Friday, February 26, 2010

THE 'SQUISH' THRUXTONS

Manxman Neil Kelly on his very special Velocette Thruxton, winner of the '67 Production TT
What is the starting point when telling the tale of a very special motorcycle; is it the delivery date from the factory? Or does one dig that little bit deeper to give the 'back story' for the reason Why a particular machine was made?

In the case of a small batch of factory-modified 1967 Velocette Thruxtons, pulling all the threads of the story left me with a pile of yarn on the floor, no scarf, and no knitting pattern! But it is the job of the writer to assemble a chaotic jumble of facts into a coherent narrative, and thus begins the tale of the 1967 Isle of Man 'Production' TT, a dozen very special Velocettes, and 50 years of engine development.

For the 60th anniversary ('Diamond Jubilee') of the Isle of Man TT, it was decided that something of the original intent of the Tourist Trophy races should be resurrected: showroom-floor motorcycles being put through a harsh full-throttle test over hundreds of racing miles on the world's most notoriously difficult race track. Thus for 1967 were introduced three capacity classes (250/500/750cc), with the stipulation that machines had to be standard production motorcycles with no Factory Special tuning parts. British manufacturers likely gave a nudge to the TT organizers for this new class, as Japanese manufacturers had bitten hard at the TT and Grand Prix races, winning championships in every class. They had not yet conquered the large bike sales market (ie, over 500cc), but Honda introduced their DOHC CB450 twin in 1965, which was far more technically advanced than any British racing motorcycle currently on offer! Thus, a guaranteed British win in the 500cc and 750cc Production races would generate much-needed good press.
Keith Heckles on the Geoff Dodkin-supplied Thruxton, which came in 2nd
June 10, 1967: all three race classes were flagged off on the same day, albeit with five minutes interval between classes (250s went last), using a mass 'Le Mans'-style start. There was suddenly a lot of machinery on the Manx roads! In the 500cc class, as the smoke from blast-off cleared, two riders could be seen kicking at their mounts - both on Velocettes! Neil Kelly and Keith Heckles were having trouble starting their Thruxtons, which due to their high state of tune are notoriously finicky and tend to sulk at the very worst moments. Neither Kelly nor Heckles had experience kick-starting a Velo: There is a Knack, and they didn't have it! Arthur Lavington, riding a third Thruxton, had no such trouble, having raced Velos since the 1949 Clubman's TT.

Neil Kelly's path to the saddle of a special racing Velocette was quirky indeed. Reg Orpin, the sponsor of Kelly's racing Thruxton, had contracted Dennis Craine (winner of the '65 Manx GP) to race the machine, but two weeks prior to the race, at a local Scrambles race, Craine had crashed, been hit by another rider, and broken his arm.... it was Kelly who ran him over! Orpin, suddenly without a rider, offered Kelly the ride for the TT.

In truth, Kelly should not have been allowed to participate in the Production race, for while the '67 was his third TT, he had not completed a single practice lap for this event! The 'Production' Thruxton prepared by Veloce Ltd for his sponsor, Velo dealer Reg Orpin, was late to arrive. Thus Kelley practiced on a borrowed MSS model, which had every sort of mechanical problem, including a badly slipping clutch, which generated a fabulous story told by every Velocette enthusiast; Kelley's clutch was slipping so badly near Quarry Bends he pulled up and considered his practice chances nil. An ancient local farmer, by legend, pulled a nail from an adjacent fence, and adjusted Kelley's clutch! But while kick-starting the MSS, the 'roads open' car, signaling the end of practice, drove by, and his hopes for a complete practice lap were dashed. Kelley in fact went to work the following Saturday, thinking himself disqualified, only to receive a frantic phone call from his pits at lunch - if he could make it to the starting line in time, he could race! His leathers were ready, the bike had passed scrutineering and was ready to go. Kelly's friends had successfully swayed Mary Driver, the Secretary of the TT, on the importance of having a local hero in the race; he DID have 6 Manx races under his belt after all, so was unlikely to be an embarrassment or safety hazard. Still, a few rules were bent.
Kelly pictured from an Isle of Man TT program, after his win.
Rules had been more dramatically bent by Veloce Ltd in providing several 'Production' machines to dealers Reg Orpin (Kelly's sponsor), Geoff Dodkin (Heckles), and Arthur Lavington, for these machines used engines which had been specially developed by Veloce in a bid to win the TT that year - hoping to come home with an Overall win in the process. All three used 'Squish' combustion chambers with specially-shaped forged pistons, and the Orpin/Dodkin machines had a host of internal improvements including needle roller bearings on the cam followers - all of which served to produce an extra 4.5hp over the standard Thruxton, according to Bertie Goodman, Managing Director of Veloce.

In the event, even with his dismal start, Kelly won the 500cc race easily at an 89.89 mph average, passing through the speed trap at Ballacraine at 116.9mph. Keith Heckles on the Dodkin machine was 2nd, with a fourth Thruxton (not a factory 'Squish' machine, and a race-prepped 'standard' Thruxton, VMT 103, purchased in '65 via Reg Orpin), ridden by Bob Biscardine, came in 10th. 
The specifics of a 'Squish' conversion;  a Manx-style piston with cutaways in the combustion chamber

What had inspired Veloce to build a batch of 'Squish Head' racers in 1967? Credit is due to Dennis Quinlan of Australia for communications with the Factory regarding Down Under Velocettes. While the rest of the world had moved away from Velos in serious racing competition, it seems the candle still burned bright for the marque on the other side of the world, and a host of very clever engineers were madly tinkering, modifying, and successfully racing their Velocettes well into the 1960s and 70s. Their ingenuity extended as far as special DOHC cylinder heads for 'pushrod' engines, lightweight frames, bronze cylinder heads for older racers, and experiments to improve combustion and generate more power from the standard article.
Correspondence between Dennis Quinlan and Bertie Goodman of Velocette

