Member postings for Nigel Graham 2

This thread risks the dreaded "P"! word, and I don't mean ticket-machines or 3am expeditions along the landing.

However, since anything imported by any EU nation needs comply with its rules including SE assessment where applicable, irrespective of country of manufacture, I do wonder why it was thought necessary, and by whom, to drop the CE laws in favour of the same with a different name. All this legalistic , politicised manouvering does is make life awkward for manufacturers and test-laboratories.

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Anyway the only people who really benefit are the so-called "Notified Bodies" (notified of what? ) and lawyers. Read the original PER 2000 and as I recall the word safe appears hardly at all. One clause says something like, "... and in fact has to be safe" , as an afterthought.

Oh, and it all refers to only two pressure-vessel materials - stainless-steel and aluminium! So come one, who says we can't have stainless-steel boilers, even if practicably a trade-only product.

DAVE W -

No-one is advocating positive ways to reduce the population. Well, I hope not. China tried but found it led to very undesirable results. The most anyone can hope for a is a gentle decline so the overall population does not become unbalanced in proportions of sex and age.

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Martin -

The "boiling" metaphor was used by one politician, (head of the UN?), so what do we expect but silly language; though presumably others have latched onto it in the usual ovine way.

Anyway he was taking about the world at large, and some areas' heatwaves in particular, not just our gentle small region of it.

The forest fires thought to be by arson were not started in populated areas, but near enough to them to be at the very least extremely unpleasant or indeed dangerous.

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Duncan -

Not only itself a silly "unit" that looks as if quoted from an advertisement. Assuming constant heat-flow (can that be assumed?), it is a mere 0.25kW/h, and anyway means nothing without the system's output temperature as well.

A heat-pump is fine within its limits: it needs to be connected to a system suitable for it (which may mean replacing all the pipes and radiators), in a home insulated and ventilated suitably for it (which means many existing houses are not.

Cost may reduce and reliability might increase with time; but you can't beat physics and they will not heat water to the same temperature as a combustion-type boiler will; hence needing an auxiliary, electric immersion-heater tank.

In theory at least the heat in the atmosphere is practically inexhaustible but an air-source pump seems to work better the lower the temperature-range for a given heat transfer (hence given electricity consumption). While others have pointed out they can freeze up, so presumably need an internal heater just to keep them defrosted!

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What is the advantage of a ground heat-pump over air one?

The ground does not freeze beyond a short depth: it is rare except perhaps in parts of Scotland for that to exceed about a foot down. (Earthworms survive by burrowing below the frost.)

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What is its disadvantage?

Apart apparently from needing a very large pipe array to be any use, the one question I have never seen asked is of depletion by the specific pump in its specific location.

Can it remove more heat from the finite volume of ground it uses, faster than Nature can replenish it? That rate will depend very heavily on the local geology and meteorology. They would probably be influenced further if all the surrounding homes use them too, and perhaps very variably as different households use theirs at different rates.

With a long, cold spell perhaps with a lot of cloud cover, or indeed snow, minimising warming from the Sun, combined with very low local heat conduction through the local rocks from deep below, how long will an individual pump's patch of ground take to regain the temperature and amount of heat it enjoyed prior to switching the worm-fridge on?

Longer, I suggest, than it took to cool it.

Conversely, if we determine the maximum heat extraction for the specific heat source, will that be sufficient to be at all useful for any more than frost-protection?

I suspect the proponents of ground-source heat-pumps look at areas of very high geothermal activity - as in Iceland but rare and far less powerful in Britain - as their exemplars, and will not think about real use in this country's extremely varied ground , weather and artificial (man-made) conditions.

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I agree with Samsaranda but I am afraid the root of the problem - too many people - is probably the hardest of all to address in any sane, humane way. That's why it is hardly addressed at all.

Anecdotally there are already couples choosing not to breed through fears of what their offsprings' world may be; but to what extent is another matter. Almost certainly the number of such couples is too low to be significant, and will stay so unless it becomes a very widespread fear, one enough to over-ride a powerful natural instinct in enough people.

The "Third" (or "Developing" as they seem to prefer) World people cannot be blamed for wanting more and better. They see the rich countries wasting precious resources such as water on idiocies like lawns in deserts... many of them lack clean, reliable, potable water just for drinking. At least the water is not finite, as metals and oil are: it all returns to the sea eventually. Similarly they can't be blamed for wanting fancy electronics or cars: many of them would not mind a simple telephone and local buses. (Nor would many in this country, mind having the latter...)

