Wide Range of Transport Papers
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ONE of the largest meetings of transport engineers ever to have been held took place in the U.S.A. last month. This was the Society of Automotive Engineers' International Congress and Exposition of Automotive Engineering, which was held at the Cobo Hall, Detroit, from January 9 to January 13. Over 170 papers were presented during the week, in addition to which there were some 69 discussion sessions and a large exhibition section in which well over 100 American manufacturers participated.
The subjects dealt with covered all aspects of road transport, ranging from the roads themselves to tyres, generating systems and even gas-turbine power units whilst, additionally, certain aviation topics were discussed, including ground-effect machines. It would obviously be impossible to record all the papers and discussions that took place at the Congress, but an attempt will be made to summarize those papers felt to be of greatest interest to British readers.
Gas Turbines
nN the opening day of the Congress six papers were ‘-'presented about gas-turbine power units. Four of these were presented by aviation engineers and were highly theoretical and complex, but members of the Chrysler Corporation and General Motors read papers dealing with developments in their field.
The Chrysler paper was concerned with the development of various types of turbine compressor, and traced the history of the work so far carried out in this direction by the Gas Turbine Component department of the Corporation. The three authors of this paper made it clear that because of the small size of the power unit required for automotive applications the centrifugal compressor was the obvious choice for reasons of cost, simplicity and intended engine environment, compared with the multistage axial and the positive-displacement continuous-flow types.
Points brought out in the paper included the desirability of efficient intake filtration and the need for silencing those noises generated in the proximity of the intake passage.
• It was stated that because of concentrated design work with regard to impeller assemblies the latest Chrysler engine was giving an efficiency in excess of 84 per cent.
The two authors of the General Motors' paper concerned
themselves with the acceleration-lag trait of an automotive gas turbine, an effect hinging around the compressor characteristics. They felt that, whilst this lag tended to be over emphasized in many quarters, its minimization was nevertheless desirable. The two design factors which had most effect on it were the polar moment of inertia of the gasifier-rotor assembly and the gasifier design speed, hut these could not be varied beyond a restricted range in an engine of specified output without sacrifices in structural integrity or aerodynamic efficiency.
During investigations with the G.M.C. GT-305 regenerative engine, deep surge characteristics were observed when running at high speeds with a reduced flow rate, as a result of which a new diffuser was designed which gave a large increase in the compressor-surge margin without involving any reduction in compressor efficiency during equilibrium operation of the engine.
The XM521 "Swimming" Military Vehicle
A NOTHER opening-day session was devoted to the 'design and operational characteristics of the U.S. Army's XM521 vehicle. Although essentially a military machine, the XM521 is a particularly interesting design, being a 2-1-ton 8 x 8 with decidedly unusual capabilities.
The design was based on the need for a military vehicle with outstanding cross-country abilities which would be able to cater water of any depth down a slope of at least I in 1.66 and then travel through the water at a speed of no less than 5 m.p.h. with complete stability and controllability.
One of the main problems was concerned with the design of the hull, and honeycomb panels were eventually adopted for this assembly, these consisting of polyurethane foam sandwiched between aluminium sheets. The resulting hull formed a complete unit of low weight, with a smooth water-tight exterior.
A light-alloy, air-cooled, horizontally opposed fourcylindered power unit was developed for the vehicle and this is mounted below the driving compartment. The engine has a gross output of 105 b.h.p. and drives through a fourspeed synchromesh gearbox and two-speed transfer box,
All eight wheels are independently suspended, using wishbones and coil springs, the springs being enclosed by rubber boots into which air can be fed under the control of the driver to give variable-rate characteristics. Conventional hydraulic !makes are employed, with a transmission hand brake, bit no details were given as to what type of brake lining is employed to withstand submersion. The brake assemblies are sealed, however, and are mounted in the hubs, outboard of the wheel discs.
