HEAVY EQUIPMENT DIVISION

 

DIVISION OF ROADS

HEAVY EQUIPMENT DIVISION

MINBHAWAN, KATHMANDU

NEPAL

 

 

 

 

 

 

 

 

 

 

A CASE STUDY ON:

THE MAINTENANCE OF THE AIR ASSISTED BRAKE SYSTEM

 

                                                             SUBMITTED BY:

ABHISHEK PAUDEL (401)

GOVIND KUMAR CHAUDHARY (416)

PRAMOD KUMAR SAH (433)

 SAGAR ARYAL (439)

 

SUMBITTED TO:

MR. KHEM GYANWALI

DEPARTMENT OF AUTOMOBILE AND MECHANICAL ENGINEERING

THAPATHALI CAMPUS, THAPATHALI

   INTRODUCTION:

Division of Roads, Heavy Equipment Division is located at the heart of Kathmandu city, Minbhawan, and deals primarily the repair and maintenance of a range of vehicles from light to heavy ones. Heavy vehicles include bulldozers, excavators, cranes, trailers, rollers, etc. and light vehicles comprise of cars, motorcycles, etc.

This is a historic place of quality service for the repairs and maintenance of a variety of vehicles. Since we as were asked to make a case study upon either management of production/maintenance of the respective firm, we chose to depict actual procedure through which each vehicle goes during the maintenance period.

To accomplish the above task, we took a sample problem that occurred on a heavy truck with a vacuum assisted hydraulic brake system. Before dealing with the problems and solutions, we would like give a brief introduction about vacuum assisted hydraulic brake system.

Vacuum assisted hydraulic brake system

 

 A general diagram of vacuum assisted hydraulic brake system is as shown in the fig.1 above which generally used in the cars. It consists of many subsystems starting from a pedal linkage using which the driver applies the brakes. The pedal linkage is connected to the input of the vacuum booster that assists the driver in applying more effort to stop the vehicle. The booster has a diaphragm that is open to atmosphere on one side, and has vacuum on the other side. The vacuum is achieved using a vacuum pump. The difference in the pressure on either sides of the diaphragm provides the assisting force. The force from the booster is used to pressurize the fluid in the master cylinder. The pressurized fluid is conveyed to the wheel cylinders of the front and the rear brakes. At the front wheel, the wheel cylinders apply pressure to the brake pads that apply force to the brake disc. At the rear, this force is applied to the drum through the brake shoes. The brake shoes at the rear are also connected to the parking brake mechanism.

What is the problem?

According to the driver of the vehicle, different problems were seen on the brake system since a few days before like difficulty in braking i.e. the brake pedal needed to be pressed hard and even if the brakes functioned, it made screeching sounds and showed pulsating behavior making it very uncomfortable to balance. Hence taking the safety considerations into account, it was finally brought for servicing at service station. And especially problem was on the rear wheels.

What will be the solution?

After studying the problems thoroughly and making some preliminary inspections, the senior mechanic suggested that problem maybe on drum brake systems and asked the junior mechanics to overhaul the rear wheels and drum brake systems. There were double caliper drum brakes i.e. double power cylinder at each of the wheel. The brake shoes had got rusty, maybe due to long continuous run without any servicing and interiors were overwhelmed in dust which also caused poor lubrication of the moving parts so that they felt very hard move. One thing worth noting was that pistons wouldn’t move with ease as they should commonly. They were actually worn out and lost their smooth shape.

Each of the rear wheels was dissembled into parts as suggested by the senior mechanic. The deteriorated lubricants and greases were also removed and each of the parts was cleansed with clothes with care. Then the pistons were replaced with new ones. The brake shoes were slightly smoothened with sand papers. The parts were assembled as they should be along with use of grease at required place.

During this maintenance period, formal communications occur among the vehicle owner or driver, CDE, Engineer, mechanic and the store officials time to time. Since we are concerned at maintenance procedure only, we skip the information flow containing the paper work that comes along as it has been discussed previously.

this figure shows the different parts of a single caliper drum brake.

Conclusion

In the heavy equipment division, a considerable number of vehicles are maintained everyday of variety of category but procedure is the same more or less. The paper work process is same, difference is that one may involve one type of store, mechanic, Engineer while other may involve others. The maintenance is purely technical aspect but can’t stand apart from information flow system. Technically, it requires thorough understanding of the problem, then inspection and overall repair and replacement.

Recommendations

During this short period of our attachment time, we involved ourselves in several activities and had chance to view them work in the stations very closely and would like make some recommendations on the way they perform their activities.

The technical personnel are sound in their technical skills and good in theoretical knowledge too but they should adapt to the changing environment of technology and time. This will make them attain higher level of skills. We would also like recommend them to use the user’s manual of the vehicles beforehand of going through the maintenance which will have a better quality upon service they offer. Also, we recommend on maintaining sufficient amount of tools at the workshop on well managed tables, using the new versions of tools that prove highly efficient, keeping the workshop neat and clean as far as possible to lift up moral of people working over there.