Member postings for Tim Stevens

One factor which runs counter to Ruskins notion:

Several firms supply exactly the same goods as each other, but at different prices. In that case, the trick is to look at the service offered by each firm - honoured guarantees, prompt supply, response to queries, that sort of thing. Then a choice can be made - otherwise cheapest, in this case, is best.

And history shows that Ruskin himself was able to charge too much for 'worse' products.

Cheers, Tim

A trendy solution, nowadays, is to add to a domestic system a lithium battery and an inverter, not primarily to cover power cuts, but as a way of using stored solar energy during the night. But such a system would meet your needs, too. It would be an advantage if you had a night-store tarriff, or were thinking of adding solar panels.

It should not be impossible, either to find a converter to drop the 50 colts DC in the llithium battery to 12v to feed lap-tops etc.

hope this helps

Cheers, Tim

I think you will find that Number Drills go by the same Gauge Standards as knitting needles, so my guess is that they are a standard but which one I can't help with.

Cheers, Tim

Hello Andy

If you have no fuel pump the carb must always be below the fuel level in the tank. Fuel will not run uphill - and you can waste hours trying to get the mixture right if the fuel is too low.

With a fuel pump (and something to power it) things are different but more complicated.

Cheers, Tim

Andy Cameron says:

Throttle closed = spins easy
Throttle open = harder to spin

Exactly as one might expect. With no air getting in there is nothing to compress, but allow the air in and I expect you have a 10:1 CR or thereabouts = hard work.

If ever you coast down a hill in gear, (ignition off) then you get more effective retarding as you press the loud pedal. But don't do this in a modern car with a key-linked steering lock, or you will also explore the hedge.

Cheers, Tim

Could this question - just possibly - be overkill in action, I wonder?

A small tank, bottle, etc someware above the required outlet, with a length of silicone pipe and an adjustable tap. If it is too much bother etc to top up the tank manually, a pump could be added with a manual switch, or even more, a pair of float switches to turn the motor on and off every few hours, days, weeks, depending on the size of the tank and the work rate of the operative.

Suitable drip- taps were used in Mercedes cars from about 1901 - and they are still in business so spares should be easy to find.

Cheers, Tim

Hello again
Dave (s-o-d) has got it about right.
The engine needs a spark at a progessively earlier time before TDC as the speed rises. In the past this was done by a centrifugally advancing cam in the contact breaker.
The ignition device needs to be set to 'open the theoretical points' when the output from the trigger coil gets to a set voltage. As the rotation speeds up, the whole wave increases in size, and therefore reaches a given voltage earlier. The system does not rely on a slotted disc, or a Hall sensor - they were a later development in vehicle use.

What I hope to do is to be able to tweak the shape and size of the voltage curve so that the advance produced can be matched (by road testing) to a given engine and given settings. The system I have already made as a first try does seem to work fairly well, and this is a fortunate accident rather than cleverness. What I seek the to change, for example, the radius of the rotor, the distance to the magnet, the strength of the magnet, the shape of any pole piece on the magnet, etc, to vary the advance curve in known ways at low, or high, revs, so the the original set-up can be improved. Or by changing things, to show that the original guess was jolly nearly right anyway and best left as it is.

Hope this helps

Cheers, Tim

I'm not sure, now, whether a computer-based solution will work well for me. The intention is to calibrate a pick-up design for an internal combustion engine. Normally such devices are driven at half engine speed to fit with the four-stroke cycle. The engines I am looking at have a peak rpm of 4,000rpm, and so the pick-up goes at 200 rpm, which is 2,000 / 60 Hertz = 33 and a bit. Feasible. But at tick-over - at a camshaft around 20 rpm or on a good day, lower, this means a signal at 3 and a bit Hertz. And I'm fairly sure that a sound card (the input mechanism used in a computer-based system) will be out of its depth. ( I love mixing metaphores).

So, perhaps the idea from Robert (resp[onse no 6) is worth a second look. Have I got this right, chaps?

Cheers, Tim

It may be that I used the wrong term when I said 'an x-y graph'. A level physics was a very long time ago. I do not need lissajous figures, I just want a plot of voltage (y) against time (x). The critical thing is to measure the bulge in output voltage as the magnet passes the coil, and to look at how that lump varies in size as the speed varies. And then to look at the effects of rsistance, diodes, capacitance, induction, distance etc, added to the circuit at a fixed rpm.

And so far, it does look as if the Soundcard prog should meet the need, but it is rather quiet about what exactly should be used as a connector to the system tested. I am ploughing through the manual, though, so hope is not lost.

And sorry, the idea of getting to grips with yet another impervious technology at the wrong end of life is what I am trying to avoid. So, not and Arduino, thanks, however clever they might be.

