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Aviation History
1911
1911 - 0480.PDF
[/OGHH JUNE 3, 1911. THE HYDROGEN BALLOON. By GRIFFITH BREWER. THE average father of a family has enough worry with the gas bill, without bothering to reflect that the gas consumed in the house during the winter would be enough to lift himself and his family up into the air as high as Mont Blanc. Fewer still know that if they were supplied with hydrogen instead of coal gas they would be able to add a respectable amount of luggage and their mothers-in-law to the ballooning party, besides doing the thing comfortably in the way of refreshments. Yet in spite of these advantages, from a balloonist's rather than from a householder's point of view, the man who goes ballooning to-day still takes the same large balloon to the gas works and fills it from the common household gas supply. It is at first somewhat difficult to realise that the air around us has substantial weight—that it actually weighs 75 lbs. per thousand cubic feet. An ordinary schoolroom 50 ft. by 20 ft. and 18 ft. high contains 18,000 cubic feet of air which weighs 1,350 lbs. Now coal gas weighs about 38 lbs. per thousand cubic feet and hydrogen only weighs 5 lbs. per thousand cubic feet, so if one fills an 18,000 cubic ft. balloon, which in itself weighs 400 lbs., with coal gas weighing 640 lbs. (the total weight of balloon and gas being 1,040 lbs.), a net lift of 310 lbs. is secured—this being sufficient to lift one man weighing 160 lbs. with perhaps 140 lbs. of ballast. If, on the other hand, this same balloon be inflated with hydrogen, weighing only go lbs., the total net lift is 860 lbs.—sufficient to lift three men, weighing 160 lbs. each, together with ballast to the extent of 380 lbs. It is therefore evident that three men can have a longer balloon trip with hydrogen than one man can have with coal gas in a balloon of equal capacity. The obvious question that arises therefore is why hydrogen is not always used in amateur balloon ascents, and why when three persons make an ascent together they should take a balloon of 40,000 cubic ft. capacity and fill it with coal gas instead of taking a balloon of 18,000 cubic ft. and inflating it with hydrogen. Everything is in favour of the smaller balloon ; it will lift more with hydrogen than the larger one will lift with coal gas; it offers less resistance to the wind, so that its descent is easier on a windy day; it should suffer only half the disturbance in equilibrium of the larger balloon, due to the expansion and contraction of the gas owing to changes of tem perature ; it weighs less, and is therefore more convenient to handle and to get to the railway station when brought to rest in the grass field selected for the descent; and last, but not least in these days of expensive rubber, it requires but about half the amount of fabric in its manufacture. Why, then, is the little hydrogen balloon, so compact and so efficient, not invariably chosen in the place of the great and more expensive coal gas balloon ? The reason that, up to the present, all amateurs have used coal gas, and put up with the attendant disadvantages, is because coal gas can be bought in London at a reasonable price, viz., from 2s. $d. per thousand cubic feet, whereas hydrogen, not being manufactured there, can only be procured in a compressed state in heavy steel cylinders, brought considerable distances by rail, at £2 per thousand cubic feet. It is, however, manufactured as a by-product of other manufactures in several places some distance away from London, and by taking the l»lloon to the place of manufacture this splendidly light gas may be obtained at little more than the cost of coal gas. It is in the hope of starting a new class of hydrogen balloons that one has just been built at Messrs. Short Bros.' Works at Battersea Park, and if other similar balloons are built no doubt the facilities for inflation with hydrogen will be improved. Even now hydrogen may be obtained at a price of 5^. per thousand cubic feet at the Knowles Oxygen Co.'s Works at Wolverhampton, and it may possibly be obtainable at a similar rate at other places in England and also on the Continent. In the future, it many of these little balloons are built, some enterprising firm may start the manu facture of hydrogen in London, and then the popularity of ballooning will be assured. The building of a balloon of unusual capacity suitable for hydrogen must necessarily be somewhat of an experiment, so the degree of departure from the usual lines of construction appears immaterial. Having decided to build an amateur balloon for use with hydrogen, I therefore introduced several modifications I had long wished to try and which appeared to be of special advantage with a balloon of this small capacity. Those who have watched the tedious process of inflating a balloon, will have seen how the men in charge have to keep working round the balloon, lifting the sand bags and hooking them on to the next mesh of the net lower down, thus allowing the balloon to rise gradually and evenly as the gas enters and distends the fabric. It is necessary to work the