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Member postings for Tim Stevens

Here is a list of all the postings Tim Stevens has made in our forums. Click on a thread name to jump to the thread.

Thread: Creating Heat for Hardening
10/10/2019 14:45:25

The link from John F includes an excellent colour chart of the various colours involved in the hardening and tempering processes. But, what is does not explain is that the lower half of the chart (up to 800F) is what you see by reflected light, and the steel surface needs to be cleaned and bright to show the colours properly. In reality, the coulrs are due to the thin layer of oxide on the steel surface (thicker as the temperature rises) - rather like the reflected colurs of a soap bubble. Above that temperature (top half of the chart) shows the colours of the radiant light (glowing) from the steel. These colours do not rely on a shniy surface, and can be seen in pitch darkness because the heat itself is producing the light. If this is not explained it is difficult to see how or why the colours change from red-ish at 500F, through blue, and back to red-ish again at 1200F.

The top half of the temperature chart is for hardening colours, and the lower half for tempering colours.

Cheers, Tim

Thread: Exactly...
10/10/2019 13:43:28

Oh dear! Tarmac roads were not invented or introduced by Macadam. The improvements to our road network which started about 1750 relied on Telford, Macadam, and several others, but they all used stone in various forms, but NO TAR. The resulting surfaces were 'water-bound' - ie stuck together by dampness. In other words dusty in the summer, and muddy in the winter. The surface was maintained by constant attention from 'lengthsmen' filling holes with new stone, and levelling the ridges, and promoted by the use of steel horse-shoes and carriage and wagon tyres which ground the stones to ever finer dust.

Only from about 1900 when motoring involved speeds over 15 mph, and rubber tyres, did the problems become unbearable, and the use of tar as a binder (adhesive) was found to be a big help. Tar was a waste by-product of turning coal into gas (for lighting etc) and coke (for heating). The term 'Tarmac' was applied to a further development, in which crushed slag from steel works was used instead of stone for metalling, and this when coated with tar proved to be a very useful, long-lasting, and cheap surfacing material. It was patented, of course, and the term 'Tarmac' was applied to the patented compound.

So - a new product which relied entirely on the waste from other processes - clever indeed. Just like Marmite - but can you tell us of any others?

Regards, Tim

Edited By Tim Stevens on 10/10/2019 13:45:16

Thread: Resistance Soldering question
10/10/2019 12:22:05

The term 'soldering' with no other words is often interpreted as soft or lead soldering, with a melting point around 200C - because in ordinary (non-specialist) workshops soft soldering is a much more 'normal' practice. It is also the case here that the OP (original poster) may not rely on English as his 'mother tongue'. Clearly the amount of heat involved here is greater than soft soldering requires, and looking at the job illustrated, would not be strong enough.

My comment was not intended in any way as a criticism of the original message, but I hope to clarify the use of the term 'soldering'.

Hope this, er, clarifies?

Tim

08/10/2019 18:16:19

I wonder whether there is a source of confusion here ?

Could the term 'soldering' as used by the OP mean 'hard soldering' - or what we might call 'silver soldering' ?

Tim

Thread: Metrication of models
04/10/2019 17:45:52

There is a lot of tosh written about the 'benefits' of the pre-metric measurement systems. Most of them seem to forget that the metric system grew rapidly in popularity around the world of commerce because it enabled everyone to overcome most of the objections to the older systems. Not only the confusion of how may whats make a wossname, and a different number each time - think ounces, inches, stones, shillings, barleycorns, pennyweight, drams (apothecary, avoirdupois, troy), grains (ditto), scruples, bolts, cables, chains (4 sorts) fathoms, furlongs, hands, miles (5 sorts), nails, points (3 sorts), rods poles and perches which were the same or not, depending, and townships. A further difference for us was being able to order material from anywhere (except the USA, where the postage rules it out anyway) and know what you were going to get.

I suppose the next solution to the problems of metrication is going to include logarithm tables, slide rules, and quite likely, the casting of lots - good luck.

Cheers, Tim

Thread: Final drive toothed belts?
04/10/2019 17:26:58

My guess is this:

Properly used - in line with the design criteria - there is less likelihood of patterning than with a gear drive, or a chain drive. Or even, perhaps, from an electric drive driven by AC.

But if the very thought gives you the shivers, why not a poly-V belt drive? No thicker than a toothed belt, and lots of torque capability.

Cheers, Tim

Thread: 3 jaw runout problems
02/10/2019 17:28:28

Mary?

Tim

Thread: Leadscrew material ?
02/10/2019 17:26:44

I'm not sure a square thread is easy to arrange with a split-nut attach & release system. Of course, yours might be different. But remember that square threads were abandoned long ago as sodding difficult to machine ...

Cheers, Tim

Thread: Antique car electrics
02/10/2019 17:03:32

Old switches are a serious problem with vintage cars. Yes, the castings (zinc or aluminium) are falling apart (or are long gone), but the wiring diagrams are usually devoid of any explanation of what the switch does, exactly. Only in the 1970s did we get sensible switch internal contact diagrams - from the Japanese.

I have a series of wiring diagrams for British, European, and American cars of this era, so let me know if I could help. If so, please specify the makes of components required, not just the car makers.

