1933 O.E.C.-Rudge 'TT Replica'

[Mitchell Barnes of Australia is an expert on Blackburne and Excelsior 'Manxman' history, and sends along this story of an O.E.C. racing chassis he found, which he built to replicate a long-lost Isle of Man TT racer from that unusual marque - pd'o]

"It was a red-letter day for small motorcycle manufacturers when Rudge's Depression-era financial woes forced them to wholesale ‘loose’ engines and gearboxes. Ironically, this move helped boost the Rudge name, as a great number of formerly mundane machines suddenly scorched around England and the Continent, Rudge ‘Python’ powered – 250cc to 500cc, the bigger engines with Rudge’s famous 4 valve cylinder heads, capable of propelling any motorcycle to 100mph.

A Rudge 'Python' 500cc engine, as sold to numerous small manufacturers in England and Europe; superior in performance and reliability to the usual JAP engine...

O.E.C. (OsborneEngineering Co.) of Gosport (in Hampshire, England) were one such small company, always on the lookout for something new. Their best days followed WW1 when they built bikes exclusively for Blackburne in a large former aircraft factory. After Blackburne cancelled their exclusivity deal, O.E.C. embarked a series of seemingly brilliant associations, most of which came to nought. Their technical director, Fred Wood, was a man bursting with ideas, and had designed the impressive ‘Duplex’ frame before leaving an indelible impression on the motorcycling fraternity with his 1926 ‘Duplex’ steering system, using a unique set of parallel links for steering stability and suspension. A couple of years later Fred added a swinging-fork rear suspension system, controlled by spring boxes and a damping link. The Duplex steering system got a serious publicity boost at Olympia in 1930 when O.E.C. displayed their World Record breaker, built by Claude Temple and ridden by Joe Wright at 137.32mph at Arpajon, France, just outside the Montlhéry race circuit.  [Of course O.E.C. also claimed a later recordactually taken by Wright’s Zenith, which you can read about here]

Joe Wright on August 31st, 1930 in Arpajon, France (near Montlhéry), where he recorded a World Speed Record of 137.32mph using a supercharged 1,000cc JAP engine in an O.E.C chassis; note the 'Duplex' forks

Like so many others, the Depression badly wounded O.E.C, and production costs needed to be cut. During 1932, Wood designed a new welded-up Duplex frame; the only lugs remaining controlled the swinging fork damping system and, on the girder-forked machines, the steering head. These welded frames were light and considerably cheaper to manufacture than traditional lugged frames…but would a conservative public accept such advanced thinking? All O.E.C. needed was an engine with sufficient urge to prove the new frames' potential.  Enter the Rudge ‘Python’.

Arthur Simcock on his 1933 Senior TT O.E.C-Rudge; note Webb girder forks and Duplex rear suspension

After some years’ absence, O.E.C. entered 4 machines in the 1933 TT: two 250s and two 500s. All were Python-powered, and both Senior and Lightweight machines used one each of the Duplex steering and Webb girder forks. The frames were identical save for the power units and brake diameter.  O.E.C. appointed ex-Sunbeam works rider Arthur “Digger” Simcock their team leader. The first machines built were the Webb-forked pair on which Simcock practiced, and subsequently rode in the TT. The Duplex machines were assembled at the TT by the second rider Alf Brewin and an assistant - no Ferrari budget here – and with little in the way of preparation, its not surprising that all the O.E.C's retired. Brewin did race them on the Continent after the TT but without success. This was typical of O.E.C's modus operandii - great ideas but poor organization.

