Though it looks
like a bit of old
and a bit of'new,
the Vincentbased RTV1200
Black Widow is
really all new,
down to the
engine cases.
By Alan Cathcart
Phptps by Dirk MelkebeeklDeadline
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hUe the whereabouts of the
legendary Australian rider factory remain uncertain, tracking
down the loca tion of one of the rather
less mythical Aussie bike factories' R&D
base reads like a page from a Hobbi t
novel. "After you exit the freeway north
of Sydney, run straight for 29 .ln two wheels in the 1950s. RTV ab:eady
has a digital electronic version of this combining revs and speedometer under development (the prototype was
fitted to the 'Widow test bike, but not
functioning), so hopefully this will happen. An RTV Black Monster would surely sell...
There were no shortcuts in designing
the RTV: Vincent engine drawings have
long disappeared, so Prince had to start
from scratch. He drew upon his 40-year
experience of the 50-degree V-twin to
redesign some aspects completely
where necessary, while retaining others
as appropriate. The main difference,
apart from the increase in capacity to
1197cc via 92 x 90mm engine dimensions (compared to the 84 x 90mm of
Irving's original 998cc Vincent motor), is
the RTV's new crankcase design. It's a
design that incorporate a Bosch electric
starter as well as a beefed-up rollerbearing crankshaft aimed at reducing
£lex, with bigger main bearings,
enlarged mainshafts and meatier 40mm
crankpins which require a'special press
to deliver their 20-ton interference fit.
The balance factor on the flywheels
has been altered from 46 percent to 60
percent, in line with Prince's past experience when fitting Vincent engines to
other than stock Stevenage frames.
"I thought of fitting a bobweight
crank or even a balance shaft to smooth
out vibration," he admits, "but decided
it would spoil the personality of the bike
if I did so. By adding weight to the flywheels instead of removing it, we've
eliminated unwanted vibration, except
at tickover. Really, in adapting the Vincent concept to a modern engine design,
I've tried to stick to things I'd already
done over the years on race-bike or car
engines which Iknow work."
