exchemist

I'm sure this is right. My assessment of Khamenei's policy was to enrich to just short of bomb grade and stop there, so that Iran could plausibly say they had no bomb ambition, but to have in reserve the capability to get there very quickly if conditions were to change such as to require it. They probably foresaw exactly the kind of pre-emptive attack by the USA and Israel that has just taken place. That would make them wise planners, not "mad mullahs". The notion they would invite destruction of their country in a retaliatory strike by Israel, if they were to nuke Israel first is I think quite absurd. Though it is what Israel has hysterically been working on the Americans about for years. The whole notion of mad mullahs misjudges them entirely. There is no evidence the Iranian regime is irrational. Quite the contrary, as recent events have shown. Brutal at suppressing dissent, yes, of course. Irrational, no.

Paraffinic heavy ends would resemble light luboil, so I’m not sure it would be that much of a problem. After all, diesel engines are built to a very similar design and don’t get gunged up. But there could be trouble with the carburettor, I’d have thought, with atomisation of the fuel.

Indeed, in fact 7.5:1 according to Wiki, with the original 803cc version. : https://en.wikipedia.org/wiki/BMC_A-series_engine By the time my Minor was built it was 948cc and a compression ratio of 8.3:1, eventually raised further to 8.8:1 by the time of the 1275cc version in the go-faster Minis, in the 1970s. It seems that, after the revamp to the A+ the same basic engine continued until 2000, by which time the compression ratio was 10.1:1. Power output was originally 28hp and in the final version was up to 76hp. Quite an evolution. But I think one does tend to get this with IC engines. The 16SVT in the Class 40 diesel locomotive was rated at 2000hp, 2700 in the Class 50 (with intercooling) and in the much later Class 56, 3250hp. I've seen similar progressions with marine diesels. It seems because a new engine is such a big investment, the basic fixed components like the block are often generously designed to allow a lot of subsequent development.

I had an awful feeling it might come to this. Let's hope the military professionals hold the line against insanity. I have a fair degree of faith in them. Especially since it is increasingly evident that the president is off his rocker.

That's nonsense. There is no justification for this attack. Iran posed no immediate threat of any magnitude to the USA. No credible level of threat has even been asserted, much less corroborated. Furthermore no clear war aims have been articulated. Nor is this in any way a war of perception. It is a war with very practical consequences. These include civilian deaths in Iran including a school full of little girls, serious damage to Iranian infrastructure and civic buildings and to oil, gas and American military installations in the Gulf States. It is having a major effects on economies right across the world. As for "perception", the perception is that Trump has screwed up. Badly. Thanks to this ill-conceived operation, Iran has learnt what a powerful negotiating card they have in closing the Strait of Hormuz, something they had never before attempted. And they still have the military means to do that, because all they need is a few drones, which they have been mass-producing for years and which can be launched from almost anywhere in the country, which is vast. There is almost nobody outside the White House who thinks this is going well, or that any outcome will be better than could have been achieved by the negotiations that were broken off by the US when they decided to attack. And the cost of it all is huge.

The A40 had the same A-series engine as the Minor. My Minor was 948cc though there was a 1098cc version and even, in some later Minis, a 1275cc version. But quite small engines and I suppose feasible to crank by hand. I think there was a free end of the crankshaft at the front to which a crank handle could be fitted, as your picture of the A40 shows. But I didn’t have a crank handle for it and would never have dared to try that. If the battery went flat one would get some mates to give it a push, just as my son now does with his Fiat Panda, or use jump leads.

Ah yes, that’s it. So originally all the timing adjustment was manual, without any automatic centrifugal or inlet manifold compensation. So the driver tuned it by ear, presumably optimal just before the onset of pinking. And sure, if you did not fully retard the spark when cranking, the engine could fire backwards, in which direction the ratchet would not disengage, so the handle would whizz round, potentially breaking your arm. But I can’t help thinking there may have been an intermediate point, later on, when automatic compensation had come in but there was still a need to adjust for variations in octane number of the fuel.

Yes but again nothing about how a driver would use the manual adjustment on old cars. Nice MGB GT, though. I had a teal blue roadster in the early 80s. XDL152L. I looked up the reg on DVLC a couple of years ago - and she’s still going! I sold her when I went off to Dubai in 1983.

Ah so it was indeed to do with variability in octane rating of the fuel. But would this have been in place of the kind of automatic adjustment of ignition timing I described on my Morris Minor, or just a supplementary control, to extend the range of adjustment to cope with fuel variation? I have now looked up the history and found the concept of "octane rating" appeared towards the end of the 1920s. It looks as if the run up to WW2 led to development of high octane aviation fuel. Shell apparently pioneered "100 octane" aviation fuel, which became adopted as standard in the high compression ratio turbocharged aviation engines of the time. However there was no real standardising of octane ratings in road-going motor fuel until the 1950s. So maybe this accounts for the need to alter the timing manually, depending on the quality of fuel available.

