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Norton water-cooled Classic


One of the more aspects in recent times of long and sometimes chequered (‘Pa’ Norton started his based business in 1898, surely making it one of the oldest companies) has been its excursion the development and manufacture of the rotary engine.

How, why, and where did Norton get involved this unusual engine? Denniss traces its fascinating

In the 1960’s the world automotive saw Dr. Wankel’s engine as a potentially competitor to the reciprocating engine. studied it and many took out from NSU/Wankel and started programmes which culminated for a of reasons in most activity around the time of the first oil in 1973.

The major Japanese manufacturers of Yamaha, Suzuki and also became NSU/Wankel and started hectic development resulting in Suzuki taking the with their RE5 model.

In the B.S.A. Group Research felt that there be a market for this type of in motorcycles because of its simplicity, low and weight, and compactness.

Therefore engaged the services of a young graduate engineer named Garside, one time employee of Royce Motors, to take on project at the Group Research Kitts Green, Birmingham. he had only one engineer and two fitters to him.

A preliminary market was carried out which indicated a rotary powered motorcycle succeed at the high powered end of the bike market and compete the complex multicylinder motorcycles offered at the time. Garside’s target, therefore, was to develop an producing 50 to 60 b.h.p. his first design choices being:-

(a) Air or cooled housings

(b) Charge or oil rotors

(c) Number of rotors

cooling appeared to be attractive as cooling would be assured, around the spark plug and port area. In the end it was rejected as unacceptable to potential customers as cooling was still rare in days and it was anticipated (subsequently to be wrong) that a weight would result.

Today, water cooling is commonplace, a decision would have taken. Indeed, the current J.P.S. racer and the Norton engines are all water cooled.

The point for research was a KM914 Sachs forced air-cooled rotor engine of 300cc and 18 B.H.P. First reaction to engine was the technical simplicity and of the charge cooled rotor, with the oil cooled rotor although the low specific power with this type of would be insufficient for motorcycle

Garside therefore decided a system which retained the of this design, but allowed for greater power potential was More about his ingenious later.

Performance of the F  S including heat rejection were fully mapped and the compared with the air cooling on a motorcycle. Practical tests carried out on a motorcycle at M.I.R.A. pilot tubes and wool

These tests confirmed air speed behind the front was approximately half that of the forward speed, Although of the B.S.A. machines then built had only 20 square per b.h.p. of finning, it was generally that 40 square inches per was the accepted norm. The F  S had about 50 square inches per and Garside felt that a rotor version of this mounted low in a motorcycle with the shaft axis mounted across the frame, would be cooled.

Also, the twin housings would be positioned side of the front wheel where the cooling air would be disturbed. So this together deep circumferential finning and the major axis 15 degrees to the thus placing the hot sector of the between the spark plug and port directly in line the air flow, should provide a cooled engine and allow potential for further power

In addition, this angle conveniently allow the inlet and pipes to pass over and the gearbox. A twin rotor engine was then built on this design using dimensions and rotors.

By 1970 the was showing such promise Garside was transferred to Umberslade where the B.S.A. Group’s development and testing facilities located.

Here, Garside set developing his ideas in retaining the charge cooled system, but its inherent power deficiencies. the charge cooled rotor allowed a very simple it resulted in low BMEP, due to charge and the long tortuous path the rotor passages and ports breathing at higher r.p.m. He that some other increased the BMEP by passing a of the induction air directly into the chamber.

However, this resulted in reduced rotor Now the colour and carbon deposits in the engine indicated that cooling was already marginal, forced air cooling and rich This system, therefore, did not itself to Garside. So he carried out an of passing the heated mixture from the rotor passageways, an air to water inter-cooler before the mixture into the induction

This showed some but would not be practical on a motorcycle. he replaced the intercooler with a chamber of about 5 litres which worked equally

However the major step came when the carburettor was between the plenum chamber and pipe so that air only, not the passed through the rotor. The was that a single rotor of this configuration produced 38 b.h.p. about 85% more the original F  S unit, indeed.

This marked in power was almost entirely due to volumetric efficiency brought as follows:-

(a) The plenum chamber the intermittent working chamber flow to a more continuous through the restrictive rotor and plate passages. It also to some degree as an intercooler the temperature by approximately 20°C.

