Surface dressing machinery

The paper deals with the machinery required for modern surface-dressing work. For convenience the subject is divided as follows: Binder distributors Gritting and loading machinery Rollers The principles involved in the design and operation of the common types of binder distributor are discussed, and photographs arc shown of representative machines. Common faults occurring in the work done by the different distributors arc considered. Tests are described for measuring transverse and longitudinal uniformity of binder film, and results are quoted to show the quality of some of the work being done at the present time; practical tolerances are suggested. Several types of gritting machine arc described and the results given of an investigation made on 12 sites to compare the number of men used and the output obtained from four types of primer. A single result is given to show how fast a normal gang can spread chippings if not held up for materials. Some measurements have also been made on the transverse and longitudinal variation in the rate of spread of chippings by the different methods. Brief descriptions are given of three modern methods of loading chippings (self-loading elevator, the mechanical shovel and the clam-shell grab) and some figures are given for the output of each. The size of roller required for finishing the dressing is discussed and an experiment is described in which sections have been laid with different weights of roller and without any roller at all.