Member postings for SillyOldDuffer

Might look like product promotion, but I vote 'not guilty'.

Blue Heeler has posted many other videos of this type covering umpteen other small engines, old, new, Western and Far Eastern. Taken as a whole, his posts don't look like a sales pitch to me. Just sharing an interest in what's out there.

Pays to suspect everything though - the internet is wild and hairy!

Dave

I insist the Groom of the Close Stool wear gloves. It's vital I don't catch anything nasty off a mere aristocrat...

Does anyone recognise the BV20 in another clone, where perhaps spares are available?

Replacing missing gears can be a pain. Although the teeth and gears will be one of a few standards, the way they connect to shafts varies, and the set of gears needed to produce thread ratios varies with model. (My WM280 came with 11 change gears, so not just one or two.)

Ideally, the needed gears and fixtures are available off-the-shelf. (Either new or second-hand.) Luck is involved - the search can be anything between easy and impossible.

If model specific gears can't be found, the nearest commercial gears can be bought and modified to fit with home-made fixtures. Though within the capabilities of a reasonably equipped and skilled home workshop, it was beyond my reach as a raw beginner, especially as I wanted to use my equipment on day one rather than mend it.

Does the lathe have any gears in it? Like as not the gears needed to do fine feed are fitted and only the threading gears have been lost. If so, lathe threading isn't a common operation - small sizes are done with taps and dies - so you may have plenty of time to sort the gears out. Plain lathes don't do threading at all! Worst case, all the gears are missing, or the banjo is set to cut a rarely needed thread, and can't do the valuable fine feed.

Depends on what's wanted of the machine. Provided the motor turns the chuck, you can do and learn a lot on a lathe with missing gears. Maybe use it to learn, if it's suitably cheap, and then upgrade later? Or use it whilst looking for replacement gears or learning how to modify commercial variants.

Dave

Well, a calorie (note small 'c' ) is the amount of energy needed to raise 1 gram of water by 1°C. This is a tiny amount of energy, so dieticians use big 'C' calories, which is the amount of energy needed to raise 1 kilogram of water by 1°C.

As Robin said Calories are measured in a Bomb Calorimeter. This consists of a sealed vessel of known weight and material, within which the foodstuff is burned in an excess of Oxygen. The before and after ignition temperatures allow the energy released by combustion to be measured accurately.

Obviously this is not how animal digestive systems work, but the calorimeter gives the maximum number of Calories available if the animal could recover all of them. Species have adapted to recover energy from different foodstuffs. Cow stomachs have four compartments which allow them to digest grass, mostly cellulose, which humans cannot digest at all - it passes straight through. Cows can't fully digest herbage either, which is why cow poo can be dried and burnt.

Although human digestive conversion efficiency is difficult to measure accurately, it's well known that we can extract almost all the energy available from certain foodstuffs, especially Sugars and Fats. As we evolved from hunter gatherers who needed a lot of energy to find food, and often went hungry, we are configured to put on weight in times of plenty, and burn it off later. This causes severe problems to modern man who mostly sits about scoffing an unlimited supply of crisps, Mars Bars, Coca Cola, Alcohol, and Steak and Chips. These are high Calorie foods in a Calorimeter and the human stomach, just the job before the winter famine starts, but we all get fat when there is no famine. Vegetables contain fewer Calories and are digested less efficiently, so we're unlikely to get fat on them. They contain trace minerals, vitamins, and roughage essential to our Biology - digestion isn't just about Calories.

Humans are unique in that we're the only species that can convert inedible food into something we can eat. Cooking, fermentation, dissolving, distillation etc. These processes are also good at removing toxins and killing bacteria. On the downside, processing often removes wanted minerals, roughage and vitamins as well, and it's not unusual for them to be chemically restored.

Digestion is complicated and still not fully understood. To avoid becoming a diabetic slob, it's best to cut back on high-Calorie foods, but Calories are only one indicator. More recently, British ready meals have started carrying a colour code. Trouble is I like food where Energy, Saturates (Fat), Sugar, and Salt are all code RED, and don't enjoy anything that's good for me.

Obesity has become a serious problem in the UK; the NHS is burdened with people who have made themselves ill due to poor lifestyle choices.

