“When a road becomes so full of holes or so worn as to require coating throughout its entire length and width, it should be hacked completely over and raked into a segmental form in its transverse section to remove irregularities, and so that the road may have a fall from the crown to the channel of not less than one inch to a yard. It should then be coated with stone broken as nearly cubical as possible and to an uniform gauge. When spread it should be slightly coated with gravel screenings, or the grit sweepings from the roads, which are equally suitable for the purpose when in proper condition. The road should then be watered and rolled, beginning with the road at the channels, and ending at the crown of the road, until a smooth surface is obtained, more stones being added to fill up any inequalities that may exist, until the whole is consolidated. By constantly sweeping the grit from the sides to the crown of the road as the roller passes over, every stone is thoroughly grouted into its bed.”
Mr. R. Read, the Surveyor of Gloucester, says:[49] “The road should be thoroughly well lifted and the metalling spread in three-inch layers evenly, and rolled once or twice before the gravel or other binding material is spread; then spread gravel or sand evenly and well watered with fine distributor until the stone is entirely covered, and the sand does not adhere to the roller. Dam up the road channels to prevent water and sand running off into sewers and let men scoop up the water, and throw it back on the road, as it collects in the gutters.”
In all cases the sides should be rolled first to such a degree of firmness that when the roller passes over the centre or crown of road, its weight, which tends to spread the metal or make it work off towards the sides, may be resisted by their consolidation.
With reference to the effect of the weight of steam road rollers upon roadways, it may be well here to compare that of a 15-ton roller with other burdens that a road has to bear, taking each case at per inch of width of tire.
An ordinary loaded two-wheeled cart presses with a weight of about 9 cwt. per inch width of tire, a loaded wagon about 7¹⁄₂ cwt., a 9-ton traction engine about 3³⁄₄ cwt., and a 15-ton steam road roller about 3¹⁄₂ cwt. So that as far as the surface of the roadway is concerned, a roller affects it the least of any of the above loads.
It has, however, been found that where rollers of more weight than 15 tons are used,[50] not only are they unwieldy, but, from their great weight, the solidity of the foundation of the roadway may be interfered with, and also there is great danger of damaging gas or water mains and services, besides any cellars that may be constructed under the roadway.
The steam rollers which are principally used in this country, are those manufactured by Messrs. Aveling and Porter, and those by Messrs. Green and Sons, drawings of both of which are here represented.
MESSRS. AVELING AND PORTER’S 15-TON STEAM ROAD ROLLER.