For water propulsion, a twin-propeller counter-rotating drive is located at the rear of the vehicle and the twin rudders can be folded flush to the body for maximum protection. The XM521 has a kerb weight of 3 tons 7 cwt. and a maximum speed of 55 m.p.h. It can handle a towed load weighing 21 tons and is 19 ft. long, 7 ft. 2 in. wide and 8 ft. high when fully laden.
A.C. Generating Systems
ON the second day of the Congress personnel from 0.M.C., Chrysler and Motorola presented papers on A.C. generator systems. The G.M.C. engineer outlined work which the Delco-Remy division had carried out with regard to the evaluation of generators and batteries, and the test methods set up in an attempt to reproduce a range of operating conditions for these components in the laboratory,
The Chrysler paper gave details of the alternator which was now standard equipment on all 1961 Chrysler Corporation cars, a unit which was stated to be 9 lb. lighter than the D.C. generator hitherto employed. The paper revealed that Chrysler had commenced work on A.C. generators 27 years ago, but that the copper-oxide and copper-sulphide platetype rectifiers then employed were inefficient and shortlived compared with present-day equipment.
Problems encountered during post-war development work with alternators included noises ranging from squeals to whines, and how these were traced and eliminated was described. The Chrysler alternator has integral rectifying equipment, whilst the voltage regulator was shown to be a particularly simple piece of equipment compared with that needed for a D.C. machine.
The Motorola paper was concerned with rectifier design and stressed the importance of accommodating the heat generated in the rectifier, the temperature at the junctions of the semi-conductors reaching 350°F. It was stated that future designs of rectifier may well have to handle larger currents as higher output alternators are required, but that the cost of rectifiers will decrease as the usage of alternators • increases. This was something which the semi-conductor industry would have to get accustomed to, as up to 45m. rectifiers could well be required in the U.S.A. in a single year in the not too far distant future.
"Super Highway" Vehicles A NOTHER Tuesday paper was that delivered by Mr. 1-11. C. Wagner of the International Harvester Co, Mr. Wagner's paper was concerned with the haulage vehicles of 15 to 20 years' time, the design of which in the U.S.A. would obviously be influenced by the 41,000-mile inter-state
• motorway system whicitis due to be completed by 1972 and one-fifth of which is already open to traffic.
The author foresaw the use of truck trains for longdistance working, with relatively low-powered tractive units to collect individual trailers from these trains and take them to the town terminals, A third class of vehicle would be employed for city deliveries, and here a small class of articulated outfit was envisaged, in which respect the Scammell mechanical horse has preceded Mr. Wagner's thoughts by nearly -30 years. With regard to power units, outputs of up to nearly 700 b.h.p. were obviously going to be necessary for outfits with gross train weights approaching 90 tons, so the author was of the opinion that the gas-turbine engine would have to be employed to provide this output for a reasonable size. The question of individual power units for the trailers was considered, however, in which case relatively small internal combustion engines would be feasible.
Rotary Combustion Engines
ON the Tuesday evening Dr. Walter Frcede, NSU, and Dr. Max Bentele, Curtiss-Wright, read papers about rotary combustion engines. Dr. Frcede's paper dealt broadly with the, by now, well-known NSU Wankel unit, brief mention being made of the use of a KKM 400 engine in conjunction with a Volkswagen four-speed gearbox installed in an NSU Sport Prinz, a combination which gave a maximum speed of 95 m.p.h. and commendable fuel economy. The KKM 400 produces 48 b.h.p. at 6,000 r.p.m.
The Curtiss-Wright paper was concerned with the considerably larger engines which this company is developing as a result of agreements with NSU and Wankel. One of the earlier Curtiss-Wright engines was a 60 cu. in. unit which gave 100 b.h.p. at 5,500 r.p.m. and a minimum specific fuel consumption of 0.47 lb./b.h.p./hr.
A very much larger engine was then built to the same basic design, and this had a displacement of 1,920 Cu. in. Operating with a brake mean effective pressure of 106 p.s.i., this engine produced 782 b.h.p. at 1,525 r.p.m. Another development had been a four-rotor engine—the first of its type to have been built anywhere—and to the designers' surprise this proved quite successful and gave 425 b.h.p. at 6,500 r.p.m.