I fear whatever we do, the future is grim, maybe not as closely as 2050 but certainly much beyond that.

Sorry, I should have been clearer. Radius of the bar, not of the thread crest. I said it leaves a flat.

Gray -

Heat-pump efficiency.

I heard that misleading figure suggesting [energy out = 3 X energy in], as well.

I suspected a muddling of Heat and Temperature, in the same way I heard one correspondent on the radio using Latent when he meant Specific Heat; but I turned to one of my old text-books. I recalled it describing not "heat-pumps" as we call them now, but A Reversed Heat-Engine As A Warming Machine, in a chapter on refrigerators. That terminology had me foxed for a time, as i was looking for "heat-pump" !

These things are not new, but the book describes the principles of commercial plant, not domestic appliances, though the physics would be the same.

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What we call a "heat-pump" relies on the amount of Heat moved being many times greater than the Work Done, which it will be if the Temperature change is low.

If H = the heat energy taken from the atmosphere at temperature t,

h = heat delivered to the room at temperature T,

W = work expended in heat units:

H/W = h / [ h-H] = T / [T -t ]

. The text then gives a worked example, presumably a real case though un-named, a refrigerator used for cooling an auditorium in Summer but reversed to warm it in Winter. The machine was driven by an oil-engine. (The book's latest impression was in 1942, hence that motive-power and all-British units.)

The temperature range ( T-t ) = (55 - 40) ºF.

The engine, we are told, used 0.5lb of oil per BHP per hour; at 20 000 Bt.H.U. / lb. .

After some sums, we have 69,900 BtHU of heat delivered to the auditorium, whereas burning that oil directly, in a lamp, would yield only 10 000 Bt.H.U. over that hour.

The text also calculates the system's efficiency, that of the engine being about 25%, the "warming machine" 80%.

It also points out more heat is available from the engine's exhaust and cooling-water, to 7460 Bt.H.U. - making the total for heating the theatre 77,360Bt.H.U. / H.P. hour.

So although not very intuitive, and I found it hard to grasp, the heat-pump transfers more energy than it consumes, by working over a modest temperature-range. That though, is one factor limiting the output temperature.

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The above is for air-air transfer; and at 40ºF, not especially cold for a British Winter day! I don't know the effect of heating water, with its different specific heat.

Also of various experiences aired on the radio, some have reported very good results from installing a heat-pump, others wish they had not, with high installation and running costs making it a loss. Some of the running-cost will presumably be the immersion-heater tank necessary to raise the water temperature to what it should be, about 55ºC.

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Reference:

Wright Baker, H. (rev. & ed. by), Inchley's Theory of Heat Engines, Longmans, Green & Co., 1st pub. 1913, last imp. 1942. pp.317-318.

Paying for the brand, not the value.

What's the betting the fuel-cap and the key-fob have identical equivalents for other but much cheaper cars, for which they are sold at much nearer their true cost?

It was a VW / Audi main-dealer who told me of that trick, although I had heard of it previously. The German firm has two huge warehouses, he explained, one labelled VW, the other Audi. The two ranges have many common parts but the warehouses store them in separate boxes with different labels and part-numbers by the appropriate brand, price them by make and model - and of course insist you must fit only brand and model OEM parts.

(I think the OEM scam is by rigid law in Germany - a gift to the car makers. Indeed, the law was quite likely by the trade's idea and lobbying!)

John Doe -

Building standards are being improved greatly, but that does not account for all the existing ones, nor for the big increase in insulating materials needed. A builder whom you might expect would find it profitable, once told me that increasing the insulation of individual homes reaches a point where it is actually less "green" than it seems. (He also frankly admitted it would be too costly and wasteful to fit his own home, a 1930s ex-Council unit, with a heat-pump, despite no labour-charges - not something you'd expect to hear from an accredited plumber!)

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Steam locomotives are indeed very inefficient but I am not sure they are relevant here. Nice to watch though!

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Solar "farms" in fields: apart from unsightly, the serious objection is taking very large areas of land that should be producing food, for relatively low output for their scale. There is also some NIMBY speculation here by the builders choosing rural areas far for their intended customers in London or other major cities. They also turn the land from agricultural to industrial use, for tax purposes, an important point for landowners to consider.

