OPINIONS FROM OTHERS.
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The Editor invites correspondence on all subjects connected with the use of commercial motors. Letters should be on one side of the paper only and typewritten by preference. The right of abbreviation is reserved, and no responsibility for views expressed is accepted.
Loan of Lorries to Workpeople.
The Editor, THE COMMERCIAL MOTOR.
[1821] Sir,—With reference to your article upon the illegal loan of lorries to workpeople, my employers have been, letting us have our Foslens whenever a party of workmen wanted to go for an outing ; for instance, with the works football team, the children's outing, and a good many more too numerous, to mention. Now they have purchased a 3 ton Kelly lorry (tax paid, 225), and we were looking forward to a good many outings, but the licence regulations have put a, stop to these pleasures. Now our several social and outing committees have asked me to write you for a little information as to whether they can apply for a further licence for carrying passengers, and what the additional licence fee would be. Any information you can give would be very acceptable.—Yours faith fully, W. J. WEST.
[We have replied direct to our correspondeut informing him that, assuming the Kelly lorry with temporary seats -would carry 26 passengers exclusive of driver, the tax upon it as a hackney vehicle (which is registered in a provincial area) would be £48 per annum, 'or 214 8s. per quarter. If seating aeconanodation for more than 26 but not more than 32 be provided, the tax would be 160 per annum, or 118 58. per quarter. Thus the difference in the taxation would be 223 for the 26 seater and 235 for the 32 seater. There would be only a small saving if quarterly licences were taken, as the quarterly licence for. a, 3 ton lorry as such would be 27 los. The application would have to be made by the owners of the vehicle under section (5) sub-section (3) of the Roads Act.—En.
A Piston Improvement.
The Editor, THE COMMERCIAL MOTOR.
[1822] Sir,—Referring to the excellent photographic reproduction of one of our fleet of Thornycroft lorries on the back cover of your valuable journal (issue of February 1st), you will doubtless be interested to leArn (and also your numerous readers who are concerned in the important question of "running costs ") that this vehicle has a further claim to distinction beyond these already advanced by the makers in their advertiseinerta • It has been in constant use since it was delivered by the makers on March 14th, 1919, up to date, during which period nothing beyond "running repairs" such as brake linings, etc., have been found necessary. On September 30th last, the total mileage conapleted was 20,399, and on this date we had a set of Allen patent pistons fitted to this engine, taking the cylinders as they were without regrinding. This work was carried out in a few hours at the Reading works of Messrs. Allen and Simmonds after the lorry had delivered its load. We consider the results obtained so extraordinary, and of such supreme imPortance to all users of mechanical transport, that we, as members of the C.M.T.T.A., deem it our duty to hand on our experience for the benefit of others, even at the risk of encroaching on your valuable space. A week after fitment (October 8th), we emptied the crank chamber of oil as we have been in the habit of doing periodically), and filled up with fresh oil to working level, taking two gallons. Since that slate we ran this vehicle constantly up to January 8th, a period of three months, without adding a single drop of oil to The crankcase; as a matter of fact, we took a small sample out at the end of each month's running for examination purposes without replacing it. On the
above date we took a half-gallon of oil out for testing purposes and put back 5i pints, viz., 1* pints more than we removed ; this broughtathe working level indicator toits normal position, and the engine is still running, on this quantity up to date. . It will be seen, therefore, that thisevehicla'has beeh in constant use 4* months with the consumption of 1:3/4pints only of oil added to the crank chamber. During this period it has completed 3,786 miles, the total being 24,185.
These pistons were supplied with two patent segmental gapless rings each in. three sections placed. near the top and bottom respectively_The depth, or contact surfaces of each ring to the cylinder wall, was * in. only. It is not, of course, our province to attempt to put before your readers constructive details of this remarkable device for the, conservation of both oil and petrol ; no doubt many of them are more or less conversant with same, but we would like to state that we keep a careful record of our running costs, which thoroughly convince us that the makers' claims of economy and etciency are amply justified. Extracts from these records show a saving with the Allen pistons on two of our vehicles of /18 5s. W. and 216 10a 6d. respectively per 1,000 miles covered, and we shall be pleased to afford facilities to any users of mechanical transport to examine our "log book" by appointment. We may say that we fitted the original Allen pistons some years ago to all our steam tractor's with such excellent results that, when some few months ago they were perfected for all types of " internal combustion." engines, we had no hesitation in trying them on our petrol engines. In view of the results obtained, we have now fitted the engines of our entire fleet with these pistons, and, as may be imagined, are congratulating ourselves on having in view a reduction in the running costs of same, which will certainly amount to some hundreds of pounds ger annum.—
Yours faithfully, . THOMAS WETHERED AND SONS, LTD.