When I was younger, Brits used to laugh at Americans because they were all so outrageously fat - not now. Modern Brits are also packed full of sugary goodness...

Dave

Edited By SillyOldDuffer on 13/07/2023 10:23:27

The new technology is hybrid, not pure IC!

I'm slightly concerned from the bursting bubble comment that some still haven't realised what's going on. The idea that a bunch of Greens have somehow managed to hijack world decision making, and they're wrong, may be popular, but it's not true! Greens have no power.

Governments and the smart money are pushing Green ideas because, whatever deniers may hope, burning fossil fuels is causing significant climate change. And, at the same time, fossil fuel reserves are running low and there are with no new big fields left to exploit. Inevitably, oil is going to get much more expensive, and it will do so over the next couple of decades.

We happen to have lived at a time when fossil energy was literally dirt cheap, but it's not "situation normal". At some point in the near future, my guess 25 years, ordinary folk won't be able to afford petrol. Though they've done a good job so far, it's obvious IC engines have a very limited future.

Not all bad news, green energy can provide affordable transport provided we get on with making the necessary changes, and it helps stop the planet overheating too. Potentially a win-win.

I judge it's already too late though. Our sluggish response to an avoidable problem means our grand-children are already committed to sky high energy prices, significant disruption of food supplies and massive population movements.

Dave

As others have calculated, Michael's Jack Hammer does about 1.3kW of work, which is roughly equivalent to six fit men, or ten weedy ones, and each blow contains as much energy as Robin's "3 lb lump hammer falling 13.5 feet".

Can't be doing with nasty old imperial measure, but that's about 55 Joules hitting the target at about 7 metres per second. The pressure is spread over the area of the lump hammer, rather than concentrated at a chisel point, but enough to deliver a nasty injury.

The Jack Hammer's acceleration figures suggest the speed of it's chisel blows are much the same as Robin's falling lump hammer. Speed makes a big difference. The amount of energy used by a human to push a car slowly won't damage the car. But if the same amount of energy is delivered quickly, the car and human are both damaged. If the human applies the energy with a spear, or hammer, then the car will be damaged badly. Pushed objects have time absorb the energy and maybe move out of the way. When a struck object doesn't have enough time to absorb the energy, the material it is made of is displaced, resulting in cuts, disintegrations and penetrations.

Jack Hammers are designed to deliver sharp blows at the chisel point without wrecking their internals. I believe it's done by the motor slowly storing energy in a flywheel, that operates a faster but still relatively slow moving internal hammer, that delivers all it's energy into the chisel point in a rapid series of short sharp blows. Although most of the energy is dissipated in the target, the chisel point is replaceable, the internals take a beating, and the motor won't last forever!

Dave

As a layout tool the Axminster device seems to fit accuracy-wise between an adjustable set-square and a vernier or digital caliper.

I don't do much layout with blue and scribing, preferring mill-table and DRO, but when within about 0.5mm is good enough, especially woodwork, then out comes my adjustable set-square. This example scribes a line on felt tip 50mm from the end of the steel flat:

Same result as the Axminster tool, but the Axminster device is handier and should be more precise because it has a vernier. The Axminster isn't as precise as a digital caliper in this application, but must be less fiddly.

I reckon an Axminster would be well worth owning if a lot of laying-out was being done. Otherwise, a caliper and adjustable set-square will do the job and can be used in other configurations.

I expected to get a lot more use out of my adjustable set-square set when I bought it, and invested in a large bottle of layout blue and a Height Gauge. Not a waste of money but in practice, I don't have much call for any of them.

How much marking out do others do?

Dave

No fear of 'Angel' being fired, Nigel - it was part of the con. You were being schmoozed, the idea being that you would make friends and put in a pity order.

Ten out of ten for wasting their time though! Ranting and abuse has no effect on criminals. What really hurts is stopping them from making money. If I have the time, I do my best to sound as if I'm innocently interested but not quite convinced. My record is keeping them going for well over an hour, during which time they lost money and where prevented from finding a real victim. Life's too short for marathon delays, but I often keep them dangling in anticipation for 5 to 10 minutes. Having been led up the garden path, they're often audibly frustrated when I finally say no.

