Infinitely Variable Transmission

Dalhousie University Mechanical Engineering

The Team

Well, Dr. Hubbard hoped we’d fail the first time… • Joel Kaser • Craig Martin • Blair Mountain • Kirby Nickerson

2006 SAE MINI-BAJA

• Infinitely Variable Transmission (IVT) – Design, Build, and Test • Improvements

DESIGN REQUIREMENTS

• IVT designed for Mini Baja power, size and shape • Weight of IVT is to be less than 31lbs • Vibration free • Maintenance free throughout Baja Competition • Total cost less than $1000.00

CVT and IVT’s

• Most CVT’s use varying pulley diameters • Range between fixed limits (1 to 4) • IVT range is 0 to 1 • Acts as a clutch • 70% versus 90% efficient

Infinitely Variable Transmission

IVT Mechanics

IVT Mechanics Fundamental IVT Functional Components RECTIFIED POWER OUTPUT VS TIME TIME

IVT Mechanics

• Output from Engine is Input to IVT • Input Yoke Spins Masses via Pins and Links • Masses are Fixed to bearings which sit on lobes • Lobes have offset shaft bore, creating moment arm

IVT Mechanics

• Rotation of masses creates a moment about arm assembly shaft • As mass spins relative to lobe, direction of torque changes • Oscillation of torque direction results in oscillation of arm shaft rotation

IVT Mechanics

• Oscillating shaft disadvantageous • Set of one-way clutches stop counter-clockwise rotation of arm assembly shaft.

• Arm assembly shaft oscillates between no motion and clockwise rotation • Do not want output shaft to exhibit stop/go movement

IVT Mechanics

• To achieve consistent output shaft rotation, additional set of clutches in output shaft – These clutches clamp onto arm assembly shaft, operate opposite direction of earlier clutches – When arm assembly shaft rotates clockwise, clutches clamp, causing output shaft to rotate – When arm assembly stops, clutches release, allowing output shaft free rotation

Infinitely Variable Transmission

Model Demonstration

Infinitely Variable Transmission

Design Improvements

• Failing Bearings • Complex Masses

Previous Issues

• Bearings shifting off lobes (axial play) • Bending in Cantilevered Arm Assembly

Improvements

•

Roller Bearings with Inner Race

- Eliminated need for hardened steel lobes - Easier Manufacturing Increased to 1.5” ID for better load rating •

Masses

– Rectangular for easier manufacturing/testing

Improvements

• • • – – – – –

Lobes

standard steel vs. hardened Lip and c-clip to prevent bearing axial motion ¼” offset for greater torque increased to 1.5” OD Brass spacers between lobes –

Yoke Pins (red)

Spacers added to restrict axial motion –

Arm Support (yellow)

Retained by spring pin to make body + arm + support one solid assembly

Improvements

•

Yoke Body

– Second bearing (red) to prevent cantilevered bending – Moved input shaft out of body ½” •

Arm Assembly Shaft

– 5/8” ASTM 1144 to resist shear – Extended ½” to allow second bearing to prevent cantilevered bending

Infinitely Variable Transmission

Baja / IVT Modeling

Baja/IVT Modeling Power vs RPM 35 30 15 10 25 20 5 0 0 500 1000 1500 2000 RPM 2500 3000 3500 2005/2006 IVT Engine Output 2004/2005 IVT

Baja/IVT Modeling Acceleration vs Top Speed 1.20

1.00

0.80

0.60

0.40

0.20

0.00

0.0

10.0

20.0

30.0

Top Speed (km/hr) 40.0

50.0

60.0

2005/2006 IVT CVT 2004/2005 IVT

Infinitely Variable Transmission

Current Status

Current Status

• Final Stages of Development • Correctly Model Baja Vehicle – Race Technology AX22 Computer • Optimization of Masses

Infinitely Variable Transmission

Conclusion

Conclusion

• IVT designed to meet all weight and geometry constraints – 52 km/hr – 28 lb • Design will work – Desktop model • Model Baja • IVT prototype functional by end of January

Questions