Tuesday, March 24, 2009
A look at Wankel engine history and the latest unit to appear, the Comotor Bi-rotor announced for the Citroen GS
ROTARY ENGINES go back in history a long way before Dr Felix Wankel's obsession with them before and after the last war. If you admit to the basic similarity between engines and pumps (the action of many engines can be reversed to form pumps), then an Italian engineer called Ramelli was the first in 1588, with his invention of the vane-type pump. Pappenheim, a German, followed this 48 years later with the gear-type pump, which did away with Ramelli’s slide valves but suffered from leaky seals, water or gas tightness being the weak point of all rotary designs.
In 1799 a colleague of James Watt adapted Pappenheim's gear pump into a rotary steam engine. Despite wooden scrapers in the tips of the teeth, there was a lot of leakage and a poor efficiency. Sixty years later an Englishman called Jones simplified the gear pump down to two double-lobed intermeshing rotors, this configuration later being adopted in the famous Rootes supercharger.
One of the first rotary engine patents was filed by an American called Cooley in 1901. His invention featured an epicycloid with internal meshing- gears and an enveloping casing with three fixed seals. In 1908 Umpleby, an Englishman, converted Cooley’s rotary steam engine into an internal combustion engine, but the gas sealing problems prevented the design from being successful.
Inventors throughout modern history have repeatedly been fired by enthusiasm for rotary engines, the attraction generally being smoothness of operation from the elimination of reciprocating parts and a high specific output for the weight and bulk, cylinders being arranged in a much more compact layout than the conventional side-by-side cylinder configuration of a reciprocating engine. Apart from the often impossibility of actually making some of the parts, in the main it has been gas sealing that has caused the designs to fail. Even when combustion was sustained, power outputs were very low due to poor combustion chamber shapes and the thermal problems of putting the cylinders so close together.
Born in the Black Forest in 1903, Felix Wankel acquired a keen interest in rotary engines during the five years he spent working for a scientific publishing house in Heidelberg. At the age of 21 he set up his own workshops and made models of rotary piston engines. Very soon he established that the weakness of all designs was the gas sealing and he set about beating this problem with a programme of intensive development. With the co-operation of BMW, he designed a practical unit in 1934 and in 1936 he received support from the German Air Ministry to set up a research organization. In 1942 the laboratories were expanded to undertake work on rotary-valve aircraft engines, but in 1945 the Allied Forces occupying Germany destroyed Wankel's whole operation.
Nothing daunted, Wankel immediately started work again in his Black Forest home and in 1951 his first contract with NSU was signed. In 1954 the discovery was made that a four-stroke cycle could be performed by the rotation of a three-lobed rotor in an epitrochoidal casing and suddenly the door to success was open. Two years later, an NSU motorcycle with a rotary-piston supercharger wiped the board in competition and took several world speed records on the Great Salt Lake.
In 1957 the first Wankel engine ran. This early type DKM was extremely complicated with both rotor and housing rotating. From a capacity equivalent to only 250 cc, 29 bhp was developed at 17,000 rpm. The next step was to make the rotor trace an orbital path and keep the casing stationary and the engine in this form (known as the KKM) successfully ran in 1958. Endurance trials the following year proved the reliability and in January 1960 at a German engineering convention in Munich, Wankel told the world about his revolutionary new engine.
Already the Curtiss—Wright Corporation in the USA had a licence to develop the Wankel engine, and enquiries poured in from all over the world. By the beginning of 1961, Toyo Kogyo and Yanmar Diesel in Japan had taken out licensing agreements, to be followed by Daimler-Benz, Alfa Romeo, Rolls-Royce, Porsche, Nissan, General Motors, Toyota, Ford of Cologne, BSA, Yamaha, Kawasaki and American Motors, to name only the automotive companies in the total list of 25 licensees. In 1967 Citroen set up a joint company with NSU, named Comotor, to manufacture and market rotary-piston engines, and in 1971 the Anglo-Rhodesian mining company, Lonrho Ltd, acquired Wankel's interest in the original design and thus became the recipient of a share of all licence fees.
The first Wankel engine to go into series production was a 300 cc unit developing 18 bhp at 6,000 rpm. lt was used as the power unit for a small water scooter controlled by a ski-mounted driver. From October 1962 onwards a total of 3,000 were manufactured.
ln 1959 the Wankel engine made history by powering a car for the first time. Two NSU Prinz minicars were fitted with a 500 cc unit developing 44 bhp at 9,000 rpm and sent out on long-term endurance testing. These cars helped convince the NSU management that the engine had potential, but it was still greeted with a lot of scepticism, all previous rotary engines having been considerable white elephants.
A year later and an engine specifically designed for fitting to a car was ready, six Prinz Sport coupés being built as prototypes. There followed a long period of development and an increasing undercurrent of unrest amongst NSU shareholders about the considerable financial commitment. This precipitated the premature launch of a production car, the NSU Spider in September 1964, powered by a single—rotor Wankel engine of 996 cc developing 50 bhp at 6,000 rpm. Like the early experimental engines, this power unit suffered from very poor bottom-end torque and a useful range of only 4,000 to 6,000 rpm, top end performance being limited by the seal life at that time. For this reason and the fact that there had to be a premium price on a low volume output, the installation chosen was a convertible version of the Sport Prinz, the idea being that sports car drivers expected engines with these characteristics. No more than 15 per day were produced, the total built until production ceased in 1968 being only 3,200.
A lot of valuable experience was gained in service, however, often at the expense and inconvenience of the customer, although NSU have always been very quick to replace Wankel engines free of charge. We ran one of these Spiders as a staff car and suffered excessive seal wear and a cracked rotor casing.
From single rotor engines work progressed to double rotors and more, Toyo Kogyo and Mercedes eventually getting as far as four rotors experimentally. NSU's great landmark was the launch of the twin—rotor Ro80 in 1967. For the first time in Europe there was a new car designed around the Wankel engine, the compact size of the power unit allowing a low aerodynamic nose and front-wheel drive. To compensate for the still-evident deficiency in bottom—end torque, a semi—automatic transmission was employed, with manual shifting and a torque convertor. The Ro80 engine had exactly the same internal dimensions as the Spider unit, two rotors being ganged together in series.
