Fig. 96.—View of Airostyle Plant for 16 Operators, showing Ventilator.
As far as the author can gather information, the processes described in this book are not used in Great Britain to any extent in the finish of tramcars, but are gradually making headway in America, particularly for the final coats. There appears to be no reason, however, why "flowing-on," as described in Chapter XIII., should not be used to a much greater extent than is at present the case. The earlier coats, being very stiff, might be applied by means of brushes, and these coats could be followed by spraying, and finally the finishing coats could be flowed on.
Formerly, this work was done almost in the same way as that by which the fine finish of a carriage body is produced, viz., the building up of a perfectly smooth surface by a large number of coats, rubbing each one down carefully and finishing with two or more coats of varnish, these being also rubbed down excepting the last.
In modern practice these methods are greatly simplified, and at least several coats, which were formerly thought to be necessary, are dispensed with. The finish is often obtained by applying a coat of a suitable enamel, rubbing this down, and then giving a final finish of a good flowing varnish.
It is suggested that spraying, or flowing-on, could be used for some of this work with very great advantage in the saving of time.
In dealing with many paints which are to be stoved, a well-thought-out system should be in use of conveying the articles from the finishing rooms to the painting apparatus and thence to the ovens. If more than one coat is given it will be necessary to arrange also for conveyance after the parts are baked back to the painting plant for the next coat.
As a rule, a system of overhead runways, such as is described for use in paint dipping, will be found the most economical method to adopt.
It will be observed that in the list of trades and articles which may be successfully painted by mechanical means, given on pages 3 to 6, there are many which are omitted from the detailed descriptions. The reason for this is that the main principles are in all cases practically the same and the details must necessarily vary, not only with the goods being dealt with, but according to the extent of the operations and the accommodation of the factory available.
Thornley & Knight, Ltd., of Birmingham, specialise in this business, and have sold, during the last few years, many thousands of gallons of their air-drying coloured japans, for use on car bodies. Many of the largest motor car manufacturers have adopted the process.