" Heavy Motor Vehicles."
Page 13
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A Digest of the Discussion which Followed the Recent Reading of a Paper Entitled as Above before the Inst. Auto. Eng.
At the conclusion of the paper entitled " Heavy Motor Vehicles," which was jointly read by Messrs. George W. Watson and D. S. Kennedy, before the Institution of Automobile Engineers, on Wednesday, the 12th inst., some discussion took place, but, in view of the very wide scope of the subject-matter chosen by the authors—chosen presumably in order deliberately to tempt criticism and discussion—the speakers who followed the reading of the paper may be considered on the whole to have made little use of the opportunity. We have already published extracts of the more interestin,g parts of the paper in our last two issues.
Mr. Max R. LAWRENCE opened the discussion. He traversed the authors' suggestions that the steam vehicle is more simple and economical than the machine embodying the internal-combustion engine. In his opinion, the locomotive in regular service receives much more comprehensive and regular attention than does even the London bus in the employment of one of the big companies. He considered that the steam engine was outclassed fur many-purposes by the internal-combustion engine—notably, of course, in the case of the Diesel motor. Criticising the authors deductions from data which they had obtained concerning standard models of commercialmotor vehicles, he considered that they did not take into account the whole of the conditions of service which such machines were intended to undertake, and that, as a matter of fact, engine capacities might well and rightly vary to a very considerable extent for the same load-carrying capacity, but over different service conditions.
Mr. CLAUDE CROMPTON, who followed, offered criticism in the same strain. He recommended that every manufacturer of commercial vehicles should so produce his vehicle, that it could take two engines of entirely different sizes, such sizes depending on the nature of the country, whether hilly or flat, in which the machine was intended to operate. This speaker asked the reason why it was thought necessary to employ a double reduction for a live axle on a commercial vehicle in default of worm drive, in view of the fact that Mr. Lanchester had recently said that worm gears of high efficiencies should be of such size that the diameter of the worm to that of the wheel should bear the same ratio as that of two spur wheels of the same gear relationship. Mr. Crompton regretted that the authors had dismissed petrol-electric transmission so briefly. He reminded the audience of the Macfarlane-Burge regenerative system of transmission.
Mr. W. REES JEFFREYS thought that the authors might have still further extended the scope of their paper and have pointed out the importance of engineers' designing the vehicles to suit the roads, on the principle that a locomotive builder has to construct his engine to suit the track. He stated that, in conversation with a leading North of England road engineer the other day, the latter told him that it might be necessary for a large part of the main roads in a certain northern county to be reconstructed with granite setts, in order to carry heavy motor vehicles whose numbers have so much increased of late years. The financial question pertaining to such an alteration would run into millions if pounds sterling. Mr. Rees Jeffreys offered the following questions for the consideration of members ef the Institution. He said he would like to know if, considering the resultant wear and tear upon average roads, the existing maximum gross and axle weights for heavy motor vehicles were a sound figure to be taken. He would like to know if the adjustment of the weights between the axles, as at present existing, is also sound. He would also like to know if engineers were agreed that the present regulations dealing with the diameter snd width of wheels, in the light of the experience that has now been obtained, are the best dimensions, having regard both to the effect on the vehicle and on the road. He would like to know, finally, if it is possible for an engineer to construct a machine which could travel over a road suffering from a rapid thaw after frost in such a way as not to damage it. He would, in summing up, like to see some sort of balance. sheet drawn up, in the light of present-day experience, as to the actual value of the mechanical vehicle for the purpose of the conveyance of goods balanced against the increased wear and tear resultant upon the road.
Mr. CHAS. NV HEELTA wanted to know how front-driven vehicles were braked, whether on the front wheels or the rear wheels; he also wanted some explanation of the drawing of the Aveling weather screen. Mr. F. THOMAS had eoniething to say with regard to the latest developments of the Thomas Transmission system. He gave an interesting exposition of his suggested improvement for propeller shaft final-drive construction.
Me C. Devies complained that Mr. Rees Jeffreys had somewhat raised his ire" on account of the allegations which had been suggested against. the steam wagon. he considered that in view of the fact that the traffic is here and is over increasing, it is surprising that the roads are not much better than they were 20 or 30 years ago. He considered that it was much better for the roads to have one unit carrying eight tone than four units carrying two tons each, assuming that road wheels are of sufficient diameter in relation to width of tread. Mr. Davies maintained that the present type of steam wagon is doing less damage to the road than any other type of vehicle, unless it be a steam roller. If, in fact, steam wagons were continually going over the roads, we should soon have roads of an ideal character.
Mr. F. CHURCHILL complained that, the authors had stated that the larger engines necessarily meant greater expense in fuel and oil tor the owner of such vehicles. He would like to ask the authors if they could bring that statement into line with the fact that in the R.A.C. 1907 trials the smallest petrol consumption was made by the vehicle with the largest engine, and that was the 52 h.p. engine on the three-ton Matidsl.ay. He did not agree with the tire costs which were quoted.
Mr. keI.EXMAN FRENCH did not agree that the British manufacturer has led in the heavy-vehicle industry from the first. The credit, he considered, should go to Germany and France in respect of the Canstatt-Daimler and De Dion machines respectively. In regard to gearboxes, the speaker quoted his own experience concerning three belonging to machines of three, four and five years of age, respectively; these had when removed been found to be in perfect order in all respects. He did not agree with the authors' costs for tires : he would be very sorry
if he had to pay them. He then proceeded to give an account of his interesting early experiences dating from the running of converted C'Anstatt-Daimler machines up to the present time and his modern Hallfords. He was a great believer in chain drives for the heavier models.
Mr. Huetrarcav coesidered it was more difficult to find suitable men to drive steam wagons than to look after petrol machines. He complained of the majority of the brake designs on standard models. He had, before coming to the meeting, taken the trouble to ascertain from the Stores Department the extent to which brake blocks were consumed by the G.W.R. fleet of 90 vehicles. These machines, he found. consumed 6800 lb. weight of brake blocks daring last year, and probably half of this was actually worn away unnecessarily. Mr. WEBB expressed a wish that the authors had paid more attention to the electric vehicle in their paper. He instanced the extension of this branch of the industry in America. Mr. D. J. SMITH also regretted this lack of reference to electric vehicles, and he gave some figures with regard to the cost of light-railway construction which could usefully be compared with Mr. Rees Jeffreys' estimates for roads. He considered that Fodens might well open a branch in New York, unless the electric trucks there were doing better than when he heard of them recently. With regard to firebox design on steam wagons, he did not consider that the 4 in. of water over the firebox is enough. Fusible plugs require more, protection than that, on account of the shortness of the Foden and other similar boilers.