This is part 2
But I miss something (may be I missed it by my bad English, when I read his
article).
The force goes in two direction - there is not only resistance from the moving
forward speed against the chute (and the force on the rope/bracket aso.),
which is a extreme deceleration (or opposite like this example with the car,
crashing against the wall) from running against the wall of air. Depends on
what kind of airflow the body of the car produce this wall is "harder" or
"softer".
There comes now a second direction of power, exactly opposite of the
"stopping" chute, this is the weight of the car which is still pushing
forward. This has nothing to do with this if the car is only rolling or still
under power. Only the pushing weight of the car produce a enormus force on the
rope. So better the aerodynamic of the car is, so higher is the product from
moving speed and weight. Jeff Shipley was two years ago very surprised, when
he shut down the engine to the end of the fourth mile and he still went an
average only 15 mph slower than the fourth mile thru the 5 mile. This was only
the weight and the aerodynamic of the car which allowed the car to stay on
speed.
A heavy car is much more (negative) affect from this weight issue than a
lighter car - here the example Al's # 76 and Tom's # 411. Which holds by Al,
can be ripped of by Tom.
This number of the opposite direction force on the rope/bracket is different
by all car's due to the different weights and aerodynamic. Also the percentage
of the weight front/rear creates a affect - a front engine is pushing more
forward than a rear engine.
What also effect the force is the chute type and size.
A open chute so as Art Arfons used on his Green Monster or Carl Heap on his
Phoenix, creates a much softer resistance than a closed one. I don't know if
someone tried ever a open chute as the first (highspeed) chute on a real fast
streamliner. Would be interested what experience he got with them.
The rope length is also important. Due to this that the most parachutes start
to "turning" the rope like a screw threat a longer rope can eliminate the
rolling effect against the car - or more important against a streamline bike.
A short rope can may be eliminate this real hard stopping from a chute which
is open before the rope is stretched, but can produce also the effect that a
half open chute close (collapse) again due to bad airflow behind the car.
May be Mayf can check his formula and find a idea how he can modify them with
my input (opinion) of the opposite force of the car. Would be great to see the
result and it would not surprise me, if the force increases.
See ya
Pork Pie
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