A paradoxical thought experiment
in [Motorcycles]
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From: ? on 7 Jul 2010 19:42 On Jul 7, 2:14 pm, sean_q_ <nos...(a)no.spam> wrote: > Isn't there some kind of plane with no wings? Where the fuselage > is designed to create its own lift? The fuselage of any conventional aircraft produces lift. However, aerodynamic engineers generally disregard fuselage lift and concentrate on achieving lift from the wings. > It must have a fairly high stalling speed. As I recall, general aviation aircraft may not have a stall speed above about 50 or 60 knots, according to FAA regulations. But if you go to an air show and watch a stunt pilot do a knife edge pass, he'll be going maybe 120 knots at a high angle of attack for the fuselage, since he's getting no lift from the wings. The rudder then assumes the function of the elevator, and the elevator that of the rudder... I don't know what the coefficient of lift of the fuselage might be...
From: brad herschel on 7 Jul 2010 19:47 On Jul 7, 4:27 pm, "?" <breoganmacbr...(a)yahoo.com> wrote: > On Jul 7, 1:08 pm, sean_q_ <nos...(a)no.spam> wrote: > > > Imagine an extremely lightweight (but very strong) sidecar > > mounted on the right-hand side of the bike (snip) > > Isn't the function of a sidecar to carry a female pasenger? > > I'm trying to imagine a female passenger which wouldn't negate your > entire thought experiment by weighing 110~140 pounds or so... Dates Fat Chicks ladies may require additional study i.e. overall effect.
From: Ben Kaufman on 7 Jul 2010 21:58 On Wed, 07 Jul 2010 13:08:29 -0700, sean_q_ <nospam(a)no.spam> wrote: >Imagine an extremely lightweight (but very strong) sidecar >mounted on the right-hand side of the bike (meaning >no offence to Brits, Kiwis, Ozzies, Sri Lankans and others). > >Make a hard left turn; the chair lifts because it lacks >enough weight to keep the bike from leaning into the turn. > I am not a sidecar experienced driver but I imagine the safe way to make a left turn with a sidecar on the right is to turn the handlebar counter-clockwise. >Then make a sharp right turn. Once again it lifts because >the rig's center of mass is offset above the wheels' >contact patches (where the turning forces are applied), >creating longitudinal torque. > >So the chair flies no matter which way the bike turns! >Surely I'm not the first to discover the Massless Sidecar Paradox. >Perhaps I should qualify this by saying, "Above a certain speed >the chair flies no matter what the turn." > >However, it gets more even more paradoxical. The turn >(and the lean) to the left would be by counter-steering -- >ie, turning right -- towards the chair! But then, >why wouldn't it just turn that way? > >So -- turn the bars left. Without the chair, that would be >counter steering for a right turn. But the chair prevents >a lean to the right, so I suppose the whole rig turns left. > >Then turn the bars right. That's countersteering to the left, >and with a weightless chair there's nothing to stop a lean >(and a turn) to the left. > >So (above a certain speed) the machine will only turn left!!?? > >SQ [being intentionally dense just for the fun of it] When the sidecar wheel is off the ground you have a two wheel motorcycle steering dynamics.
From: Beauregard T. Shagnasty on 7 Jul 2010 22:36 Ben Kaufman wrote: > sean_q_ <nospam(a)no.spam> wrote: >> Imagine an extremely lightweight (but very strong) sidecar mounted on >> the right-hand side of the bike (meaning no offence to Brits, Kiwis, >> Ozzies, Sri Lankans and others). >> >> Make a hard left turn; the chair lifts because it lacks enough >> weight to keep the bike from leaning into the turn. That's wrong. Making your left turn will press the sidecar onto the road. > I am not a sidecar experienced driver but I imagine the safe way to > make a left turn with a sidecar on the right is to turn the handlebar > counter-clockwise. ...commonly called "steering to the left." >> Then make a sharp right turn. Once again it lifts because the rig's >> center of mass is offset above the wheels' contact patches (where >> the turning forces are applied), creating longitudinal torque. Well, I guess that's one way to describe it. I usually just say it's centrifugal forces at play. >> So the chair flies no matter which way the bike turns! Only in Canada. <g> >> Surely I'm not the first to discover the Massless Sidecar Paradox. >> Perhaps I should qualify this by saying, "Above a certain speed the >> chair flies no matter what the turn." >> >> However, it gets more even more paradoxical. The turn (and the lean) >> to the left would be by counter-steering -- ie, turning right -- There is no counter-steering with a sidecar rig. >> towards the chair! But then, why wouldn't it just turn that way? It will. >> So -- turn the bars left. Without the chair, that would be counter >> steering for a right turn. But the chair prevents a lean to the >> right, so I suppose the whole rig turns left. >> >> Then turn the bars right. That's countersteering to the left, and >> with a weightless chair there's nothing to stop a lean (and a turn) >> to the left. Umm, no. >> So (above a certain speed) the machine will only turn left!!?? I've driven sidecars many thousands of miles and have made a few right turns along the way. Oh but wait, my sidecars were not weightless! >> SQ [being intentionally dense just for the fun of it] Oh. I see... > When the sidecar wheel is off the ground you have a two wheel > motorcycle steering dynamics. No, I'm afraid not. :-) Solo: counter-steer Sidecar: steer -- -bts -Four wheels carry the body; two wheels move the soul
From: The Older Gentleman on 8 Jul 2010 01:53
sean_q_ <nospam(a)no.spam> wrote: > Isn't there some kind of plane with no wings? Where the fuselage > is designed to create its own lift? The US built an experimental lifting body, yes. It crashed. Oddly, film of the crash was used in the opening sequences of the Six Million Dollar Man. <Reads on> Ah. Someone else got there first. -- BMW K1100LT Ducati 750SS Honda CB400F Triumph Street Triple Suzuki TS250ER GN250 Damn, back to six bikes! Try Googling before asking a damn silly question. chateau dot murray at idnet dot com |