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

RECTIFIED POWER OUTPUT VS TIME

0

0

TIME

PO

WE

R

Fundamental IVT Functional Components

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

Previous Issues

• Failing Bearings

• Complex Masses

• Bearings shifting off lobes (axial play)

• Bending in Cantilevered Arm Assembly

Improvements

• Masses – Rectangular for easier

manufacturing/testing

•Roller Bearings with Inner Race

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

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

0

5

10

15

20

25

30

35

0 500 1000 1500 2000 2500 3000 3500

RPM

Pow

er (k

W) 2005/2006 IVT

Engine Output

2004/2005 IVT

Baja/IVT Modeling

Acceleration vs Top Speed

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.0 10.0 20.0 30.0 40.0 50.0 60.0

Top Speed (km/hr)

Acc

elle

rati

on

(m

/s2 )

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