No evidence it works, but I hope they might be clever enough to register me as a "time-waster". Unlikely, because they use an auto-dialler, which just ploughs through telephone numbers.

Dave

The usual - trying to run before you can walk, changing horses in mid-stream, and leaving a gap long enough to forget Alibre! If you can possibly avoid it, don't take long breaks whilst learning CAD, and don't attempt two or more CAD packages at the same time!

Changing horses in mid-stream is a classic mistake. Both horses run away, everyone laughs when you fall in, even if you hit your head, drown, or die of pneumonia. Though I know FreeCAD, Fusion360, and SolidEdge moderately well, I find it difficult to switch between them. Their basics are all a bit different, so even simple stuff like creating a cube with a hole in it require a mental reset. Imagine owning two lathes where the controls are in different places and set up in the opposite sense: turning the carriage wheel clockwise moves the saddle right on one and left on the other; lever down to engage cross-feed vs lever-up; lever down to engage half-nut feed vs lever-up'; and then all these controls are positioned on their respective aprons in the opposite order. Even experienced operators take time to switch between contrary machines and are liable to get the controls wrong in an emergency. Alibre and TurboCAD have far more differences than a pair of topsy-turvy lathes.

I advise spending the time necessary to manually convert all the TurboCAD drawings into Alibre, and then dump TurboCAD. (Or the other way round if you must - the only daft choice is doing both!)

When 3D-CAD has been used to develop and assembly of parts, routing pipes between parts is relatively easy once how to draw lines in X, Y and Z has been mastered. But I would say pipe routing is advanced work, because it depends on mastering a raft of simpler tools and concepts first. Routing isn't beginner friendly.

I wonder if if would be better to develop the design using traditional methods rather than 3D-CAD?

Before plunging into Drawing Office detail, the original truck would have started as a series of rough sketches to pinned down the approximate location, size and weights of all the major components. Quite likely, several candidate designs would have been crudely small-scale modelled to check fit. Boiler represented by a cardboard tube, wooden discs for wheels, plasticine, wire and balsa etc.. This type of simple model makes it easy to spot major errors before tackling details, and it's likely several models of increasing accuracy would be made before the Drawing Office started work. And more models were often made to check and steer the Drawing Office as the design improved. Full-size prototypes were common: hopefully ready to go, but deliberately built expecting to find trouble before going into production. The process is slow and costly in time and materials, but not difficult.

Once 3D-CAD has been mastered, modelling on a computer saves an enormous amount of time and effort compared with developing physical models. But learning CAD is a major challenge, and the effort may not pay-off, especially if CAM isn't on the agenda as well.

So instead of struggling with 3D-CAD, why not tackle it traditionally. Make a simple model of the model to get the GA, and produce 2D drawings from that. The downside of course, is making models of models is time-consuming and not very rewarding - after a lot of work is put into painfully solving a problem, they're thrown away!

Here's a modern example, a Renault Twizy, made of clay, full-size by the look of it. Note the wheels, which aren't models!

Dave

Speed isn't quite the right word, books all use 'amplitude'. Much the same thing though.

Amplitude is a measure of how high a pendulum rises, usually expressed as the angle swept by the rod. High amplitude gives high speed, not useful, and the amplitude is kept low.

At the top of each a swing, both sides, the bob comes briefly to a stop, speed zero. Then gravity accelerates the bob downwards, and it's travelling at top speed at Bottom Dead Centre. After passing BDC, the bob de-accelerates to speed zero as it climbs to the other side, then repeats. The pendulum oscillates, and the time taken to go from side to side depends almost entirely on the length of the rod.

Almost! Period also varies slightly with amplitude, enough to be a problem. A pendulum loses energy each time it swings, causing the amplitude to fall, altering the period. And to keep going, the clock has to replace the lost energy by impulsing the pendulum, which also causes the amplitude to vary.

For accuracy, it pays to have the impulse apply a constant amount of energy to the pendulum each time. Unfortunately, in a spring powered clock, the impulse weakens as the spring unwinds, causing noticeable drift. A fusee fixes this by regulating the power delivered by the spring; it keeps impulse power nearly constant between rewinds.

