The post-war Sunbeams - an alternative history by Peter Bird

One so very often one reads something to the effect that "BSA's post-war Sunbeam was Earling Poope's re-design of the BMW R75" - Robert Cordon Champ. The same author writes in his renowned (and often regarded as authoritative) 'The Sunbeam Motorcycle' (Haynes Publishing) "Although the machine (the S7) that Poppe produced for the Directors was emphatically not a copy of the R75 it was certainly strongly based on the BMW and included that machine's telescopic forks, wheel, tyre and brake design and sizes, frame and running gear layout, pancake dynamo, shaft drive, clean handlebars and inverted levers."

Personally, I am not convinced by that.

Undoubtedly the BMW has some brilliant, if very complex design engineering

But before we accept that the Sunbeam S7 was a rip-off of the German BMW, let us look closer to home and to other influences, and again put things in context

The first Sunbeam S7s, now commonly referred to as the early bikes, were introduced at the end of 1946. This was a period of extreme post-war austerity and national debt. Britain and the Empire was all-but bankrupt and the government directive to industry was to 'export or die'. Petrol was to be rationed for four more years yet and what was available was of poor quality, which necessitated low compression ratios.  The first post-war London Earls Court 'cycle show' was not to be until October 1948.

The mighty BSA group had owned the 'Sunbeam Cycles' name (including the motorcycles) since November 1943, having acquired it from AMC (Associated Motorcycles) ostensibly because they (BSA) wanted the prestigious Sunbeam bicycle brand name to compete with Raleigh bicycles.  Back in 1937, AMC had bought the rights to Sunbeam from Noble Industries (later known as ICI chemicals), which in turn had acquired the interests of a consortium of investors, who had bought John Marstons Ltd in 1920. Some say that ICI bought Sunbeam just to learn the secrets of their first-class enamel finishing.

Aside from supplying BSA rifles and machine guns, along with thousands of tons of munitions throughout the war, BSA also supplied over 60,000 folding bicycles, a similar number of military bicycles and over 125,000 BSA girder-forked (mainly) M20, 500cc motorcycles to the war department. That was more than any other supplier to any war department in the world. They justifiably claimed that “one in four was a BSA”.

However, these motorcycles were not a favourite with the men. Although of an almost identical specification to the Norton, critics said that the M20s were heavy and slow and had poor ground clearance. Others said that it was less than reliable. None of these are endearing features if you are a despatch rider on debris strewn roads, under fire. The Norton model 16 of 490cc felt a little more powerful, possibly because it was taller and just a little lighter. Norton were a preferred supplier to each of the services before the war and so their bikes were much better proven in the field. Norton's Big 4 of 630cc was more powerful for sidecar work, while the Matchless 350cc G3L (especially in its later war-time version with telescopic forks) was an altogether better bike than BSA could offer.

D-Day, on June 6th 1944, had seen the Allied armies regroup and push back into Europe, along with the Americans, in the European theatre. They, had of course, been in the Pacific* and in North Africa** working their way up via Sicily to Italy, taking Rome, also in June 1944. Very soon thereafter, the course of the war showed every sign that it had turned.  The hostilities would, possibly very soon, end.  And then, almost overnight, any outstanding order for munitions, weapons or vehicles would be cancelled. [* Pearl Harbour Dec 7th 1941.          ** from 11th  May 1942]

On the back of lucrative war-office orders, Birmingham Small Arms had gone from being a band of gunsmiths (working together to mechanise production and to compete against cheaper imports) to an industrial world power in 80 years.  In the 1880s BSA began to manufacture bicycles. In 1903 the company's first experimental motor-cycle was tested. Their first prototype automobile was produced in 1907 and in 1910 BSA purchased the British Daimler Company for its automobile engines.  By the second World War, the BSA group already had sixty-seven factories and employed tens of thousands of workers, either directly or indirectly. These captains of industry were both savvy and pushy (enough at least to have earned their chairman, Bernard Docker, a knighthood). [Extraordinary modern history that most of us are unaware of: Timeline of the British Army]

BSA may have been the world's biggest bicycle and motorcycle manufacturer but, as a munitions company of old, they had frequent experience of post-war situations. They would be left with numerous factories with tens of thousands workers and a dire civilian market economy.  So, in the midst of this turbulent war, with their cities being bombed, the Group's management had to anticipate and plan for survival. After the Great war, the world and the United kingdom too, crashed head-first into the great depression. Each country was struggling with this, even before incurring the even greater debt of the 2nd-world-war.  This time around, how would the country recover and its industry survive? 

