7/29/2019 Leaf Pointer

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Leaf (Pointer)Purpose/ Function:

1. To indicate correct value of parameter such as speed, rpm, fuel level, temperature, air pressure, oil pressure etc.2. To accommodate bush for mounting of pointer assembly over pointer axle.3. To get accommodated inside pointer cap.4. To accommodate counter weight for balancing.

Possible Modes of Failure:1. Bending failure at the base of pointer leaf.2. Vibrations may lead to error in reading.

Design Considerations:-1. It acts as a Cantilever Beam so, it should be broader at the base.2. The other end should be narrow to match precisely with dial markings.3. The taper provided on the stem should be such that, lower base is to be parallel to dial and upper surface to be slanted.4. Flatness of the lower surface of leaf pointer should be controlled.5. The taper provided on stem should not make leaf susceptible to vibrations.6. Sufficient clearance between dial and pointer leaf is to be specified. This avoids jamming of pointer leaf over dial.7. Its stem should be raised at higher level as compared to round base.8. Provision should be made for accommodation of counter weight for balancing.9. Projections should be provided on round base. This avoids slipping of counter weight and acts like stopper for counter

weight.10. Pointer Bush to be insert molded in the leaf (pointer).11. The material should be able to hold the pointer bush firmly after cooling.12. There should not be any cracks around the bush after leaf pointer solidifies.13. It should be free from molding defects such as flash, warpage, shrinkage etc.14. Holes for hot sealing of pointer leaf with pointer cap to be provided. The holes should be Counter Bore type.15. Adequate clearance between sealing projections and holes to be specified (about 0.1 mm).16. The height of sealing projections should be 1 1.5 mm above the round base to ensure enough material for hot sealing.17. The C.D. of holes on leaf pointer should match with C.D. of projections provided on cap pointer.18. Its stem should be painted with bright color so as to assure visibility.19. The color of the stem should be fluorescent to facilitate night vision.20. Adequate clearance to be provided between O.D. of round base of leaf pointer and I.D. of cap pointer.

Material: - Polycarbonate (Bright Colored).

Properties of Material:

POLYPROPYLENE

PHYSICAL PROPERTIES

Density 0.0325-0.0448 lb/in3

Water Absorption 0.01-0.1 %

Moisture Absorption at Equilibrium 0.10%

Moisture Vapor Transmission 23.9 cc-mil/100 in-24hr-atm

Oxygen Transmission 241 cc-mil/100 in-24hr-atm

Environmental Stress Crack Resistance 1000 hour

Linear Mold Shrinkage Min. 0.006 in/in

Melt Flow 0.5-136 g/10 min

MECHANICAL PROPERTIES

Hardness, Rockwell R 70-113

Hardness, Shore D 68-83

Tensile Strength, Ultimate 2860-11600 psi

Tensile Strength, Yield 1740-6240 psi

Elongation @ break 3-887 %

Elongation @ Yield 3.5-110 %

Tensile Modulus 72.5-1100 ksi

Flexural Modulus 79.8-350 ksiFlexural Yield Strength 3450-7250 psi

Compressive Yield Strength 6820-7250 psi

Izod Impact, Notched 0.3-NB

Izod Impact, Un notched 12-31.1 ft-lb/in

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Izod Impact, Unnotched Low Temp 4.96-40.1 ft-lb/in

Izod Impact, Notched Low Temp 0.506-2 ft-lb/in

Charpy Impact, Unnotched 6.66-NB

Charpy Impact, Notched Low Temp 0.619-80.9 ft-lb/in2

Charpy Impact, Unnotched Low Temp 3.81-109 ft-lb/in2

Charpy Impact 0.952-45.2 ft-lb/in2

Gardner Impact 0.885-21.8 ft-lb

Low Temperature Gardner Impact 8.11-35.4 ft-lb

Tensile Creep Modulus, 1 hour 79800-102000 psiTensile Creep Modulus, 1000 hours 31900-63800 psi

ELECTRICAL PROPERTIES

Electrical Resistivity 1E+14-1E+17 ohm-cm

Dielectric Constant 2.2-2.3

Dielectric Constant, Low Frequency 2.3

Dielectric Strength 559-3560 kV/in

Dissipation Factor 0.0002-0.002

Dissipatin Factor, Low Frequency 0.00007--0.00081

Surface Resistance 1E+10-1E+14 ohm

Arc Resistance 136 sec

Comparative Tracking Index 600 V

THERMAL PROPERTIES

CTE, linear 200 C 13.9-103 in/in-F

Heat Capacity 0.478 BTU/lb-F

Thermal Conductivity 0.694-0.902 BTU-in/hr-ft-F

Melting Point 266-334F

Maximum Service Temperature, Air 111-298F

Deflection Temperature at 0.46 MPa 55.4-460F

Deflection Temperature at 1.8 MPa 98.6-298F

Vicat Softening Point 95-298F

UL RTI, Electrical 149F

UL RTI, Mechanical with Impact 149F

UL RTI, Mechanical without Impact 149F

Flammability, UL94 HB

OPTICAL PROPERTIES

Haze 11%

PROCESSING PROPERTIES

Processing Temperature 396-486F

Rear Barrel Temperature 428F

Middle Barrel Temperatue 428F

Front Barrel Temperature 428FNozzle Temperature 428F

Mold Temperature 95-120F

Drying Temperature 180F