Seven years ago I acquired a brace of OECs; one a race frame with Webb forks, the other a road bike with Druid forks, housing a genuine Blackburne racing engine. Years of research finally revealed that in 1936, the Australian O.E.C. dealer had acquired a racing machine with a Blackburne engine to promote the brand. Naturally, I wanted to re-unite the racing frame with its original engine, but this left a ruddy great hole in the “restored” frame. I decided Simcock's ‘lost’ Lightweight TT bike would be the inspiration, but no photos of it exist; I do have photos of his almost-identical Senior mount, so that became the template. The 1933 O.E.C. catalogue offers a J.A.P-engined, Druid-forked bike for £37/15-, and for an extra £7, you could buy Rudge or Blackburne power. This was the only year OEC offered ‘Python’ engines in this frame, for OEC fell into receivership later that year and Matchless engines were used thereafter. A 250 Rudge radial engine was what I really wanted but I couldn't find one in Australia. They are as rare as an ethical media baron here. In the absence of a Rudge engine, I briefly toyed with a J.A.P engine but my brain fade only lasted a few weeks. Five years ago the Australian Dollar was low against Sterling but it started climbing and eventually I was able to acquire a 1932 engine from the UK without having to mortgage the kids.

The O.E.C. rear-fork suspension system, introduced in 1928

The biggest problem was the gearbox. I could not find a Rudge 250 box anywhere and so

reluctantly used the original Albion one. Interestingly, Dunelt's 1933 Lightweight TT bike combines a Python engine with an Albion gearbox, so a protocol existed. It took only three tries to successfully marry the engine and gearbox with the frame, thanks to laser cutting. The gear change mechanism required several cups of tea to sort, because unless you are Toulouse Lautrec or a contortionist, the original is far too high for aging hippies. Although O.E.C./Rudge 'TT Replica' engines did not have bronze heads, the exposed radial-valve arrangement is Rudge's signature and deserves pride of place. Heat resistant gold paint applied to the head and new laser-cut stainless rocker side plates should help drag people's eyes from the awful Ariel-green rear wheel.

As it turned out, the hardest part was the easiest. The exhaust pipes really are impressive. We are lucky to have a master in the otherwise lost art of exhaust pipe bending. Exhaust pipes should have an ever changing radius which, to achieve without flat spots, is a precious art form. John d'Arrietta uses the traditional method of packing the pipes with sand and skilfully applies heat in exactly the right places with exactly the right temperature before bending. The pipes hug the frame and primary cover where they should and are mirror images of each other. To my knowledge (and I have spent countless hours googling O.E.C, Python, Rudge, etc), it is the only OEC-Python 250 in existence and while not an exact clone of Simcock's historic machine, save for the hidden magneto pulley arrangement, all parts are correct for the period. It's on its way to northern France and the new owner intends to use it. It will soon be seen at historic events in England and the Continent.

Special thanks to Greg Rowse (splines and precision machining) and John Harris (welding), and Mervyn Stratford for advice on timing."

Read more »

OEC, POST LSR

After a successful career housing a supercharged 994cc JAP engine for several attempts at the Motorcycle Land Speed Record with Joe Wright aboard, the unusual OEC chassis built for the specific purpose of breaking records was host to another blown engine, this time from a car.

The Aug. 30, 1934 edition of 'The Motor Cycle' has a short article on a 'A New Racing "Four"', detailing the attempts by J. Granville Grenfell (what a name!) to create a 500cc machine, with the specific intention of being the first motorcycle to achieve 100mph for an hour, and win a 'Motor Cycle' sponsored trophy for a multi-cylinder/100mph/1hour British motorcycle.  While the OEC was being built, a New Imperial 500cc v-twin took the prize with 'Ginger' Wood the brave rider - it was said he was the only person willing to risk his life aboard the evil-handling New Imp, which spat him off with a tank-slapper at 100mph on the Brooklands banking, while practicing for the record. By comparison, the OEC was a far safer bet at over 100mph; the 'Duplex' steering system being almost too stable at speed, taking some effort to deflect from a straight-line course.  Of the two possibilities, I'd take stable over wobble.