Certainly BSA would have anticipated the market's need for cheap everyday transport, bicycles by the million and tens of thousands of motorcycles, both with and without side-cars.  Yet the harsh reality was that their motorcycles had no edge over their competitions. In fact, they were already dated. Tied in to their War Office specification, their 500cc M20 was too big for a (1940's) commuter bike and too small to pull a family sized chair. 

Conversely, Triumph already had their Edward Turner designed 500cc Speed Twin (since 1938) which was a sweet little vertical twin that showed a lot of potential and looked great. AMC had their more advanced Matchless G3 and Norton had the 16H and Big 4 which were ready and well proven for pulling heavily laden sidecars. Ariel had recently been bought* by BSA, along with Hudson and Sunbeam, but other companies like Panther, Royal Enfield, and James were all going to be vying for these same markets. BMW and the other German and Italian brands were equally successful in top level competitions before the war and so it wouldn't be long before they would be back and nipping away the market. In short, BSA were in danger of being caught with their pants down.

[* BSA bought-out numerous engineering supply companies, as part of their financial control over supplies and technology. The fact that they bought three cycle or motorcycle companies during the second world war reflects their never having lost sight of what happens when a war ends.]

They needed to buy time to develop something to dissuade the buying public (the soldier with accumulated war-pay)  from spending with the competition until they (BSA) had something as good to offer, which (underwritten by corporate wealth) they might offer cheaper. Although founded on their model range offerings, these speculations are further supported by the wording in their 1944 advertisement  1st Announcement "to spur interest … to keep the ball rolling … Sunbeam inaugurates a Forum on Design "

In what might be regarded as an inspired pre-launch publicity campaign through The Motor Cycle  magazine, BSA succeeded in keeping their name in the motorcycling press (when they had no new bikes to show) and built up an unprecedented level of anticipation and intrigue for their stunning all-new post-war machine. They kept this up for two years and, in fact, the new model Sunbeam appears to have been (possibly deliberately) postponed, as the first bike wasn't released until Dec 1946.             [Frame and engine number : S7-101   (21.12.1946)]

Clearly, this 'forum' was aimed at having motor cycling enthusiasts all talking and sharing design ideas, with the Sunbeam name as a backdrop to every conversation. Excellent marketing. It is noteworthy that, at the start of this forum in November 1944, the preamble states " the masterpiece is under lock & key.  Behind closed doors. Replete with a crop of big surprises. Waiting for the ceasefire to sound and production to begin ", which sounds to me like the design and pre-production development was well under way,  if not all but done. But it was radically different so BSA felt the need to re-educate the public into thinking about design rather than tradition.

BSA group's flamboyant chairman Sir Bernard Docker * (knighted in 1939)  liked big news  and was justifiably proud to furnish the silky silent Daimler limousines for Royal processions (the BSA group still owned Daimler motor cars.  Daimler also made the 'Scout' armoured-car). From a company supplying limousines to a niche market, it is a very small step indeed to speculate that to escort the Daimlers, BSA may have flag-shipped the prestigious  Sunbeam brand, and specifically the extraordinary S7  for such a stately role.  Look again at the Sunbeam S7 and consider how it might so easily have been conceived for a role as escort to State processions.

[ Sir Bernard and Lady Norah Docker (her 3rd marriage in 1949) were avid socialites and, aside from their yacht and other lavish lifestyle appendages, especially commissioned a series of  Daimler limousines. These limousines were also supplied to Royal families around the world. The first of half a dozen or more 'Docker Daimlers ' was a DE-36 Hooper-bodied convertible which dominated Daimler's stand at the 1948 Earls Court British Motor Show. The massive convertible was dubbed 'the Green Goddess' by the motoring press, in tribute to its special  jade green  paintwork, a remarkably similar colour to the s7-deluxe introduced just months later.  Following its début showing, the car was put into the service of Sir Bernard and Lady Docker.  'Green Goddess']

As it transpired, things did not go to plan. Apparently the police escort bikes for the  South Africa Royal Tour “vibrated so badly as to be un-rideable*

BSA had hoped to cap their brilliant marketing campaign with providing not only Daimlers but also the police escort motorcycles  for King George VI's 1947 Royal tour of South Africa (17th Feb - 25th April 1947 ). And of course, the hoped-for spin-off would be to supply Police forces, Embassies & top ranking dignitaries and Royal families around the world.