As early as 1964, Citroen, who have never been afraid of complication or advanced engineering, established an association with NSU, the aims being to develop a joint rotary-engined car. There can be little doubt that some of the Citroen thoughts on passenger car layout went into the Ro80.
In 1967 Comotor was established in Luxembourg as the Compagnie Europeenne de Construction Automobile, with objectives more specifically towards the manufacturing and marketing of rotary engines. Two years later a large factory site was acquired in the Saar and in June this year the first phase was opened with an initial work force of 200 and an output of 30 engines per day. Eventually the plant will be four times its present size and capable of producing between 5,000 and 6,000 engines per day.
Since the original formation of Comotor, NSU have been taken over by Volkswagen, so there is now a potential of Wankel—powered cars from NSU, Citroen, Audi and Volkswagen. Of these companies, Citroen are most in need of a new engine range, especially for their big D—range of saloons. To gain experience of the Wankel engine in production, they first embarked on a massive proving trial with single rotor units using components from the Ro80 engine. Originally it was planned that 500 experimental cars based on the Ami 8 and called the M.35 would be placed in the hands of typical high—mileage French drivers for endurance testing. Later the number was reduced to 350 and in fact between 1971 and 1972 only 260 were delivered. The M.35 was a fastback coupe using mainly Ami 8 body panels but also fitted with prototype hydropneumatic suspension which was later introduced with the GS saloon.
Logically speaking the M.35 should have led directly to a twin—rotor saloon, but Citroen were nervous about the Wankel and wanted more time to prove its reliability. Consequently the GS was launched with a flat—four reciprocating piston engine while the M.35 prototypes continued to build up a total mileage of more than 18 million miles between them.
At Last, the Bi-rotor
Development wheels turn slowly when new factories and new designs are involved, but at this year's Paris Salon the twin—rotor Citroen saloon was launched officially, even though the model will not go on sale until next March. As expected, the engine is a double version of the M.35 unit, which brings it back to being very like the one in the Ro80. Equivalent swept volume is 1,990 c.c. and from a compression ratio of 9 to 1 107 bhp (DIN) at 6,500 rpm is produced. This is 8 bhp less than the Ro80 (115 at 5,500) but the shape of the torque curve has been improved dramatically. As the graph shows, the Citroen engine's torque rises rapidly to reach 90 |b.ft. by about 1,600 rpm and is then flat (apart from a slight peak of 100 lb.ft. at just over 3,000 rpm) all the way to 5,000 before it tails slowly off. On the Ro80 engine the torque rises slowly to a peak of 117 lb.ft. at 4,500 rpm and then falls off sharply.
To increase the life of the vital rotor tip seals, Citroen use sintered iron rubbing against a nickel—silicon liner to the alloy trochoid casing. Both the rotor and its side seals are made from cast steel. To minimize the danger of over revving (rubbing speed is the critical factor for seal life), a warning buzzer is fitted which is triggered at 6,800 rpm.
The installation of the Comotor engine in the GS saloon is so neat that it must have been envisaged before the reciprocating piston engined version was conceived. Mounted transversely, the engine drives a torque converter and manual three-speed transmission in line with the rotor shafts, before the final drive which is ahead of and slightly below the gearbox. A unique arrangement is a cross-shaft with bearing on the opposite side to permit equal length drive shafts. To make the installation even more compact, the air injection pump for the anti—pol|ution equipment is mounted in front of the gearbox and driven by a thin shaft connected to the back of a jockey pulley at the other end of the engine. This jockey is driven by twin vee-belts off the rotor shaft nose, as is the water pump. A single vee-belt drives the alternator off a pulley on the air pump.
As well as air injection into a reactor, emissions are controlled by electronic ignition timing which is varied according to gear lever position, oil temperature, engine speed, air intake temperature and induction vacuum.
According to the terms of their licence, Comotor can develop Wankel engines with power outputs between 40 and 200 bhp for land vehicles. This more than covers all the Citroen needs, even the Maserati engine in the SM developing only 178 bhp. In its present stage of development, the Comotor engine would be eminently suitable for most of the D-range of cars, with the exception of the DS 23. By the time Citroen are ready with a replacement large car (1975 is my calculated guess), Comotor could easily have developed a three—rotor unit with around 150 bhp. The attraction of Wankel engineering, apart from the simplicity and small size, is that the ganging up of modules is feasible and relatively easy. For this reason I think Comotor will stick to the 67mm rotor width that has been a feature of NSU Wankels since the Spider unit designed in 1962. All the combustion development has been based on this rotor width with the radial dimension to its tip of 100mm and an eccentricity of 14mm.— However, the terms of Wankel licences stipulate an exchange of technical information with licencees and that other producer of Wankel car engines, Toyo Kogyo, have wider and bigger rotors in their Mazda RX range, so Comotor could get to 130 bhp another way.
Whatever turns up in 1975, Citroen seem to have committed themselves to a big stake in the Wankel engine and l doubt if we shall see them design another four, or even a six cylinder reciprocating engine. From what we know, the GS Bi—rotor will sell for a premium price in France next year, partly to throttle the demand and partly to allow for the possibility of trouble in service. Despite the complicated manufacturing process, however, Comotor have the advantage of starting manufacture from scratch in a new factory, so eventually the unit cost per engine must come down to the level of conventional engines. By then, Citroen believe, the few remaining snags will have been eliminated.
Saturday, March 21, 2009
From Motor Magazine, September 11 1971
Former deputy editor Rob Cook is now working in Australia where he’s been trying the Austin Kimberley for us
The Austin 3 litre wasn’t the only production car with an 1800 centre section, revised extremities and a six-cylinder engine. Oh no! The Austin X6 in its Kimberley and Tasman versions is in full production in the British Leyland factory at Sydney, Australia. And it’s rather a pleasant motor car.
In fact, if you want a saloon that is really different from all the others, then the economics of importing a Kimberley aren’t all that frightening, and the majority of the spares are available in Britain unless you happen to crumple the nose or the boot.
The engine, for example, is a six with overhead camshaft which has, with the exception of the seven-bearing crankshaft, all the moving parts of the four-cylinder E series unit. Its capacity is 2,227 cc and in the two carburetter Kimberley version, it produces 115bhp at 5500 rpm with a torque of 118 lb.ft. at 3500 rpm (the Tasman, with single su, has 102 bhp and 116 lb.ft. torque at the same revs).
