Road Roller
The most essential machinery which is required in road marking is a road roller. It is used for making any surface, subgrade base or the wearing coat. A road roller may be driven by men, animals or by power.
Types of Road Roller
The types of road rollers which are being used these days are:
(a) Smooth Wheeled Roller
(b) Pneumatic Tyred Roller
(c) Sheep Foot Roller
Smooth Wheeled Roller
This type of roller has several kinds as given below :-
(i) The Hand Roller : It is a light Roller made of cast iron, stone or concrete. It is about 1 meter in diameter and 1.67 meters long. It is drawn on the ground by hand or by animal power. It is exerts a pressure of about 6.5 kgf/cm^2 on the ground. It has weight of about 2 tonnes. It is used for smoothing the play grounds etc.
(ii) Tanden Roller : A tanden roller is Light weight roller having only two wheels. It is used for initial rolling of roads and for dressing the surface only. This roller usually weights 4 to 8 tonnes and exerts an approximate pressure of 7.5 kgf/cm^2 to 16 kgf/cm^2. This type of rollers are generally driven by diesel oil.
(iii) Three Wheeled Roller : This roller has three wheels, one steering wheel and two rear wheels. The weight of such roller varies from 10 tonnes to 15 tonnes. These are driven by steam or diesel oil. These roller are quite suitable for hard surface. In order to increase the rolling pressure on the road, the wheels are filled with water or loaded with some weight.
Pneumatic Tyred Roller
A pneumatic tyred roller is a small size truck having one or two axles on which a number of smooth rubber tyres wheels are placed. The truck is provided with a platform on which the load may be put in the form of sand bags or in some other form in order to get the required intensity of pressure.
These rollers are very efficient in consolidating earth sub grades. These are very useful for granular soils and in final operations, bituminous surface dressings etc. These rollers are also very useful for sandi-soil compaction.
Sheep Foot Roller
A sheep foot roller consists of heavy metallic cylinder having 1 to 1.5 meter diameter and 1.2 meter length. These cylinders have 19 to 23 projections extending out of the curved surfaces of the cylinders. These projections are arranged on the periphery of the cylindrical drums in rows and have the shapes of sheep feet.
This is the best machine for compacting soil because the feet of the roller penetrates in to the soil and presses it ensuring the proper compaction of soil from the bottom itself. The cylindrical drums are hollow from inside and can be filled with some material to increase their weights.
The efficiency of a sheep foot roller is as high as that of a flat wheeled roller. As tractor is used for pulling the sheep foot roller. The speed at which the roller is pulled by the tractor is 3 to 5 km/hour.
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