The impulse (hence amplitude and period) is also disturbed by winding, so better mechanical clocks feature a remontoire - an independent source of energy that keeps impulses constant during winding.

The purpose of the fusee and remontoire is to keep the pendulum swinging at the same amplitude (speed at BDC), no matter what the input energy source is up to. Then the clock keeps better time.

Dave

+1

Paint is a poor filler - no bulk to it, and optimised to stick to a flat surface.

For covering small holes in a levelled floor, I think almost any fine filler knifed over the surface would do.

When my son had a section of floor levelled with goo, the result was similar - mostly flat with a scattering of small dints. His are hidden under a carpet.

Dave

Well, "fly-by-wire" systems are used on submarines, and the military do use ordinary Games Controllers - sometimes.

Conventional submarines are partitioned by bulkheads to protect the vessel against leaks and fire, increasing the chance of survival. The ideal bulkhead is solid, but in the real world they are penetrated by a hatch and a multitude of pipes, cable, and maybe mechanical linkages. And many of the systems passing through the bulkhead are duplicated to provide resilience.

As every hole made in a bulkhead is a risk, much thought is put into minimising them. A power bus and Ethernet are one way of massively reducing the number of separate control wires and pipes needed. In practice balancing the risks and opportunities. Hydraulic control is simple and robust and the technology well-developed, but miles of heavy high-pressure pipe and thousands of joints are unwelcome inside a submarine. Electrical systems are lighter and better than hydraulics in many circumstances, but have other issues - like catching fire! Ethernet is robust on the wire, but relies on somewhat delicate electronics driving various types of electric motor, none of which work well in salt water!

Titan's interior was empty, a good thing up to a point, but not if it was achieved uncritically. Using a games controller and Bluetooth eliminates dangling wires, which are risky in a vessel with no seats. Doing without seats simplifies the design, reduces weight, and increases air-space, but assumes the vessel will never lurch. Bolting the hatch on from outside much reduces the chance of water leaks, and saves space inside, but made the vessel a death trap if anything caught fire. Locating most of the control and power cabling outside the pressure hull with the motors is good, except it becomes vulnerable to snagging and the elements. And the pressure hull has to be penetrated in some way to control the motors: can a Bluetooth signal get through 5" of Carbon Fibre? And if a games controller were used, I'd expect to see at least one spare.

I think the problem here is not the experimental nature of the vessel, but the way it was designed. It appears that an unchallengeable optimist was in-charge, who didn't think the risks through. Taking necessary risks is brave, taking unnecessary risks is Incompetent.

Maybe I'm completely wrong. I'd dearly like to see the Risk Assessment. Possibly it was done correctly and came honestly to a faulty conclusion: that's allowed - everybody makes mistakes. Unfortunately the evidence - much of it direct from Mr Rush - suggests serious persistent bodging. Maybe the only 'Risk Assessment' done was inside his mind.

I blame Hollywood! I must have watched hundreds of films in which the plain-speaking maverick hero defeats evil by breaking all the rules and single-mindedly ignoring advice and orders. In Star Trek the emotionally unstable but gallant Captain James T Kirk always triumphs over Mr Spock's cold logic. All rubbish. Hollywood presents a fiction on which, we the audience, can stamp our desires. We all want to be the leather-clad gunman taking brutal revenge on shoals of unsympathetic baddies wearing black hats; no-one identifies with the cowardly bar-keep (who has 6 children and elderly parents to support.)

Real-life is much more complicated, and mavericks generally fail miserably. Results are mostly achieved by learning from experience and doing an analysis, not by taking wild guesses and hoping for the best. Films rarely depict real-life because it's a bit boring.

Arrogant gung-ho amateurs are rotten at designing safe systems; what's needed is expertise, attention to detail and a positive attitude to criticism.

Permissible of course to accept risk when the circumstances demand it, but not to ignore it. During WW2 many submarine commanders chose to bolt-down escape hatches. In peacetime this was stupid because it guaranteed no escape from survivable accidents. Different in wartime! Escape hatches are easily damaged by depth-charges, and bolting them down made it more likely the boat would survive to fight another day. Rules help, but it's always necessary to think.