sand-bags down evenly, so as to prevent the fabric of the balloon becoming pleated below the net, because if any folds of the fabric eet caueht under the net the pressure of the gas holds them tightly aeainst the net, keeping the balloon out of shape, and this irregu larity besides involving the balloon being reduced in size, causes some'danger of the fabric becoming torn. Now if this labour of working the sixty or more sand-bags, each of which weighs 40 lbs., could be obviated without danger of unevenly inflating the balloon, a considerable advantage would be secured by reducing labour and increasing the speed of inflation, so with this object in view T decided to dispense with the upper portion of the net, and to attach the lower portion to a fabric band situated round the equator of the balloon. The weight of the car, passengers and ballast, would thus be suspended to the fabric composing the balloon itself, in a similar manner to that employed in dirigible balloons. If it is safe to do- this in dirigibles where the fabric not only carries all the weight but also is subject to a certain internal pressure from the gas, it must certainly be safe to employ a similar means of suspension from a sphere where all the strains are equally distributed and where no- internal pressure is allowed to accumulate. The circumference of the balloon is about 100 ft., and the total strain with hydrogen is- 860 lbs., consequently each foot of fabric is called upon, to take a weight of about 8i lbs. I tested the fabric to 200 lbs. per foot and found no sign of it breaking, so we may feel happy in the fact that the material will stand at least twenty times any strain it is likely to encounter when carrying its- party for an afternoon's excursion. This construction also adds a, further factor of safety to the balloon, because if, through any remote cause, it became necessary for the balloon to parachute, it would form a parachute equal to its full diameter of 32! ft., without any tendency for this parachute to roll in, and thus reduce in diameter. The valve employed is also an innovation, it being the new elastic annular membrane valve recently invented by Messrs. Short for use in the Naval airship. The mouth of the balloon is not made with the rigid removable hoop usually employed heretofore, but is limp and permanently attached to the fabric. The net is reduced from. 128 meshes at the equatorial band down to 16 leading lines by doubling, and eight carlines coinciding with alternate leading lines- carry the car directly from the net through the medium of the hoop. The practical balloonist will readily recognise the advantages- gained by these features for simplifying the construction. In the first place the inflation in calm weather can be carried out without using sand-bags, because the balloon can look after itself and inflate evenly by simply having the gas turned on, while at the same time the details of preparing the car can be carried out. The net cannot get out of position during the inflation, because it only contacts with the side of the envelope below the equator where it is not pressed to any material extent, and therefore cannot grip the fabric, and the pleats which would become formed by this method of inflating an ordinary balloon fitted with a net extending over the upper portion, are entirely avoided. The process of inflation is thus effected with a much increased speed, which is only limited by the speed of gas- supply. On making the descent, the rip cord may be pulled in the ordinary way and the gas is thus discharged in a few seconds, and then instead of having to remove the net, valve, mouth and hoop, ife is sufficient to remove the valve and hoop only, and the balloon, net,, and mouth can he rolled up into a single pliable package ; whilst the car receives the hoop, valve, grapnel and trail rope. Everything, should be ready therefore for loading on the cart in ten minutes instead of about half an hour, which is the time usually occupied in. this performance. This saving of time at the descent is of considerable importance, because in addition to avoiding the collection of an inconveniently large crowd, it often means catching the last evening train back to London. Apart from the advantages- of these alterations, the main improvement is of course the reduction in size and weight of everything due to the employment of hydrogen gas for the inflation, but even this is, as I have already said, an experiment which adds a special interest to the experience now being gathered at the first ascents. ® ® ® © Flying to the Assizes. ALTHOUGH it is true that Mr. Grahame-White was the first to keep an appointment at the Police Court by aeroplane, Mr. Graham (.llmour s trip to Salisbury last week, in order to take his trial at the Wilts Assizes, was of more than passing interest. The aviator left the Shoreham Aerodrome on his Bristol biplane at a quarter to five on Friday afternoon, and at half past six he was at Salisbury. Koundmg the Cathedral spire he then flew to the Bristol head quarters on Salisbury Plain, where he landed about 7 o'clock.
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