As the raison d'etre of the revised OEC had passed, the Grenfell's (under the sponsorship of Minnie Grenfell, a trials rider) entered the machine in the 'Hutchison 100' race at Brooklands that August of '34.  F.W.S. Clarke was the pilot, although the machine 'failed to distinguish itself' in the races, as the engine was yet 'too tight'...although building a record-breaking engine to 'tight' clearances is dubious. The motor in question is an Austin 7 four-cylinder sidevalver, sleeved down from the original 742cc to 490cc, making a very long stroke indeed at 46mm bore x 76mm stroke.  The crankshaft, notoriously prone to breakage on 'sporting' Austin 7s, was an especially strong one-piece item, yet retained only one main bearing at either end (in '36, Austin introduced a '3-Bearing' crank).  The crank end held a sprocket, presumably between the main bearing and flywheel clutch, which drove a Centric supercharger, mounted above the Morgan 90degree bevel-drive box, which 'turned the corner' and made a rear drive chain possible.  There was no gearbox per se, making the OEC a supercharged four-cylinder single-speed racer!

More technical points on the modified engine: the Centric blower began puffing at 25rpm, giving maximum pressure of 20lbs/sq" at 6000rpm, producing an estimated 46hp 7000rpm...about twice the safe revs of the standard Austin engine, and nearly 3 times the original 17hp.  A sporting Watmough cylinder head gave a better combustion chamber shape, although the compression ratio remained a lowly 4.5:1...not an issue with a supercharger, which needs neither high compression nor radical valve timing to produce maximum power.  In fact, a very tame camshaft with little 'overlap' of valve openings produces the best results with a blower, as it's the job of the compressor is fill the cylinder completely with fuel/air mix, no fancy engine tuning is required, other than the ability to hold the engine bits together, after a dramatic increase in horsepower.

To keep the engine cool, a Scott radiator fits snugly at the front of the engine; hopefully a waterpump was used rather than the 'thermosiphon' system of the Scott, notoriously prone to boiling, although the OEC used glycol rather than water for cooling - a novelty at the time.  The OEC frame was modified to fit all this machinery, and it was estimated the bike would be good for 118mph, and although 'nothing like this speed' was achieved during the 'Hutchison 100', the 60" wheelbase chassis was reported to handle 'extraordinarily well'.

Of course, the OEC wasn't the only motorcycle using an 'Austin 7' engine, as Brough Superior used the engine as well - see the Road Test here.

Read more »

OEC, ZENITH, AND THE STOLEN RECORD

In a funny twist of lingering history, the FIM book of Motorcycle Land Speed Records notes that on 6th November, 1930, Joseph S. Wright took his Temple-O.E.C. (Osborne Engineering Company) with supercharged JAP 994cc engine to 150.7 mph down the rod-straight concrete pavé at Cork, Ireland. The 1930 record was a significant advance on the Ernst Henne/BMW record of 137.58mph, achieved only weeks prior at Ingolstadt, Germany, on a supercharged 750cc ohv machine.  But in this case, the history books are all wrong.

150 MILES AN HOUR ON A MOTORCYCLE!

 (Click on the image above to see the film from the Record attempt)
The O.E.C. was an unusual motorcycle, using 'duplex' steering; an OEC trademark, although not all of their bikes used this system.  The advantages of this arcane steering system on these early motorcycles was great stability at speed, plus the possibility of front wheel suspension which didn't alter the steering geometry when compressed by bumps, giving totally 'neutral' steering under all conditions.  In practical use, the OEC chassis was reported to be very stable indeed, although resistant to steering input!  So, while potholes and broken surfaces brought no front wheel deflection, neither did a hard push on the handlebars...perfect for a speed record chassis actually.

A pair of machines was present at Cork that day; the OEC which had been prepared by veteran speed tuner Claude Temple, and a 'reserve' machine in case it all went pear-shaped.  The second-string machine was a supercharged Zenith-JAP, of similar engine configuration to the OEC, but in a mid-1920s Zenith '8/45' racing chassis.  Zenith at that date was technically out of business, so no valuable publicity could be gained for the factory from a record run, nor bonuses paid, nor salaries for any helpful staff who built/maintained the machine.  While Zenith would be rescued from the trashbin of the Depression in a few months, and carry on making motorcycles until 1948 in fact, the reorganized company, with its star-making General Manager Freddie Barnes, never sponsored another racer at Brooklands or built more of their illustrious special 'one off' singles and v-twins, which did so well at speed events around the world - from England to Argentina!