King George and Queen Elizabeth (later of course to be most affectionately known as the Queen Mum) were extremely popular with the people, having resolutely stayed for most of the war at Buckingham Palace, whose grounds had been bombed nine times. Together, the Royal couple had visited severely bombed areas in London's East End and other sites in the country. In 1940, the King instituted the George Cross & the George Medal, which unlike the Victoria Cross was to be awarded for acts of bravery by citizens.  And then, having served in the Navy during the Great War, including the Battle of Jutland, he was keen to visit servicemen and women in the field.  In 1939, he went to France to inspect the British Expeditionary Force and, in 1943, to North Africa, after the victory of El Alamein.  Just 10 days after D-Day, in June 1944, the King visited his Army on the Normandy beaches. Later that same year he was in Italy and then the Low Countries, meeting and encouraging the troops and the wounded. Unsurprisingly, Buckingham Palace was a focal point for VE (Victory in Europe) Day celebrations, on 8th May 1945.

The Royal family were also great Ambassadors for Britain and the Empire. Even before the war, King George VI paid state visits to France (in 1938), and to Canada and the United States in 1939 (just three years after the abdication of his brother, King Edward VIII in 1936). And, as such, he was the first British monarch to enter the United States. And so, the first post war overseas visit in 1947 to South Africa, accompanied by the Queen and their daughters, Princess's Elizabeth and Margaret (the first time a monarch had undertaken a tour with his family), was very BIG news, not only to the British public but to the Empire, the allies, and to the watching world at large.

[* “vibrated so badly as to be un-rideable”?  At the time the details were lost in amongst other news. Many authors attribute the later bike's rubber mounted engine to have been a quick-fix cure to the problem.  But perhaps that is just another one of those stories that get passed around, because some people believe that the rubber mountings had been designed from the outset by Erling Poppe, but was dropped for production. C.1927-30 Erling Poppe worked with John Wooler, who long previously (1911) had patented an 'anti-vibratory' frame.

Why would any 25hp, short stroke 500cc twin, with just 6:1 compression, that had taken two years to develop and an important enough bike to specially prepare and then ship all the way to South Africa, should have “vibrated so badly as to be un-rideable”?  After all, Triumph's 500cc twin didn't,  nor did any production big-single,  nor even did the long-stroke 1000cc v-twins that needed a valve lifter to start. In fact the contrary was reported by Graham Walker in the Motor-Cycling 1946 road-test. He made a point to emphasise just how easily one might ride the Sunbeam at walking pace - slow enough for a precession?

But then, some time ago I'd spoken to the son of a very early S7 owner, who reported of his father's bike, which did suffer quite a bit of vibration until a rear mudguard stay came adrift. Then the bike was transformed to being a nice smooth bike, despite its still solidly mounted engine.

I'd suggest that the early s7 engine (which has a more aggressive cam-profile than the later engine) had a vibration frequency in harmonic sympathy with cycle parts and in particular with the rear mudguard. This might have been perfectly acceptable or even quite good for a civilian bike at normal road speeds, in the context of other bikes of the day.  For the South African Royal tour, it is possible that police equipment was fitted onto that mudguard in place of a pillion seat.

It is perfectly plausible that the resonance amplified what was only a slight vibration into something awful. Possibly like having a heavy jelly wobbling out-of-control on top of the mudguard. The local police, with no experience of even having ridden the new Sunbeam, experienced an extreme case of 'the tail wagging the dog'.  So it might have been impossible for them to ride a dignified straight line, in State Procession, at speeds of 5 to 15 mph.  If I am correct then the problem was not with the Sunbeam S7 itself but with the mounting of that equipment.]

Sunbeam s7-deluxe fitted with radio equipment c.1951

Still, the somewhat ingenious marketing gambit to produce a motorcycle especially for the role of escort to State Processions was lost and with it the publicity that would have been worth millions.

However, my own '53 Sunbeam s8 (also with straight sided mudguard valances) has a pillion seat mounted to the rear mudguard. This seat sits on 4 coil springs, which I can confirm does (somewhat annoyingly) resonate in sympathy with the engine vibration. The bike feels notably nicer with a pillion rider.  Start your own bike up, ease her off the centre stand and note the wobbling tail light. Many British bikes (of any engine configuration) have the same problem.

Interestingly, around this same time, the S7's rear mudguard design was changed before the 1947 catalogue (see below), from having a valance to not having one. Whereas, in that same catalogue, the engine remained solidly mounted. Because model years ran from April to March, this catalogue would most likely have been used from April 1947.  The mudguard stays were redesigned with more substantial brackets for the s7-deluxe.

