Racecar Engineering - November 2005

GWR Predator
Upright pick ups were
dictated by the chosen
geometry and the
original gearbox pick up
locations
Gould, a more forward weight distribution
enabled higher cornering speeds, especially on
corner entry. The car also had a lower polar
moment so now we’ve taken that a step further.
‘Getting off the line was not a priority. We can
use the car’s electronics to aid that (and other
aspects) later. The main thing was to get good
mechanical balance. Just about every hillclimb
car understeers, but that’s not a bad thing,
depending on what stage it’s at, but quite often
with my previous cars I’ve sacrificed traction to
make them loose to help the front end. With this
car we tried to not create an understeerer – and
we haven’t! Even from the limited running so far
we know we’re going in the right direction. In fact
we’re actually working the other way, shifting grip
from the front to the back.’
Gear selection
It seemed to onlookers during early running that
the car’s paddle shift-operated, electropneumatic
assisted gear change mechanism was
misbehaving causing some missed runs. Wight jnr
corrects this misconception: ‘Although I’ve been
frustrated at not being able to drive as much as I
should, the issues have not been with the gear
system itself – that works without problems. The
car’s installation of the gear system has been the
problem. There have been difficulties getting the
engine control unit to allow the gearbox control
unit to do its job, but the electrics have been
working fine. Ian Haley of MIL who supplied the
shift system and controls has been frustrated too
when people have erroneously blamed his
system. Also the incredible heat build up from the
engine was causing the gear selection mechanism
to drag and not change properly. That hopefully
“
THE MAIN THING
WAS TO GET GOOD
MECHANICAL
BALANCE
”
has been resolved now [with larger radiators and
more ducting out of the engine cover].’
The bulk of the Xtrac-manufactured gearbox
internals have been retained, complete with the
final drive. The drop from the original 18,000rpm
maximum to the chosen limit of 15,000rpm has
effectively lowered the gearing to suit the
hillclimbing environment without needing a
different final drive or different gear ratios. But
the differential has been swapped to a cam and
pawl unit supplied by Jack Knight Developments.
‘We bought the Moog valve control systems for
the engine and the original active differential as
well but couldn’t afford the software side of
things just now. We intend to install the systems
at some point though,’ commented Wight jnr.
Aerodynamics
Targeting the smallest, tightest, smoothest
package achievable, the Predator nevertheless
has an aggressive look to it, mainly because of its
wing package. But appropriately Martin Ogilvie
describes the aerodynamics as ‘very much a finger
in the air design.’ The underbody reflects the
freedom in the technical regulations – no flat
floors mandated in hillclimbing – and though the
Predator’s underbody owes much to long
outlawed, ground effect single seater concepts
Front wing with F1-style end plates
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November 2005 Racecar Engineering 45