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From: Peter Ceresole on 19 Feb 2010 04:27 Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > Indeed - which makes me think that *IF* Harrison held the opinion you > claim, *IF* your allegation were the case, I think he would have been of > the opinion that his H4 wasn't going to be good enough to do the job > needed, but found that despite his pessimistic opinion of his own > ability, he was better than he thought and the elegant solution (just > take the pocket watch) was a goer. Yes. That's what I was trying to say; it's what the curator of the Greenwich collection told me; these aren't my opinions, they're my memory of what he told me. I haven't see this stuff in print, which may be why you haven't come across it. I just had a long conversation with the curator, illustrated by a tour of their collection; I was preparing a series for the turn of the year 2000, which was eventually never made, but was really interesting to research. By the way, H4 was no pocket watch- or at least, it wouldn't fit in any pocket I have ever seen. Even if it's small compared to the earlier full sized chronometers, it's still a big fat thing. I suspect, although I don't know, that one of the reasons for its great accuracy was the very high frequency of the escapement. As I remember (I can't find a reference, so this is from memory of Greenwich, 12 years ago) the ticking rate was around 20Hz, which is amazingly fast but in a meticulously built mechanism would be more accurate than the 1Hz of the larger clocks. > > No; those were not chronometers and the smaller components were fob > > watches, and extremely inaccurate; > > They weren't as inaccurate as all that, or they'd've been utterly > useless for navigation purposes even if corrected once a day. As I said, they weren't chronometers, and were nothing to do with navigation. They were in fact (very) rich gentlemen's possessions, a fix for the great inaccuracy of contemporary fob watches. -- Peter
From: David Kennedy on 19 Feb 2010 04:42 Woody wrote: > > Ahh - thought it may be leyland as, well, if you are talking about > classic UK management it is the best example. But I couldn't find > anything on google with that name! > The in-house fighting was superb. Jaguar v Daimler, MG struggling for funding, Rover v everyone, a laugh a minute while they managed to run the company into the ground. -- David Kennedy http://www.anindianinexile.com
From: David Sankey on 19 Feb 2010 04:42 In article <1je58ly.1njbd4m1eot1wN%real-address-in-sig(a)flur.bltigibbet.invalid>, real-address-in-sig(a)flur.bltigibbet.invalid (Rowland McDonnell) wrote: > Bruce Horrocks <07.013(a)scorecrow.com> wrote: > > > Peter Ceresole wrote: > > > Chris Ridd<chrisridd(a)mac.com> wrote: > > > > > >> Even modern digital clocks drift quite a lot, so it isn't surprising > > >> that all of his reported different times. > > > > > > <http://www.sciencedaily.com/releases/2009/04/090416144525.htm> > > > > > > One second in 300,000,000 years. I guess it'd do me. You'd need a big > > > fob pocket for it, though. > > > > I had a very enjoyable little tour round NIST last year. The actual > > clock they use for the broadcast time signal is an off-the-shelf atomic > > clock, which they are able to calibrate extremely accurately. > > My word, who'd've thought it! A national standards lab being able to do > accurate calibration... Sorry, sorry... > > > It's kept > > in an environment controlled chamber aka a commercial chicken egg > > incubator. :-) > > They need cheap temperature stability, at a guess. > > The gadget itself is temperature stablized and compensated to hell and > back (I assume - it would be if I designed it), so they don't need > super-duper temperature stability, I wouldn't have thought, just a wee > oven to keep it more or less right there. > > There's a lot of stuff like that - odd bits of `kit from unexpected > sources' that turns up in hairy labs. Always good for a giggle, I find > - and always a lesson in appropriate technology that the wise pay > careful attention to. Yip. When we want something temperature stabilised a few degrees below 0 degrees C we tend to stick it in a polystyrene box with a heater inside a domestic freezer. The freezer provides cheap cooling and we stabilise the temperature with the heater, at a cost an order of magnitude less than a proper temperature stabilised freezer (domestic fridges and freezers tend to follow so many degrees below ambient temperature rather than hold an absolute temperature). Back on time, where we really care we no longer use the radio signal, rather we have one or more GPS receivers to give local stratum 1 time servers feeding stratum 2 servers that feed the clients. The stratum 1 servers are on average good to a few tens of ns with a jitter of a few us, see for example <http://service-ntp.web.cern.ch/service%2Dntp/>. Kind regards, Dave
