Triumph Ricardo
 
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www.hd-classic.be
Having established an enviable reputation in the
early days of motorcycle competition, Triumph chose
to ignore events such as the Isle of Man TT for several
years. So when they performed an abrupt about turn
in 1922 it could be expected that they were pretty
confident of the bike they chose to enter - the super
sports Triumph Ricardo.
Sir Henry (Harry) Ricardo was a renowned combustion
expert who had worked on behalf of many companies
when he was asked by Triumph to advise on a replacement
for their trusty side-valves. Ricardo produced a number
of alternatives before Triumph announced that their
new overhead-valve model would use a four-valve head
design. In fact, from the cylinder barrel down, the
rest of the bike was virtually identical to Triumph's
tried-and-tested Model H side-valve.
The theoretical advantages of a four-valve head were
numerous. Gas flow could be more efficient, the spark
plug could be positioned centrally for more efficient
combustion and lighter components would respond quicker,
allowing higher revs. In fact, Ricardo's design was
quite conservative, using small ports and unusually
recessed valves. Each pair of valves was parallel,
set at 90 degrees to each other, with stems and springs
exposed; the piston, which was of light alloy, had
a concave crown and a slipper-type skirt. The cylinder
barrel was made of solid steel and had deep finning,
while the head, which had two parallel exhaust ports,
was iron.
From there down, the engine was based on the Model
H. The flywheels were slightly smaller, to allow free
revving, while lubrication, relying on constant-loss
fed by hand pump, was later changed to dry sump fed
by external oil pump. The resulting Model R Fast Roadster
was marketed as a fully equipped sports model and
attracted favourable reports. In this form, it lapped
Brooklands at 68mph, while a racing version also took
the hour record at almost 77mph and a flying mile
at nearly 84mph.
Three were entered for the 1921 TT but handling deficiencies
meant that only one finished. A year later, the Triumph
Ricardo was back with the new lubrication system,
stronger valve gear, a modified cylinder with new
dimensions and made of cast iron, a three-speed gearbox
and new front fork. This time it finished second in
the TT and the following year went on to take a number
of continental wins and gold medals in the ISDT.
After 1924, Triumph switched their development efforts
to a new model, although the 'Riccy' stayed in their
range as a sports model until 1928. But the four-valve
layout had proved its potential for the future.
Triumph Ricardo
- Years in production - 1921-28
- Engine - single-cylinder four-valve ohv four-stroke
- Bore and Stroke - 80.5 x 98mm
- Capacity - 499cc
- Power - 20bhp @ 4600rpm
- Carburettor - Triumph twin barrel
- Tyres (front/rear) - 3 x 26in/3 x 26in
- Transmission - Triumph three-speed gearbox
- Weight - 250lb
- Top speed - 70mph
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