A little background history ...

I'd suggest that it's best to think of our Sunbeam motorcycles in context...

In1946, Britain was very close to bankrupt, from the cost of the war so soon after the Wall-Street crash and subsequent 'great depression' of the 1930's.  Not only was this country,  its industry,  shipping,  military forces,  and many,  many homes facing the cost of rebuilding being bombed out,  but so was its Empire - which Great Britain was obliged to rebuild and maintain. 

Because the State was all but bankrupt, and in extreme debt to America - the government was forced to tax both industry and the people.  We think that Tax is high nowadays but corporate tax (tax on profits made by businesses) was +/- 50%.   ie., for every £1000 in profit made by a company the tax man took £500.   That money then was not available for new product development,  investment in modern equipment or new tooling,  or for volume buying (to benefit from lesser unit prices).  Industry was both starved of the basic raw materials (like the steel) they needed,  but was also being strangulated with taxes.

Most of the country's production was needed for export.  If a company did not export then their quota of raw materials was strictly limited ...so they were in fact forced to export or die.  Of course many small to medium businesses had no experience of developing opportunities in overseas markets, or even of what those foreign customers wanted,  nor did they have the marketing, sales, or distribution infrastructure.  And even if they did..,  then they had very little capital to stockpile enough produce, and then to pay for its shipment to far off countries, and then of course to wait for items to sell and payment to be received.  And yet again - if & when they did..,  then they'd find the competition was so great within their 'new' markets - from other companies and countries pushing just as hard to export.

On the home market things were equally as bad a situation.  Not only were many families faced with homelessness &/or major property repairs,  and the support of any family widowers and orphans,  and/or their health care*,  but those who had jobs were taxed heavily, not only as income tax but also in what they bought.   The Sunbeam was an exclusive brand and was already 30% more expensive than a Triumph, Matchless, or BSA,  but then there was the additional purchase tax too.  The first British (London) motor cycle show was not held until 1949, when the Sunbeam S7  cost £200, and the 'purchase tax' on this was an additional £54.  

* Social services & healthcare services were stretched to the limit - a consequence of the often squalled lifestyles and crude sanitation conditions,  an explosion of newborns,  plus thousands of refugees and the displaced,  orphans,  p.o.w.'s and other injured war veterans - including many with long-term psychological problem or foreign disease.  From July 5th 1948,  all Britain's were entitled to the new < National Health Service >  (click to open).  This in effect superseded the 1911 National Insurance Act, which gave the British working classes the first contributory system of insurance against illness & unemployment. That however only applied to waged earners. Their families and those without wage had to rely on the charity or support of family or others, if any.

Rationing of food, clothing and petrol continued for years after the war.. (until 1954 !) and so things like fuel consumption were crucial to the buying public.  The staff reporter of Motor Cycling reporting on the first post-war Motorcycle Show, went by train because petrol was "too precious to use for London trips".   The grade of petrol readily available was poor and so engine's compression ratios were kept low, to avoid pre-detonation (pinking).  The market for motorcycles was flooded with both ex-wd and pre-war girder-forked bikes (many adverts for the Vincent), which were being sold to pay for food and clothing of young and growing families.  And then , as soon as the free trade markets opened - there were many cheap bikes and scooters from other countries, which also needed to survive their war debt.  These in turn competed with economy cars and 3-wheelers (including those from Bond, Isetta and Reliant)

Ministry of Food ..sounds like something from Monty Python but was a reality even in 1953 - 1954  (in 1954 - nine years after the war - meat finally came off ration) (c) the Dock Museum, Barrow in Furness.


  Motor fuel ration book for September 1947 to February 1948, for a private motor car. Fuel was rationed until May 1950.  (c) the Dock museum, Barrow in Furness.

Victory celebrations and optimism were short lived in the harsh reality of everyday life - Unemployment was high and wages were low, because no-one could afford to buy what was made, and so industry could not afford to employ.  Manufacturers were directed by the government to export as much as they could, just to get foreign money back into Britain.  Of the first 2,100 or so early S7's (1946 -1949) Sunbeam motorcycles, fewer than 300 stayed on these shores. 