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Tidal Flow (submarine equivalent of wind-turbines) - I agree. Actually British firms are among the word's best at designing these but we've governments set on wind and sunlight, so not encouraging them. I think a tidal-flow scheme is being built by the Shetlanders?

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Re(?)-foresting. Apart from aesthetics, this is already encouraging swathes of ecologically harmful, monocultured, import-species pines in neat rows, by major companies with no interest in the countryside or the environment at large, just for "carbon-trading" and "green" posturing. A lot of the Welsh and Northern English moors are also sheep-grazing land.

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Ground-source heat-pumps next to every house? Fine until one cold day your heating all goes off because your pump has extracted heat from the ground much more rapidly than its natural replacement rate. Even worse when every home along the road has the same installation. Although not affected by cold fronts as I imagine an air heat-pump could be, this depletion, analogous to pumping a water-well dry, may be why we don't hear much about ground heat-pumps. Also, as with air ones, the maximum amount of heat energy and its temperature would be quite low, few existing homes are suited to it, and installing one could mean replacing the entire heating-system and putting in masses more insulation.

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New homes next to railways, with new stations (by your suggestion, potentially one every mile!). Hard to see how that can be achieved. Such ribbon-development, like most NIMBY (i.e. not in the speculator's back yard) estates now, would take no account of local geography, needs, services, other transport, etc. There are sprawling housing-estates being built around the country, within a few miles of existing main-line stations, but aimed mainly at London commuters, even 100 miles from the capital. A billboard I saw advertising a new estate near Banbury boasted of its 45-minute train times from there to London.

(Brimsmore Estate's 3000 houses, just outside Yeovil, was advertised by double-page spreads in the London Evening News. A friend, a local man, living in Yeovil told me there is very little local employment available for such estates, but by train it is about 100 miles from London and 50 from Bristol, the latter offering the more efficient rail route from the South-West to Wales, most of England and Scotland.)

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Re-opening branch-lines closed not by Dr. Beeching but by a government wanting to do that. He was the consultant: it was really the Ernest Marples Plan, after the Minister of Transport who held a lot of shares in a motorway-building company and thought the future lay in road transport anyway. I think Barbara Castle managed to rein the anti-rail lobby in a bit.

This is good idea where possible, and a few have been rebuilt as Network Rail, not heritage, lines. It is not practical in most cases because under the plan, British Railways rapidly sold key areas - junctions, stations and lengths of track-bed - for development of buildings and roads, precisely to prevent any future re-opening.

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"National, integrated plan." What, as if by a joined-up government?

Fortunately we are not China, even if we do give away vital assets to it. Unfortunately though we lack that nation's ability or will to make long-term, integrated plans based on governments of (in our, not its, case) all hues thinking ahead and understanding anything related to science, engineering and business. (Knowing only Annual Accounts and Dividends, is not good enough!)

Some while ago I read HS2's official web-site. I do not know if the management has improved since, but not one of its named Directors was an Engineer, let alone anyone with any stated railway building, operating or service-selling experience. They were all support staff, necessary but still support roles: legal, personnel, accounts. Oh, and some mystery magisterium called "Director of Strategic Partnerships". I rest my case.

Really, if it is a "climate emergency" it is because we face serious problems that were becoming evident but largely swept under the hearth-rug decades ago.

At one time people talked happily about "taming Nature" but we are now learning Nature can't be tamed, and if we bite it, it will bite back, and bite far harder.

No, "we" won't "boil to death" but if heat-waves in Southern Europe and parts of the USA become more frequent and severe, many will die from heat-stroke while many more will place enormous collective strains on their electricity supplies by trying to run air-conditioning systems flat-out.

While the loss by policy or depletion of minerals like petroleum will also mean the major loss of all those materials equally as important as Diesel fuel.

Fuel? Fine - let's see how we can use hydrogen as a fuel for ships, trains, agricultural plant (JCB is working on that), etc; but how do we generate enough electricity to produce the gas? Oh, from offshore wind-turbines and on-shore solar arrays.

Oh dear... though, no more materials readily made and effective in use for making, installing and servicing such plant; and how much food-producing land do we need lose to solar arrays (and to the bison-cuddlers and corporate tree-monoculturalists)?