This engine, at 346lb, is 14lb lighter than the 1800 unit and the whole car is 34lb lighter than an 1800, giving a Kimberley power/weight ratio of 99 bhp/ton. The 1800 had 75 bhp/ton so the increase is 32 per cent.
The gearbox is the 1800 one and the unit is mounted east-west, driving the front wheels. However, the radiator is at the front and cooling is assisted when necessary by a thermostatically controlled electric fan which ems in at a water temperature of 205°F.
Other changes from 1800 specification include, 1.5in greater ground clearance and, since this increases the drive line angularity, constant velocity joints have been fitted to the inboard ends of the drive shafts as well as the outers.
The Australian engineers have played around with the valving in the Hydrolastic suspension and fitted rubber helper springs at the rear to reduce attitude changes under full load and pitching. They have succeeded in full measure.
On the manual gearbox version, the gearing gives 16.9 mph per 1000 revs and on the automatic, 17.9. Almost needless to say, the automatic box is the Borg-Warner Model 35.
The boot is almost big enough for a country dancing class— 5 cu.ft. bigger than that of the 1800, but for some reason which escapes my limited intelligence, the fuel tank remains at 10 gallons, giving a range of 230 miles if you keep a quart in reserve, but that’s cutting it a bit fine and the gauge is of the usual "rough estimate" type, but very fail-safe - zero equals l.5 gal.
I went rushing off in a Kimberley to the next city—some 600 miles—and despite thinking that various things could be improved, ended up liking it rather a lot. The weather was pretty foul with a raging gale at right angles most of the time (blowing straight from the south pole), and I have never been in a car less affected by such gusty conditions. Only if the accelerator were suddenly raised did the wind have any effect on the steering, and that was fairly minimal.
The suspension I found firm but jolt free and roll something that doesn’t happen. Plenty of feel in the steering with very little front wheel drive reaction, and what there was only became apparent at low speeds during my "getting to know you" initial few miles.
The gearbox was rather noisy—a deep whine in the intermediates—with very good synchromesh, and the cable-operated change absolutely horrible. It felt as though the cables were in dire need of greasing and I’m told that as the miles build up the situation improves but if you can imagine stirring a crowbar through a drum filled with cobblestones, you’ll have a fair idea of the feel of the thing.
Oddly enough, this doesn’t matter a great deal because the engine has so much torque that you hardly ever change down once on the move. The non snatch speed in top, is 5 mph, and a normal pull away from a stand-still can be made in third.
The engine will certainly never be wrecked by over revving because the camshaft/valve spring set up is such that when you get to a given speed in each gear, the power curve just goes horizontal and the only way to go faster is to change up. The unit hustles up the range with a gradually increasing sound of cams thrashing on valves, reminiscent of a Rover 2000 unit getting frenzied, but once you reach 32 in first, 55 second, 82 third and 98 in top, that’s it. Full point. With a long downhill grade you might just top 100 but it’s rather an academic thing and doesn’t matter a great deal, because the comfortable cruising speed is between 85 and 90 and it will do that all day long.
In fact, I averaged 84 for half an hour on one stretch without topping 90 which is as much a tribute to the car as it is to the road because the gale was really wild. Yet it was a one hand steering job, completely relaxed. On this run, by the way, we did 23 mpg and that seems to be the figure that most folks get with Kimberleys, whether in town or on flat out inter-city belts.
The acceleration figures aren’t all that startling with 0 to 30 in 4.6sec.; 40, 6.7; 50, 9.1; 60, 14.9; 70, 19.2; and 80, 30.0. The standing quarter needs 19 seconds. But there are two points to bear in mind: 1) this is better performance than that of the larger engined Austin 3 litre; and 2) it isn’t an easy car to take acceleration figures with from a standing start. The driver has a choice of wheel scrabbling, clutch slipping, a combination of the two, or neither.
I found it hard to decide which gave the best results and one early attempt at 0 to 40 gave 7.8 seconds against the final 6.7. It doesn’t matter a lot—what does matter is that when you press your foot down at 30 mph, the Kimberley slides smoothly up the scale to its cruising speed and only the wind roar really indicates that you are going rapidly.
Road noise is acceptably low, even on coarse granite chips, and the good through flow ventilation means that you can keep the windows firmly shut, and the seals were fairly noiseless. But one of the eyeball air inlets whistled in its closed position and stuffing Mr Kleenex into it seemed to be only cure.
I reckon that a competent mechanic could improve the gear change cables and, with that done, there would seem to be little or no need for the automatic version because top gear is very nearly in the steam-engine category. The seats aren’t all that clever because the cushions are too short and the backs non-adjustable, so when you import your Kimberley, get it without
seats and then fit 1800 or Wolseley ones. Forget the Tasman—it is the cooking version.
In Adelaide I drove a three carburetter version with stronger valve springs and modified seats and it gave me a pretty good idea of the car’s hidden potential, but, even as it stands, it’s a very pleasant piece of mechanism, very safe, very comfortable, and easy on the eye.
The economics of the deal might be a little frightening, though. The shipping costs aren’t too bad at about £150 and there might even still be some sort of Commonmarketwealth preferential treatment when it comes to import duty (note the tinge of bitterness creeping in) but when the whole deal was over you mightn’t have a lot of change out of £3,000. And you’d have to make the arrangements direct with British Leyland in Sydney because, of course, the X6 isn’t listed in the UK.
However, the model is being exported to a few countries around this segment of the globe and there would be no harm in having a word with your friendly Austin dealer. When he says "A what?", show him this article. Tell him I said it’s a fair dinkum beaut motorcar.
I’m sure he’ll understand.
Friday, March 20, 2009
To place the K70 we have to look briefly back into NSU history. When NSU marketed the R080 they were aware that its public acceptance might be a bit of a gamble, that they still had a great deal of piston engine manufacturing machinery to use and that there was a vast price gulf fixed between the inexpensive rear-engined models and the costly rotary-engined car. All this pointed to an intermediate model with a piston engine and this is how the K70 was born. It was announced very early in 1969 for the Geneva Show and then withdrawn again when VW took over NSU and formed the new subsidiary called Audi NSU Auto Union AG in April 1969.
