OPINIONS FROM OTHERS.
Page 24
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Steam Vehicle Developments.
(1,702] Sir —I have read with great interest the article on the above in your issue of December 16th, from the pen of Mr. T. A. Jones, and would like to congratulate the writer upon the lucid manner in which he has called attention to such an interesting subject.
If I may be allowed to say so, it is regrettable that such an otherwise excellent article shbuld be spoilt by inaccurate statements, which are obviously the offspring of a lack of experience with the action of thimble tubes for the generation of steam.
Mr. Jones states that "from a functional .point of view thimble tubes are far from being satisfactory, and that free circulation of water cannot be obtained with these solid-ended tubes." 2.dr. Jones recognizes that the thimble tubes are a departure from ordinary practice, but I venture to submit that this is insufficient justification for condemnation, as it may be said with truth that all advances in the acienee of engineering are departures from established usage. In considering theadoption of thimble tubes, naturally the first question on which information was desired was as to the possibility of securing effective circulation. Accordingly investigations were conducted to settle this paint. In some of the tests glass tubes were used in order to permit of circulation being observed.
It is interesting to record what was actually .observed in the glass tubes. Starting from cold, when flame was first applied to the tube, it was observed that two separate currents -were at once set up—the water in the tube divided itself into two strata. In the lower of these the water passed from the reservoir into the tube, and on taking up beat it escaped into the upper current, which flowed in the opposite direction. These two currents were clearly observed by having sawdust and other finelyalivided solid par i ticles n circulation. .
These two currents continued until the boiling point was reached, when a different action began.
Bubbles of steam flowed upwards from the lower stratum and formed the return current in the upper stratum. This action proceeded until the ebullition was slightly checked by the-reduced volume of water, then the, thimble tube was instantly. refilled with ,water., and the generation of steam proceeded with practically no interruption. In other words, after the boiling point is reached, the circulation is of a pulsating character, and at ordinary atmospheric pressure the pulsations -occurred about three times a minute.
The pulsating circulation has an interesting result in preventing the deposit of solid matter in the thimble tubes. Several times. solid matter was intentionally placed in the tube, and in a very short time this was all washed out by the vigorous circulation. The above statement records actual observation with glass tubes. In actual practice, using steel tubes and at working pressures of 300 lb. to 350 lb. per sq. in., the same cleansing action is observed, the inside of the thimble tubes after prolonged service showing clean metal with a Barffed gun-barrel surface. Dealing. now with Mr: Jones's statement that thimble tubes will not stand long forcing.
This statement will not stand in the light of experience. The following test is given as showing the ability of thimble tubes to stand excessive forcing:— Starting from "all cold," a coke fire was dumped into the firebox and a strong draught created by artificial means. The boiler had not been under steam for three days, BO everything was dead color It contained 18 gallons of water up to half glass. In. 12
eal2 minutes from the charging in of the coke fire, not only were the 18 gallons of water raised to boiling point, but over and beyond this eteam had been raised to 200 lb. per sq. in. The forcing involved in raising steam to 200 lb. from "all cold" in 12 minutes in a boiler (not of the flash type), but containing 18 gallons of water, will be recognized as a far more severe test for forcing circulation than any met with in ordinary practice. In fact, the ability of the thimble tube to stand forcing is one of its strongest points, inasmuch as there is no chance of causing it to leak. It will be recognized that as the tubes are only held at one end, the other end is perfectly free and puts no strain upon the tube plate.
Another advantage of thimble tubes is their great simplicity ; they do not even require to be expanded, but are just pushed into the tapered holes, and the pressure in the boiler holds them in. position tightly just like the stones of an arch.
There is one condition that is essential for the operation of thimble tubes, viz., they must be correctly proportioned, the ratio of length to diameter not being greater than shown in Fig. 2 in the article.
I trust you will excuse my taking up so much of your valuable space, but must plead justification of en'gineering truth, and in this I am confident that Mr. Jones will be in agreement.--Yours faithfully, T. CLARKSOrN.
Bankrupting Industry.
[1,703] Sir,—The Prime Minister and various members of the Government are telling us every day that filling exchanges, high prices and over-taxation will all disappear by production. Production isthe keynote of our aspirations and endeavours and the keystone of our destiny.
Many manufacturers are in deadly earnest to secure production and, if serious energetic efforts count for anything, ,they should succeed It is, however, a fearful struggle and a life-long battle with a variety of obstructions. One of the chief of these is railway transport. My firmis 20 per cent. &Jam OD its schedule of production this month, owing to the railway either refusing to accept goods coming forward to us from suppliers or by delays in delivery of such material that they have been induced to accept.
Without the constant pressure of an energetic progress staff and innumerable "hat in hand" visits to railway officials, and inquiries and telegrams, production would be in a state of total inhibition. What on earth has happened to our railways, and how long is this state of affairs to last? If this is nationalization or a preliminary taste of it, then let us have the old wholesome days of competition once more. The present state of affairs almost savours of a railroad "em canny," as if the moulders' strike itself has not done sufficient injury to the industries of this country. Is it constructive or collusive obstruction, or are the railwaymen playing the game, the muddle being due to dry rot in the executive and directorate l Sir Eric Geddes is entitled to have his chance to remedy matters, but Rome is burning ip the meantime. The expense and trouble to which my firm has been put in obtaining the necessary raw material and details (ordered up many months ago) to enable them to deliver the first few chassis of their post-war programme because of railway incompetence and mismanagement is truly appalling. Drastic methods of reform and amelioration must be instituted at once ; otherwise I cannot see how profitable ,production is possible in this country.—Yours faithfully,
For Palladium Autocars, Ltd. J. Ross MAcMAHolq.