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What of water?

Oh dear... no more polythene for the water-mains, assuming we can still find enough electricity for the pumps. Copper becoming rarer, too, by increasing demand and over 90% of the world's reserves all now owned by China. Best start using iron and lead pipes again. At least metals are salvageable, with some attrition, but not enough can be returned to cope with the demand.

I have yet to follow it up to establish the sources, but I have a leaflet printed with pretty-coloured ink (made from??), published by something calling itself "Weymouth Climate Hub". New to me but as far as I can tell, a group with rather more knowledge, sense and manners than "Just Stop All" , though still stuck on "energy" - only, and that as a synonym for "electricity".

The leaflet carries a map of predicted stress on water supplies by 2040, by bands of ratio of consumption to supply.

The worst-affected (averaging >40%) are unsurprisingly Iberia, most of the Middle East, North Africa and Eurasia, Australia and the entire USA including (surprisingly) Alaska. The UK and France are rated as at Medium to High Risk, 20-40%: higher than Canada, Russia - and most of Africa! The figures probably reflect not just population density, but how mains water is used, and its availability.

The WCH gives its web-site as holding the necessary citations.

Awful problems, awful quality of public debate - and no easy answers.

Chris -

You raise a very important point about the electricity used by the Internet; and the problem has been raised many time but so far no-one seems to want to do anything about it. The biggest single culprit appears to be digital currency; but the drive for ever-faster broadband for mainly entertainments-carrying can't help.

Your observation about reverting to using fuels from fossil minerals misses that even if in time we decide to do that, they will anyway run out in time, earlier still if their consumption rises as it has been doing. New reserves are still being found but it is becoming harder and costlier to do so, the rising population and its development raise demand, the resources are finite and no new reserves will develop within the likely span of our own species as a whole*.

We did not start burning coal at any significant rate until the last few centuries, and using petroleum products started in the 19C; but the great rise in using coal started in the 18C. Until the early 20C coal was the universal fuel for domestic heating, powering factories (and later electricity-generating) and transport. It was also vital for iron-ore reduction and a major source of fuel gas and a range of useful chemicals.

Even then it was causing problems and some early-20C scientists were already warning of possible climate-change, but based on contemporary coal use and giving the danger point well into the 21C.

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*Humans appeared on Earth less than 1 million years ago, though with precursor species up to about 4M y previously. The average life-span for a mammal species seems to be about 3M years. So we've a way to go yet, before Nature withdraws us; but not long enough for new coal and petroleum to be there for our distant descendants. The Coal Measures are between 300 and 400 M years old; most petroleum and natural-gas from around the 100 - 150 My mark; but though they formed in much less time than that and have "simply" lain buried ever since, it still takes some millions of years of the right conditions for the original organic sediments to form, and still more millions to be buried and fossilised under their cover-rocks. And none are being formed now in time for us!

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David -

Yes it is possible, by using hydrogen in electric furnaces, and this method is being at least developed if not already in use in some countries.

In the 1890s a sort of half-way method was invented in Italy and used widely for a few decades; in which a mixture of pulverised carbon (presumably coke), iron-ore and limestone was melted in electric-arc furnaces. It still used carbon but only enough to reduce the ore to iron, so still producing carbon-dioxide but much less in proportion than by having to add coke as fuel.

Yes, a thread should be to the stated diameter but unless you can finish it to the correct profile - with full-form tool, chaser or die- it will have a very sharp V-crest. The reduction is no more than about 0.002" radius, to leave a tiny flat.

For most practical purposes that tiny reduction in contact area is insignificant: tables of tapping-drill sizes can give tapped holes with a much greater truncation, in proportion, than that shaving off a turned thread..

You are right of course about petroleum but trying to get that Petroleum is not a "fossil fuel" into the heads of politicians of all flavours, campaigners, journalists and the General Public is probably akin to rolling a whole barrel of the stuff up Ben Nevis.

Indeed the one thing conspicuously lacking from all the debates / discussions / campaigns / policies / waffle, most loudly by people who seem barely to know what is energy and its relationship to power, is the question of materials.

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Sorry, I don't see your point about coal though. The aim is to "capture" not the "carbon" despite all the silly slogans and headlines, but carbon-dioxide; the main by-product of burning coal. The idea is to reduce and eventually stop using carbon and its flammable compounds as fuel.

