EFFICIENT VENTILATION AT ALL SPEEDS.
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A Scientifically Designed Device which has Achieved Much Recognition.
MHE Airvac ventilator, which is manufactured by Messrs. Airvac Ventilators, Honeypot Works, Darlington, has been on the market for about four years, and during that period it has won considerable recognition in passengervehicle circles for use on all types of motorbus and motor coach, quite apart from the uses to which it has been put in ambulances and other types of vehicle. It is only a few months ego that the company introduced its improved models, iehich were produced after much additional data had been obtained concerning the action of air over specially shaped surfaces and apertures under different conditions and varying velocities, this research work having been carried out not only in the works of the company hut under actual running conditions on the road in all weathers.
In connection with the new models it is claimed that quicker action at low speeds and a better performance over the complete range of speeds are now obtained, thus giving accurate ventilation balance in relation to the rate of travel —a factor of the utmost importance in securing satisfac tory ventilation at all times. In general appearance the new models are similar to the earlier designs, the chief features now being wider exterior vanes of a different crosssection, larger side and interior apertures and a new arrangement of the interior vanes.
Another innovation consists of a patent mounting block (shown in an accompanying illustration) for use with the interior fittings. This block is designed to eliminate the retarding influence set up to air extraction as the result of the presence in the interior of the vehicle of a grille or shutter, which covers the aperture in the roof below the
ventilator. By fitting a grille or shutter to this patent block no such obstruction occurs, as specially shaped grooves communicating with the main aperture in the roof, as well as
with each other, are cut on the upper surface of the block above the interior fitting, the arei . of the grooves being greater than that of the solid portions of the grille. The blocks are made in three sizes and can be stained, polished, varnished or painted to suit individual requirements. In the Airvac ventilator two distinct cycles of operation are employed, both of them being automatic. The low-speed cycle enables the ventilator to produce the maximum ejector action at extremely low speeds and, as a matter of fact, extraction commences at m.p.h., whilst the other takes effect under higher speed conditions. Jt is this principle which enables the company to claim that its ventilator possesses the unique feature whereby balanced proportionate ventilation to the rate of travel is secured. There are no moving parts in the Airvac. It is weatherproof and operates automatically and continuously whatever the weather conditions.
Type RM is the standard bus•model, for which two types of interior fitting are made, type II,MP consisting of a plain grille, and type RAIL of an electric roof light and grille combined. There is also a Smaller model, type RA, which
was designed primarily for touring ears, ambulances, etc., but this is also being used with success on buses of different sizes. The general constructional details of the two models can be clearly seen from certain of the accompanying illustrations.
It is interesting to know that the Airvae ventilator is patented in 19 countries, and in this connection we should state that the company is prepared to negotiate for certain agencies overseas.
For those who wish to secure fuller details of the design and application of this particular type of ventilator we would recommend them to secure a copy of a fully illustrated and descriptive catalogue, entitled "Travel Comfort," which the company has recently issued. This contains much infcrmation relating to the general subject of ventilation on vehicles and embodies certain performance charts.