08.2010 fsae hybrid 3rd presentation gen-3 geared bldc motors, planetary transmission, & early...

Wheel Motor Design

Race Car Engineering - Summer 2010

by

Chad MolyetTobias Overdiek

Project Objective• Development of Geared Front Wheel

Motors on the F11 Hybrid Race Car

Project Objective

Presentation Outline

• Gear Concept• Assembly• Materials and Analysis of Critical

Components• Performance Characteristics


• Gear Concept• Assembly• Materials and Analysis of Critical

Components• Performance Characteristics• Conclusions

Gear Concept

• Increased power to weight ratio• Increased efficiency• Reduction in heat loss

Gear Drive Wheel Motor Advantages

Gear Concept

0 50 100 150 200 2500

500

1000

1500

2000

2500

3000

3500

4000

Heat Loss of Direct Drive Motors

Motor Output Torque (Nm)

Heat

Los

s (W

)

0 50 100 150 200 2500

500

1000

1500

2000

2500

3000

3500

4000

Heat Loss of Geared Motors

06210 geared 1.840 : 1

03014 geared 2.727 : 1

04512 geared 2.727 : 1

06211 geared 1.840 : 1

06212 DD

Torque generated at Wheel (Nm)

Heat

Los

s (W

)

Planetary Gear

Strengths• Strong• Compact• Ease of lubrication• High reduction ratio

Trade-offs• More parts• Complex assembly• Difficult to manufacture

internal teeth• Cost

Ns (sun) 15 17 19 21 39

Np (planet) 28 27 26 25 16

Nr (ring) 71 71 71 71 71

Gear Ratio 5.7:1 5.1:1 4.7:1 4.3:1 2.8:1

Planetary Gear

Strengths• Strong• Compact• High reduction ratio• Ease of lubrication

Trade-offs• More parts• Complex assembly• Difficult to manufacture

internal teeth• Significant lateral load

with helical teeth

NS + 2NP = NR

Load Distribution

• Load divided among planets• Planets spread load further

– Sun teeth– Ring teeth– Planet carrier


• Gear Concept• Assembly Overview• Materials and Analysis of Critical


Assembly Overview

Critical Components

• Sun gear teeth

• Hub / Planet carrier

Gear Loading and Stress

• Design life too short for surface wear• Bending stress limiting factor• Max stress occurs

at the root

Gear Loading and Stress

• Stress computed with Lewis Equation and backed up by ANSYS analysis

RPM 4246

Input Torque N-m 35Input Torque lbf-in 309Wt – max single tooth lbf 205Wa - max planet lbf 118Wa – sun lbf 370

Sigma-b Sun psi 23158

Steel for Gears

• 4130 Steel– Good ductility

• Case hardened– Nitriding– Induction heat treatment

• Bending FatigueStrength (107 cycles)– Raised from 30 ksi to 60 ksi

• Safety Factor > 2.8

Hub Loading and Stress

Titanium for Hub• 60% weight reduction

vs. steel• Minor loss of stiffness• Max stress well

below BendingFatigue Strength

• Safety Factor > 7– Dependent on

specific alloy used

Performance Characteristics


0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.00

20

40

60

80

100

120

140

160

180

200

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

Torque / Power vs. Velocity

K127 Wheel Motor Torque K127 Wheel Motor Power

Velocity (mph)

Torq

ue (N

m)

Pow

er (h

p)


0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.00

100

200

300

400

500

600

700

800

900Torque vs Velocity

Front Axle Rear Axle Combined

Velocity (mph)

Torq

ue (N

m)


0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.00

100

200

300

400

500

600

700

800Force

Resistance+Drag Electric Exclusive Engine + Electric

Velocity (mph)

Forc

e (lb

)


0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.00.00

0.20

0.40

0.60

0.80

1.00

1.20Acceleration - 700lb Vehicle

Engine + Electric Electric Exclusive Engine Exclusive

Velocity (mph)

Acce

lera

tion

(G)

Summary


Components• Performance Characteristics

Questions?

Gear Design Worksheet 1

Assumptions Gear Ratios

Reliability 99Ka 1 Ns (sun) 19 21 23 25 39

Face Width <2 in Km 1.6Np (planet) 26 25 24 23 16

Loading Mod shock Ka 1.25 Nr (ring) 71 71 71 71 71Idler? No Ki 1 Ratio 4.737 4.381 4.087 3.840 2.821

Yes Ki 1.42

Selections

Pressure Angle Phi 20 20 20 20 20 20 20 20 20 20Helical Angle Sci 30 30 30 30 30 30 30 30 30 30

Diametral Pitch (Pd) 19.714 19.71 19.71 19.71 19.71 19.71 19.71 19.71 19.71 19.714Ns (sun) 19 19 19 19 19 19 19 19 19 39Np (planet) 26 26 26 26 26 26 26 26 26 16Nr (ring) 71 71 71 71 71 71 71 71 71 71RPM 2500 3000 3500 4000 4246 5000 5500 6000 7000 4200Input Torque N-m 35 35 35 35 35 27 22.5 17 7 339Input Torque lbf-in 309 309 309 309 309 236 194 150 62 3000

Qv 10 10 10 10 10 10 10 10 10 12Sun J Factor 0.44 0.44 0.44 0.44 0.44 0.44 0.44 0.44 0.44 0.47Planet J Factor 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.43