Dave

Alas, the emerging evidence is that OceanGate were warned repeatedly during development that the vessel was unsafe. Mr Rush chose to ignore all the warnings and deliberately circumvent regulations, for example by describing passengers as "Mission Specialists". Said so openly and in public too.

Only became newsworthy after the accident, but multiple concerns were expressed well before the vessel failed. This was predicable.

I was surprised to find that the disaster has developed a political dimension. To me it's just another technical failure that we can and should learn from - there's the usual 'accident chain', albeit with an unusually high level of human error. Situation normal, do better next time.

However, seems the incident has upset the body of opinion who think that experts know nothing. Odd really, I find getting technical stuff correct works far better than ploughing on regardless. In my workshop I take advice, assess and mitigate risks, and learn from mistakes. Hardly controversial that I messed up on the lathe yesterday and have do the job again, properly this time.

Dave

People usually think BASIC is interpreted because that's what they learned. It's very common, and it was unusual for amateurs to invest in a compiler. If they'd done so, they'd have found compiled BASIC isn't as cuddly as interpreted!

But, the assumption misses an important point, which is computer languages and their implementations aren't the same. Interpreted, compiled, and combinations are all possible, with pros & cons.

Python, like Java and many others, compiles to an intermediate byte code, which is then interpreted. This approach combines many of the advantages of both implementations,:

• the compile phase error checks and optimises the code - loop unrolling, moving stuff that doesn't change outside the loop, minimising branching, reordering, factoring duplicate code, removing dead code, keeping busy variables in registers etc and many other tricks.
• The interpreter provides efficient base functionality and memory management. It's fed clean fast byte code, without the complexities implicit to machine code.

Although the approach works well, it means Python is a hefty beast, too big in full form to fit on smaller microcontrollers, not a good choice for embedded computing. However, there are Python compilers than do generate machine code, the main problem being implementations aren't identical.

As with all tools, the best computer language is determined by what it's for. Most languages have glass ceilings that stop the programmer doing what he needs. In my experience:

• The original interpreted BASIC has a low glass ceiling. Fine and dandy up to a point, then, a shattering stop, maybe forcing the whole program to be rewritten in something else. Compiled BASIC removes some obstacles, but not all, and converting people and code causes £delay. Worse, having to switch to a compiler, suggests a need to think again. Having failed to choose the right tool once, it would be foolish to do it again! Not the sort of language problem the average internet Joe can advise on. If the code is focussed on a system-like problem, then C/C++ is a good choice. But if the code is focussed on efficient number crunching, then maybe the answer is FORTRAN. Back in the day, even horrible old COBOL was massively better at data processing that BASIC. Today there are many alternatives. If it were a road car, original interpreted BASIC would be a Citroen 2CV.
• C/C++ probably doesn't have a glass ceiling! It's a high-performance system language, close to the machine, used to develop other software tools. Chances are BASIC is written in C, as is much of Python, and many other languages. The downside is a lot to learn and much of the work is a slow low-level plod. The programmer is responsible for almost everything. If it were a road vehicle, C would be a MV Agusta Brutale 1000 Nürburgring with bald tyres.
• Python has a high-glass ceiling, and is extensible. Although it can do system work, the main focus is productivity. For example, classic BASIC only had two data-structures, strings and arrays. which aren't enough for advanced work. Say a program is needed to count how many times each word occurs in a book. An array can be used to keep tally, but they're fixed size and we don't know how many unique words are in a book. A different data-structure is needed, one that can grow, and BASIC doesn't have one. Python provides sets, dictionaries, deques, counters, maps, lists and tuples. Their availability makes Python highly productive. If Python were a car it would be something like a high-end SUV. Comfy cabin in the front, big carrying capacity, reasonable on and off road performance, winch on the back, and the driver is an ordinary chap with an plain licence.

In the distant past I wrote BASIC for money and it caused many problems. Later, perl was wonderful for several years, but it couldn't keep up with Python. I also wrote C/C++. Now retired, I find Python and C/C++ complement each other delightfully. Python is good for rapid development of big complex general purpose programs that don't need space/time optimisation. C/C++ is excellent when space/time and performance are vital, for operating system level work, and embedded code (Arduino and friends).

