The Conveyance of Corrosive Liquids by Road Tank Wagons.
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TN a considerable number of important Indus-1-tries use has to be made of corrosive liquids, such as certain gelds and alkalis, of which hydrochloric, sulphuric and caustic soda are typical examples. Likewise, there are processes which involve the production of such liquids in comparatively large quantities, and the problem in either case is to provide suitable containers in which they can be transported or stored.
Until comparatively recently _glass carboys were practically the only type of container available where the corrosive strength of the liquid was considerable. A certain amount of success has been achieved by the use, for tanks, of what is often called rustless steel, but even when made of that material they did not always last for any great length of time. A. certain amount of work was also done In connection with the employment of containers lined with ebonite, but here trouble was experienced with cracking due to the unequal expansion of the metal and the ebonite securedto it. Wood containers have also been employed to a certain extent, but they are inconvenient, not of any great strength and, moreover, it is essential to tighten them by means of the liquid which they are to store.
Now, the carboys and other containers of small size are difficult to handle, extremely easy to fracture in transport and liable to be knocked over; they constitute a considerable expense, occupy a lot of space either when stored or in transit, and are not at all suited to bulk conveyance.
A solution to the problem has arrived in the shape of the metal tank lined with soft, flexible rubber, actually vulcanized to the metal by utilizing a chemical flux and heat derived from steam. The metal tank acts really as nothing else but a means for supporting the rubber, the liquid-tightness being purely in the latter. Consequently, a cheaper form of tank may be employed, and to make up for the cost of the rubber lining it has been essential to adopt this procedure.
The tanks for transport by motor vehicle do not codstitute the whole of the necessarSi equip
ment. For efficiency it is essential that works employing large quantities of liquid should also be provided with suitable tanks and these can, with advantage, be raised to give •a head of liquid so that discharge can be made to any part of the works through suitable conduits, in which case the vehicles must be able to discharge the contents of the tanks they carry to a height sufficient for the refilling of the stationary containers. This, however, is easily effected by the employment of an air compressor and the actual pressure required is not great.
The system opens up great possibilities because the quantity of these liquid g which have to be dealt with in the course of a year amounts to many thousands of tons. At present the small number of tank wagons of the rubber. lined type is in the employ of the chemical makers, but there may be an opening here for a transport contractor. With enough capital available it would be a paying proposition to hire out storage tanks, which would enable more road tankers to be employed.
Those Conversions to Pneumatics.
lk if. ANY misunderstandings are sure to arise 1.11-out of the conversions of tyre equipment from solids to pneumatics which are taking place in such large numbers just now all over the country. Some owners, we gather, make the change with diffidence, having the fear that it will involve extra expenditure in other directions which may equal—may possibly exceed— the saving to be effected in the annual tax. Others, going to the opposite extreme, have exaggerated anticipation of economics and increased earnings, which will be the outcome of the alteration.
The actual results will most certainly lie between these extremes and, other things being equal, it is reasonable to expect that direct economy in running costs should result from the substitution of pneumatics for solids. We say "other things being equal," and therein is a warning for our readers. Economy in operating costs is only certain in the case of converted vehicles when the speeds and conditions after conversion are very nearly the same as before. If speeds be increased, then it may be that petrol consumption will go up. Definite savings in fuel are only sure, weight for weight and mile for mile, in vehicles designed to run on pneumatics, having gear ratios and wheel sizes proportioned to give economic engine speeds at the higher rate of road travel. This circumstance does not, however, in any way operate to falsify hopes of increased earnings from higher weekly mileages with the converted pneumatic-tyred machines. Those higher mileages will be possible because of the capacity of the vehicle to run at higher speeds as well as because of the removal of the legal ban on such speeds.
Incidentally, the keenness with which vehicle owners are turning to pneumatics should be an Indication to the• Chancellor of the Exchequer of the very serious way in which heavy vehicle taxation is regarded by users as a whole.
Free Wheels for Sleeper• Coaches.
NrOW that the sleeper coach is likely to be
brought into use in fairly large numbers, it behoves chassis and body designers to work in concord to produce vehicles which will give the greatest possible degree of satisfaction to travellers. It must not be thought that we wish in any way to depreciate the types which already exist, but however good a product may be there is always room for improvement. Thus, it is quite possible, and even probable, that the night coach of a few years hence will be totally different from that in service to-day.
There is one particular point which requires attention. We allude to the disturbance of sleep often occasioned by the changing of gears and the. consequent variation in the transmission hum. Even if the change be effected quietly the ear, which has become attuned to one note, quickly takes cognizance of any considerable variation in the pitch.
So far as the actual gear-changing is concerned we believe that the employment of a good type of free-wheel device would prove extremely beneficial. Such a fitting would also assist in other directions, for much of the noise from the transmission results from the overrunning which takes place when proceeding downhill with the engine in gear.
It is, of course, essential that the brakes on a vehicle equipped with a free wheel should be really effective, and with an unusually large area of friction service. Coasting often necessi tates considerable use of the brakes, and their life must not be unduly shortened, whilst any danger of overheating must be obviated.