Transcript Infinitely Variable Transmission
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