P.S. to be there in time for the Royal Tour, the 25 or so 'escort Sunbeams' must have been shipped to South Africa some weeks before the very first S7 was officially despatched from the factory.  However, they don't appear to be listed in the company's despatch records, which probably indicates that they were works bikes. This in turn lends weight to the theory that they were especially built for that specific task. But of course, with their having not been used, some, if not all, were subsequently sold on.

1947 UK brochure

And that next big media publicity stunt was :  

The Opening Ceremony of the first post-war London Earls Court Cycle Show 1948,  when Sir Bernard Docker (Chairman of Birmingham Small Arms) presented National war hero, Field Marshal Bernard Montgomery (Commander of the Allied Forces in Operation Overlord) with BSA group's  flagship motorcycle :  a Sunbeam s7. Although as it was just a few weeks before Monty's 61st birthday, he would probably have preferred a Daimler.

And so, finally the Sunbeam s7 was properly launched

1925  advert by  Packman & Poppe

Badged under the Sunbeam name, the s7 was deliberately targeted at the connoisseur of fine motorcycles, a limousine of the motorcycle world, and a Gentleman's motorcycle, when the word 'gentleman' still meant upper class and very exclusive, when riding a motorcycle was next best thing to being a fighter pilot. It was never expected to sell in huge numbers but by association it was an ace up the sleeve of any BSA salesman. It brought many an inquisitive motorcyclist into BSA's showrooms when their main model range lacked lustre or innovation.

Undoubtedly, many who saw the Sunbeam for the first time remembered it as being something very special indeed. Anything so exclusive is intriguing so an aspiration to own one would stick with many of them, to the benefit of BSA's showrooms, for a very long time indeed.  Even today (in 2014)  it amazes me as I ride one or other post-war Sunbeam model and meet people,  just how many know the  Sunbeam to be a 500cc in-line shaft-drive twin.  

The Sunbeam S7 was, if nothing else, a brilliant marketing coup.

The design of the post-war Sunbeam S7 was attributed to Erling Poppe.  "Who was he?" you might ask. In motorcycle design, the big names of the era were Bert Hopwood, Val Page, Freddie Clarke, and Edward Turner. But they were busy. Erling was the eldest of three sons and one daughter of Peter August Poppe (1870-1933) from Norway.  In 1897, Peter Poppe, backed by a wealthy gentleman, Mr Alfred White, moved to Coventry, England as co-founder of White and Poppe Ltd., an engine and motor-car manufacture.  By-the-way, Alfred White's father was a Director of Singer bicycles.   Peter, an engineer by training, had been with Norway's government munitions department. As fortune was to have it, when the (second) Boer war (1899-1902) broke out, the company switched to supplying munitions. This was very lucrative, which fuelled development and expansion.

Within a short time, White and Poppe was supplying some 22 different motor manufacturers, including William Morris and Ariel motor-cars, which included their hugely powerful racer. Twelve years later they were back to supplying munitions for the Great War.   In 1914, White and Poppe was recorded as employing 350 but by 1918 employed some 12,000 people, due to the large contracts in supplying munitions.  At the end of 1919, the Dennis Brothers (Commercial vehicle builder - perhaps later best known for their fire engines) purchased White and Poppe, via an exchange of shares to the value of £204,365. In 1919 that was a huge amount of money. All but a very few shares were held by Alfred White and his family. Peter Poppe stayed on until 1922 when he joined Rover Motor Cars as Chief Engineer.

During the Great War Erling Poppe attended Birmingham University and it is probable that is where he first met a Mr Gilmour Packman. Not only did they share a common interest in engineering but their focus largely revolved around motor cycles. Preferably fast but luxurious ones.  These youthful Gentlemen were privileged and liked the best.

Erling, at the age of 24 (in 1922), and Gilmour Packman, started their own business, Packman and Poppe, to build rather special motorcycles. Although they built their first engine, they soon bought-in proprietary engines from the likes of JAP and Barr & Stroud. Their Silent Three model first appeared with a sleeve-valve Barr & Stroud engine. A sleeve-valve motor is already mechanically quiet but P & P went to great lengths to make the exhausts exceptionally quiet and offered (optional) acoustic shrouding for the engine, along with purpose designed leg shields & foot boards. 

Furthermore, their frame design was also very special, sloping directly from the headstock to the rear wheel. It was an advanced duplex cradle design with the down-tubes sweeping back along either side of the motor. Their early models also had a rather interesting centre-cum-side-stand and a quick release withdrawable rear wheel spindle. These were both most innovative features in an age of drop-down rear mudguard stay stands and bicycle-type fixed axles.

