Gyroscopic effects
in [Motorcycles]
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From: S'mee on 10 Jul 2010 11:34 On Jul 10, 3:49 am, CindiK <cindi.k...(a)gmail.com> wrote: > On Jul 9, 10:12 am, "S'mee" <stevenkei...(a)hotmail.com> wrote: > > > > > > > On Jul 9, 3:10 am, CindiK <cindi.k...(a)gmail.com> wrote: > > > > On Jul 8, 10:26 pm, sean_q_ <nos...(a)no.spam> wrote: > > > > > S'mee brought this up in another topic, but since > > > > it's likely to get buried there I thought it deserved > > > > a thread of its own. > > > > > Of course as a spinning object a motorcycle wheel is > > > > subject to gyroscopic effects. The question is, how much, > > > > and are they significant? > > > > > I can think of two gyro effects to consider: > > > > > (A) Because a bike leans in a turn, its wheels rotate > > > > (or pivot) about a horizontal axis through the contact patch. > > > > > (B) In a curve, the wheels also rotate about an axis > > > > vertical to the road surface. If you enter a turn northbound > > > > and come out heading east, both your wheels have been rotated > > > > 90 degrees to the right. > > > > > I'm pretty sure everyone here has at one time or another held > > > > a spinning toy gyroscope in their hand, given it a sudden > > > > twist and felt the "strange" reactive force. However, > > > > on a moving motorcycle changes don't happen that abruptly. > > > > The faster the bike (ie, the higher the rotational inertia > > > > of the wheels, which means the higher the potential for > > > > gyro effects), the more gradual the turns. > > > > > Well I don't have any metrics. My guess is that type (A) isn't > > > > all that significant, especially for me. My chicken strips are > > > > probably as pristine as the day the tire was made (I ride for > > > > pleasure, not because I've something to prove). > > > > > Type (B) causes a precessional torque on the wheel through > > > > a horizontal axis tending to force it back to the vertical. > > > > This can be demonstrated using the Right-Hand Rule > > > > on a left hand turn (the easiest case because all rotations > > > > are clockwise): > > > > > Point your right index finger away from you (the direction > > > > of travel) with your thumb pointing straight up. Your 2nd > > > > (long) finger points to the left, representing the axle(s), > > > > the axis of wheel spin. The Observer's POV is the place > > > > on your palm where these 3 fingers "meet". > > > > > The Observer (a fictional construct for purposes of clarity) > > > > looks along your long finger and sees the wheel spinning > > > > clockwise. Then he looks upwards along your thumb and sees > > > > the wheel *turning* clockwise. Ie, to the left from > > > > the rider's POV. According the Right-Hand Rule, > > > > the precessional gyroscopic torque acts on the wheel to rotate > > > > it clockwise about the axis represented by your index finger, > > > > resisting the force acting to lean the wheel over to the left. > > > > Steer to the right and the same gyro effect resists -- not > > > > the lean itself, but the rotation into leaning that direction > > > > as well. > > > > > BTW I just did a quick test and verified the above, using > > > > the handiest "gyroscope" I could lay hands on -- in this case > > > > an electric fan (it's been a hot day here). > > > > > Again, is this effect strong enough to be significant? > > > > I don't know. If anyone does I'd appreciate them > > > > commenting on it. > > > > > SQ > > > > I know the angular momentum of the driveshaft in shaft-driven bikes > > > makes it impossible for them to wheelie. > > > Only in Oz does this not happen. > > Of course. It's on the bottom hemisphere, so the Coriolis effect flips > the gyro effect so shaft driven bikes are in permanent wheelie. Exactly, but the real question is: Are you sure that the southern hemisphere is the bottom and if so why. I would suggest that 2,000+ years of conventional wisdom and assumptions of geographers is not a good answer.
From: CindiK on 10 Jul 2010 13:53 On Jul 10, 10:34 am, "S'mee" <stevenkei...(a)hotmail.com> wrote: > On Jul 10, 3:49 am, CindiK <cindi.k...(a)gmail.com> wrote: > > > Of course. It's on the bottom hemisphere, so the Coriolis effect flips > > the gyro effect so shaft driven bikes are in permanent wheelie. > > Exactly, but the real question is: Are you sure that the southern > hemisphere is the bottom and if so why. I would suggest that 2,000+ > years of conventional wisdom and assumptions of geographers is not a > good answer. How about "I was trolling the aussies and kiwis"?
From: S'mee on 10 Jul 2010 14:57 On Jul 10, 11:53 am, CindiK <cindi.k...(a)gmail.com> wrote: > On Jul 10, 10:34 am, "S'mee" <stevenkei...(a)hotmail.com> wrote: > > > On Jul 10, 3:49 am, CindiK <cindi.k...(a)gmail.com> wrote: > > > > Of course. It's on the bottom hemisphere, so the Coriolis effect flips > > > the gyro effect so shaft driven bikes are in permanent wheelie. > > > Exactly, but the real question is: Are you sure that the southern > > hemisphere is the bottom and if so why. I would suggest that 2,000+ > > years of conventional wisdom and assumptions of geographers is not a > > good answer. > > How about "I was trolling the aussies and kiwis"? oooo, an ole big mouth bass dragged the fisherwoman in...you don't see that every day or night for that matter.
From: Bob Myers on 10 Jul 2010 16:03 Beav wrote: > How pleasing to see> >> our leading Self-Proclaimed-Expert-On-Everything-Troll caught >> like that. > > I was somewhat surprised too, although I really shouldn't have been. Nope, as Pete pointed out, it was pretty much inevitable. Calling Dr. Pavlov... Bob M.
From: S'mee on 11 Jul 2010 00:56
On Jul 10, 2:03 pm, "Bob Myers" <nospample...(a)address.invalid> wrote: > Beav wrote: > > How pleasing to see> > >> our leading Self-Proclaimed-Expert-On-Everything-Troll caught > >> like that. > > > I was somewhat surprised too, although I really shouldn't have been. > > Nope, as Pete pointed out, it was pretty much inevitable. Calling > Dr. Pavlov... Yep he's always doing the "Spicy McHaggis Jig" about something. p.s. look it up on youtube. |