Energy Trade Offs and TIRES 10.17.09

1. Energy Trade Offs and TIRES10.17.09 Credit to Shaw Lewisfor the initial presentation A presentation by: Jason GreenblattB.S. in Mechanical Engineering Clean Transportation Analyst Regional Utility Employed

2. Why Theorize Energy? Energy is constantly lost while driving All parts of the car are constantlyRESISTING motion Energy loss and usage may be reduced

3. Mechanical Energy Bearings surfaces Acceleration and Braking Friction (non-regen) Rolling Motion Sidewall Flexion Linear movement (driving) Aerodynamic Drag Tires have 5 out of 6! Electrical Energy High Voltage Low Voltage Resistance Material property (i.e. copper) Mechanical connections (i.e. bolted lugs, crimped cables, terminal blocks, plugs) Chemical property (corrosion) Heat anywhere Where is this stuff called Energy?

4. What does Energy Look Like? Mechanical • Rotational Energy = (½)*Inertia*angular velocity2 • Linear Travel Energy = (½)*Mass*Velocity2 • Side wallSpring Energy = (1/2)*Kspring constant *X2(distance compressed) Exponent means speed contributes more then mass!! Judge if smaller, shorter or narrower tires would suit your needs Electrical • Energy = Volts*Amps*Time Low Voltage, half hour driving, running the head lamps 12 volts* 10amps* (1/2) Hour = 60 Watt Hours High Voltage, 1 minute, 1 mile, 60mph, 120volts, 200amps 120*200*(1/60 of an Hour)=

5. Lets compare some Driving You can follow your amp guage to maintain constant current

6. Watching your Energy Flow Gauges are IMPORTANT; only if you need them Use your gauge as an economy dial Driving in lower gears will consume less energy Watch the Amp Gauge in any gear Cruising may should low amps (150-200amps) Know vehicles limits, don’t push too hard up hills The heavy EV may just not want to go faster uphill Don’t waste juice trying to push it harder

7. Amp Guage relates to Controller • Curtis Controller has following limits: • Watching the Amp gauge to prolong Controller life

8. LOW ROLLING RESITANCE TIRESShaw Lewis - EV Enthusiast, and Jason Greenblatt, Engineer

9. Take Stock of You’re Rolling Stock Tires do the following: Elevate a vehicle wheels from the ground Support vehicle payload Provide modest suspension damping Accelerate and decelerate a vehicle Provide cornering forces to steer a vehicle

10. Each vehicle has its own characteristics and drive cycle with unique needs This will affect the choice of tire required or possible

11. Low Rolling Resistance tires are designed to improve fuel efficiency of a car (especially electrics) by minimizing the energy wasted as the tire rolls down the road. A tire may not be marketed as LRR but may still qualify. Consider the following LRR attributes: Manufactured for higher pressures, 40-45 psi or above Additional sidewall construction plys (layers) will be stiffer (light truck tires denoted as LT on tire sidewall) Higher Tread wear rating (harder rubber compound) Stable tread lug design, large lugs, more continuous shoulder Some vehicles may be able to use a narrower section width tire to put less material on the road surface and less drag through the air General Definition

12. Air Pressure • Based on vehicle curb weight • EV’s are typically heavy! • Do not over inflate tire • Uneven tire wear • Higher pressure resists sidewall deflection • Eats up energy, think of rubber bands • Low Pressure increases road contact • Think of a mountain bike versus a road bike • Increases cornering ability, maintaining speed

13. TREAD DESIGNS AND PATTERNS • Larger blocks are stable, avoid flexing and heat generation • Larger blocks can enhance handling, preserve cornering speed • All weather tires may have more voids • Open areas create air drag The more detailed the tread design, the more likely it will grip the road better. But this also creates the opportunity to trap air in each of the pockets when touching the road surface. When trapping the air/water/dirt/snow in these pockets, the tire is compressing the material that is in the pocket. Therefore, the engine has to do more work to compress these pockets. This makes the tire less efficient to turn, and reduces the mileage of the vehicle.

14. TREAD DESIGNS AND PATTERNS It boils down to personal preference. For a sporty ride you might want softer rubber with better road adhesion. If you’re a fanatic for mileage and a very mellow driver, then you may want the lowest resistance tire you can find on the market. Economy and Sport Traction can some times go hand in hand Show models of tires with tread design BFGoodrich g-Force T/A KDW 2 50psiI Dunlop Direzza DZ101 50psi

15. TIRE PRESSURE LRR tires make an important difference, but they will not be as important as having your tires properly inflated.

16. KEY INFORMATION FOUND ON TIRES

18. Don’t forget your wheels These guys rotate, translate and spin Tirerack.com is awesome for details

19. CAUTION A tire with stronger LRR characteristics may be less safe in adverse weather conditions or safer in good driving conditions. If the tire is over inflated (too round), the tire-patch (the area of tire that is in contact with the ground) will be too small to grip the road surface effectively. This in turn will allow the wheel to skid easier when trying to stop or allow the wheel to slip and spin when accelerating from a stop. If using Stock tires pay attention to recommended tire pressure on your vehicle Pay particular attention to ratings displayed directly on the tire itself

20. For typical EV conversion tires, consider these characteristics: Manufactured for higher pressures, 45 psi or above Additional sidewall construction plys (layers) will be stiffer (light truck tires denoted as LT on tire sidewall) Higher Tread wear rating (harder rubber compound) Low Rolling Resistance tires are designed to improve fuel efficiency of a car (especially electrics) by minimizing the energy wasted as friction as the tire rolls down the road.Some vehicles may be able to use a narrower section width tire to put less material on the road surface Pay attention to how heavy your car is and the load capacity of each tire. The weight balance front to rear of the car needs to be considered when choosing tires as well so as not to underrate a tire. CONCLUSION

21. Appendix • Moment of Inertia I=Mass* Radius2 • Radius is taken as the CENTER of Mass • Average Radius can be estimated for tread section Sidewall section

22. Vehicular Phenomena Transportation in California represents nearly 40% of Carbon Dioxide emissions Combustion engines are typically less then 25% efficient

23. references Combustion engine efficiency picture http://ffden-2.phys.uaf.edu/102spring2002_Web_projects/Z.Yates/Zach%27s%20Web%20Project%20Folder/EICE%20-%20power%20losses.htm