Good example of production work!

Be aware that although our lines are not Network Rail distances, they can still be affected by expansion and contraction if quite long and built up too tightly.

We found this in my club, which uses 25 X 10mm steel bar rail, with some in plastic moulded chairs screwed to the sleepers, some with welded lugs with a screw-hole each side of the rail.

There are a few steel cross-ties welded on but not on every sleeper, mainly some with a hole for a stake to give some lateral stiffness to the whole formation on curves where a combination of expansion strains and the behaviour of the clay ground gave us problems.

One part in particular became quite sinuous, and was cured by using L-section fishplates with a narrow flange to support the bar, oversized holes (6.5mm I think, for M6 fasteners) and of course expansion-gaps.

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(In full size the fish-plate is profiled to the rail web, and has elongated holes. I believe it is also greased on the mating surface.)

Food for thought in that lot.

I must admit I'd often wondered the same problem, such as only yesterday when cutting a 1/4" X 19tpi BSP thread and had to creep up on the last bit beyond the theoretical feed depth for the commercially-made union nut to fit.

I was using an insert tool, squared to the chuck face, and direct in-feed, starting from and allowing for a slightly under-diameter surface so as to give a little flat along the crest.

Unusually for me I'd also set the cross-slide to count up to 0, rather than starting from 0 and counting up to depth value. This clearly showed a considerable discrepancy which I put down to accumulations of slight setting error, springing and wear in the lathe (a Myford ML7)... and wear in me.

It had just not occurred to me to consider the geometry. Usually I close-cut a thread then finish with a die but of all the dies I lack or cannot find, 1/4" BSP is one.

So Thank-you, Jim, for asking!

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I have only once had to analyse thread geometry to any extent.

This was to tap the hold-down holes in the four feet on my Harrison L5 lathe cabinet for the levelling-screws the Manual reckons are there, at 1" BSW. Unable to drill the holes that little bit larger through the 5/8" thick steel, I resorted to partially tapping the holes M24, easing the developing thread to Whitworth, taking another bit out at M24... Took all day, lying on my side in a very cramped position, turning the taps barely a 1/4 turn at a time.... I won't make a habit of such antics.

To prepare for it I drew the thread profiles, ignoring the roots and crests, to establish the interferences and errors. I forget if I drew them completely or in fact plotted them as a pair of traces on an "Excel" graph, but it worked.

I would be very surprised (at Clive's implication about NASA, not Mrs. Ady's complaint about 'Im Indoors!).

Surely all the specification, operations, commands, etc. would be compiled into hand-books, probably both .pdf and real paper?

Also although it's very likely most of the original team would have retired by now,. that would be a slow, steady progress so keeping continuation of accumulated experience.

I have had no sight of any NASA documents but do have some experience with using both Hewlett-Packard and RN-issue instrument-operating manuals so would envisage NASA having something similar. These assume the reader understands the subject, but are written in very clear, logical and unambiguous styles. A bit like a Haynes Manual but more formally set out - and a darn sight easier to follow than a certain booklet with orange printing on a white cover!

Anyway, anyone can make a mistake. Just look at the spare holes in my steam-lorry chassis! Though for something like a space flight you'd expect tight error-traps and command-verifying.

The point perhaps is not that someone in NASA made a mistake - whilst Voyager's flight is extremely costly and future information-gathering lost by an operating-error would be serious scientifically, no-one's lives are at stake.

As SpeedyBuilder says, it is a magnificent achievement that something man-made, nearly 50 years old and so far away is still working and still controllable at all without any physical overhaul since being placed atop a rocket. It will be very sad if Voyager disappears from the world's radio-telescopes prematurely by irretrievably facing the wrong way, but human error or not, no human will have been harmed.

Whatever actually went wrong I hope they can correct, and 'Voyager' will still be 'phoning home for as long as she can before vanishing for ever from radio-telescope receiving-range.

Jason -

I see. I need add its own origin plane.

However...

Andrew -

Your question raises something I had not realised; that a shaft created by extruding it through an existing part such as a gear might not be a discrete part (in CAD terms). Would it be an extension to that part?

