car jack

UNIVERSITI TENAGA NASIONAL COLLEGE OF ENGINEERING DEPARTMENT OF MECHANICAL ENGINEERING

MESB443 ELECTRO MECHANICAL SYSTEM Project Title: MOTOR SELECTION FOR AN AUTOMATED CAR JACK SEM 1 2013/2014

GROUP MEMBERS

:

1. KIRANRAJ A/L KUPPUSAMY

ME085582

2. MANORAJ A/L MOHAN

ME085593

3. ATHIQURRAHMAN

ME

4. RUBAN A/L AVADIAR

ME085654

LECTURER

: DR KHAIRUL SALLEH

SUBMISSION DATE

: 24/09/2013

INTRODUCTION

An automotive jack is a device used to raise all or part of a vehicle into the air in order to facilitate vehicle maintenances or breakdown repairs. Most people are familiar with the basic car jack (manually operated) and it’s included as standard equipment for most of the new cars. Vehicle owners who would like to rotate their tires themselves either front to back and so forth or who may install snow tires before the winter and remove them in the spring need to use a jack to perform the job. Changing a flat tire is not a very pleasant experience. Nowadays, a variety of car jacks have been developed for lifting an automobile from a ground surface. Available car jacks, however, are typically manually operated and therefore require substantial laborious physical effort on the part of the user. Such jacks present difficulties for the elderly and handicapped and are especially disadvantageous under bad weather conditions.

In light of such inherent disadvantages, commercial automobile repair and service stations are commonly equipped with large and hi-tech car lift, wherein such lifts are raised and lowered via electrically-powered systems. However, due to their size and high costs of purchasing and maintaining electrically-powered car lifts, such lifts are not available to the average car owner. Such electrical-powered portable jacks not only remove the arduous task of lifting an automobile via manually-operated jacks, but further decrease the time needed to repair the automobile. Such a feature can be especially advantageous when it is necessary to repair an automobile on the side of a roadway or under other hazardous conditions. There also reports on car jacks which lead to a serious number of accidents. A specified jack purposed to hold up to 1000 kilograms, but tests undertaken by Consumer Affairs has revealed that is fails to work after lifting 250 kilograms and may physically break when it has a weight close to its 1000 kilograms capacity. Tests have proven that the jack has the propensity to buckle well under the weight it is promoted to withstand, and it doesn’t meet the minimum or performance requirements of the Australian Standard for vehicle jacks [5]. The purpose of this project is to develop a car jack which is easy to be operated, safe and able lift and lowering the car without involving much physical effort.

MOTOR SELECTION

The development will be based on this scissor jack. The screw shaft which can be rotated and raise the head load up and down. The screw shaft is very important because in this design will need a system which can withstand the load and lock the raised level of the jack. The screw will be the mechanism to adjust and hold the height level.

Factor of safety, FS= 2 A 12V DC was chosen to be the motor for this car jack . The main reason for this is to make this car jack portable and to use car battery as the power source . Therefore , the motor will be connected to a car socket power supply . For designing this car jack , a lesser rpm and a higher torque are needed. So , that it can carry a heavy load. However , if we have a higher gear ratio then a lesser torque motor can be used .

MOTOR SIZING CALCULATION System Requirement Total mass of the work, m

1000 kg

Linear speed, V

0.008 m/s ± 0.002 m/s

Lead screw tilt angle, θ

0o

Total length of lead screw, LB

0.35 m/s

Diameter of lead screw, DB

0.015 m/s

Lead screw pitch, PB

0.005 m/rev

Total distance moved, A

0.002 m

Lead screw efficiency, η

0.7

Material of lead screw

Iron

Internal frictional coefficient of pilot pressure nut, µo

0.3

Frictional coefficient of sliding surfaces, µ

0.05

Motor power supply

12V DC

Speed Range at Gearhead:

Minimum speed: 72 rpm Maximum speed: 120 rpm

Gear Ratio, i :

Gear ratio of 25 is chosen due to availability

Torque Load weight in the direction of lead screw shaft:

Pilot pressure load:

Load Torque:

Peak Torque: =

=

= 0.0285Nm Multiplying with the safety factor of 2 0.0285Nm x 2 = 0.057Nm Hence the motor chosen is IG-38PGM 01&02 TYPE motor. This motor has a rated torque of 0.09 Nm and a max rpm 1100. Inertia

Gearhead shaft total load inertia:

2

2

6.88 x 10-2 kgm2

Jmotor < Jtotal

CONCLUSION After calculating the requirements of the car jack system, the motor selected would be IG38PGM 01&02Type motor. This is a 12V DC motor that has a rated torque of 0.09 Nm and a max rpm 1100 with gear head of 25:1 ratio because it fulfills all the requirements. This DC motor can meet the load inertia requirement while other types of motor cannot. Car jack need to carry lots of weight . Thus, the high gear ratio would help the car jack to lift the car. As the torque needed to lift the car is 0.057N.m. This motor apply a 0.09N.m ( from catalog) . Plus , the factor of safety is 2 . This proves that this mechanism is not overdesign. Therefore , this DC motor is the suitable motor to be used in this car jack system. Plus the voltage make it easy to use with car power socket . The torque and rpm suit the requirement of the car jack .