Businesses could barely afford to invest in new machines and tooling, nor to replace those worn out &/or modified to feed the war machine, but still industry sprouted from every workshop needing to use their machinery to produce something.. anything.. just to break even.., for the company to survive, to keep people employed and feed the communities.  It was from these efforts and the dogged determination that the impression of post-war optimism came from. Women had worked to keep their families, and now 'ordinary' men realised that they could lead others in battle (..and so also in a small business). Many others had new found mechanical skills - derived from war equipment and transport, or even from just servicing their BSA or Enfield rifle. Cultural change, self reliance, and a new expression of freedom was happening.

Still, in the immediate post war years ; motorcycle performance was not much of an issue, except that many buyers needed it to pull a sidecar for their families.  The Sunbeam's 500cc short stroke engine was really not so ideal for this, as it lacked torque compared to the BSA, Matchless, AJS, Norton and Panther long stroke singles. On the other end of the scale, machines like the James made nimble little commuter bikes, while the Italians imported their scooters. The small bike (economy commuter) market vied with those powerful enough to 'pull a chair'.  But often just to getting to work was a challenge, as these machines needed a lot of coaxing and maintenance to be reliable.

The performance side of things - was largely focused on club-level off-road competition,  track racing,  and  the all-important money-earning Export Sales.   Triumph had already introduced their 500 Speed-Twin (1938) which although only 25bhp (same as the Sunbeam) was lightweight and had the more efficient chain drive.  It was a good performance bike for commuting &/or for taking the girlfriend to the American soda bar / British beach.  It was more fun and youthful than any wartime big single - and so (because this is where the export money really was) other makes followed suit. 

Back on the home market, and in the Empire - because of the need to pull ever-larger family-sized sidecars - engine capacities began to grow. In the 1948 Motor Cycle Show, just two makers had bikes over 600cc.  By the mid-fifties a 650cc twin was not uncommon.  However, unlike most - the 'Beam couldn't just wear bigger barrels to grow up ..the complete cast aluminium crankcase (and then also the cylinder  head) would need to be changed.   There was not even room in the crankcase for a larger crankshaft nor the height to give a longer stroke. The cylinders were already close together - so the bore couldn't be increased. In short.. the Sunbeam motor would need all new tooling ..but then probably wouldn't fit in the frame ? 

The early nineteen-fifties saw prevalent enthusiasm for off-road motorcycle competition (keen with ex-dispatch riders) and with it - the widespread introduction of swinging-arm rear suspension.   Concurrently, the silver screen showed Hollywood icons riding the sporting Triumphs..  This struck a maverick cord (long live Rock & Roll !) with those who had grown-up too muddy, bloody, and fast.  Their still youthful exuberance, boosted by a real assertion to live how their fallen friends and comrades never would, needed a beacon - beyond the damp realities and daily trudge of smoky grey Britain.   

Daring performance and youthful image became selling features..,  and already the Sunbeam was dated...

The S8 fitted with a dual seat looked more the fashionable part, and the silver colour made it stand out as a quality machine worth the price tag.  But being what they are - the kids on the block liked chromed twin-exhausts and flash youthful colours. Perhaps the Sunbeam was BSA's (deliberate)  antidote to their own range of A7 and A10 twins, whose motors offered more flexibly to build a broader product range - from slogging sidecar work-horses (including those used by the breakdown services) right the way through to off-road machines, wall of death, and racing-side-car outfits.  

BSA were, at this time - the world's biggest manufacturer of motorcycles, and they had racers like the DB34 Gold Star, and the ever faithful workhorses like the A10.  They were respectable, in their boardroom grey haired arrogance and conservatism., they failed to respond to (or held steadfastly against the fads of) an ever youthful market - before it was almost too late.

BSA didn't put money into the Sunbeam's development because it had always cost too much for the depressed post-war market economy.., and then because their market demanded more capacity for pulling a sidecar,  and then again because the 'new look' was for the more youthful - in short the youthful public wanted Triumph twin performance & agility,  &/or Norton (Roadholders) handling.  And, to retool the Sunbeam's motor, the frame, and everything else - to make it lighter (and perform more competitively) was just not going to be cost effective.  The bike had been designed for a different purpose.

It, the Sunbeam S7 was in 1946 an optimistic ideal - but one which never really fitted the needs, nor culture change of Joe public.., either in Britain, across the Empire, or over the Atlantic divide.  It was an indulgence ...and soon out of fashion. 

read more on 'an alternative history'

All that said - when the Sunbeam is properly set up - then they're actually a usefully quick and good handling bike.  I certainly very much enjoy riding them (despite having other fine and more powerful bikes in the stable). 

