Okay, this is wierd. I was doing my usual after-work timed 5-miles down the Hudson River Greenway. It's going south. There was a 25 MPH west wind off the river. There's a heliport at 34th street -- sometimes the choppers land or take off at an angle where a cyclist can really feel it. Anyway, this one chopper had over-corrected and was recovering just as I was passing by and I got hit with the combined west wind and his rotor wash, and the entire bike "slipped" sideways. I was lucky I didn't get blown into the highway. I never stopped moving forward, the wind just pushed the bike sideways without me tipping over.
I figured the rotational inertia (angular momentum?) of the wheels kept the bike upright while the force of the wind was being applied laterally, and it overcame the static friction of the very small area of contact between the smoothish tires and the smooth road surface. Afterward, I tried to "tip" my bike while moving but _without_ turning the handlebars, and I couldn't do it, not that I tried too hard.
Does this make physics sense? What should I have done if I was really in danger of entering the highway? Fortunately, there was a wide dirt buffer. Should I have steered into the "slip" direction, or away from it, or just jumped off?
Okay, this is weird. I was doing my usual after-work timed 5-miles down the Hudson River Greenway. It's going south. There was a 25 MPH west wind off the river. There's a heliport at 34th street -- sometimes the choppers land or take off at an angle where a cyclist can really feel it. Anyway, this one chopper had over-corrected and was recovering just as I was passing by and I got hit with the combined west wind and his rotor wash, and the entire bike "slipped" sideways. I was lucky I didn't get blown into the highway. I never stopped moving forward, the wind just pushed the bike sideways without me tipping over.
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I figured the rotational inertia (angular momentum?) of the wheels kept the bike upright while the force of the wind was being applied laterally, and it overcame the static friction of the very small area of contact between the smoothish tires and the smooth road surface. Afterward, I tried to "tip" my bike while moving but _without_ turning the handlebars, and I couldn't do it, not that I tried too hard.
Inertia of its wheels plays no role in keeping a bicycle upright, except when riding no-hands. In that event, wheel inertia (gyroscopic forces) are used to steer the bicycle... and that does not work with even a moderate crosswind.
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Does this make physics sense?
No.
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What should I have done if I was really in danger of entering the highway? Fortunately, there was a wide dirt buffer. Should I have steered into the "slip" direction, or away from it, or just jumped off?
Make all the usual crosswind corrections that only work up to a certain lean angle and turbulence. At times, stopping is the only recourse.
You blew with the wind because you steered that way to keep the bottom of the bike under the top of the bike.
Otherwise you would have fallen over.
The way I read it he didn't steer the bike that way, it slid that way. Which seemed pretty unlikely if he was on dry pavement, IMHO, but that's how I read it.
You blew with the wind because you steered that way to keep the bottom of the bike under the top of the bike.
Otherwise you would have fallen over.
The way I read it he didn't steer the bike that way, it slid that way. Which seemed pretty unlikely if he was on dry pavement, IMHO, but that's how I read it.
You blew with the wind because you steered that way to keep the bottom of the bike under the top of the bike.
Otherwise you would have fallen over.
The way I read it he didn't steer the bike that way, it slid that way. Which seemed pretty unlikely if he was on dry pavement, IMHO, but that's how I read it.
I think he was very lucky.
Rich
He steered that way whether he noticed it or not.
Are you saying that Andy corrected for the extra force perhaps without realizing it? That sounds like the only way he might have avoided being tipped over by it.
>You blew with the wind because you steered that way to keep the >bottom of the bike under the top of the bike. > >Otherwise you would have fallen over.
The way I read it he didn't steer the bike that way, it slid that way. Which seemed pretty unlikely if he was on dry pavement, IMHO, but that's how I read it.
I think he was very lucky.
He steered that way whether he noticed it or not.
Are you saying that Andy corrected for the extra force perhaps without realizing it? That sounds like the only way he might have avoided being tipped over by it.
I suspect he is saying that - and I would second it. I've ridden in VERY windy conditions along the ocean in Florida, and often the wind would be blowing VERY hard one direction and shift 180 degrees almost immediately due to turbulence caused by a wall of condos.
I've had rides where I'm leaning heavily into the wind to compensate for the force, and been blown several feet one way or the other by a gust, a wind direction changes or a car passing (and blocking the wind). There was never any "sliding" though - it's just a matter of the change in lateral pressure causing me to lean more or less into the wind, and the correction the bike HAD to make to stay under me (fortunately).
Ron Hardin <[email hidden]> wrote in news:[email hidden]:
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Rich said:
Ron Hardin said:
You blew with the wind because you steered that way to keep the bottom of the bike under the top of the bike.
Otherwise you would have fallen over.
The way I read it he didn't steer the bike that way, it slid that way. Which seemed pretty unlikely if he was on dry pavement, IMHO, but that's how I read it.
I think he was very lucky.
Rich
He steered that way whether he noticed it or not.
I think I would know if I was steering or not! I was riding fast with enough corrective lean _into_ the wind to keep moving straight, then the rotor wash hit me. If I were steering I would have steered _into_ the wind and the bike would have travelled diagonally. At all times in this process both wheels were parallel to the center lane marker.