Withdrawn but not suppressed. On the contrary, VW thought it was such a good car that they decided to give it their own name and produce it in very much larger numbers than NSU could possibly have afforded. In the meantime they have built a new factory at Salzgitter, not far from Wolfsburg, with a potential capacity of 500 K70s a day. And, of course, development has been continued by both NSU and VW.
We described and illustrated the K70 early this year (Motor, w/e March 7). To recapitulate briefly, it is designed very much after the lines of the Ro80 with front-wheel drive, a very long wheelbase and wide track, a short overhang body with rather similar lines, MacPherson Strut front suspension and irs by semi-trailing rear wishbones and coil spring /damper units. It has anti-roll bars at both ends, inboard disc brakes at the front and outboard drums at the rear with a pressure limiting valve and dual circuit operation. Steering is by rack and pinion but unlike the R080 (and contrary to earlier reports) it does not have power assistance.
The big difference, of course, is in the power unit which has a strong family resemblance to that of the Prinz 1000 series (but water-cooled) with a single chain-driven overhead camshaft operating V inclined valves in hemi-spherical heads through rocking fingers. The engine axis is longitudinal, the four-speed, all-synchromesh, all-indirect gearbox is behind the engine and the final drive is underneath it. Because of this the Ro80’s low bonnet line is not possible, even though the engine is canted 32° to the right to keep it low.
Two versions of the 82 X 76 mm. short stroke 1605 cc engine are available, both with five main bearings and a twin-choke side—draught Solex carburetter; one version has a compression ratio of 8:1 and gives 75 bhp (net) at 5200 rpm on 90 octane fuel, the other with 9.5 ratio needs 98 octane but gives 90 bhp at the same engine speed.
So much for the broad outline. Of course the last 18 months’ extra development has brought some further changes to the original design but most of these are of a very minor nature. The wheel size, however, has gone up from 13 to 14 in. and the 4.5j rims have 165SR radial tyres. Many of the engineering modifications have been inspired by VW’s production expertise and of these the most conspicuous is the change from a light alloy to a cast iron cylinder block.
The first public appearance of the K70 will be at the Paris Show but we recently had the chance to drive it for 150 miles in France. The question which obviously arises is, how does it compare with the Ro80, a car which has had rave test reports all over the world? In some ways it compares very well—it is a roomy five-seater car with an enormous boot of 24.5 cu.ft. capacity. It isn’t, of course, as fast. VW claim a maximum speed of 98 mph for the higher·powered version as against our test figure of 113 mph for the rotary car although the 0-60 mph figures are very similar. Road noise is very low and the K70 has that rigid, rattle-free feeling which adds so much to driving enjoyment on rough roads. The ride is generally good although it is characteristic of stiffly damped cars—a bit jerky at low speeds, but smoothing out at higher speeds.
Wind noise is also low and the ventilation system, a high flow, low velocity system, gives a draught-free air movement which is all you need up to quite high ambient temperatures. The engine is not as smooth as a Wankel but for a piston engine it is very smooth at high rpm, even if you take it right up into the red sector at 7000 rpm.
Probably the most disappointing feature relative to the Ro80 is the handling; the car is unusually stable, predictable and vice-free but the Michelin ZX tyres squeal at quite low cornering speeds and understeer builds up as you go faster until you can find yourself practically on full lock on sharp bends. We would want to try higher tyre pressures than the recommended 21 lb. all round—certainly much higher at the front on a car with 60 per cent of its unladen weight at this end.
Right hand drive K70s will not reach the UK until October 1971. In Germany, where the first batch will all be sold, its chief competitors will ironically be two other products of the VW group—the VW 411E and the Audi 100. No British price is yet available, of course, but the best possible estimate would put the current price at about £1600; in a year’s time it will probably be higher. Excellent though it is in many ways, it isn’t sufficiently distinguished we feel to command large British sales in this highly competitive price category. CHB
Thursday, March 19, 2009
It is hard to say exactly what killed the MGC, but the most likely cause was the bad press the car received, together with its failure to sell in the USA. Our own road test, published in 16 November 1967, was far from enthusiastic about the engine, gearbox, handling and fuel consumption. Exactly when production ceased is hard to determine, but it was sometime last year. University Motors bought the last batch of cars and have been selling them successfully since. Their theory was that, with only a little attention, the model could be improved significantly and as they still have some 20 or so cars in stock, we decided to test one to find out for ourselves.
Basically they are offering an MGC GT in standard paint, with wire wheels, delivered with number plates, seat belts and four months tax for £1,370. At the Motor Show in 1968, the listed price was £1,337 without any of these extras, or even a heater. By today's standards this is about £130 less than a Triumph TR6 coupe and not very much more than a GT6 delivered to the same specification.
To improve the appeal though, they are also offering a long list of extras, most of these being fitted to the test car. Added together these came to another £460, making the test car £1,830, or about as much as an Alfa Romeo 1300 GT or a little more than a BMW 2002. Some of these make so much difference as to be near essentials, while others like the stereo tape player and radio (£92) are pretty obvious luxuries.
Items like the Downton engine conversion make such a difference as to qualify as essential extras and the overall effect on the car leaves one wondering why it could not have been made like this in the first place, and if it had, would the fate of the model have been more successful? It would certainly have been much more enthusiastically received by our staff.
As a single item the Downton kit costs £l75 fitted. It comprises the usual kind of head improvement, coupled with special manifolds and a complete transformation of the induction system. In standard form the MGC is a real pig when cold, developing hardly any power until warm and never idling reliably. The Downton—converted car suffers from none of these troubles, pulling eagerly straight after a cold start. More than just this, the conversion gives the engine the "right" kind of sporty response, which it never displayed in standard form, climbing "on to the cam" at about 3,000 rpm with a real bark to its straight—through exhaust. In many ways it reminds one of the works rally Healey 3000, both in overall response and the noise it makes.
Actual improvements in acceleration time are not spectacular, but very worthwhile none the less. In top, for example, about 2sec is knocked off each 20-mph increment. Standing start times show similar slight improvements, and we could probably have made the differences greater if we had not been fooled by the rev counter, which over—read by almost 500 rpm at the top end.
As well as improving the performance, the conversion works wonders for the overall fuel consumption. Driving the car hard we got very nearly 20 mpg, which compares with only 17.5 mpg for the standard product.
