| Title: | Bicycling |
| Notice: | Bicycling for Fun |
| Moderator: | JAMIN::WASSER |
| Created: | Mon Apr 14 1986 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 3214 |
| Total number of notes: | 31946 |
The latest issue of AW&ST reports success in Human Powered flight -
Helicopter Division. Cal Poly got their 100' rotor machine off the
ground recently for almost 10 seconds. The flight was witnessed by an
observer of the international sanctioning body (whatever it's name is)
and pronounced official.
If you haven't been following this, the machine is the one with
small propellers at the tips of the rotors. They are powered by
(kevlar?) string that is pulled into the cockpit area by the pedals.
Not what you'd term an endurance type drive. Having the propellers on
the rotor eliminates drive torque and the need for a tail rotor or
counter-rotating blades. - Chris
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 1385.1 | Basso N99123 requesting departure, runway 12 | BOOKS::MULDOON | I'll be right back - Godot | Wed Dec 20 1989 10:26 | 30 |
This is quite an accomplishment and I don't mean to take
anything away from the Cal Poly team, but they have a way
to go before they can call it "flying" in the strictest sense.
They're actually operating in what's called ground-effect. This
means essentially that they're using the force of the air dis-
placed by the rotor against the ground to help get into the air.
In a fixed-wing aircraft this effect is significant until you
reach an altitude equal to roughly half the wingspan. Above this
point the aircraft (fixed-wing or rotorcraft) is being held up
by the aerodynamic lift generated by the flow of air over the
airfoil (wing or rotor). My guess is that it would take an effort
an order of magnitude greater to get past this point, and I'd hate to
be 50 feet or so above the ground and start to cramp up.
As I said before, I admire the accomplishment of these folks.
It seems that every day we get closer and closer to practical,
sustained human powered flight. Maybe in twenty years we'll all
be pedaling our Basso or Vitus rotorcraft around town! :^)
Steve (who can barely
raise his bulk
out of his chair
let alone off the
ground)
Maybe an aero seatpost would help them get that beast out
of ground effect. Yeah, that's it - That's the ticket!
| |||||
| 1385.2 | LEVERS::LANDRY | Fri Dec 22 1989 11:15 | 22 | ||
Ground effect helps some, but there's another factor that works against them. Hovering helicopters work real hard 'cause as the column of air is pulled through the rotor disk it is thinned above the rotor and there is less air to "bite" into. You'll notice that "real" helicopters (powered) seldom take off straight up but get some forward motion as soon as possible. It's not even uncommon for even a skid equipped helicopter to drag along the ground for a short distance before takeoff on a hot day. There's other things to consider as well - like the effect of flying the human powered 'copter inside. Does the circulation of the air through the rotor then back up the walls have an effect? This has been discussed at length in rec.aviation with many people offering opinions but few with the technical expertise to back them up. As far as I can tell we (mere mortals) can only guess at the impact of various factors but can't know their real impact without understanding the whole system. chris | |||||