Which side is the fuel tank filler on?
in [UK Drivers]
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From: Ian Jackson on 28 May 2010 17:09 In message <lmvFTqDG87$LFwZX(a)g3ohx.demon.co.uk>, Ian Jackson <ianREMOVETHISjackson(a)g3ohx.demon.co.uk> writes >In message <hto2pu$dqk$1(a)heffalump.dur.ac.uk>, Albert T Cone ><a.k.kirby(a)durham.ac.uk> writes >>Ian Jackson wrote: >>> In message <htjasi$ab4$2(a)heffalump.dur.ac.uk>, Albert T Cone >>><a.k.kirby(a)durham.ac.uk> writes >>>> boltar2003(a)boltar.world wrote: >>>>> On Wed, 26 May 2010 14:55:58 +0100 >>>>> Albert T Cone <a.k.kirby(a)durham.ac.uk> wrote: >>>>>> Another way to imagine it is that, given a low-resistance path to >>>>>>earth, the charge on the car will discharge to earth in a very >>>>>>short time, producing a short current pulse (with a high peak >>>>>>value, hence the putative spark risk), in which the bulk of the >>>>>>energy is contained in high frequency (RF) components. The >>>>>>effect of the rings is to increase the reactance of the >>>>>>conductor preventing a short current pulse and reducing the peak >>>>>>current the concomitant spark risk. >>>>> Ah ok. They're just acting like inductors in other words. >>>> >>>> Indeed. >>> Maybe I'm sticking my neck out a little, but I think that >>>explanation is simply not true. It may be why they put the rings on >>>the hoses (assuming they are ferrite - which I doubt), but the >>>increase of inductance obtained is unlikely to have any appreciable >>>effect on the amplitude of a spark discharge. >>Indeed it does. Not excatly the same application, but the same >>physics, if you are interested: >>http://cdsweb.cern.ch/record/556605/files/fpah302.pdf >> >I've had a quick look at the article but, apart from sharpening up the >high-voltage pulses, I don't immediately understand what else happens. >[I also think it suffers a little in the translation from Russian.] It >needs to be read very carefully. > >>Even the few microhenries offered by a handful of rings offers a >>reactance of several ohms at frequencies in the MHz... >> >>> It all sounds like a mixture of snake oil and 'SWAR' grease! >>Dickering about with forces wot we didn't ought to wot of, eh? > >The object of the exercise seems to entail sending high voltage pulses >down coax cable. If the ferrites embrace both the inner and the outer >conductors, I feel that what the ferrites are doing is to force the >pulse 'signal' to propagate in a differential mode, and to suppress any >tendency for common-mode propagation (possibly caused by, at RF, >less-than-perfect mutual bonding of the 'earthy' side of the system - >especially as the pulses are required to have very fast rise-times, and >therefore considerable high frequency content). > >However, the effect of the ferrites on the propagation in the coax >lines (130 of them on each!) will be quite different from that of a >couple of ferrite rings loosely slipped over a single conductor - >which, our situation, is the hose of the petrol pump. I'm yet to be >convinced that the rings are, in fact, ferrite, and are not rubber or >plastic, put there to reduce scuffing of the hose on the ground. I still haven't de-ciphered the article, but I've had another thought. At low frequencies, coax loses a much of its screening properties. Also, its characteristic impedance becomes much higher than the 'expected' value. A nominal 50 ohm cable could possibly rise to several thousands of ohms. A sharp electrical pulse will cover a large frequency spectrum (from DC to many MHz), and a frequency-dependent characteristic impedance will cause the shape of the pulse waveform to become distorted (broaden). I suspect that encasing the coax in what is effectively a tube of ferrite will force the coax to retain its properties down to a much lower frequency, allowing the pulse to pass with less distortion. But all this waffle is little to do with the anti-scuff rings on fuel hoses! -- Ian
From: Ed Chilada on 29 May 2010 05:54 On 28 May 2010 16:12:34 GMT, Adrian <toomany2cvs(a)gmail.com> wrote: >Ed Chilada <nospam(a)nospam.com> gurgled happily, sounding much like they >were saying: > >>>Indeed. Try asking a few 'ordinary' motorists about the >>>advantages/disadvantages of bigger wheels and see what they come up >>>with. > >> Bigger wheels have a larger circumference and therefore cars with bigger >> wheels are faster. > >Would you like to do the maths based on (f'rexample, for that Astra) >205/60 16, 215/50 17 and 225/45 18? > >No, thought not. > >Clue : +/- 1%. Clue: It was a joke <facepalm>
From: Adrian on 1 Jun 2010 05:03 Ed Chilada <nospam(a)nospam.com> gurgled happily, sounding much like they were saying: >>>>Indeed. Try asking a few 'ordinary' motorists about the >>>>advantages/disadvantages of bigger wheels and see what they come up >>>>with. >>> Bigger wheels have a larger circumference and therefore cars with >>> bigger wheels are faster. >>Would you like to do the maths based on (f'rexample, for that Astra) >>205/60 16, 215/50 17 and 225/45 18? >> >>No, thought not. >> >>Clue : +/- 1%. > Clue: It was a joke <facepalm> Ah, that old "Whoops, I fucked up - how do I try to recover some credibility?" excuse...
From: boltar2003 on 1 Jun 2010 05:08 On 1 Jun 2010 09:03:39 GMT Adrian <toomany2cvs(a)gmail.com> wrote: >Ed Chilada <nospam(a)nospam.com> gurgled happily, sounding much like they >were saying: > >>>>>Indeed. Try asking a few 'ordinary' motorists about the >>>>>advantages/disadvantages of bigger wheels and see what they come up >>>>>with. > >>>> Bigger wheels have a larger circumference and therefore cars with >>>> bigger wheels are faster. > >>>Would you like to do the maths based on (f'rexample, for that Astra) >>>205/60 16, 215/50 17 and 225/45 18? >>> >>>No, thought not. >>> >>>Clue : +/- 1%. > >> Clue: It was a joke <facepalm> > >Ah, that old "Whoops, I fucked up - how do I try to recover some >credibility?" excuse... Seemed like a pretty obvious tongue in cheek remark to me. B2003
From: Ed Chilada on 4 Jun 2010 12:27
On 1 Jun 2010 09:03:39 GMT, Adrian <toomany2cvs(a)gmail.com> wrote: >Ed Chilada <nospam(a)nospam.com> gurgled happily, sounding much like they >were saying: > >>>>>Indeed. Try asking a few 'ordinary' motorists about the >>>>>advantages/disadvantages of bigger wheels and see what they come up >>>>>with. > >>>> Bigger wheels have a larger circumference and therefore cars with >>>> bigger wheels are faster. > >>>Would you like to do the maths based on (f'rexample, for that Astra) >>>205/60 16, 215/50 17 and 225/45 18? >>> >>>No, thought not. >>> >>>Clue : +/- 1%. > >> Clue: It was a joke <facepalm> > >Ah, that old "Whoops, I fucked up - how do I try to recover some >credibility?" excuse... Er.. riiight, yes that's right if it makes you feel better about it. Sorry if I didn't add a smiley or something but it seemed pretty obvious to me. |