The standard gearbox, with its enigmatic choice of ratios, remains unchanged, as does the final drive ratio with its long-legged 26.95 mph per 1,000 rpm in overdrive top. The test car was fitted with Cosmic light alloy wheels (£60 for five) which did little for the roadholding, but improved the appearance no end. They were fitted with the standard Dunlop radial-ply tyres.
Another worthwhile improvement came from the substitution of Koni dampers (£16 the pair, fitted) at the front and a 15in. dia. Motolita laather-trimmed steering wheel (£12 12s). Standard wheel size was 16.5in., so the steering becomes that much more responsive and the view out ahead that much better. Wooden packing strips under the seat runners also improved the driving position, which on the standard car was far too low for anyone much under 6ft tall.
Giving less leverage, the smaller wheel increases the already heavy steering effort, making fast cornering quite a muscular struggle. Excessive understeer from the extra nose weight of the six-cylinder engine makes the MGC a much less lithesome car than the MGB, but it is impressively stable in a straight line as compensation. Poor turning circles (almost 36ft between kerbs) hamper one when manoeuvring.
It would be wrong for a true sports car enthusiast to look at the MGC and expect it to be one better than the MGB. In the vital qualities of handling and engine response, it is no match for the four-cylinder car. But as a long—distance touring car, where a lot of the distance covered will be on motorways, it definitely has a place and in University Motors' guise begins to look much more attractive. At £1,545 (£1,370 plus the essential Downton conversion) it has few direct competitors, and anyone worried about spending this much on an obsolete model can take comfort in the fact that its rarity alone may one day make it a sought-after classic. According to factory records, only 2,199 MGC GTs have been delivered in the UK.
Sunday, March 15, 2009
Rather disappointing engine conversion offers small gains in performance and mpg, and requires premium fuel. Tinted windows for a black world. Tape stereo and radio, and a television option, in an £1,892 10s 6d package deal
PROMPTED BY increasing demand for the more expensive motor caravans, Wilsons introduced earlier this year a number of modifications for the Bedford Bedouin coachbuilt design. All the items are available separately, or the whole caravan may be ordered with an even fuller list of options at a total price of £1,892 10s 6d. In this form it is called the Executive and has a distinctive matt radiator grille. There is also, at £100 extra, a conversion for the 2-litre engine. The Bedouin with the Executive specification in full, and with the GT engine, has been submitted by Wilsons Motor Caravan Centre for a brief test.
To deal first with the engine conversion, we must confess to being a little disappointed. The modifications include a twin-choke Weber carburettor, higher compression ratio and revised induction. For the third time in our experience of the Bedford van, the bonnet release catch was not working, so we were only able to see the engine conversion by removing the cowling in the cab. This is enough to show the difficulty which lack of space makes in any attempt to modify the power unit, and the right angle junction in the air inlet cannot do much for efficient breathing. The table shows the small improvement in performance which resulted, and the gain in fuel consumption was offset by the need to use premium fuel instead of regular.
Not apparent from the figures alone is the fact that the vehicle felt much crisper and more responsive, and it was not until performance figures were taken that it was found that the improvements were more marginal than had been expected.
Air silencing was less effective on the modified engine, and a lot of induction hiss could be heard on light throttle openings, changing to a throaty roar under full power. The power brakes are a useful improvement on the Bedouin.
It is surprising how greatly the tinted windows alter the external appearance, but inside the effect is a little funereal, and the interior is very dark. Whatever the weather, you take your own dull day along with you. However, many people will no doubt value the privacy, especially when eating meals in the caravan, when one feels much less like a goldfish in a bowl. We were informed that the suppliers of the tinted glass have been requested to make it less dark on future production.
This is not the first time that a motor caravan has been offered with a tape stereo unit, but one would have thought that one of the combined tape and radio units would have been preferable to the two separate items listed at a total price of £86. Further, the stereo was not working, and both units were out of reach of the driver. Wilson's now offer Sony portable television as an alternative to the tape stereo and the tinted glass which seems a much more sensible option for a motor caravan. When this option is specified the Executive costs £1,869, showing a reduction of £23 10s 6d. There are difficulties of thief—proofing a television in a motor caravan, but half the battle is for the set always to be stored out of sight when not in use.
In the full specification of the Executive there are a number of lesser items, such as a fire extinguisher, gas refrigerator and tax for four months, in the attempt to offer a really comprehensive specification without extras; and the price has been maintained in spite of an increase in the basic cost of the Bedouin.
The idea of tailor—made modifications for a motor caravan is attractive, and there is considerable scope. This is quite a good start, but we would like to see some more practical refinements, such as the pressurized hot and cold water system of the Landliner, a conversion to servo-assisted disc brakes, and a more effective increase in power in future modifications. No doubt Wilson's will be looking again at the luxury market to see what further developments can be made for even greater comfort and refinement.
Rolls-Royce Make A Wankel
Original two-stage diesel design
By J. R. Daniels, BSc
Alone among British firms, Rolls-Royce have shown an abiding interest in the Wankel principle. After six years of research. details are revealed which shows the originality of their work and its promise for the future
WE have long deplored the fact that Britain's motor industry has chosen, by and large, to ignore the Wankel engine. By following a policy of masterly inactivity they may be saving development effort and leaving themselves the option of taking up the rotary engine if it becomes really attractive; but this sort of approach is at present tightly controlled by the licensing arrangements centred on NSU. The only two British licence-holders to date are Perkins and Rolls-Royce, and only Rolls have done any serious development work. For a long time their approach was shrouded in secrecy, except for whispers that their thinking was highly original and intended primarily for application to military vehicles.
Details of their six—year development programme, however, have recently been given in a paper delivered to the Institution of Mechanical Engineers by F. Feller, C Eng, MIMechE. The story is something of a classic, starting with basic research on modified NSU engines and culminating in the design of a 350 bhp engine for military vehicle use. Even at this stage, Rolls-Royce regard the story as only half-written; much more development will be needed before the projected engine becomes a full production unit, even for the Army, while commercial prospects are even farther off.
The basic Rolls requirement was for an engine of small size and low fuel consumption. Existing standards were set by the opposed—piston two—stroke, and it was decided in 1964 by the Military Vehicles Engineering Establishment that it would be worth trying the Wankel engine as a diesel, for the sake of economy and the ability to operate on a wide range of fuels.