That is why one needs the ignition timing to vary with engine speed and load but my question was not that. It was about why it was apparently controlled manually on early vehicles and what would be the circumstances under which the driver would adjust it.

I am somewhat intrigued by the bit about the spark being advanced. I seem to recall the spark advance was controlled pneumatically on my old Morris Minor (1961 model) by a diaphragm in the distributor, connected to the low pressure in the inlet manifold. But I have a faint memory of being in an ancient vehicle, perhaps a school bus, in which there was a control on the dashboard with "advance" and "retard" on it, presumably so the driver could alter the ignition timing manually. Seems rather extraordinary. Was this common in the early motoring era and why was it done? I wonder if it was before fuel ignition quality (knock rating) was standardised.

So are removable oven doors. Maybe this topic will get all us oldies fessing up to various mechanical amateur repair experiences. I’m reminded of James Thurber’s comments on psychological traumas inflicted by early motor cars:”Yonder toddles an ancient who once tried to crank an old Reo with the spark advanced…”

In my limited experience, trying to repair anything with a spring-loaded mechanism is fraught with danger. There is often some kind of mechanical advantage issue, whereby the spring needs to be very powerful to exert force at what is in effect the wrong end of a lever. Fiddling with such things is a recipe for taking your finger off or something.

For some reason it seems to be only the Italians that have exploited this, in their aliscafi on the Italian Lakes (and Emilio Largo’s Disco Volante in Thunderball) I remember someone once made a hydrofoil bicycle, with a propeller driven by pedals, which could just about beat a sculler in a racing shell. The snag was it had to be launched artificially, as the energy barrier to getting it up on its foils was too much for the athlete pedalling.

I'm no physicist but I had understood there is an unresolved incompatibility between the two, i.e. as the two theories stand today if one is right then the other can't be, and that is why there is a search for a resolution that unifies them. But no doubt a physicist will show up and explain.

This "Engineering Made Easy" is a YouTube Indian woo channel: https://www.youtube.com/@EngineeringMadeEasy There is a whole bank of videos taking turd about "spirituality". It has nothing whatsoever to do with either engineering or science. I think this poster is just spamming. It certainly does not belong in the Physics section anyway.

What great flood has science proven? Please provide a reference.

Interesting example of a faux ami. I gather the English word calamity comes, via Old French, from Latin calamitas, which has no connection to calamus.

Yes of course they are not real. There is all kinds of stuff on the internet, a lot of it fictional or misrepresented. You must know that, surely? Anyone with any sense will check the sources of what they find by browsing the internet, to see whether it is what it may initially seem to be and if it is genuine. This is basic critical thinking in the internet era. When I saw your picture of the giant skeleton, I looked up "giant skeleton picture" on the internet and within 30 seconds I had a written explanation of this Milan sculpture, complete with telltale details about the long nose the sculptor includes as a "signature" feature and which you can see in the picture. So the moral of this story is: do at least a bit of basic research before asking questions that risk making you look a fool.

Looks like a modern take on Ozymandias.

Sure. But with a half life that long, I'd have thought you would never be able to measure a discernible decrease in radioactivity. But thinking more about it, I suppose with a big enough sample, if you can detect every individual decay event, you can count the decays of individual atoms and, knowing how many atoms there are in your sample, you can work out the decay rate that way.

It's a sculpture in Milan, you credulous person: https://www.atlasobscura.com/places/giant-skeleton-sculpture

Uranium-lead radiometric dating makes use of an isotope with a half life of billions of years: https://en.wikipedia.org/wiki/Uranium–lead_dating Mind you, I’m buggered if I know how the hell they determine a half life that long. Must be by dating rocks using other, shorter, half lives, I imagine, and then inferring from that the half life of U238.

Oh yes sweetbreads are very good. I've had them on a couple of occasions and thought they had a slightly similar taste to that of liver, though far more delicate. But it seems they can be two types of offal: either the pancreas or the thymus gland. I can understand why the former might have a taste similar to liver but, not really the thymus gland. (By the way, the reference to thymus glands reminds me of the idiotic story of a man allegedly strangled by his own thymus gland in cold weather, posted on another forum by a nutter who specialises in posting daft questions and asking, mock-innocently, if there is any truth in them. )

Military Watch Magazine appears to be an outlet for Russian propaganda: https://mediabiasfactcheck.com/military-watch-magazine-bias/ I would not trust their figures.