Regards, Tim

A few comments:

The coil for use with a Kettering* battery system is not the same as one for capacitor discharge. The proportions of the two windings are quite different, as is (usually) the design of the magnetic circuit. So, when buying a coil you need to say which sort of coil, as well as single or twin output.

Single output coils can be used on a twin with a crank-speed contact-breaker - the idle spark has no real effect on plug-life, or electric consumption. They also work on a V-twin, but you need a contact cam at camshaft speed and with two lumps to match the angle of the engine.

The idea of a six-volt coil on a 12v system using a resistor to knock the voltage down, was used mainly on big cars which were not always good starters. there was an extra contact in the starter solenoid that shorted out the resistance when the starter was operating - compensating for the reduction in battery voltage as the starter drew 200 amps or so. And relying on the fact that the boost to the coil was only for a few seconds so overheating was not a problem. Some systems also used a resistor which as it warmed up in use, increased its resistance. So, you got a boosted spark at start-up, and less drain on the battery as the engine warmed to running temp (and so needed less biff in the spark).

* Kettering ignition is the proper name for what is often called 'coil ignition' or battery and coil ignition'. Confusion can be caused as almost all ignition systems have coils, and almost all vehicles have batteries too. Kettering was the Chief Elecric Engineer for the DELCO company in the USA, and his work led to the eventual abandonment of magnetos - especially (you guessed!) in American cars - starting about 1912.

Cheers, Tim

I need to see a plot of the voltage produced as a magnet passes a pick-up, at varying rpm. Can you recommend a program to use on a lap-top or tablet (Windows 10) - to produce a plot either in degrees round a circle or on an x-y graph? It is only for one series of measurements, so cheap if possible.

Regards, Tim

One further factor -for next time - that i don't think anyone mentioned, is that on most modern bolts the hexagon head is not likely to be central to the thread. Pre-war bolts were more often turned from hexagon bar, so the problem hardly arose, but mass production, while cheaper, is not always as 'accurate' in factors which don't matter most of the time.

Do come back if you get stuck again, but try to do this when you are properly awake ... !

Cheers, Tim

I can offer a possible reason for passports to say the town (etc) of birth but not the country. In the last 100 years many country borders have changed, but fewer town names have. So, if the border of eg Poland changes (as it has been known to do) your passport still remains a true and up to date statement, even though the town was in Russia and then in Germany for a while.

Quite how this helps regarding Bombay and Mumbai I cannot explain, though. Other confusions are available.

Cheers, Tim

Edited By Tim Stevens on 17/09/2022 15:44:34

Sorry, my mistake ...

Tim

Edited By Tim Stevens on 28/08/2022 10:56:25

Good - because caustic soda (NaOH) dissolves zinc almost as quickly as it dissolves aluminium.

Cheers, Tim

Duncan - yes of course you can. You will need a significant space(see below*) to put the devices in, and it is not likely that the output, even if you have shower after every meal, will match the cost of the installation or its servicing. *And of course, the only spare space in the average house to put such a thing is where the shower used to go.

Cheers, Tim

Edited By Tim Stevens on 09/08/2022 17:17:44

Goodness me, Hopper, philosophy on a Tuesday morning.

Yes, you are right, in so far as I cannot prove that you are wrong. But in order to survive, we learn early on to follow certain conventions which work out to be useful, as long as others do the same. We say 'The sun is bright today' on the basis of a convention that what we percieve as (or think we do) a blob in the sky which dazzles us whenever we gaze at it is called The Sun, and so ad infinitum.

If we don't accept these conventions, nothing I write here will mean to you anything remotely like what I intend it to mean, so is there any point in pretending to discuss the matter further?

Yours conventionally - Tim

Neil - I suggest you ask Mr Schroedinger. He might know (but I doubt it).

Cheers, Tim

Blowlamp seeks to know why energy prices have risen.

1. Demand has risen as
a. lots of folk set off on their world-tour holidays
b. Lots of firms have returned to full production
c. etc

2. Supply has reduced because of
a. attempts to reduce emissions:
b. war in Ukraine and sanctions on Russia
c. etc

Simple economics - increased demand increases prices as users compete for supplies, reduced supply increases prices as users compete for supplies.

Still not sure? Ask yourself - why are diamonds more costly than sand?

Hopper views everything as fairy stories, but in my view, some of those fairy stories are backed by evidence - which can be repeated and tested and makes sense. Of course, relying on this does rely on the existence of, and confidence in, sense. Other theories are available, but many of them don't work.

Regards, Tim

Edited By Tim Stevens on 09/08/2022 11:10:57

Blowlamp reminds us of 'one of the problems we have'

Can i remind us of another - the tendency, when we don't know what is going on, or why, to invent fairy stories and spread them around as if they were 'gospel'. Well, there's a clue there - this has been going on a long long time.

Please, everyone, if you don't know the facts with a good degree of certainty, guess if you like, but DO IT SILENTLY.

Thanks - Tim