In fact, the Wankel in its familiar form makes a poor diesel. Its geometry makes it difficult to obtain a high enough compression ratio, and the long, thin combustion chamber has a poor surface—to—volume ratio (which results in high heat losses and poor combustion). Changing the geometry to push up the compression ratio results in a much bigger engine and an even worse surface-to-volume ratio, and so another solution was sought. The obvious answer was to pre—compress the ingoing air, by means of a Roots blower, a turbocharger, or a positive-displacement unit. Since the Wankel is itself a positive-displacement machine, the most elegant solution was to run two Wankels in series, as it were, with the first merely serving as a compressor for the second, in which combustion would take place. The first unit would then complete the thermodynamic cycle by acting also as the expansion stage for the exhaust gases.
The compressor stage must actually be larger than the combustion stage, since the initial compression depends directly on the relative size of the two units. In effect, one chamber of the compressor feeds air into the much smaller chamber of the engine proper. The basic compression ratio of the combustion stage is thus multiplied by the ratio of the displacements of the two units.
Physically, the compressor does not have to be very much bigger than the engine to give a multiplication of two or three. Together, the two-stage engine turns out to be little bigger than the equivalent single—stage one (since, as already explained, the latter must be made much bigger to obtain the same compression ratio). At the same time, the two-stage engine has a much better——i.e. lower surface—to-volume ratio.
Work was thus concentrated on the two-stage layout, with a three-rotor design as a back-up. This had separate rotors of simpler design to serve as the inlet compression and exhaust expansion stages. In the event, this alternative was not needed, but after a period in engineering limbo it is now being studied as an advanced exercise by the Royal Military College of Science.
Aside from the design of the two-stage engine, a great deal of basic research has been done on both combustion and on apex seal design. The combustion research resulted from the decision to use direct fuel injection rather than to` have a pre-combustion chamber in the wall of the rotor housing; there were. several design disadvantages, including leakage past the tip seals and difficult starting, which overruled the possible advantages of pre—combustion.
Combustion conditions in a Wankel are very different from those in a conventional reciprocating engine. Instead of the nice, stable column of air in the centre of the combustion chamber, and the very low piston speed around top dead centre when the fuel injection takes place, the chamber and its charge of air are travelling past the injector very fast indeed. These conditions are not necessarily worse for combustion; it was just that the engineers were working in a field where very little was known, compared with the extensive work which had been done on the reciprocating engine. Such work as had been done on the Wankel related to the petrol-burning, spark—ignition engine.
Using a small NSU Wankel engine as a test bed, 30 different combustion chamber shapes were tried, along with six different fuel injector positions. Some of the combinations were incompatible, but even so, over 100 different arrangements were tried before the best chamber shape was arrived at. In this design, the fuel is injected into a relatively wide recess carefully shaped to induce air swirl. Air for the combustion process comes from above the trailing half of the rotor, and squirts into the area through a narrow delivery channel.
It must be emphasized that this research applies to the Wankel in its diesel form, and it remains to be seen how much of it may be applied to the four-stroke petrol engine.
While the combustion test work was going on, the little Wankel engine had to be modified to withstand diesel operating conditions. An early change was made from carbon to steel tip or seals, and it was found necessary to make new seal springs out of Nimonic 90 nickel alloy.
Early studies showed signs of misfiring which were soon traced to seal misbehaviour. Since the seals cannot be a perfect fit in their rotor-tip slots, they were tilting and jamming. The solution here (also adopted by NSU before the appearance of the Ro80) was to machine slots in the leading face of the seal to admit high—pressure gas underneath it and force it upwards into contact with the rotor housing. Later, a tendency of the seals to lose contact with the rotor housing as they passed into a lower-pressure area was overcome by recessing the trailing edge of the slots. This resulted in a 30 per cent improvement in low-speed fuel consumption. A further development was the use of a stepped apex seal, retaining the advantages of the recessed slot while also reducing the seal mass.
Again, these studies were carried out with the diesel engine in mind; but it would be surprising if designers of passenger-car Wankels did not take them into account in future.
The first Rolls—Royce development engine was the R1 which was conceived purely as a research tool. With a compressor stage of 1,126 c.c., and a combustion stage of 500 c.c., it produced over 50 bhp and achieved specific fuel consumptions of better than O.5lb/bhp/hour. Among other things, it was used to develop the best inter—porting arrangement between the two stages.
The R2 engine was the alternative three-stage layout, built but not investigated in detail. R3 refers to a combustion stage only, which is being used as a basic unit to build up a range of engines; it has a displacement of 1,216 c.c., and has produced 180 bhp at 4,500 rpm under test conditions.
The remaining engine of which details may be given is the 2—R6. This is a military engine formed of two banks of a two—stage engine. Each high pressure (combustion) stage has a displacement of 1,265 c.c., and is fed by a low-pressure stage of 3,250 c.c. The design power is 350 bhp at 4,500 rpm, for a weight of 939lb-a spectacular power-to-weight ratio for a diesel.
Rolls—Royce emphasize that this engine is not even running as yet, and that it will be some years before it sees even military service. But it is encouraging to see at least one British firm indulging in advanced and original Wankel research.
From Autocar Magazine, week ending 17th December 1970.
ALL THE SAME
That's the trouble with our cars
By J. R. Daniels, BSc.
What has led Britain's car makers to try to outdo one another in utterly conventional engineering and styling? There has to be a way out, but there are risks involved.
I was driving a Triumph Toledo earlier this year. The car was not to be announced for another month, yet nobody spared it a glance on the road. An isolated experience? Far from it; nobody looked at the HC Viva either, and only two people realized the Hillman Avenger was something they hadn't seen before. In fact, it was obvious that as far as the great mass of the population was concerned, all three cars looked pretty much the same as most other cars.
lf the firms producing them are to be believed, each of those cars represented a unique set of virtues, suiting it best to the needs of many—if not most—family motorists. So why on earth is it necessary for them to look like four peas out of the same design pod?
One is driven to wonder how these cars are to be sold. Since they all look the same to the untutored eye, it can be said that none of them appeals more than the others—none of them will sell itself in the face of the opposition, so to speak. The selling must be done for the car—but how? By undercutting the market? Ridiculous; the economic pressures don't permit it. By dint of superior reputation? l’m sorry, but don't make me laugh.