What though if the shaft is extruded through a matching hole in the existing gear, without using the "New Part" tool? That is what I had done: viewing the face of the wheel in 2D, adding a circle to the same diameter as the hole then extruding it.. Once I found how to do that: it is not so obvious when the drawing is an Assembly not a Part.

I experimented.

That works!

First I tried to move it. I could not despite making a very fancy symbol in bright colours appear. (I have not grasped that Component Placement tool).

Then I discovered the extrusion was listed in the index down the left-hand side as a "New Part", and because I had saved the whole "New Assembly", the shaft was saved as "New Part (1) " . Not only that, I managed, though did not save, a dimensioned, orthographic drawing of it.

So that way round does give separate parts.

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You mention one advantage of Assemblies is ensuring aligned holes, e.g. for screws, do align. Is there any way to leave the holes off the Parts to start with, then extrude them through both Parts in the Assembly? Sort of modifying the Part from the Assembly, not modifying the Assembly by modifying the Part?

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Though if I could ever to learn Alibre Atom to anywhere near the level you show there, I think I'd still be wary of trying to generate components in that way, at least above simple sub-assemblies.

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[Drawing even spur gears to full form is too advanced for me, but anyway my mathematics is too weak for designing gears and I have no CNC machine-tools! I'd have to modify commercial stock gears for bevel drives.]

Come on chaps....

Most of us here might have had academic and working careers very different from Engineering, but we still like to think ourselves "Engineers", so let's not stoop to the level of the "red-top" newspapers.

Just tried it as I think you mean....

I made a new Assembly, stuck my two gears together, using them simply because they already exist. then gave them a short shaft in situ. Too short for any real machine-part but that was not the point.

I could make it start from one face and protrude 5mm from the far face, but could not find how you would make it stick out of both faces. I tried that "dual" geometry choice but that just stuck two 5mm "discs" to the starting end.

The error made the probe turn its antenna away from Earth!. Luckily it seems they were still able to receive enough signals from it to know it is still in "good health" (sayeth the News!) so are hoping to be able to turn it round again.

Well, presumably both approaches still need you know the eventual outcome.

Thank-you for explaining that way - it seems based on starting from the primary components of the assembly then building the rest around those more or less as they dictate. So on a reduction-gear, starting with the gears then forming the shafts etc. to suit them. Well, gears then bearings perhaps. I can see the logic of that.

Yes, the introductions assume knowing all the shapes and sizes at the start, but though that might make learning the programme easier, for a real project you would need almost design the thing in some detail before you can draw it. The people who write the tutorials have already done that for you; and if the same reduction-gear was one of their exercises you could draw its parts in any order.

That original MEW exercise, the scribing-block, was in a logical manufacturing order but that also suited the point of the exercise itself (learning the basics of Alibre) by putting the simplest parts first.

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If you went on to make the scribing-block that's your own bonus, but with a full set of drawings the parts-making order does not matter!

Nick -

I'm still confused!

So you'd put your two gears together then draw the shaft "through" them with the right amount protruding at the far end? You still need some idea of sizes, such as the gear's thicknesses, and the protrusion - even if you do then find the manufacturer's gone and made them thinner.

I know changing a Part in its own drawing automatically up-dates it in an Assembly that's already used it; and an extremely useful feature of Alibre that is. However, in your example having thinned the gears, won't the shaft now protrude 10.7mm from the gear face? Or does having Constrained it at 10.0mm in the first place automatically shrink it to maintain that 10.0mm when you make the wheels thinner?

Does that shaft you've drawn as an extrusion though two existing parts "exist" as a third part in its own right, or would removing either of two gears leave a rather peculiar space or a 10mm thick disc floating in fresh air?

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I abandoned TurboCAD's 3D mode, and kept to its 2D mode, but I don't recall drastically re-drawing the whole thing to change one part. Modifying the associated components yes, because TC does not work by parts and assemblies (though an expert user might be able to drive it that way), and it lacks Alibre's facility to carry changes through. Well, it might now, I don't know; but likely only in the advanced 3D realms of its latest editions.

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Ady -

I've just looked at that vertical-slide drawing set you cited.....

Thank-you, but that would be far too advanced for me, certainly at the moment.

I might manage one or two of its simplest bits but if I struggle to create 8 simple cylinders and string them along a rod, I'm not going to cope with something as difficult as that project.  

Edited By Nigel Graham 2 on 01/08/2023 00:00:39