"Mark Hickey" <[email hidden]> wrote in message news:[email hidden]...
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catzz66 said:
Ron Hardin said:
Rich wrote: >Ron Hardin wrote: > >>You blew with the wind because you steered that way to keep the >>bottom of the bike under the top of the bike. >> >>Otherwise you would have fallen over. > >The way I read it he didn't steer the bike that way, it slid that way. >Which seemed pretty unlikely if he was on dry pavement, IMHO, but that's >how I read it. > >I think he was very lucky.
He steered that way whether he noticed it or not.
Are you saying that Andy corrected for the extra force perhaps without realizing it? That sounds like the only way he might have avoided being tipped over by it.
I suspect he is saying that - and I would second it. I've ridden in VERY windy conditions along the ocean in Florida, and often the wind would be blowing VERY hard one direction and shift 180 degrees almost immediately due to turbulence caused by a wall of condos.
I'm with Mark. You can get very odd wind shifts around skyscrapers in Chicago on windy days. It does feel like the bike slides, but I think it's autonomic compensation -- from years of practice keeping yourself upright while walking / cycling / etc. your body knows how to compensate and does so before you have time to think about it.
"andy gee" wrote: (clip) If I were steering I would have steered _into_ the wind and the bike would have travelled diagonally. At all times in this process both wheels were parallel to the center lane marker. ^^^^^^^^^^^^^^^^^^^ Balancing a bike is ALWAYS done by steering. As Ron Hardin said, you steered the bike AWAY from the wind. This is not sonething special that happens in a cross wind. It is going on all the time you ride. Tiny balance errors are corrected by introducing a turn.
This is also how you turn corners. You steer AWAY from the corner, and the bottom of the bike puts you into a lean which is proper for the turn, and you then ride a curved path with that lean. To complete the turn, you steer INTO the turn, putting the wheels back under you, standing the bike up.
If you froze the headset bearings in a straight ahead position, and somehow managed to ride the bike, a cross wind would not slide you sideways--it would blow you over.
Okay, this is wierd. I was doing my usual after-work timed 5-miles down the Hudson River Greenway. It's going south. There was a 25 MPH west wind off the river. There's a heliport at 34th street -- sometimes the choppers land or take off at an angle where a cyclist can really feel it. Anyway, this one chopper had over-corrected and was recovering just as I was passing by and I got hit with the combined west wind and his rotor wash, and the entire bike "slipped" sideways. I was lucky I didn't get blown into the highway. I never stopped moving forward, the wind just pushed the bike sideways without me tipping over.
I am just speculating here, but maybe the rotor wash was at a much higher velocity close to the ground and so it exerted more pressure below your center of gravity than above resulting in the tires slipping sideways rather than you getting blown over. In my minds eye I am picturing a column of air shooting down towards the ground from the rotor and then spreading out laterally when it hits the ground, creating a very high velocity zone close to the ground. Who knows if that is the way a column of air hitting a flat surface really behaves, but it makes intuitive sense to me.
Anyway, this one chopper had over-corrected and was recovering just as I was passing by and I got hit with the combined west wind and his rotor wash, and the entire bike "slipped" sideways. I was lucky I didn't get blown into the highway. I never stopped moving forward, the wind just pushed the bike sideways without me tipping over.
Nah, the wind didn't have anything to do with it.
You just unwittingly rode through a Hilbert space :-)
cheers, Tom
-- -- Nothing is safe from me. Above address is just a spam midden. I'm really at: tkeats [curlicue] vcn [point] bc [point] ca
"Andy" <[email hidden]> wrote in news:[email hidden]:
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I am just speculating here, but maybe the rotor wash was at a much higher velocity close to the ground and so it exerted more pressure below your center of gravity than above resulting in the tires slipping
I was thinking that might be the answer... but I'm still trying to calculate in general terms exactly what force would be required to overcome the "gyroscope effect" of the wheels. But yeah, a directed blast would do it.
Okay, this is wierd. I was doing my usual after-work timed 5-miles down the Hudson River Greenway. It's going south. There was a 25 MPH west wind off the river. There's a heliport at 34th street -- sometimes the choppers land or take off at an angle where a cyclist can really feel it.
You may find this weird as well, but your post made me think of fire engines. I ride past a fire station regularly, and a few times the engines have emerged as I went by or passed me down the road. I proffer the advice that anytime a fire engine, police car, or ambulance gets anywhere near you with its lights and/or siren going, you should do the same thing you should do when there's a helicopter taking off or landing nearby: get completely off the road ASAP and stay there until the vehicle or aircraft is gone. Things like that distract drivers, and may motivate them to pull off the road (as they should for emergency vehicles). They won't be looking for cyclists.
Bill
__o | Look to the past and remember no empire rises _`\(,_ | that sooner or later won't fall. (_)/ (_) | --Al Stewart
I was thinking that might be the answer... but I'm still trying to calculate in general terms exactly what force would be required to overcome the "gyroscope effect" of the wheels. But yeah, a directed blast would do it.
You were there and are the only one who knew what you felt. I am not making light of your observations, but sometimes I have done some things on my bike that made feel it was just the "E.T." effect that kept me upright.
