|Entry #||Driver Name||Car Name||Mass
|7||21||Terry Scharton||Turbo Creeper||80||11||6.75||9||0.17||0.50|
Balloon car designer Terry Scharton writes:
A water impulse turbine is most efficient when the turbine blade circumferential velocity is one-half of the jet velocity. Since the balloon jet velocity is ~200 ft./sec., this implies that the turbine velocity should be ~100 ft./sec. Therefore a 10:1 reduction gear is required to reduce the turbine speed of 100 ft./sec. down to a car speed of say 10 ft./sec., which is very optimistic. (This assumes that the turbine and car wheel diameters are the same.)
Plastic reduction gear obtained from hobby store for approximately $10. Electric motor replaced by small turbine wheel.
Turbine wheel made from wife's sewing bobbin and straw blade segments. Remainder same as Turbo Dasher.
Turbine thought to make energy extraction more efficient for reasons stated above.
Friction in the turbine was too great. Car wouldn't move under its own power. (Hence the nickname, "ISO 9000".)
The calculations on the energy available from a balloon may be of interest to someone. As the calculated energy, 44 ft-lb., seems too high, I would appreciate comments, or corrections, anyone might offer. Email them to Terry Scharton.