Inverted handlebar levers were commonly regarded as being safer for racing circuit bikes, which also left clear handlebar space for the decompression valve-lifter and advance-retard levers. The engine sat low and well forward, for the best possible weight and balance.  The exhaust silencer swept upwards for improved ground clearance when corning hard.  Clearly some of these features were derivatives of ideas picked up around the racing circuit rather than from other production bikes. P & P bikes, or at least their frames, were probably built under contract by W. Montgomery & Co., Coventry, who also supplied George Brough.  The Silent Three was advertised as “a demonstration of the Perfect in Principle machine”, while even the press reports made claims for it to be the quietest. One might speculate that these were among the notable features recalled by BSA's Directors some years later.

Within just three years (in 1925) P & P had three entries into the T.T.  Two in the lightweight class & one with the sidecar. Their best placing was 5th in the lightweight class with D G Prentice riding. This by anyone's standard was outstanding. The TT is a long and treacherous circuit, and the engines & cycle parts of the day were prone to failure, on top of which the tyres would tend to shred or to blow without notice. For a small and new company, being run by young men without the pull to attract top riders, against the best major manufacturers from Britain and abroad, just to finish would have been a success on their first T.T. outing.

Sadly, the event was bitter sweet in the extreme. Gilmour Packman, on his way to the T.T. had briefly to stop in at their workshop, had a heated argument with a salesman and shelves were knocked. Items fell, including an exhaust silencer, and Gilmour was killed. 

Despite a serious factory fire that same year, Erling fought to keep the business alive for another five years.  Most probably the 'Wall Street Crash' (October 1929) brought things to a final conclusion. He and his wife had two of their three children during these years.

Even the casual observer might take note of Erling's underlying pursuit of motorcycling excellence. Clearly, there were strong aspirations for P & P machines to be up there with the very best. Not only did the marketing: 'The Silent-three' for example,  aim to catch the attentions of the most discerning clientèle, but the 500cc  - 1000cc  engine sizes were aiming at the Vincent and George Brough end of the market.The latter in particular appears to have been a great inspiration.

Of course, any young company with limited capital also needed to make sales at the lower capacity end of the market but even then, the smaller engines were the very best available. The Blackburne engines in 1924 were advertised as "the first 350cc engines to do 100mph" (at Brooklands).

C. 1927, P & P became linked with Wooler Engineering Co., who were clearly facing difficulty. John Wooler (Chief Designer) was a most inventive Engineer who was noticed (in 1911) when he created a two-stroke engine using a double-ended piston. The bike, which he also built, featured a final drive with gearing by belt riding on a variable pulley. It also had both front and rear plunger springing and a patented 'anti-vibratory' frame. Most unusual features in an age of solid rear frames and girder forks. The frame was made almost entirely of straight tubes and, aside from its advanced suspension, it also had 'withdrawable road wheel spindles'.

In 1929, P & P introduced an option of plunger rear-suspension for all road-models of their bike. These were available with either JAP or Blackburne engines. The two Blackburne-engined bikes were also used for Dirt Track competition. 1930 records only four models of P & P motorcycle in production. These were the 500 Silent, the '90' with ohv, the '80' with ohv JAP, and the '60' with a two-stroke engine. It was the company's final year.

Erling, at the age of 32, then most likely offered his services as a freelance Design-Engineering Consultant. Almost certainly he worked with Dennis, the company that had bought the rights to the White & Poppe engines. It seems that he also worked with a coach manufacturer in Bristol but neither role implies any loss of interest in either motorcycles or racing. He did in fact design a motor scooter for another manufacturer. His third child, Julie, was born in 1937.

In 1942, reportedly after a blazing row with Jack Sangster (Triumph's Managing Director), Edward Turner moved to BSA as Chief Designer, where he worked on a military specification side-valve 500cc vertical twin. In the meantime, Bert Hopwood had taken over as Chief Designer at Triumph and was working on an in-line four-cylinder 700cc engine. In late October, Turner was enticed back to Triumph and Hopwood's work was dropped. Coincidently, Turner built an in-line four-cylinder engine in the early 1960's. 

Erling Poppe was, in the years preceding and during the war, a successful design engineering consultant, having numerous top level West Midlands motor & motorcycle industry connections. Certainly his occupation was exempt or his work must have been important enough to avoid being drafted into the armed services. It seems that he was a man who had never let go of the dream to build the very best motorcycle. As a successful Design Engineer and a man of worthy reputation, through his own P & P motorcycles and noteworthy success in the TT, we might recognise that Erling Poppe brought something very worthwhile to BSA's boardroom table.

