Member postings for Geoff Theasby

Rather a case of fundamentals being deposed by 'whizzy stuff'. Great fun, but doesn't teach you anything. Log tables destroyed maths in school, so did electronic calculators, then computers, or so it is alleged. If you don't know how a manual lathe works, you can't get the best out of CNC, which is still subtractive machining. The dangers lie in relying upon such technology until it fails. Then your entire TV, music system, computer, diary, house control system is unavailable. I used to feel like this about transistors succeeding valves. Now it's microprocessors. Most of these can not be used unless programmed first, for which you need a computer and an extra box to do it. Until then it is all so much junk, like a car without an MOT. Even if programming (Coding) is not required, I need only hang a few components on a micro, and Bingo! An audio filter, or radio transmitter, or other gadget/test gear. Not that I advocate filing down a round bar to fit in a square hole, but studying electronics yet can't solder? First things first!Geoff

A sliver? Probably it set. Neil certainly knows his onions. Ha ha! Sliver and onions...

Going to bed now... <Rousing cheer>

Geoff

SDL, I was referring to the cooling fan blowers. I am not familiar with the torque characteristics of AC motors, but the same basic principles no doubt apply. From rest, the motors are drawing current but turning only slowly, so they need help to stop them overheating.

Geoff

• Norman, the mechanical diff feeds power to the wheel that is slipping. Hence the 'limited slip diff' in sports cars, which avoids this. Electric motors in each drive wheel don't do that, as a DC electric motor draws most current, developing most power at maximum load, ie the wheel that is NOT slipping. This has been the case ever since electric cars existed, about 100 years ago and more. This is also why DC motors are so good for traction purposes, and also why maximum cooling air is required when starting, since the motor is turning slowly, yet drawing maximum current, and getting hot. Hence particularly the air blower noise on Eurostar trains and other such railways.

Geoff

No, Neil, in a given medium, 'free space', open wire line, coaxial cable etc., the velocity is the same for all frequencies. In a comparison between mediums, the velocity may be different, one to another, and a resonant or tuned length will be longer or shorter by that factor.

Geoff

Haha! Why am I thinking of Cerenkov radiation? Anyway, coaxial stubs, filters, Hi-Q breaks, on 144 & 432 MHz

Geoff

Speaking theoretically here, but so what if a Myford lathe was designed 70 years ago? All lathes follow principles set by Henry Maudslay, but the basic design dates back thousands of years. The old hobbyists created great models from treadle lathes, or motorised them with i/c engines as in Greenly's book. With electric motors they became self-contained and stayed that way. Build quality surely matters more, and the lathes coming from the Far East have made our hobby much more affordable.

Geoff

The advantage of LEDs is that they run cool and last much longer. It helps if they are low voltage types, fed from a transformer, rather than mains powered ones. CFLs also last a long time, some of my domestic lights have lasted 10 years w/o replacement. Individual mains bulbs, esp. in a multi-branch fitting have a worse record. BTW, CFLs are not incandescent. There is no hot, glowing filament giving off light, but an electric discharge in the gas within.

Geoff

I'm replacing fluorescent tubes with strips of LEDs from a reel. If they aren't bright enough stick up some more!

Geoff

eLyrics.net

"Both: I had a little gramophone, I'd wind it round and round. And with a sharpish needle, It made a cheerful sound.

And then they amplified it, It was much louder then. And used sharpened fibre needles, To make it soft again.

Today for reproduction, I'm as eager as can be. Count me among the faithful fans, Of high fidelity"

Geoff

Thomas,

Catch a bus from Donc interchange, underneath the shopping centre, adjacent to the station. It goes right by the racecourse. If you or anyone wishes to meet me, I'll be there on Saturday, look for my ID badge on a yellow ribbon. tall, bearded, glasses, camera, Bunny Girl,

Geoff

Yeah right!

Spanners I could hardly pick up, Kango hammers I definitely couldn't, Ahhh, track laying for KWVR and Welsh Highland, when I was young and fit... "How tight should I make this fishplate screw?" " 'Till you can't tighten it any more!"

Geoff

Yes, 'drying oils'.

Geoff

I may be stating the obvious, but whilst a digital caliper is very convenient, LH or RH, a standard micrometer is usable in either hand, even upside down...

Geoff

https://en.wikipedia.org/wiki/Camphor

Geoff

That would be one of the Six Kingdoms you can see from the top of Snaefell.

Geoff

You mean I'm not a senile delinquent, even after trying so hard for so long? Oh drat! And double drat!!

Geoff

I discovered the Coriolis effect as a child, playing on a roundabout. Trying to kick the central pillar whilst facing inwards, my foot was deflected to the left.

In John Haine's posting just above, consider a small scaffold on a record turntable. A ball bearing suspended above the centre is set swinging. Now start the turntable and watch.

Geoff

OK, Russell, I didn't look up exactly how accurate the very best clocks are.

Sorry.

Geoff

I think that the lack of accuracy in a clockwork assembly would be much greater than the difference of one extra swing of the pendulum. If it swings once a second, that is 60 x 60 x 24 times per day, or 86,400, but he clock mechanism is accurate only to within several seconds a day, even in the best clocks. One extra swing of the pendulum is 0.001% of the day.

Geoff