(b) The of the carburettor resulted in the latent of evaporation of the fuel being at a more favourable point, a lower mixture temperature. (c) The of the carburettor also allowed a length of induction pipe to be

(d) Increasing the quarter moon port in each end plate one to two allowed greatly increased air at any rotor shaft angle.

there were penalties these changes; first the bulk of the plenum chamber and ducting, and secondly the petrol oil was no longer possible, a separate and oil system being required.

It apparent at a later date a sheet metal spine which would incorporate the chamber and oil tank would be a neat solution and incidentally, the chamber would act as a very intake silencer.

Garside that there were advantages with this in that the rotor cooling remained stable in spite of the power. These were to be as a result of the following:-

(a) The available cooling air is used more by being passed more through several passages in rather than through one intermittently at high velocity.

(b) The final charge temperature gas temperatures throughout the cycle and reduces heat input the rotor flanks.

(c) The cooling air passing through the passages has a higher density the petrol/air mixture which is of density as used in alternative

The system provided near balance for all load and speed Any increase in power output and heat input to the rotor, due to r.p.m. or BMEP increase, was balanced by a corresponding increase in air through the rotor ports. any weakening of mixture to optimise economy did not affect rotor as any increase in heat input was by an increase in airflow.

Overall, system proved to provide a compact design, with low losses, few moving parts and low production costs.

However, clouds were on the way. engine may have been much promise, but B.S.A. sales were going a disastrous period. Funds needed urgently so in 1972 became part of Norton under the chairmanship of Mr.

R. D. Poore. He saw the advantages of the Rotary engine and it when Umberslade Hall was together with certain key back to Kitts Green, Here further development, related to improved reliability and was carried out.

Two machines built using a sheet chassis to assist in development.

In 1975 the N.V.T. Group of failed. However, Poore had had the to retain the Rotary project, was moved — again Garside and other key personnel, to a modern factory at Shenstone, Lichfield, Staffordshire.

A small now set about designing, under the control of R.V. Trigg to move to Yamaha), the definitive which utilised the now familiar metal frame, Marzocchi Brembo brakes and the distinctive which became the hallmark of the Norton until 1988.

of the detail developments are interesting to For example, it was found that the steel rotor shaft diameters, which are casehardened, in diameter during the first few of use due to the high temperatures developed in early engines. It was only a cryogenic treatment was introduced the production process that problem was overcome.

The rotor are cast in LM9, an aluminium for its low copper content which good adhesion of the Einisil This nickel Silicon provides a very hard which is entirely compatible the IKA3 cast iron used for the rotor apex These two-piece seals wear rates as little as 15 per 1000 miles, although a number of cold starts and journeys will naturally the wear rate.

The side and intermediate plate are cast out of a material chosen after testing and techniques developed to the high percentage of silicon to proud after etching. finish has been found to an excellent working surface scuffing or wear, particularly at low This is largely due to there not being any piston sidethrust, as in the of a reciprocating engine.

They provide a flat wear for the rotor side seals. It be noted also, that surfaces are not highly loaded oil scraper rings as in the case of oil rotor Wankel engines. advantage with this of material is the high standard of finish, a most important for motorcycle applications.

A number of cases of side plate was experienced during endurance in 1981. Garside eventually these failures to skewing of the needle rollers, causing loads to be transmitted from the shaft to the rotor. This was by specifying needle roller assemblies guaranteed to have low creep, from selected

The decision to grade the rotor and to ensure a consistent diametrical was also taken at this to reduce mechanical noise and wear.

The rotors in the earlier engines were the F  S These had a symmetrical straight-through recess that was produced by During 1980 different of recesses were investigated.

and trailing shapes with changes of spark plug were tried. The leading proved to be the most successful, up to 10% increase in torque and improved consumption, compared to the original type. However, this brought about serious problems. The original F  S rotors had been satisfactorily tested to 60,000 miles failure, whereas the revised cracked after only miles.

Indeed cracking be reproduced in less than two at a continuous 7500 r.p.m. on the bed. To add to Garside’s troubles, yet power was required to ensure the would be able to compete with its contemporaries. Comparative against Kawasaki machines at had shown that the Norton could comfortably outsteer and the Japanese machines, but were not to beat them over the quarter.

An instant cure for was brought about by screwing plates on the flanks of the rotors to the compression ratio. The prototype was affectionately known as the ‘hand bike’ by the testers, as they knew when the engine blow up.

