Opinions and Queries
Page 72
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Early Success of Oxycat Predicted
WE have read with interest the article, "'British "-Operator Tries Exhaust Cleaning," by " J.S.," in your issue dated April 6. It is unfortunate, however, that this article, which has inevitably raised Considerable interest, should have appeared at a time when we have so many developments at present under consideration which will answer the disadvantages which your contributor. levels against the adoption of the device.
In his last paragraph your contributor refers to the restraint of our company in making claims comparable with those put forward in other countries for this same device. With the knowledge of new developments on which work is now proceeding, we have considered that it is inopportune to create interest by publicity until we are in a position to offer a technically proved and commercially marketable product to meet the rigorous requirements of both leaded-petroland oil-driven vehicles. We feel confident that this happy position will be realized very shortly.
In the second paragraph the article says:. "The principle of operation is similar. to the catalytic cracking process used in oil refineries." The Oxycat is a catalyst the function of which is the acceleration of oxidizing reactions, whereas the catalyst used in the cracking process, . as its name implies, catalytically assists the cracking operation.
In paragraph four it is stated that: "Hot gases passing over the rods cause a chemical reaction with the catalyst." But the definition of a catalyst is "A substance which causes or hastens a chemical change in other substances without being changed itself.". The reaction is between the combustible materials and the atmospheric oxygen, the catalyst assisting to accelerate this reaction but not being changed itself. The continuation: "This, raises the temperature of the rods sufficiently for the reaction to continue even if the temperature of the gases is subsequently lower," is likely to be obscure to the average. reader. It is only the proportion of oxidizable materials in the exhaust gases which determines the temperature rise of the catalyst and, therefore, the maintaining of catalytic activity.
With reference to the catalyst used in petrol-engine mufflers, this is brought to the active state by the sensible heat in the :exhaust gases.
It is stated that: "The working-up period lasts from 10 to 15 minutes." The actual time, when using the standard Oxycat on petrol-engine exhausts, is between two and three minutes.
In paragraph six the issue has become somewhat clouded by combining the functions of the Oxycat as a muffler and in its use in connection with industrial effluents. In general, the catalyst can purify effluents if the objectionable features in these are caused by oxidizable elements. In most cases, these elements are hydrocarbons, carbon monoxide, hydrogen, ammonia, etc., which, under the influence of the catalyst, are broken down and oxidized, the end products being CO, and 11,0 (carbon dioxide and water).
Where reference appears to he towards the catalyst as used on oil engines, the writer says: "Efforts are being made to lower the operating temperatures." This is not correct; the operating temperature must be maintained, and present developments are proceeding with a view to obtaining and maintaining more easily the correct
n22 operating temperature in cases where the engine is running light for much of its operating time.
It is to eliminate oil-engine heavy smoke that the high temperature is required to obtain satisfactory functioning of the catalyst, and in cases where operating conditions have been such that the correct activating temperature could be maintained, the Oxycat Muffler has given completely satisfactory results.
. In paragraph 10,it is stated that: "Whilst an Oxycat operating on an engine consuming unleaded petrol will last for 2.000 hours or more, carbon deposits on the rods -will soon destroy their effect." The accompanying illustration shows that provision is made for introducing fresh air. It is only when air is prevented from entering the exhaust stream that the carbon vapour is permitted to condense and build up as a film on the element rods, thus covering the catalytic film. When operated normally it is the unburnt fuel, in the form of CO and unburnt petrol vapour, that provides the material which, when combined with oxygen, produces the exothermic reaction transforming these elements into harmless CO, and HO.
The cost of the Muffler could have sorrie influence upon the economic possibilities, but none whatever upon the practicability of the catalyst.
London, W.1. A. AMENS, Technical Director, Oxy-catalyst Co., Ltd.
How the " Buck /, was Passed
T HAVE read with interest your leading article, 1 Shifting 'Indirect' Responsibility," commenting on the case of Herdman v. Walker and published in your issue for April 13.
You end with the comment that, had the sub-hiring contract in the case under discussion contained the same clause, the hirers would themselves have been able to be re-indemnified by the sub-hirer.
The report of this case in the All England Law Reports makes it clear that, in fact, the Sub-hiring contract did contain the same clause written into it, but the sub-hirer crossed out this clause before signing the contract.
London, W.11. 0. S. MASEFIELD.
Another Diamond T Conversion
WITH reference to your article of February 10 dealing
with the equipping of a Diamond T tractor with a Meadows oil engine, it was stated in this that it was the belief of the writer that this was the first instance of a British engine being used in this model.
I would point out that, some two years ago, Mr. F:ank Annis of Annis and Co., Ltd., Hayes. Middlesex, installed a Gardner 8LW oil engine in a Diamond T /1'2 ctor.
As a further point of interest, this vehicle was fitted with a Mack gearbox, which, I believe, gave a total overall gear ratio of 196 to I.
It seems that this machine is operated solo with gross weights up to 75 tons and has given satisfactory service since the conversion was made.
Hayes, Middx. M. B. EVELEY, Managing Director. Everley Bros., Ltd.