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The Folded Vee Story
"Graham Diedericks,
Johannesburg bike enthusiast, nightclub owner, bouncer, classic bike restorer
and ex drag-racer is off to Halco Engineering in the UK to show them a crank
he built. Phil Irving, doyen of bike designers and writers, and designer of
the Vincent HRD v-twin, wrote in 1962 that a parrallel twin should have a
76 degree crank. This means that one piston is at maximum speed while the
other piston is stationary (either TDC or BDC).
Graham, who has four classic 1970 650 Yamahas, tried this theory on one of
them... and it worked! He relocated one crank pin, made the camshaft adjustable
with removable lobes and relocated the ignition timing. "Vibration was
halved" said Graham, "just like Phil Irving said it would be".
A chap called Tony hall in England does development and kit work on 650 Yamahas,
which are in demand worldwide as the Japanese Bonneville. Tony had heard about
Grahams work and invited him over to England to set up a motor for future
possible manufacture and sale.
The conversion gives a parrallel twin the charachteristics of a v-twin known
as a "folded vee". The power charachteristics are better, there
is less vibration and there is more mid-range power available. The off-beat
v-twin sound is something else!
Grahams trip is a bit of a sensation. In England it has been asked how a mere
colonial can have such mechanical aptitude, fortitude and insight, especially
when there are wars and things to keep our minds occupied!!! The Brits can
hardly believe that such an engine can come from anywhere other than Britian
itself, or perhaps America or Japan."
Thanks to Bike SA (August 1993)