Joe Wright had already taken the Motorcycle Land Speed Record with the OEC, back on August 31st at Arpajon, France, at 137.32mph (see top photo with news story), but Henne and his BMW had the cheek to snatch the Record by a mere .3mph, on Septermber 20th. That November day was unlucky for Wright and the team, as the Woodruff key which fixed the crankshaft sprocket sheared off, and the OEC was unable to complete the required two-direction timed runs to take the Record.  As you can see in the photo below, the engine mainshaft drove the supercharger as well as the primary chain/gearbox, and was a one-off for which there was presumably no replacement, with probably no time for repair in any case.

Supercharging a v-twin motorcycle is a difficult business, as the compressor blows fuel/air mix at a constant rate into a shared inlet manifold for both cylinders, but as the cylinders aren't evenly spaced physically (as they are on a BMW, for instance), one cylinder inevitably gets a much bigger 'puff' of built-up pressure.  Figuring out how to accommodate a different charge for each cylinder led to all sorts of compromises, from restricting the inlet port of one cylinder, to the use of different camshafts/compression ratios/valve sizes for each cylinder, in an effort to keep one cylinder from doing all the 'work' and overheating.  It was an imperfect science, as supercharging was still relatively new to motorcycles, and only a handful of blown motorcycles were truly 'sorted out' for racing or record-breaking before WW2.  Typically, these had flat-twin or four-cylinder engines, with even intake pulses!  (Although, of course Moto Guzzi, typical of their genius at the time, had a lovely 250cc ohc blown single-cylinder which worked a treat).

With the OEC out of action, and FIM timekeepers being paid by the day, as well as the complicated arrangements with the city of Cork to close their road (and presumably police the area), a World Speed Record was an expensive proposition, and the luxury of a 'second machine' (above) was in fact very practical...although this may be the only instance in which the second machine was of a completely different make.  Imagine Ernst Henne bringing a supercharged DKW as a backup for his BMW; simply unthinkable!

But, such was the English motorcycle industry at the time; several very small factories (Brough Superior, Zenith) competed on friendly terms for national prestige the in record books, while the largest makes (BSA, Triumph, Ariel), nearly ignored top-tier speed competitions such as the Grands Prix and Land Speed Records.

In the event, Wright did indeed set a new Motorcycle Land Speed Record with his trusty Zenith (above, setting the record, quite clearly on a different machine than the OEC below) at 150.7mph, although the press photographs and film crews of the time were solely focused on the magnificent but ill-fated OEC, as Zenith was out of business and OEC paying the bills.  Scandalously, all present played along with the misdirection that the OEC had been the machine burning up the timing strips, and the Zenith was quickly hidden away from history, a situation which still exists in the FIM record books!

Photographs from the actual event show the Zenith lurking in the background (above), while Joe Wright poses on the OEC, preparing himself for a blast of 150mph wind by taping his leather gloves to his hard-knit woolen sweater, and wrapping more tape around his turtleneck and ankles to stop the wind stretching them, and dragging down his top speed.  His custom-made teardrop aluminum helmet is well-documented, but the protective abilities of his wool trousers and sweater at such a speed are dubious at best...but there were no safety requirements in those days, you risked your neck and that was that.  Nowadays, when any young squiddie can hit 150mph exactly 8 seconds after parting with cash for a new motorcycle, Wright's efforts might seem quaint, but he was exploring the outer boundaries of motorcycling at the time, and was a brave man indeed.

The record-breaking Joe Wright Zenith was a rumor for decades, becoming a documented story only in the 1980s via the classic motorcycling rags, the whereabouts or existence of the Actual machine known only to very few.  I've had the great pleasure of making the Zenith's acquaintance, it does still exist, and is currently undergoing restoration, to be revealed when the time is ripe.

As the OEC also still exists and is in beautiful restored condition, a meeting of the two machines is almost a certainty, at the right event.  If motorcycles could talk, I bet the Zenith would have something to say to the OEC...

Read more »