All that is left are conventional advertising and promotion techniques. For the rest, there's a massive reliance on brand loyalty, still one of the most potent sales factors in this country. Of course, it helps to have the cars available when people want to buy them. Failure in this respect explains some, but by no means all, of the drift towards foreign cars in 1970.
Origins and explanations
There are five British entries in the supposedly hotly contested 1100-1300 family saloon class. The newest Viva is a straight replacement for the old one, continuing the line started in 1963 with the angular HA model. ln many ways, the Viva has been the styling leader for cars in this class throughout most of the past decade.
When Ford's Escort emerged to replace the Anglia, it looked like a slightly crude, bulbous copy of the HB Viva; a pity, because the Anglia had been a distinctive design. What went on under the skin was another matter, but then there are thousands of motorists who are far more concerned with what their car looks like than anything else.
Even though the Hillman Avenger was not a replacement for anything, but intended to give the Rootes—Chrysler faithful a chance to buy something bigger than an lmp and smaller than a Hunter, it emerged looking far too much like a Viva or an Escort. Why? Apparently because somebody had decided that to compete with a car, you have to look like it.
When the Triumph Toledo was introduced, we had our fourth virtually identical car. This body shell had a slightly odd lineage; basically a squashed version of the Triumph 2000, it was treated to a new nose with the near—obligatory little rectangular headlamps. Thus endowed, it looked a good deal more like the other three than had its predecessor, the front—drive 1300. And in so far as the Toledo can be regarded as a Herald replacement, we have yet another case of the "Standard British Small Car" supplanting a highly individual design.
Has nobody the courage to build a car which looks different? Are the customers so regimented that they would refuse to buy something which stood out from the common herd? Well, consider the one car in this class which is different, the Austin-Morris 1100/1300. You can't mistake it for anything else. It was originally introduced as a rival for the Cortina, only the Cortina has grown up so fast that comparisons are no longer apt. Hard—headed fleet managers refuse to consider the Austin-Morris car for presumably good reasons of their own, and yet it still sells in Britain in larger numbers than any other car.
One would like to think that there was a lesson here for all car—builders. Yet the most open of motoring secrets is that the Austin—Morris ADO 28, due to emerge in the first half of 1971, will be a thoroughly conventional car aimed at the fleet market and the conservative user. Engineering aside, would anybody like to bet that the average Briton will be able to tell the ADO 28 from an Avenger or a Viva at 100 yards?
This horrid uniformity seems not to afflict our cousins in the Common Market. The three biggest producers. Fiat, Renault and VW, pursue different lines. Fiat's 128 (and the earlier 124) are stark. clean three-box designs. So was the Renault 8: but the newest Renault, the 12, is a highly individual and a very sensible shape. Volkswagen still depend on the Beetle which is equally individual if not as sensible.
The smaller ECM producers do not slavishly follow one of their big three. Simca's 1100 is a five-door fastback; Peugeot's 204 leans more to the conventional, but only on the surface. NSU and DAF have their own views, and the Citroen GS is the most way-out of all. Only Opel and Ford Germany remain faithful to convention, and they are a special case in several ways. Not only are they American-controlled, but the German market has never much cared for cars as small as this anyway. Opel have done nothing to update the Kadett for several years, while Ford Germany build the Escort to take care of the demand.
The upshot of all this is that the ECM car buyer has a choice of shapes from which to choose. It is not so much a good thing in itself; but it underlines the fact that the cars really are different, encouraging him to shop around intelligently to find the one which suits him best. This in turn must encourage the car builders to look for fundamentally new solutions, instead of fiddling round trying to improve the ride a bit here, keep out a bit more noise there, save a few pounds weight and always—but always—cheeseparing pence off everything.
The styling is no more than the outward sign of a whole attitude of mind. ln many ways, though, styling is the easiest thing to change. lf the designers were willing, they could at least try to make their cars lock different, even if fundamental differences were longer in coming. Somehow we have to break out of the stalemate caused by market research feeding on the results of its own findings.
Not just the styling
It isn't just a matter of finding a pretty shape. People have to sit in those cars for hours at a time, and the Standard British Car just doesn't fit them, especially if they are ill-advised enough to sit in the back. A couple of minutes' sketching should convince anybody that, if they are to sit properly, the back passengers must sit at least as high and preferably higher than the driver. Yet our car roof slopes downwards towards the rear from its highest point over the driver's head (Fig. 1). This is no good from any point of view except that of the conventional stylist. It makes for poor aerodynamics (boundary layer separation can take place at almost any point on the roof), and causes a dreadful headroom problem for the back passenger. In an endeavour to restore some room, several firms seat the rear passenger too low (Fig 1A), so that he ends up in an unstable and uncomfortable knees-under-chin position.
The sensible approach is to have a roof line which rises gently towards the rear, as far as the point where it is aft of the rear passengers' heads. After that, there is much to be said for dropping the line sharply. By doing this, you pin down the boundary layer separation point and stop it shuffling noisily backwards and forwards along the roof. One car which employs just this approach is the Renault 12.
There are various ways of finishing off the back end aft of this sort of roof (Fig 2). One possibility is the reverse-rake window of the old Anglia, which again was a highly sensible design in many ways. Other possibilities are the 'notchback' in the manner of the Simca 1100; the true straight-line fastback; or the more humpy approach seen in the Renault 16.
There seems also to be a universal determination to build cars lower and lower. Taking the Fiat 500 and the Chevrolet Impala as being the smallest and largest practical cars, the Chevrolet is nearly twice as long as the Fiat, and almost 50 per cent wider; yet it is only an inch higher! Every so often we lay hands on something higher—built than average, like the Range Rover. When we do, we are apt to revel in the superb view which makes traffic driving easy, and in the decorum with which the vehicle can be entered. lt is surprising, too, how iittle seems to be lost from the handling, at least where normal, sane driving is concerned.
The same might well be said of performance and fuel consumption penalties caused by the increased frontal area. This may well matter for those few genuine GT cars which are actually
used as such, but is that a good reason for trying to turn honest family saloons into styling imitations of them?
One thing we are all short of is road space. Fig 3 shows (admittedly by using two extreme cases) that the lower the car, the longer it must be to carry the same people in comfort. The first designer to add rather that subtract height will be performing a social service, as well as gaining some useful sales points.