In truth, I personally find the S8 is a little less comfortable (..but then I am 60 years old,  6'-5" and over 200lb),  otherwise it very much has it's own chirpy and fun character.   My own S8  'Nudge'  is fitted with a pillion seat,  a tall screen,  saddle bags  and a luggage rack - and I prefer her for everyday use and commuting.   So encumbered, she's no lighter nor less bulk than the S7, but somehow does feel it - most likely because the steering is lighter, and (because of the narrower rear mudguard) the luggage bags sit tighter to the frame. 

The S8  somehow looks and feels more modern than either S7 model, and that I think works against her.  Perhaps we expect more power (particularly torque) from a (1950's) 500cc twin. ?  Certainly it seems quite common for owners to ask about tuning options, whereas S7 & S7d owners seem happier with their bike (from the late 1940's early 50's) and the performance is fine as it is.   Or maybe the extra bulk, and seemingly extra weight (although there's only 25lb difference) of the S7  makes their riders more aware of the limitations of their bike's brakes.?

Ironically, the bare (devoid even of a pillion seat) S7 or S7d  is my first-choice for days out, and a good ol' jaunt across country.  It's a sublimely classy lady who is  an indulgence.  It's forte is on quiet 'A' and fast B-class country roads, where the journey itself is pleasurable - not just a destination to be reached.    If one is able to travel light, by staying in series of welcoming characterful inn's.,  then the S7 is a wonderful oldie world touring bike - practically in a class of it's own. (other bikes as good tend to have double the engine size - Vincent, Brough, etc ..and ten-times the price tag !).  

And yet somehow and for irrational reason, I prefer to laden up the S8 - for camping and long distance hauls.  It doesn't have to make sense,  it's just the way I see it ! ?

Peter

https://sites.google.com/site/sunbeams7s8/home/Sunbeams---post-war/P1070244A.jpg  'Nudge' - my own S8

https://sites.google.com/site/sunbeams7s8/home/Sunbeams---post-war/Pudge%201.jpg
 'Pudge' - my own S7-deluxe
..as bought - before restoration and taking back to original spec. the exhaust,
 air filter & ape hangers.  NB. an S7 in original '
Monochromatic' silver livery is extremely rare. This particular bike was first road-registered on the day after the Queen's Coronation. I speculate it was specially painted by the London dealership to celebrate that event.
 
the eagle-eyed might have spotted the London registrations of  'the sisters'..


Sunbeam S7 and S8 motorcycles

In the context of pre-war and post-war production bikes, which were mainly pre-unit side-valve singles, the Sunbeam was really very advanced engineering.  Designed by Earling Poope, working for BSA-Sunbeam before/during the war,  but not introduced until 1946 - the 'S' motor is often likened to a car's wet-sump engine and in-series gearbox layout, with rubber mountings. It also utilities a sizeable flywheel & dry clutch,  shaft drive & differential,  coil ignition with auto advance distributor, and even the exhaust down-pipes with carburettor situated between them was common feature of automobile engine design. 

Sunbeam &#39;Perfection&#39; advert

But., unlike production cars or motor cycles of the era - this motor had a short-stroke with chain-driven overhead camshaft,  all-alloy crankcase & barrels (cast together as one) and an aluminium cylinder head, each with all-internal oil ways.  The crankshaft was one piece with replaceable big end shells.  The distributor's armature mounts directly onto the front end of this, and the flywheel with clutch onto its back end.  The engine was of course air cooled and cleverly uses each of its castings as a heat sink, including the bell housing. 

It's also noteworthy that unlike almost anyone else., the Sunbeam's engine/gearbox rubber mounts include a friction damper in its head steady (..the 1970's Norton Commando's Isolastic mounts might well have learnt from this !)

Comparable with other 500cc motorcycles of their date, they produced 25 bhp - but from just 6 : 1 compression (later 26 bhp with 6:5:1, and then 27bhp with 7:2:1 compression pistons).   There was no need for a decompression lever, nor advance / retard lever.  These bikes are very easy to start (via kick start lever on RHS., as most other British m/c of that time, despite it having an in-line engine).   Easy to ride,  high quality & comfortable, reliable, and aside from very minor seeping are generally oil tight - the Sunbeam S7 and S8's were to the very highest motor-industry standards. 

