v=3.5m/s

30. Concluding Thoughts Minimize unsprung mass –If rear suspension is pivoting, move motor forward. Avoid placing center of mass far forward. Avoid making suspensions too stiff. –Thin, long sheets (k~(t/L) 3 ) –k parallelogram =2*E*b*(t/L) 3 ω n,c ≈30rad/s, ω n,us ≈100rad/s –