The Avenger, Toledo and Viva all have four-cylinder, in-line, ohv engines, front-mounted and driving the back wheels. All have live back axles, located by four trailing links. The Toledo and the Viva have similar front suspensions as well—although the Avenger uses MacPherson struts. The Escort lines up pretty well with the other three. Again, it is the Austin—Morris 1100 which offers the alternative of transverse engine, front wheel drive and hydrolastic suspension. The example set by Issigonis with this car has been followed with enthusiasm on the continent. The Fiat 128, Simca 1100 and Feugeot 204 all follow its broad principles, while the Renault 12, Citroen GS, Volkswagen K70 all use front wheel drive, with rumours of Alfa Romeo preparing to follow suit. Back in Britain, we often ask about front wheel drive. The typical answer goes like this: "Ah, but you would see all the front wheel drive development cars we have run! But the cost engineers can never get within £20 of the equivalent conventional car . .
We have heard this from many engineers, (not that we have ever actually been shown the development cars!). What we are still disposed to argue is their definition of equivalent. Front wheel drive cars have inherent advantages in terms of providing decent passenger space. Since they leave the back end free for a good but simple independent suspension, they should ride better as well. lt is also relatively easy to get them to handle and hold the road well, although not as easy as some people thought when the Mini was the only example they had to work from.
True, a conventional equivalent can be produced—but it takes a good deal of engineering, unless your definition of equivalent stops at square inches of car and cubic centimetres of engine. If we are not careful, we alone will remain convinced that front wheel drive is uneconomic. Even the Japanese are getting in on the act, and up to now they have been the epitome of conservatism in small car design. There is, surely, still room for the slightly better car at the slightly higher price?
The market was once full of firms looking for a slot in the market—an unfulfilled need. When it
worked, the formula could be a very successful one: the Cortina, the Rover 2000, the Ford Mustang are pre-eminent examples. Now, it appears, one goes bald-headed for a share in an existing market, hoping that a slight price advantage, a favourable press reception and (with luck) no teething troubles and no strikes will add up to a couple of percentage points gained on the sales front. What one does not do is take anything which might be construed as a risk.
Table 1 shows how closely matched are the five British cars in the 1100-1300 class. Wheelbase and track are the really significant dimensions, since they tend to govern the amount of interior space. Overall length is a much less reliable guide, since it can so easily be boosted by an unreasonable amount of boot or an empty stylist-special nose.
It is surprising how much difference to interior space can be made by increasing the wheelbase by a couple of inches. There is of course still scope for ingenuity within a given wheelbase; otherwise the Austin 1100 would be no more roomy than the Escort. Looking at the table, one can see how there is an element of slot-seeking with the Avenger, which is aimed between the Escort—Viva and Cortina-Victor markets. Even so, it comes perilously close to the Hillman Hunter, which appears to be under-sized for its class (Table 2).
ln this class, the Maxi offers an impressive space advantage, though the same cannot be said of the slightly bigger 1800 vis—a-vis the Vauxhall Cresta and particularly the Ford Zodiac. This big—car class, however, is becoming increasingly depopulated; the real Austin—Morris contender is the 3-litre, now on its way out. lt may well turn out that the 1800 is about as physically big as anybody will want a car within the foreseeable future. The really big cars lose a lot of their meaning if they take up more road space without being really commodious inside.
It seems that the tendency of cars to conglomerate into groups has left a hole or two to fill; one below the Escort—Viva group, and one above it: with the growth of the Cortina—the Victor was already quite big—the Avenger is not quite big enough to fall square in the gap. Above the Cortina-Victor, the Austin—Morris 1800 is very well established and not too far above; but it might be worth speculating on the form of a conventional—type car in the same bracket. At the same time, consider whether the Maxi was pitched too close to the 1800 in size, since its dimensions put it much closer to its big brother than to its smaller one, the 1300.
Table 3 shows the main foreign competition in the Escort-Viva class. One or two of the cars—Citroen GS, Peugeot 204 and Simca 1100—-are really large enough inside to qualify
as gap-fillers. It is really their limited engine size which leads to our thinking of them in this
class, but then the ECM attitude to engine size is rather different.
At the bottom of the table, note the three smaller Japanese cars, about the right size to fill the sub-Escort gap. There is a staggering similarity between the three from an engineering point of view, emphasising the extent to which their major firms have pursued a policy of matching development for development.
Table 4 shows some of the main foreign competition in the Cortina-Victor class. One point of interest is that it is in this class that technical innovations——overhead cam engines, independent rear suspensions and so on get a real run for their money: and again, five of the cars have front wheel drive.
Laying down a policy
I long for the day when a policy will be laid down for project engineers, designers and marketing men. It would go some way towards ensuring genuine technical and styling competition, to the benefit (I am sure) of the customer. lt would go something like this:
1) Look for gaps in the market, taking the physical size of the car as the yardstick—and the wheelbase as the main criterion of the car's size.
2) Ensure that the car is recognisable in its own right; try to give the sales people some real interior room to boast about.
3) Achieve comfortable seating by using height. Take the overall height of the preceding model as the absolute minimum for the new car.
4) Introduce sufficient technical innovation to give the sales people a real talking point. It doesn't have to be whole—hog stuff like a Wankel engine and hydrostatic four wheel drive. The trends are already being set, and the introduction of the right advanced feature will set people thinking even if they could never point to it under the bonnet.
My gap-filling projects in table 1 have this sort of approach in mind. I am convinced, for instance, that proper independent suspension has to come, with or without front wheel drive. I cannot really see that the current rash of four—link live axles is anything but a dying fling. Where engines are concerned, l have stuck my neck out and postulated a flat-four and a flat-six linked by a building-block arrangement so that the six is, in effect, one and a half of the four—cylinder unit.
Although Volkswagen and Porsche have carried the flat—four banner for many years, I am also encouraged by the brilliant little engine in the Citroen GS, and the fact that light aero-engines have used this layout almost universally for many years and in power outputs up to 200bhp. What l have not done is to go any further and add shapes to the ideas; although Geoff Howard's essay into the mid-engined sports car, published last week, serves notice that we are ready and willing to indulge in further prompting. It would be nice to think that somewhere, someone in the industry—preferably the British industry—is already thinking in terms of breaking out of his engineering straight-jacket. lf this tirade does anything to help him, it will have served its purpose.