With its advanced duplex frame - their handling and general nippiness is better than most observers might have expected !  In comparison with the big single cylinder 'rigid' motorcycles, and even the 'new' sporty (but buzzing vibrating) twins of the early fifties with rear hub suspension & oily chain rear drive - the Sunbeam is a 'sporting gentlemans'  machine, refined with plunger rear suspension.  Indeed, these bikes are perfectly usable - even in today's town traffic and for across-country routes.  

Below is a brief model specification  

Please - If anyone from the BSA, TOMCC, Norton, Jampots, Vincent, BMW or whomever Sunbeam's contemporaries, would be so kind as to furnish me with the correct specifications of those marque's 500cc model c. 1949 - 1953,  then I'd be delighted to show it as a comparison..

Sunbeam 500 Spec. sheet :


  Sunbeam   Sunbeam
model :   S7 deluxe   S8
Price £   (08/11/1956)   £285-4-0   £260-8-0
         
Engine Capacity   487cc   487cc
Bhp (std)
  26 @ 5,800   26 @ 5,800
Number cylinders   in-line vertical Twin   in-line vertical Twin
Engine type   Air cooled OHC   Air cooled OHC
valve drive :   chain   chain
Bore   70mm   70mm
Stroke   63.5mm   63.5mm
Comp. (UK Std)   6:1 ,  6.5 : 1 or 7.2:1
  6:1 , 6.5 : 1 or 7:2:1

Eng construction :
       
Crankcase & covers   one piece cast Al. + sump pan   one piece cast Al. + sump pan
Barrels   integral to crankcase w/ liners   integral to crankcase w/ liners
Cylinder head   1 pc cast Al cyl. head + 1 pc large vol. rocker cover w/ crankcase breather
  1 pc cast Al cyl. head + 1 pc large vol. rocker cover w/ crankcase breather
Eng mounting   rubber isolation w/ friction damper   rubber isolation w/ friction damper

Lubrication system :   wet sump   wet sump
oil feed to valves   internal oil ways   internal oil ways
capacity (Engine)   3.5 pints   3.5 pints

Carburetion :   1 : Amal 276 D0/3A   1 : Amal 276 D0/3A
Inlet manifold(s)   integral   integral

Ignition :   Points / Distributor / single coil   Points / Distributor / single coil

Clutch :   7" single plate dry   7" single plate dry
Gearbox :   4 speed   4 speed

  1 up, 3 down   1 up, 3 down
gear ratios :   5.3 / 6.5 / 9.0 / 14.5 : 1   5.3 / 6.5 / 9.0 / 14.5 : 1
Primary Drive   direct   direct

Final drive   shaft + worm drive   shaft + worm drive

Wheels / tyres - Front   450 x 16   325 x 19
                      - Rear   475 x 16   400 x 18
Brakes     - Front   8" SL drum w/ cast Al. back plate   7" SL drum w/ chrome plated back plate
                      - Rear   8" SL drum to cast Al. final drive housing   8" SL drum to cast Al. final drive housing
Suspension      - Front   telescopic w/ hydraulic damping   telescopic w/ hydraulic damping
                      - Rear   sprung plunger type   sprung plunger type
Electrical :   60w  6v  + earth   60w  6v  + earth
Charging :   Dynamo   Dynamo
Headlamp   8" : 6v 24/24w   8" : 6v 24/24w
standard spec   dedicated electrical & battery boxes + ammeter + oil & charge warning lights   dedicated electrical & battery boxes + ammeter + oil & charge warning lights

       
Colours (std)   Mist green / blk frame   Monochromatic Silver or Black  Lustre
wheels   Blk Painted   chromed rims
Silencer type   Absorbtion type chromed steel   Baffle type : Cast Aluminium
Petrol Tank Capacity   3.5 gals (imp)   3.5 gals (imp)

Stands
 
centre- pull dwn + side
 
centre- pull dwn + side
Tool box   std   std

       
General Dimensions :        
Wheelbase   57"   57"
Saddle height / type   30.5" / cantilever saddle   30"  3-point sprung saddle
ground clearance   4.5"   5.5"
Overall height   40.25"   40.25"
solo bike - Dry weight   430 lb   405 lb
Power to Weight ratio        16.5 lb/hp      10.1 w/kg
        15.6 lb/hp         9.5 w/kg

© Sunbeam R & R 


read more of  an alternative History   


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