Anyway a new design was called for so Garside, remembering a known North American engine had similar problems, their engineer, who was able to on a possible solution. (interestingly, contact subsequently resulted in being granted a collaborative contract in 1984, which is current.) With the new design the gear teeth were cut as an of the steel rotor bearing race. The rotor is a precision S.G. iron casting no integral bridges across the

It is interference assembled with the sleeve, with only contact both axially and Relative rotation is prevented by the axial grub screws and the assembly is dynamically balanced. The of all this is a rotor which, over 75 hours at 7500

WOT is still perfectly sound.

A semi surface gap with centre electrode spark was chosen as it enabled the spark to be close to the working chamber having an unnecessarily large hole at the trochoid surface would allow increased gas past the apex seal at load/speed conditions when the across the seal is unbalanced. A area that increased in to increases in power output was around the spark plug

Various modifications were including a copper inset, eroding through the Einisil surface to form a fan-shaped of slots and finally a heart patch. These palliatives reasonably well, but it was only water cooling was introduced a complete cure was found.

inlet ports were in order to give good efficiency at high r.p.m. At load the relative long overlap of the inlet and exhaust would normally give problems due to the low pressure mixture in the pipes being excessively by the exhaust gas. The problem is by locating the throttle butterflies in the housing as close to the trochoid as is practical.

S.U. constant carburettors with hydraulic are standard, other then the normal throttle valves Positioning the throttle butterflies in the ports has two other advantages:-

(a) At load a high pressure exists at the throttle disc causing high turbulence and mixing at a point very to the induction chamber, This is to inlet valve throttling of a engine, which has been to be beneficial for fuel consumption and emissions.

(b) There is a much reduced variation in the inlet pipes as the is varied. Therefore less enrichment is necessary during throttle opening.

Garside had difficulty to face, that was to a satisfactory idle quality would be compatible with a engine. The reasons for this include the late closing of the port, giving high with the exhaust gas of the related charge, the relative poor gas at idle speeds and the 50% extension of working …, relative to a engine, allowing more for heat loss and gas leakage.

Norton water-cooled Classic

The was aggravated by the adoption of the air-cooled because of its low mechanical losses. results in a low fresh charge volume requirement at idle and an even higher percentage with the exhaust gas. with an air-cooled engine, it is that a reasonably low idle is achieved to restrict high rejection rates that overheat the engine.

Garside’s solution was to restrict the idle to one rotor. The parasitic drag of the rotor imposes additional on the engine by extra load on the rotor. This rotor requires a larger charge per and the dilution is thus reduced. A steady 850 r.p.m. is achieved this system, fuel being about 850cc per

The other ingenious aspect of development was that the non-firing acted as an air pump, drawing in a large quantity of additional air the centre of both rotors. is achieved by the closing of the throttle activating a microswitch, This controls a solenoid valve in a between the plenum chamber and the port of the non-firing housing, this brought in another of snatch which was eventually — the current Commanders excellent in this respect.

is nothing unusual with the system other than the high gas temperatures require the use of steel to achieve an acceptable This is particularly so on the Norton application where the exhaust are short and partially shielded. The of the silencers achieves a legal level with a back of about 140mm Hg at 8500

Lubrication is achieved by the use of a pump output is varied in relation to the opening. The oil output is directed the induction airstream in the intermediate From there it is carried to all the and rubbing surfaces by the cooling

Drain tubes are fitted to a at the bottom of the induction air transfer in each end plate and at the base of the chamber. These small pipes are connected to the main pipes between the carburettors and the valves. Thus the oil is purged these recesses each the throttle is opened, due to the additional from the damped carburettor

By 1981 the motorcycle scene had water cooling was well noise limitations were more stringent and yet more was going to be required. Garside see that water cooling be the answer, At about this Mr.

Poore, (incidentally he was a very racing driver with Martin and Jaguar and was 1949 Climb champion driving an Romeo) who had always taken a personal interest in Norton, Shenstone every two weeks or so, was very keen in fitting an into a car. On learning thoughts on a watercooled version he for the cost. Garside said ten to thousand pounds for the patterns, etc.

Go ahead and do it was Poore’s reply and by the make sure it will go in the . Garside went a stage by designing the castings so that would have some of the required for an aircraft engine as Two weeks later Poore had an Metro delivered together instructions to have the watercooled fitted forthwith. Garside with his priorities and during one of visits asked which take first priority.