From: Rowland McDonnell on 19 Feb 2010 04:49 David Sankey <David.Sankey(a)stfc.ac.uk> wrote: > real-address-in-sig(a)flur.bltigibbet.invalid (Rowland McDonnell) wrote: > > > Bruce Horrocks <07.013(a)scorecrow.com> wrote: [snip] > > > It's kept > > > in an environment controlled chamber aka a commercial chicken egg > > > incubator. :-) > > > > They need cheap temperature stability, at a guess. > > > > The gadget itself is temperature stablized and compensated to hell and > > back (I assume - it would be if I designed it), so they don't need > > super-duper temperature stability, I wouldn't have thought, just a wee > > oven to keep it more or less right there. > > > > There's a lot of stuff like that - odd bits of `kit from unexpected > > sources' that turns up in hairy labs. Always good for a giggle, I find > > - and always a lesson in appropriate technology that the wise pay > > careful attention to. > > Yip. When we want something temperature stabilised a few degrees below > 0 degrees C we tend to stick it in a polystyrene box with a heater > inside a domestic freezer. The freezer provides cheap cooling and we > stabilise the temperature with the heater, at a cost an order of > magnitude less than a proper temperature stabilised freezer (domestic > fridges and freezers tend to follow so many degrees below ambient > temperature rather than hold an absolute temperature). Oooh! I like that. And I bet the heater can be something like a 5W resistor in many cases, yeah? > Back on time, where we really care we no longer use the radio signal, Hmm - why not? > rather we have one or more GPS receivers to give local stratum 1 time > servers feeding stratum 2 servers that feed the clients. The stratum 1 > servers are on average good to a few tens of ns with a jitter of a few > us, see for example <http://service-ntp.web.cern.ch/service%2Dntp/>. 2ns is `accurate to 2 feet'. Ish. (1' is 1ns at lightspeed, ish) Are you really getting `time on the ground' or `time where the satellites are', or what? I know nothing about the details of GPS operation. Rowland. -- Remove the animal for email address: rowland.mcdonnell(a)dog.physics.org Sorry - the spam got to me http://www.mag-uk.org http://www.bmf.co.uk UK biker? Join MAG and the BMF and stop the Eurocrats banning biking
From: Graeme on 19 Feb 2010 04:55
In message <1je5jrv.19n95lnr6mq4gN%real-address-in-sig(a)flur.bltigibbet.invalid> real-address-in-sig(a)flur.bltigibbet.invalid (Rowland McDonnell) wrote: > Graeme <Graeme(a)greywall.demon.co.uk> wrote: > > > real-address-in-sig(a)flur.bltigibbet.invalid (Rowland McDonnell) wrote: > > > > [snip] > > > > > > There's a lot of stuff like that - odd bits of `kit from unexpected > > > sources' that turns up in hairy labs. Always good for a giggle, I find > > > - and always a lesson in appropriate technology that the wise pay > > > careful attention to. > > > > > > > One bit of odd kit that turned up in a lab was a ZX81 at Sperry's when > > they were doing calibration work on missiles. They needed to do a lot of > > coversions from decimal to binary and vice versa. They didn't want to > > chew up main-frame time and doing it by hand was a pain so I wrote them a > > program to run on the ZX81. Was apparently still in use when the labs > > folded. > > Once upon a time, that would have been done using a programmable calculator > - quicker, at least, unless the ZX81 were wired in to accept non-typed > input. > AFAIK it was conventional keyboard entry. No programmable calculator available at the time I presume. For obvious reasons I never saw it in use. -- Graeme Wall My genealogy website <www.greywall.demon.co.uk/genealogy/> |