Sun Diameter 0.964 0.964 0.964 0.964 0.964 0.964 0.964 0.964 0.964 1.978Planet Diameter 1.319 1.319 1.319 1.319 1.319 1.319 1.319 1.319 1.319 0.812Sun Radius 0.482 0.482 0.482 0.482 0.482 0.482 0.482 0.482 0.482 0.989Planet Radius 0.659 0.659 0.659 0.659 0.659 0.659 0.659 0.659 0.659 0.406Wt 205.2 205.2 205.2 205.2 205.2 156.7 128.8 99.6 41.2 970.5Wa - max planet 118.5 118.5 118.5 118.5 118.5 90.5 74.4 57.5 23.8 560.3Wa - sun 370.2 370.2 370.2 370.2 370.2 282.7 232.4 179.7 74.3 1751.1

Face Width 0.905 0.905 0.905 0.905 0.905 0.905 0.905 0.905 0.905 0.944

B 0.397 0.397 0.397 0.397 0.397 0.397 0.397 0.397 0.397 0.000A 83.776 83.776 83.776 83.776 83.776 83.776 83.776 83.776 83.776 106.000Vt 630.8 757.0 883.1 1009.3 1071.3 1261.6 1387.7 1513.9 1766.2 2175.2Kv 0.901 0.893 0.886 0.880 0.877 0.869 0.864 0.860 0.851 1.000

Sigma-b Sun 22545 22741 22919 23082 23158 17854 14761 11475 4790 86247

MPH N-m lbf-in RPMN-m

(at wheel)lbf-ft

(at wheel) HP KW0 35.0 309.8 0 166 122 0.00 0.001 35.0 309.8 77 166 122 0.38 0.282 35.0 309.8 154 166 122 0.76 0.573 35.0 309.8 232 166 122 1.14 0.854 35.0 309.8 309 166 122 1.52 1.135 35.0 309.8 386 166 122 1.90 1.416 35.0 309.8 463 166 122 2.28 1.707 35.0 309.8 540 166 122 2.66 1.988 35.0 309.8 618 166 122 3.04 2.269 35.0 309.8 695 166 122 3.42 2.55

10 35.0 309.8 772 166 122 3.79 2.8311 35.0 309.8 849 166 122 4.17 3.1112 35.0 309.8 927 166 122 4.55 3.4013 35.0 309.8 1004 166 122 4.93 3.6814 35.0 309.8 1081 166 122 5.31 3.9615 35.0 309.8 1158 166 122 5.69 4.2416 35.0 309.8 1235 166 122 6.07 4.5317 35.0 309.8 1313 166 122 6.45 4.8118 35.0 309.8 1390 166 122 6.83 5.0919 35.0 309.8 1467 166 122 7.21 5.3820 35.0 309.8 1544 166 122 7.59 5.6621 35.0 309.8 1621 166 122 7.97 5.9422 35.0 309.8 1699 166 122 8.35 6.2223 35.0 309.8 1776 166 122 8.73 6.5124 35.0 309.8 1853 166 122 9.11 6.7925 35.0 309.8 1930 166 122 9.49 7.0726 35.0 309.8 2007 166 122 9.87 7.3627 35.0 309.8 2085 166 122 10.25 7.6428 35.0 309.8 2162 166 122 10.63 7.9229 35.0 309.8 2239 166 122 11.00 8.2130 35.0 309.8 2316 166 122 11.38 8.4931 35.0 309.8 2394 166 122 11.76 8.7732 35.0 309.8 2471 166 122 12.14 9.0533 35.0 309.8 2548 166 122 12.52 9.3434 35.0 309.8 2625 166 122 12.90 9.6235 35.0 309.8 2702 166 122 13.28 9.9036 35.0 309.8 2780 166 122 13.66 10.1937 35.0 309.8 2857 166 122 14.04 10.4738 35.0 309.8 2934 166 122 14.42 10.7539 35.0 309.8 3011 166 122 14.80 11.0340 35.0 309.8 3088 166 122 15.18 11.3241 35.0 309.8 3166 166 122 15.56 11.6042 35.0 309.8 3243 166 122 15.94 11.8843 35.0 309.8 3320 166 122 16.32 12.1744 35.0 309.8 3397 166 122 16.70 12.4545 35.0 309.8 3474 166 122 17.08 12.7346 35.0 309.8 3552 166 122 17.46 13.0247 35.0 309.8 3629 166 122 17.83 13.3048 35.0 309.8 3706 166 122 18.21 13.5849 35.0 309.8 3783 166 122 18.59 13.8650 35.0 309.8 3861 166 122 18.97 14.1551 35.0 309.8 3938 166 122 19.35 14.4352 35.0 309.8 4015 166 122 19.73 14.7153 35.0 309.8 4092 166 122 20.11 15.0054 35.0 309.8 4169 166 122 20.49 15.2855 34.2 303.0 4247 162 120 20.42 15.2256 33.5 296.3 4324 159 117 20.33 15.1657 32.7 289.5 4401 155 114 20.22 15.0858 32.0 282.8 4478 151 112 20.09 14.9859 31.2 276.1 4555 148 109 19.95 14.8860 30.4 269.3 4633 144 106 19.80 14.76

08.2010 fsae hybrid 3rd presentation gen-3 geared bldc motors, planetary transmission, & early...

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