P & P motorcycles aspired not only to be high-performance but also super quiet, with refined design detailing.  At that time (five years into a war - 1944), BSA happened to be in the market for a capable designer to lead the design of a new flagship model. BSA's Directors knew that the new model must be something that the post-war, lucrative US market would want. They wouldn't want to compete head-on with Harley Davison or Indian, but they might slip in with something attractive and 'very British'. Something more along the lines of a Brough. Something that would intrigue and tease the American buying public. Something easy to start and ride and yet long legged enough to cover distances. Certainly their motorcycle styles and their cruising comfort must be factored in and US dealerships would probably have been involved.  

The American market was of course very different to BSA's home corner-of-the-street dealers. That market, with the projected costing of such a new motor-cycle, would benefit from being badged as a Sunbeam rather than BSA. US servicemen may have associated the BSA brand with their battlefield experiences of the military-spec M20 single cylinder model. It might also profit from having an independent and respected name tag.

With the resources of the BSA group, Erling brought everything he'd ever worked on, read, discussed or seen into play.  It is likely that most of what was to become the Sunbeam S7 was already floating around in his head or perhaps in numerous sketches and press-cuttings. As a freelance designer with this 'dream of a bike' growing and evolving since 1930, he may even have approached someone influential within BSA at the opportune moment with a draft proposal.

His 1924 P & P duplex frame worked exceedingly well with racing 1000cc motors. The claims that the “Perfect in Principle” Silent Three was the quietest, set the tone. George Brough had been there in 1932 with the in-line Austin 7 engine (modified with a light-alloy cylinder head) and an in-line gearbox with shaft drive but possibly got it wrong by fitting two rear wheels for a solo bike. Still, the mind's eye picture was probably there - the balance of the bike, the duplex frame, the curves of the tank, and even the under-saddle electrical box with ammeter and ignition / lighting switch.

More recently was the Indian 841 shaft-drive transverse v-twin, whose pressed-pan saddle hangs out in space, whose front forks look telescopic until one notices the central spring in front of the steering head with rear plunger suspension and foot gear-change. The Indian was designed to a US military specification for use in desert conditions, where as much as possible was to be encased to keep the abrasive sand out of moving parts. It was shown at the World Fair in New York in 1939 but the US Military chose to run with Harley Davison. The Harleys used by the Americans in the North Africa campaigns needed the big fat tyres to prevent sinking into the sand. All these features and a thousand other details were already in the public domain long before 1944 and before a wartime R75 was ever brought into the BSA works.

1940  Harley-Davidson(s) offer 500 x 16" tires  as an option on all models)  -  for  the  World's  Smoothest  Motorcycle  Ride ...

Claims that the Sunbeam s7 was “a redesign of a BMW”, taken as a part of reparations against Germany after the war is, in my opinion, largely unfounded. There may have been elements of BMW, not least because that company successfully campaigned at the TT just before the war. The R75's frame is sectional (it's bolted together for ease of field repair). The central spine of the R75 and its brace before the rear wheel are pressed-steel-fabrications, not tube. Its front forks are hydraulic, not unlike the Matchless G3's of the era, whereas the early Sunbeam had no hydraulics. The BMW has a horizontally opposed engine, driving a rear bevel-gear differential, which through complex reducer gears drives the sidecars wheel. It has a hand gear change, along with numerous other cables and linkages, a transverse kick start mechanism, an under-slung exhaust, no electrical boxes, springs under the saddle, external mudguard stays  (to allow clearance for snow chains). Under close examination the list of differences just goes on and on. The style of the front fork gaiters appear to have been inspired by the BMW. Then again, are they that different from those on the Sunbeam badged sidecar (AMC built in 1941)  in the photo above left?

In its own right the BMW has many innovative and often brilliant design features but the BMW is not an elegant bike, particularly when you see one in real life. In comparison, the Sunbeam is a much cleaner design and refined in detail, which leans more towards the 1924 P & P, the Indian 841, the Harley Davidson, and the Brough Superior but it is not a copy of any of them.

1951  Sunbeam -  the  World's Smoothest  Motorcycling

.. you recall the wording of the Harley-Davidson advert above ?

and. “Perfection” an often repeated theme in post-war Sunbeam Advertising  c.1956

.. you recall the wording of the 1924 P & P  advert  ?