Engine Oils
rIN the Thursday three papers dealing with engine
oil development criteria were presented, the first dealing with low-temperature cranking and the flow properties of waxy polymer-thickened motor oils. The paper described a method of obtaining reliable viscosity characteristics of a multigrade oil at 0°F. to supplant the existing methods based on extrapolation, using measured viscosities at 100°F. and 210°F. It was felt that the cone and plate viscorneter appeared to provide a means of classifying winter-grade motor oils containing polymers.
The second paper dealt with a variation of the now familiar radioactive-tracer technique. The method was to indoduce a radioactive additive into the lubricating oil so that the course of this additive through the engine could be discovered.
Experiments showed that nickel dithiophosphate sought out points of high pressure and temperature, such as camlobe tips and tappet faces, and transferred itself to these points of high mechanical and thermal stress. It was also suggested that the anti-wear properties on piston rings of zinc dithiophosphate were of negative value.
The third paper was concerned with the use of a CLR engine for evaluating the sludging tendencies of motor oils. Experiments conducted by Texaco technicians had shown that this research engine could be used to reproduce shortdistance running conditions, such conditions having the most adverse effect onengine life_ It was shown that sludge and varnish deposits were caused by fuel-combustion residues from unburned and partially oxidized fuel and that the CLR engine could be used in the laboratory to ascertain the value of additives produced in small quantities with the object of combating these undesirable products.
Braking Developments
NOTHER RThursday meeting was an international
one on disc brakes and anti-skid devices. The first paper dealt with the Ausco oil-cooled brake, as previously described in The Commercial Motor, whilst the second paper was delivered by Mr. J. W. Kinchin of the Dunlop Rubber Co. in which details were given of the Maxaret anti-locking device and British disc brakes.
The third paper was given by a representative of the German concern, Alfred Teves, and this gave details of general vehicle-brake developments, and sOme anti-skid devices introduced into the hydraulic systems of vehicles in order to correlate braking efforts to dynamic axle loadings. Such devices could only minimize the dangers of wheellocking however.
Importance of Containers
THE growing importance of road-rail containers was emphasized by three papers, delivered on Thursday. All the papers pointed to the vital need for standardization of container dimensions and that any standard that was drawn up should contain the minimum number of points in
order to simplify compliance. The speaker from the Fruehauf Trailer Co., felt that the establishment and general acceptance of container standardization would be a "transportation milestone," greater in significance than the adoption of the S.A.E. semi-trailer kingpin.
An interesting paper was read by an engineer from Pullman Incorporated, and this dealt with the development of railway wagons for handling piggy-back traffic as well as containers. This speaker's company felt that the major problem so far as the railways were concerned was that of obtaining proper information from transport economists and materials-handling experts on the economical requirements for container operation.
The operator's viewpoint was put forward in a third paper, in which it was outlined that container sizes and the methods of handling between road, rail and water should be standardized, whilst the railways ought to offer lower rates for the carriage of containers than for handling piggyback semi-trailers.
Seven other desirable factors were put forward in this third paper, and the author felt that because of the difficulty of providing all these optimum features the "revolution in transportation initially promised by the introduction of containers was not readily obtainable.
Aluminium Engines
SEVERAL papers delivered on the Thursday were devoted
to the design and developMent of aluminium engines, with speakers from Oldsmobile, Pontiac, StudebakerPackard, American Motors, Buick and Chrysler. Although the engines described were purely for private-car use, the conclusions arrived at as a result of experience with the Buick V-8 155-b.h.p. unit are of interest.
These show that pronounced weight savings had been made without loss of engine output or durability; the basic goals of a quiet, durable yet responsive engine had been attained by combining aluminium and cast-iron; normal care of the cooling system was entirely adequate in the control of corrosion; engineering problems connected with the design of an aluminium car engine had been satisfactorily overcome; and that the further extension of aluminium to future engines would be governed primarily by economic considerations.