Anyone remember Filetab? This is/was a decision table language used for report writing. Back in the 70's it was brilliant, far better than COBOL, apart from its glass ceilings! Really hot at reading files, but not for writing them - this limited what it was useful for. Not good at maths. A more serious shortcoming appeared as the code grew in size. Up to about 2 pages, decision tables sparkle, but after that people start having trouble following the logic. Above a certain level of complexity it was easier to write COBOL, even though COBOL is clunky.

My advice, look for language limitations! Likes are secondary.

Dave

It works reasonably well, and is quite fast, but don't expect anything like the same level of accuracy or finish as a boring head. And the resulting hole is unlikely to be accurately circular or straight. Whether the hole is acceptable or not depends on what it's for. Not engine cylinders!.

Several sources of error. Emgee mentions backlash and climb milling, and Jason covers a light mill and sloppy rotary table. The state and size of the cutter relative to the hole radius matter too.

In comparison, a Boring head eliminates all these errors, plus the head provides an independent accurate adjustment of the single point cutter that avoids moving the job - always a source of mistakes and error if it can be avoided.

Dave

Oh, go on then, I'll take the bait! Python may not be simple in the 'Up Jumped Baby Bunny' sense, but I can't think of a real language that's easier to learn, especially good when taken with a small dose of Computer Science. What languages are easier to learn than Python and why? What are these other languages good and bad at?

Hating Python's indentation rule suggests a misunderstanding. All computer programs are more readable when their structure is made clear, and indenting is good for readability. Highlighting the structure is vital as soon as someone else has to read my horrible code, and the concept is so important that Python enforces it. Learning with Python avoids a common bad habit which is writing compressed code that only the author comprehends. And even he can't decode if when he comes back to the mess after a long gap.

How do you 'shoot yourself in the foot' with Python? My toes are intact!

Straightforward for individuals to write short simple programs in most languages, but doing that is a very poor test. The real trouble starts when programs get so big that teams have to manage hundreds of thousands or maybe millions of lines of code. C was designed from the outset to play in that space, which is why it has a complex pre-processor and linkage system. The C environment allows teams to work on complex debug, test, and live versions, and it can also target multiple platforms from the same code base - Window, Linux, Mac, Android and others. C is also very good for microcontrollers and other tiny computers

May not be the best of all possible languages for all time, but so far C has proved a hard act to follow, and in many ways C++ is C on steroids. The two are close relatives.

Tracking the rise and fall of computer languages over time is 'quite interesting'. Hugely popular big hitters like perl, Ruby, PHP, Scala, Rust, Objective-C, Visual Basic, COBOL, Pascal, FORTRAN and BASIC have peaked and waned. A few bombed! Despite many likeable features and having the full support of the US DoD behind it, ADA failed to get traction.

If you want a programming job in 2023, learn C#, Javascript, Java, C/C++, Python, and SQL. C/C++ and Python are predicted to be in hot demand next year, but who knows. Whatever their warts, C and C++ surely deserve the endurance prize - C was much in demand back when COBOL and FORTRAN dominated the industry.

Dave

I'm afraid the 'better in the past' perception is mostly an age thing John. Old men have ended up convinced the world is going to the dogs throughout history. Actually it's us who are in decline.

The general thrust of technology is upward. Better understanding of materials and improved techniques mean modern industry routinely makes stuff that was impossible 20 years ago.

The benefit isn't always improved 'quality'. I believe it was George Stephenson who said 'An engineer is a man who can do for a pound what any fool can do for a guinea.' Cost control has always been a top-priority in engineering because although customers burble nonsense about the importance of 'quality', they're extremely reluctant to pay for it! So professional engineers have to target what people will actually pay for with products that are 'good enough' and 'value for money'.

