Triumph’s First Twin: Triumph 6/1
By Simon Davis
1935 Triumph 6/1
Claimed power: 25hp @ 4,500rpm
Top speed: 85mph (est.)
Engine: 649cc air-cooled OHV parallel twin, 70mm x 84mm bore and stroke
Weight: 412lb (187kg)
Triumph’s first production vertical twin was not, as many enthusiasts
believe, Edward Turner’s epic 1938 Speed Twin; it was, in fact, Valentine
Page’s Triumph 6/1. Almost unheard of in the U.S. and rare even in its home
country, had it been successful, Page’s Triumph 6/1 could have changed how we
look at Triumph twins.
From 1928 until 1932, Valentine Page and Edward Turner
worked together in the drawing office at Ariel motorcycles. Between them, they
would design many of the most successful British motorcycles from the late
1920s to the late 1960s. The phenomenal success and influence of Turner’s later
Speed Twin, and the relative failure of Page’s 6/1, reminds us that motorcycle
design involves a precarious balance between emotion and engineering.
By the late 1920s Page was already well-known, both for his
work at the London
firm of J.A. Prestwich (whose J.A.P. engines were used by many manufacturers,
including Brough Superior) and for his range of single-cylinder machines at
Ariel. Regarded as a quiet, studious and kindly man, Page was generous with
help and advice for his young assistant. Turner — although largely self-taught
and without formal qualifications — was employed on the strength of an idea he
showed Ariel boss Jack Sangster for a revolutionary 4-cylinder engine design.
That design would become the Ariel Square Four. Working with Page, Turner
squeezed a unit construction, 500cc prototype Square Four engine into the frame
of the existing Ariel 250cc single. Weighing around 280 pounds, the bike
performed admirably. Although manufacturing and cost considerations
necessitated changes, the production version (now with a separate Burman
gearbox and running gear from the 500cc Ariel SG31 Sloper) was the hit of the 1930 Earls Court
motorcycle show in London.
While working with the new engine on the test bench, Turner
and Page removed the front crankshaft as an experiment. The resultant 250cc
vertical twin delivered such smooth power that Page wondered why they were
“bothering with a four.” This was, quite possibly, the “eureka” moment for them
both — the instant in which, however dimly, the 6/1 and the Speed Twin were
first conceived by their respective designers. They tested both 360-degree
(pistons rise and fall together) and 180-degree (one piston up, one down)
crankshaft designs and concluded there was little difference between the two
arrangements, although the 360 worked better with a single carburetor.
The first Triumph
Toward the end of 1932, Page left Ariel to take up a new
post at the struggling Triumph factory, where he designed a range of
workmanlike but rather uninspiring singles — and one twin, the 6/1.
Introduced in 1933 as a new model for 1934, the 6/1’s 649cc
parallel twin — the engine type that would later become synonymous with the
Triumph name — was the first of its kind offered by the marque. Featuring a
360-degree crankshaft, it had the flywheel in the primary case, outboard of the
crankcase. The primary drive was by a pair of large helical gears, which meant
the engine had to run backward. The massive crankcase contained a 7-pint oil
tank and a single, gear-driven camshaft mounted to the rear of the cylinder
The cylinder heads were formed from two separate castings
and, in an unexpected design throwback to an earlier era, had exposed valve
gear. The design featured a single Amal Type 276 carburetor with a small 1-inch
bore to promote good gas flow at low engine speeds. Output was a claimed 25
horsepower at 4,500rpm. Interestingly, the engine was offset to the right in
the frame. A unitized 4-speed gearbox (with handshift on early models)
completed the powertrain. Sturdily constructed and weighing 412 pounds, the 6/1
was primarily suited to sidecar work.
The machine certainly performed well enough on the road.
Late in 1933, a 6/1 hitched to a Triumph Gloria sidecar and ridden by Triumph’s
sales manager Harry Perry won a silver medal in the International Six Days
Trials (missing a gold medal by just five marks because of time lost repairing
a damaged front tire). The outfit was then taken to Brooklands, where it covered
500 miles in just 498 minutes, including refueling stops. This earned the
factory the coveted Maudes Trophy for endurance that year.
Yet showroom performance was another matter, and the unit
sold poorly. In many ways the 6/1 was a typical Page design, durable and
dependable, but hardly handsome. Aimed at the sidecar market and meant to
replace the traditional big V-twin, the bike arrived just as the sidecar market
was in decline. Consumers were opting instead for the first small, inexpensive
cars that were coming on the market. Total production is open to question, with
estimates ranging from 100 to 600 built over the model’s two-year life span.
What Triumph needed was a bike as beautiful as it was fast,
something to capture the hearts — and wallets — of the buying public. The
company — and the public — would not have to wait long, as Triumph introduced
the exciting and now iconic 500cc Speed Twin in 1937.
Riding the Triumph
After the usual routine of tickling the carburetor, the 6/1
I’m fortunate to be riding starts readily, responding to a blip of the
throttle, the mufflers giving a healthy bark that shouts “British Twin!”
It is mechanically quiet, even with exposed valve gear,
which is not what I expected at all, and the clutch is nicely weighted.
First gear selects easily and the bike moves smartly away
from a standstill. The other gears all select nicely, but respond best to an
unhurried and deliberate change, especially between second and third. I had
been expecting the torque reaction from the backward-running engine to be
somehow intrusive, but it’s not at all noticeable and the engine is more than
acceptably smooth. The Triumph 6/1 certainly doesn’t lack power. For a machine rapidly
approaching 80 years old it is actually something of a revelation, and it must
have been exceptional when new. The well-sprung saddle and girder forks isolate
the rider from all but the worst bumps — with the large chrome headlamp dancing
entertainingly in front of me — and, on smooth roads at least, ride quality is
better than I expected. The large wheels help here (19 inches front and rear),
riding bumps well with a long, slim front tire contact patch for steering
The brakes are standard fare for the time, with the rear
providing most of the stopping power and the front a gentle action. The
inverted front brake lever takes some getting used to.
Overall, my brief spin on the 6/1 is enjoyable, even
allowing for the fact that its rarity makes it a slightly nerve-wracking
enterprise, as there are only somewhere between 17 and 25 left, depending on
whose figures you choose to believe.
Having ridden a Triumph 6/1, I have to conclude that Page aimed his
twin at the wrong buyer. Yet the 6/1 did not sink without a trace. Comparing
the specifications of the 6/1 and the later BSA A10, launched in 1949 — which
Page had a heavy hand in — it is difficult to refute claims that the A10 is
simply a 6/1 with a central flywheel and chain primary drive. It may have taken
him a while, but Page got there … eventually. MC
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