Hello all,
Don and Mike have been talking about the rules on LSR cars touching the
ground and moving aerodynamic devices.
The Arfons Green Monster had a front wing which adjusted as the load on the
front axle changed. All mechanical - no computers used at that time on
Pickle Road. At 600 mph Craig Breedlove had front wheels barely in ground
contact with Spirit of America Sonic I and at 633 mph Richard Noble was at
the limit before Thrust II would have lifted its front wheels (they
adjusted the vehicle attitude to reduce rolling resistance). Neither had
any device to add downforce. Thrust SSC used the active suspension as Mike
explained but they still had a further back up device to slam the front
into the desert if all 10.5 tons started to nose up - two ejector seat
rockets pointing upwards.
With a special motorcycle on an FIM attempt you have to be able to prove
that for 90% of the mile or kilometre timed distance and 750 metre before
and after the timing trap, the wheels were in ground contact. Quite how
the FIM Steward would confirm this except on a surface where marks are left
I do not know. It gives them something to look at other than the clocks of
course. Moving devices to give down loading on a bike could result in a
turning moment which will have the machine on its side. We put the full
size Gillette Mach 3 Challenger in a wind tunnel to confirm that
aerodynamasist Dave Watson (now working on Champ Cars) had got the nose
shape correct. No wings or canards were fitted or needed. Instrumentation
measured the loads on both wheels.
On water the aim is to get most of the boat away from the drag of water so
most of the craft structure flies and just some small planing areas touch
the water. Big wings help lift the heavy tails of boats into a planing
position and to an extent control tramping (side to side motion). The US
unlimited racing hydros, with their turbine engines and 200 mph chute
speeds, have aerodynamcic surfaces at the front of the air tunnels which
the pilot can adjust to trim the boat. Yet they still flip over when
disturbed air gets into the tunnel and the bow lifts. Class 1 offshore
power boats have adjustable devices but they too help little when you fly
from wave to wave and go in nose first. These devices are a mix of aero
and hydro. With the dangers of Water Speed Record boating (three
fatalities from the last four contenders) I would urge anyone to have a
safety device to keep the nose on the water.
Ken Norris who designed the Bluebird K7 Boat and CN7 turbine car has stated
that you should build for safety first and then worry about the rules. If
you need adjustable aerodynamics use them. The UIM may not like it because
it is not purist boat design, but a life is worth more than building
something dangerous.
If you are running wheel driven on a known surface, salt or dirt, you
would surely be looking for tractive force to achieve propulsion and this
will be by static weight downforce ? If the body shape is producing more
lift force than vehicle weight at speed then its time to look again at the
air management over and under the vehicle. 'Ground effect' aerodynamics
needs no moving surfaces. The Chapparell Sports Car and Brabham FI car
used fan produced suction systems might work at Bonneville and you can
argue that the fan(s) are there primarily to cool a radiator. These forced
ground effects work at zero forward speed of the vehicle and drag is
minimal. Would someone then argue that a fan car is thrust powered when it
blows salt out of the rear ?
Malcolm Pittwood, Derby, England.
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