Three teams independently produced 'Squish Head' Velocettes in 1964, using post-1951 Norton Manx cylinder heads and pistons as their model. The Aussie tuners found through trial and error that their engines produced significantly more horsepower, with a marked reduction in 'pinking' under load, cooler running, less spark advance, and clearly a far more efficient combustion process. Quinlan wrote to Veloce that his Squish Velo, when road-tested by his co-builder Keith Smith, got 75 miles per gallon!  Which is not unheard of mileage for a standard Thruxton, ridden mildly...
Quinlan and Smith's notes to the Veloce factory

Bertie Goodman was a racing enthusiast to the core, and the beating heart of all competition success at Veloce Ltd post-war. Had he but a majority stake on the Board, racing Velocettes would have graced the race tracks of the world for many years after 1953, when the factory dropped all race support, to concentrate on their humble 'LE' model. It was Bertie who supported the amazing 24-Hours at 100mph World Record with a 500cc Venom at Montlhery in 1961 (which still stands for a 500cc single, by the way), as well as the attempt with a 350cc Viper model at the same record. Bertie also ushered in the Thruxton model, having taken a good look at some American-brewed special cylinder heads and realizing the potential for an excellent Clubman's racer, or Café Racer!
Dennis Quinlan (left) and Keith Smith, with their home-built 'squish' racer in Australia, 1964

Thus, it was Dennis Quinlan's loyal correspondence with the factory about his tuning efforts which set Bertie's ambition on a Production TT win. The Thruxton was already fast, producing 8hp more than the Venom Clubman model; an extra 4.5hp would give that much more of an edge at the Island. Velocettes had already proven their reliability with their 100mph/24hr success, as well as wins in 12- and 24-hour Endurance racing at Barcelona, and of course at the eponymous Thruxton airfield race circuit. While the Australian Squish cylinder heads were far away, Norton Manx cylinder heads were certainly available for inspection, and Goodman had special pistons forged to the Norton pattern, which mated to modified Thruxton cylinder heads.

It seems clear that two engines were heavily developed with many internal modifications as noted above; these went to Reg Orpin and Geoff Dodkin. Between 5 and 10 more Thruxton engines were modified with the 'Squish', albeit less heavily modified. These were sold to selected friends of the factory; long-time racers or dealers who sponsored Velo racers. One of these engines was sold to Arthur Lavington, legendarily stalwart Velocette racer, the last man to race a MkVIII KTT in a Grand Prix, who in fact died in practice for the 1969 Production TT, when he was struck by another rider and his Thruxton struck a stone wall. He almost certainly used a Squish engine in his '67 race machine - the engine of which was VMT 816RC. A photograph of this engine is shown below.
An original, TT-used squish piston, with a new replacement, ready for fitment!

The development of the 'Squish' engine itself deserves a telling, and is the subject of several more posts.



3 comments:

Dave Robinson said...

Hi there. Not a comment intended for the whole blog audience (although I don't mind). I think this is one of the very best sites about old motor cycles, so much so the link is on my Chrome toolbar. I've noticed I'm not able to jump to the larger image when I click on the page image. There is a hyperlink there, but it just remains. I've tried different computers and browers, all to no avail. Is it just me or is there something amiss? Having been a webmaster for my flying club, I've learned that if no-one tells you, you don't know... Very kind regards and an excellent resource. Thanks again. Dave Rob Yorkshire, England.

Anonymous said...

I've heard about the American engine-guru Jerry Branch's trick Velocette, he did all the improvements noted by our blogger, DQ, the squish too, using a modded 350 head on the 500. I heard from Allen Dudley-Ward there were several motorcycle dealers acting as unofficial development-engineers for Velocette, Dodkin, Orpin, Seymour, Rhodes. My brother moved to Aylesbury (?) near Oxford and met Seymour a few times (think he died shortly afterwards?) and, ex-MOV owner as my brother was, got to chatting and heard a few things corroborating what DQ writes, and what I recall of D-W's comments. Branch showed the Goodman's his improvements when they were over one time, suggesting moving the pivot-points for the rockers closer together to shorten the rockers (he had welded his head) thinking he could make some money, to be bruskly told by these other lads, also over sometime, that he'd see no money, they never did, even had to buy most parts at cost, rarely given anything, and were getting stroppy with the Goodmans who seemingly wanted something for nothing. With permission, based on Branch's ideas, Seymour shortened the rockers and splayed out the pushrods to match, thus the signature of a Seymour-Velo was conical pushrod-tubes, wider at the top. He told my brother he gave up and, the last time they ever met, used a rude 'C' word describing what he thought of Bertie. The Goodman's changed just enough on the Thruxton to avoid being sued by Branch. I met Goodman sister Ethel Denley and hubby via D-W's friend Stephen Ward, and she was equally scathing about her brothers' business acumen. Quiet a tirade, I got the impression if SHE had been in charge Velo's would still be in business!

Anonymous said...

Tte Velocette Thruxton ridden by Bob Biscardine had a standard engine. I purchased it new from L Stevens Ltd (Reg Orpin)in 1965 and production raced it myself in club events. The only work done on the engine was to lighten the valve gear and have it crack tested at De Havillands. Bertie Goodman agreed to supply spares on a sale or return basis through Geoff Dodkin
Malcolm Lowe