Gyroscopic effects
in [Motorcycles]
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From: S'mee on 10 Jul 2010 00:36 On Jul 9, 3:59 pm, "Beav" <beavis.origi...(a)ntlwoxorld.com> wrote: > And NZ too. AH! Thankyou for the correction sir.
From: High Plains Thumper on 10 Jul 2010 00:50 Mark Olson wrote: > High Plains Thumper wrote: >> Mark Olson wrote: >> >>> I remember reading that roadracers had to develop significant >>> upper body strength to steer their bikes on twisty courses due to >>> the gyro effect. >> >> Perhaps, but IME, I have never had a problem running the twisties, >> FWIW. I think target fixation would be a greater problem, IMO. > > I doubt you are going 120 in the corners and 180 on the straights > either. True, but I never had a desire to do, and regular street and highway traffic, will never encounter those speeds. -- HPT
From: CindiK on 10 Jul 2010 05:49 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.
From: High Plains Thumper on 10 Jul 2010 08:33 CindiK wrote: > "S'mee" wrote: >> CindiK wrote: >> >>> 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. I see, now I understand all those YouTube videos from down under. -- HPT
From: S'mee on 10 Jul 2010 11:32
On Jul 9, 3:59 pm, "Beav" <beavis.origi...(a)ntlwoxorld.com> wrote: > I was somewhat surprised too, although I really shouldn't have been. Surprised in what way? That CindiK used such obvious bait or that it got a hit? |