Sadly there's a huge difference between what most people say they want, and what they actually buy. It's because many things in life compete for our time and money. Most people, most of the time, buy the cheapest that does the job, not the best available. The best is expensive. You can't just pile on 'quality' and expect it to sell

Clocks are a good example of mixed results. Quartz movements consist of an accurate crystal oscillator, an electronic divider, and a simple motor and gear-train. The gears are plastic. The divider contains several hundred transistors, that before 1960, would have filled a 19" equipment rack with unreliable valves and cost as much as new car. The crystal is high-tech synthetic quartz, grown and cut in a specific way, and only cheap because they're mass-produced in billions. The movements are reliable without special bearings, and normally last at least 5 years. Apart from an occasional new battery, zero maintenance; replace on failure. In terms of accuracy, they beat most mechanical clocks hollow. For most purposes they are 'good enough', and more reliable in the short and medium term. But they will never become family heirlooms!

The bearings in an ordinary cheap clock are 'fit for purpose', not the best modern industry can do. Computer hard-drive bearings are considerably more impressive - take one apart! Hard drive technology is well beyond anything that could be made with a Myford, or by anyone in the world in the 20th Century, and now they cost as little as £15.

Alas and alack, old simplicities have gone . Brand-names are untrustworthy, and cost isn't a sure fire indicator of quality.

Disposable goods were enthusiastically adopted by Boomers. We are all guilty. Not a good thing in my opinion, because disposable isn't sustainable in the long run. It will have to change and grandad will hate it, because it will cost him money!

Dave

Melting Tin and Copper isn't a problem given enough heat and a suitable crucible, and the Tin won't vaporise unless the furnace is run far too hot. (Shouldn't be a problem unless Oxy-acetylene or an Electric Arc is used.)

However, Zinc fumes easily, and it's dangerous to breath it. 'Brass Founders Ague' was one of the first industrial diseases, and it's still a problem today - chaps poison themselves welding Galvanised Iron. The 'special process' is keeping the workforce away from the fumes. I don't think melting a small quantity in the open air whilst standing well up-wind of the furnace is too risky. Doing it in a small garden might worry the neighbours though!

Scrap Brass (such as old water taps), melts more easily than Copper, so I'd start with that. Then add Tin. It's usual to add a little Zinc during the melt to keep the alloy proportions about right because Zinc slowly evaporates.

How to get 86% copper, 11% tin and 3% Zinc? I think the Ancients got the mix right by experience - either able to judge how much Zinc was lost over time from a given mass of metal in their particular furnace, or perhaps by recognising the right moment from flame colour or how the liquid poured. I guess a modern foundry would use a horribly expensive spectrographic gun to measure the proportions accurately.

The 'gunmetal' may not need to be accurately made for amateur purposes, but if it is, might be done by weighing a known volume and checking the alloy's density.

Dave

Come now, Peter, unkind to refer to us poor old pensioners as an underclass. Admittedly we're the largest financial burden the country has to support but I like to think you and I aren't complete wasters!

Dave

+1 No need for Beardy Mike to take a risk though because the risk is easily tested.

Take two shiny nails. Half submerge one in a jar of clean water, and the other in a jar of suspicious suds made with a dash of detergent. Compare how quickly the nails go rusty. If the suds are good, the nail should rust much more slowly than the one in plain water.

Expect quick rusting if the detergent contains an Anionic Surfactant - most Washing-up liquids do. I like John Haines suggestion though - unlikely that Car Shampoo has anything in it that encourages rust.

Might be easier just to buy new and protect from frost. However, whether a cheapskate remedy works or not is always entertaining. There should a Model Engineering Award for the most audacious use of an unknown potion in the workshop. Special category for traditional methods known to be dangerous because these are widely believed to work better than any modern preparation. Volunteers needed: Red Lead makes an excellent cutting paste! Double points scored if the operator chain-smokes Capstan Full Strength whilst machining.

I believe Science doesn't understand how surfactants work - anyone know? For example, seems unlikely that a smear of WD40 would make any difference when cutting Aluminium, and yet it does - a big difference. Thought to be something to do with the electronic bonding between atoms that occurs at surfaces, causing hardening at the boundary. How much depends on the materials in contact. HSS biting deep into Aluminium has no effect on surface hardening, but a drop of surfactant weakens it considerably. Then HSS cuts better.

Whatever causes boundary hardening gets stronger the more a surface is polished. That suggests to me it's related to the powerful force that sticks wrung Gauge Blocks together, another scientific mystery.

Dave