Marlow. F. E. STEVENS} Managing Director.
The Need for Effective Brakes.
The Editor, THE COMMERCIAL MOTOR.
[1823] Sir,—We have read with interest the first part of the article appearingon page 16 of the issue of February 22nd under this heading, and we are quite in agreement with your contributor as to the necessity for effective brakes both for goods'vehicles and for chane-a-bancs.
There is little doubt that defective brakes have been a, contributory cause of a, number of serious accidents. It was to meet this difficulty that the, firm of 7?aurer designed and produced their well-known patented engine brake, which has been brought to a state of perfect working. The chassis is fitted with the usual two brakes. which are necessary to fulfil legal requirements, and these are employed for sudden stoppages or for holding the vehicle when at rest. As you are aware, the Saurer vehicles are constructed in an extremely mountainous country, and it was found that the ordinary -type of brake was insufficient when fitted to a vehicle carrying heavy loads down. very steep and long declines. The 'billy previous solution of this difficulty was by employing watercooled brake drums. This system was adopted on a number of Italian .cars and, up to a point, proved effective by absorbing heat generated inthe drums. The Saurer air brake has the great advantage of simplicity and lack of complication in use. Further, it is extremely gentle in action, and, thus, does not damage
any portion of the transmission, nor does it develop "fiats " at the tyres such as. are caused by a sudden locking of the wheels with the ordinary type of brake. The principle on which this engine brake works is that of transforming the engine into an air compres. sor, so that. the power unit absorbs energy instead of producing it.
LEI order to attain this object, the cycle of operations is modified so that, the inlet and exhaust valves are opened and closed at abnormal stages of the piston position by sliding the camshaft so that another set of cams is put in operation. .All that is necessary for the driver to do is to push the lever controlling the gas inlet beyond top centre position, when the brake comes into operation. When this is done, the mixture is completely cut off from the engine which, hereafter, only draws air. The cycle of operations is as follows in each cylinder:— In the first place, on the suction stroke the inlet valve is closed and tho exhaust valve opened. Air is then drawn in thisiiugh the exhaust' valve. When the piston rises the exhaust valve is closed and the inlet valve opened. The air which has been drawn into the cylinder is compressed along with the air, already upder slight pressure, in the induction pipe. At the top Of the stroke the pis is forced back again into the next cylinder. This compression stroke has already a slight braking effect. The piston again descends the exhaust valves and inlet valves are closed and a reduction of pressure is effected in the cylinder. The air already compressed and contained in the induction pipe automatically opens the inlet valve owing to the difference in pressure assisted by the opening of the valve by means of .a cam. When the piston again rises, both valves are shut and the air is compressed to 7 to 10 atmospheres, which has a strong retarding effect on the speed of the vehicle. This procedute is gone through in each of the four cylinders in .turn. 'The braking effect obtained is sufficient to pull up the vehicle under all normal conditions, without the use of the ordinary brakes, which are only used for sudden stoppages. As only air as drawn into the cylinders, this acts so as to cool them, and', as the inlet of gas is cut off, no petrol is used.
As an instance of the advantage of this system of aaing, we would mention unit, during the war, a military convoy of the Swiss army had to make a jcurney three times a day along the famous St. Gothard road, which is approximately 36 miles long,. and, at one portion, four miles.. in length, it has an average gradient of I in 6. It was found that no other make of lorry could carry out this work. The Saurer vehicles that were used did the journey three times daily without the use 'Of any brake other than the patented engine brake. We quite agree with your contributor when he states that it requires considerable skill to change down from top speed to second speed with a vehicle already travelling at its normal speed. The employment of. the Saurer engine brake has no such disadvantages. We claim that the engine brake fulfils all the requirements, as set forth by your eontributer.—Yours faithfully
for THE SAITRER COMMERCIAL VEHICLE CO. RALPIE E. WILSON, Sales Manager.
Coach Stations Coming.
The Editor, TIEE COMMERCIAL MOTOR [1824] Sir,—I was more than usually interested to read your account of the intentions of Shaw's Depositories, Ltd., to create a Motor coach station at Blackpool. The facts given by you show that you, are in touch with the whole scheme, and the information thus bears the stamp of reliability. I am convinced that these stations must be established at pleasure resorts throughout the country. The use of our roads and streets as coach termini creates inconvenience, is " ragged," and causes much unnecessary risk—for I have rarely met anyone more reckless of his life than the passenger alighting from a char-h-bancs. The existence of a coach station—the recognized startingplace for pleasure journeys--is going to create custom, for visitors at holiday resorts take some days to find out the various coach services, their starting places, and other particulars. Concentration would simplify this . task and bring business to the coaches.—Yours faithfully Brighton. COACH OWNER,