Cheers, Tim

Thread: Black crackle spray paint
28/09/2019 17:31:56

I used this sort of paint about 15 years go. First attempt was a failure - no wrinkles. My wife suggested I need to get a pension book for it (ha ha). Then I read the intructions, and got results. But there is a difficulty: the wrinkling starts as the surface skins, and is prompted by small irregularities which might be scratches in the surface, bits of old paint not removed, and dust in the atmosphere. Best results are obtained by regular use, so perhaps there does need to be the right sort of dust in the atmosphere?

Cheers, Tim

Thread: Half round brass beading
28/09/2019 15:16:30

I suggest that you might use small rivets to hold the beading in place while the soldering is completed. Brass wire would be ideal, with the ends simply bent slightly, as this will cause no distortion of the work. The solder should flow into the rivet gaps and give a very neat finish, with the rivets only detectable able a year or so as the solder becomes grey rather than bright. Use lead-free solder and this will take even longer.

Cheers, Tim

Edited By Tim Stevens on 28/09/2019 15:17:33

Thread: Water in fuel
27/09/2019 22:41:09

That's how you get fuel in your water.

Tim

Thread: How many Hammers
27/09/2019 17:21:04

If you use hammers to shape metal directly (no punches or other intermediate devices) it is important to have a face that nearly matches the finished surface curvature, (smaller never larger), and a handle at a position so that you can get a good swing. It is also sometimes necessary to have the contact surface quite a long way from the handle axis because something else gets in the way. As there is a wide range of surface radii, handle positions, and extensions, trades like silversmithing and panel beating are very hammer-rich. And of course, they also need all the other types for closing rivets, using with cold chisels, driving pins, pegs, and nails, and punches. And if they also do repousse work or chasing, they will need two or three sizes with wide flat faces, and very springy handles, to keep up the continuous steady vickers-gun on each of at least 30 punches in turn.

So, the answer is a clue to the trade.

Warrington was a centre for steel wire production, much of it for winding gear in coal mines. So what was a Warrington Pattern hammer intended for, originally?

Cheers, Tim

Thread: M&W rules now better...
27/09/2019 16:54:50

A little jokette from the 1960s;

'Ive got a foot but I don't use it as a rule'

I can't bring myself to recall the context

tim

Thread: Water in fuel
25/09/2019 14:38:52

Water plus Alcohol injection was common for fighter planes as soon as extra max speed (however briefly) could save lives. Mainly the water does the charge- and cylinder- cooling and the alcohol stops it freezing before it is needed. And I suspect that the level of instruction, the degrees of skill, and the intense post-use checking led to Spitfires being more reliable than Morris Minor Vans.

Cheers, Tim

Edited By Tim Stevens on 25/09/2019 14:39:57

25/09/2019 13:05:55

Dave Halford suggests leaving the fuel cap off. This will perhaps tend to reduce problems of condensation (as the inside and outside temperatures stay much the same). But it will do no favours for cold starting. This relies on fairly light and easily evaporated molecules, and they are the ones that will evaporate into the air when the cap is left off*. This is the main reason that 'stale petrol' is used for washing off oily parts, rather than as a fuel. [But not, of course, in the working environment, where in any case the open tank should have been flagged up as a hazard]

*and this is a major factor making a choke necessary. To increase the amount of volatiles going in, we increase the amount of fuel going in. Modern sealed injection systems are quite different, the major reason being that they are sealed.

Cheers, Tim:

Thread: citric acid
24/09/2019 17:07:28

I wonder if the 'mould' seen by Howard Lewis was actually crystals of SO3, and not a fungus at all. Fuming H2SO4 is so eager to combine with the tiniest speck of water that it would not make a good environment for anything living - mould, germ, or virus. Just because it looked fluffy, do not be misled.

Cheers Tim

Thread: Water in fuel
24/09/2019 16:59:26

Try to remember that old cars always include a small amount of water in their fuel tanks. Condensation, mainly, and the only cure is to live in Wagadugu. The problem is, I guess, not really to do with the water that's in there and has been since Stanley Matthews was in short trousers, but to owners who read an article which includes 'faults', and who then are convinced that they have got a problem. No real symptoms. Another cause is owners of up to date fuel injection motors for work, who expect their MGA to warm up in exactly the same style.

Imagine the situation in the old days - no air filter, bike or car. Drive in heavy rain and you certainly have water mixed with your petrol as it goes into the engine. Did it cause problems? Very rarely.

Start your engine on a nice autumn morning with a light frost, and look at the body of the carb. It will be drenched in nice clean water - condensation again. If you were too eager, the engine might fluff and die. So, leave the engine at about 1500 rpm for a few minutes, and all should be well.

Happy motoring

Tim

Thread: Caravan Insurance
23/09/2019 14:06:25

We are surrounded in all our doings by people who will take our money and offer nothing in return. In reality, the only motor insurance you need to pay for is to cover the risk of serious injury or death you cause to a 'third party'. This is because the financial burden of such a claim is very likely to be beyond your means. I am sure that Peter Shaw has already worked this out. UK car insurance law does not require even this level of insurance - as long as you deposit a serious bundle of notes with the authorities.

Another oddity is the fact that county councils do not need such insurance either. This is because in legal terms a CC cannot become bankrupt - so even the biggest claim would be paid out. And backed by Her Brittanic Majesty's Government. In other words, by you and me, Peter.

Cheers, Tim

Thread: An astronomical model in New Scientist
23/09/2019 13:34:34

Here is the article (I hope ...)

Equinox model from New Scientist

You will see the source of my confusion in the small black circle around the earth axis, marked 'precession'. 

Tim

Edited By Tim Stevens on 23/09/2019 13:37:12

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