Malcolm Pittwood wrote:
>
> 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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