The of course , was the reply. But within a few Poore’s enthusiasm for cars had him when could he drive the

Eventually, Carbodies (makers of the taxi and part of the Manganese Group) were asked to the engine, This was duly and the vehicle returned to Norton for By 1983 Poore judged development had progressed far enough. The car was to Austin Rover who lost when they found it their MG Metro Turbo. Mr.

drove the car around London for a and to the Shenstone works during his bursting a front tyre on the MI at 115 on one occasion. This didn’t bother him, but the fact someone had stolen the jack Mr.

Poore felt that the was OK, a bit tame in fact, so he persuaded to fit two 87 b.h.p. watercooled engines together in line into a Scimitar SSI. Suitably passengers said they liked it, but the Ford Cortina and rear axle didn’t.

In Mr. D. Hele, Cert.E.,M.I.Mech.E. rejoined the (he had previously worked for Norton) the specific task of refining and Garside’s unique concepts. great experience and practical to problems resulted in solutions from curing leaking caps to reversing the oil flow the engine. This came in 1983, when further development was resulting in occasional shaft bearing failures.

The system then employed in the bearings being at the end of the lubrication as oil entered at the centre of the engine and outwards across the engine it reached the bearings. Hele the air flow so that it entered. via into each end plate, the lubricating oil and then passing the rotor shaft bearings

The air/oil then continued the engine and out of the centre intermediate into the frame plenum This change very cured the problem. Another related to Garside’s ingenious and reliable single idle

Interpols, used for police work, where constant speed crawling was used for distances, showed up a severe problem during the single to twin rotor firing, stage. Hele overcame problem by reverting to a twin system and building in a temperature and controlled ignition retard which could now be done due to the in electronic technology.

In 1983, Mr. J. a director of Norton, contacted Continental Motors, a major engine manufacturer in the U.S.A. to try and them in the Norton work and its for light aircraft. Negotiations concluded in February 1984 T.C.M. signed a contract them to develop and manufacture the for aviation use.

Norton was contracted to supply 20 engines and out development work on their T.C.M. have also developed the Norton engine to a heat pump and have had a running on natural gas for over hours without overhaul. ceramic apex seals and supplied by Norton) gave an life of 10,000 hours.

For the light aircraft application the engine develops its maximum at about 7000 r.p.m. it is necessary to fit a speed reduction to the front of the unit to enable the to run at its most efficient speed. The design took the form of a compact epicycle gearbox allowed the output shaft to be with the engine rotor

Unfortunately, its high cost and a vibration problem which it only a 5 hour life, a complete redesign, the final is a neat helical spur with a rubber drive Incidentally, a very well-known consultancy predicted that the would turn to liquid and drip onto the floor the engine was operated at its torsional period. Garside is still for the first failure.

During testing of unleaded fuel (no seat recession problems was carried out and with the potentially low requirements, test running on is showing initial promise. injection and turbo charging are areas which are to be developed.

In Manganese Bronze sold to a London based industrial company, under the directorship of Le Roux. Under his progressive the Rotary engine programme has and expanded, so that a range of Commanders are now available in civilian, and M.O.D. specifications together an ultra sporting P55, developed.

In the aviation field, units are available from 38 weighing only 23lbs, up to 90 b.h.p. In this form, an Shaw Twin Eze aircraft, with twin Norton engines flew for the first in July 1989.

The Norton spares business continues to with hitherto more parts such as crankcases, oil pumps and 750 pistons now being

Brian Crighton’s modest in 1987, whereby he transformed the 2 with its 85 b.h.p. into a racer with over 130 is well known. His dogged has resulted in millions of people able to see on the T.V. Norton new outright lap records at circuits the U.K. four in 1988 at the time of writing, two in 1989 and the Formula One class.

So, whatever the authorities may finally rule the engine capacity, one cannot these facts.

Undoubtedly, the engine has and is proving to be one of Norton’s significant milestones; may it be as successful as enthusiasts the world over hope.

Finally it would not be to complete this brief of a fascinating subject without the reader’s attention to the fact over the years of development, their names are not mentioned many gifted and dedicated fitters and draughtsmen have to the engine’s development and that it has very much a joint But when an army wins a it is usually only the general who is

© Tony Denniss, Norton Ltd.

Originally published in the Owners Club Classic for 1990

Norton water-cooled Classic
Norton water-cooled Classic
Norton water-cooled Classic
Norton water-cooled Classic
Norton water-cooled Classic
Norton water-cooled Classic

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