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From: Moike on 6 Feb 2007 03:20 jlittler(a)my-deja.com wrote: > On Feb 6, 2:56 pm, "Theo Bekkers" <tbekk...(a)bekkers.com.au> wrote: >> Knobdoodle wrote: >>> "Mad-Biker" <mad-biker(a)westnet(Panties).com.au> wrote: >>>> tyres including valve cap tightness, air pressure, tread, check >>>> (apparently if the valve caps arnt on, a tyre can suck in the valve >>>> stem and cause a blow out under extreme highload according to >>>> instructors?!) >>> ~ >>> [boggle] I've never hear THAT one!! >> I think the centripetal force sucks it in to the centre. >> >> Theo >> New to me too. > > FWIW I have *heard* of that issue but it's one of those "mate of a > mate" stories so I wouldn't call it proven, a friend who used to drag > race professionally in the 70's and 80's (in the US but he's an > Aussie, no not Bray :-) ) told me about that one quite a few years > ago, claimed to have had it happen to a drag car he built - can't > prove it either way though. > > JL > I've met someone who claims it happened to him at the end of the main straight at PI. Front tyre inexplicably deflated. No damage to tyre. He's not someone whose word I doubt, and having seen him ride he's not one who needs to make up stories. Says the problem was fixed by replacing the valve. Moike
From: Knobdoodle on 6 Feb 2007 03:30 "Moike" <bmwmoike(a)gmail.com> wrote in message news:kTWxh.3552$sd2.745(a)news-server.bigpond.net.au... > jlittler(a)my-deja.com wrote: >> On Feb 6, 2:56 pm, "Theo Bekkers" <tbekk...(a)bekkers.com.au> wrote: >>> Knobdoodle wrote: >>>> "Mad-Biker" <mad-biker(a)westnet(Panties).com.au> wrote: >>>>> tyres including valve cap tightness, air pressure, tread, check >>>>> (apparently if the valve caps arnt on, a tyre can suck in the valve >>>>> stem and cause a blow out under extreme highload according to >>>>> instructors?!) >>>> ~ >>>> [boggle] I've never hear THAT one!! >>> I think the centripetal force sucks it in to the centre. >>> >>> Theo >>> New to me too. >> >> FWIW I have *heard* of that issue but it's one of those "mate of a >> mate" stories so I wouldn't call it proven, a friend who used to drag >> race professionally in the 70's and 80's (in the US but he's an >> Aussie, no not Bray :-) ) told me about that one quite a few years >> ago, claimed to have had it happen to a drag car he built - can't >> prove it either way though. >> >> JL >> > I've met someone who claims it happened to him at the end of the main > straight at PI. Front tyre inexplicably deflated. No damage to tyre. > > He's not someone whose word I doubt, and having seen him ride he's not one > who needs to make up stories. > > Says the problem was fixed by replacing the valve. > OK; I can accept the logic of centrifugal force causing the centre of the valve to pull down (towards the outside of the tyre) at high speed and letting the tyre deflate. (Sorry Nathan; I didn't understand the equation and sorry Theo; I didn't understand the explanation.) -- Clem
From: Iain Chalmers on 6 Feb 2007 03:37 In article <45c80c97$0$25315$5a62ac22(a)per-qv1-newsreader-01.iinet.net.au>, "Nev.." <idiot(a)mindless.com> wrote: > if the moving parts > of the alternator are in constant motion which is determined by the > crankshaft, and is producing a supply of electricity, and the current > produced is drawn on my the engine electrics, other electrics, whatever > is left is stored in the battery, and whatever is left over after that > disappears into void, and the load on the crank of the moving parts of > the alternator is constant, how does adding more load to the alternator > output increase the physical load on the crank and increase fuel > consumption? On the off chance that you _really_ want to know... In your car, you've almost certainly got an alternator with the current in the rotor windings controlled by the regulator - the regulator detects how much electricity is actually being used at any time (including whats required to charge that battery) by measuring the voltage, and it adjusts the current in the rotor which changes the strength of its magnetic field, which in turn changes the torque with which it resists turning and hence changes the power consumption of the alternator. The angular velocity is, as you point out, controlled independently of the electrical requirements, but the torque is variable and so the power output (and consumption) is variable. So you don't have "left over" electricity "disappearing into the void" because you don't have a constant load on the moving parts of the alternator. (think of it as being like the difference in the engines output power at 5000rpm at 5% throttle compared to the power at 5000rpm at 100% throttle) In your bike though, you probably have a permanent magnet alternator. In these you do have the alternator generating power proportional to the angular velocity, and you do in fact have "left over" electricity which ends up generating heat in the regulator/rectifier - ask any VFR owner about the cpu heatsink mod's they all do to their reg/rects... (It's actually not always _quite_ as bad as that makes it sound, at least some 3 phase systems on some bikes will balance two phases against each other to cut output by 66% when it's not needed so you don't end up with a glowing red regulator whenever you ride around without your lights on - my 99 Monster does this but the Monsters from a few years earlier only ran two phase systems where this trick doesn't work...) big -- "Everything you love, everything meaningful with depth and history, all passionate authentic experiences will be appropriated, mishandled, watered down, cheapened, repackaged, marketed and sold to the people you hate." Mr Jalopy quoting Hooptyrides (on jalopyjunktown.com)
From: Dale Porter on 6 Feb 2007 03:38 "Knobdoodle" <knobdoodle(a)hotmail.com> wrote in message news:XFWxh.3542$sd2.564(a)news-server.bigpond.net.au... > > "G-S" <geoff(a)castbus.com.au> wrote in message news:12sg9upj9fcbc38(a)corp.supernews.com... >> Nev.. wrote: >>> >>> My alternator keeps my battery at a full charge, which means it must be providing more charge than I actually use, all the time, >>> which means that any charge required for accessories like lights and radio is being produced all the time, regardless of whether >>> or not I'm actually using them, which means that no more fuel is required. >>> >>> How's that for logic? >>> >> Going well until the last bit which should read... "which means that fuel use varies partly according to alternator output" :) >> > Well yessss... but I think Nev's point was that the alternator output is not affected by headlights, accessories, etc,.. so that's > not something you have any control over. > -- > However Nev has oversimplified. An alternator will only produce the required amount of amps needed to run the operating electrical systems in the car (charging, lights, stereo, heater/air-con fan, etc) up to the output capacity of the alternator. As the amp demand increases, so does the load on the alternator, which in turn puts an added load on the engine running the alternator. So yes the battery will stay charged provided the power demands of the alternator are not exceeded, but that does not mean there is constant load on the alternator up to it's production limit. -- Dale Porter GPX250 -> CBR600 -> VTR1000 + VT250F-J
From: Iain Chalmers on 6 Feb 2007 03:42
In article <O0Xxh.3553$sd2.9(a)news-server.bigpond.net.au>, "Knobdoodle" <knobdoodle(a)hotmail.com> wrote: > OK; I can accept the logic of centrifugal force causing the centre of the > valve to pull down (towards the outside of the tyre) at high speed and > letting the tyre deflate. (Sorry Nathan; I didn't understand the equation > and sorry Theo; I didn't understand the explanation.) Whether it's a "real world" effect or not I don't know, but that's the marketing spin Ducati use to hype up the 90 degree valve stems they use on the 99* and 74* range... big -- "Everything you love, everything meaningful with depth and history, all passionate authentic experiences will be appropriated, mishandled, watered down, cheapened, repackaged, marketed and sold to the people you hate." Mr Jalopy quoting Hooptyrides (on jalopyjunktown.com) |