Member postings for Geoff Theasby

Peak4, Sir Patrick Moore specifically warned against using solar filters on telescopes. If they fall off you get the full blast of heat and light, and will fry your eyeball.

Cameras should be OK in fog, as the light is dispersed as if using a neutral density filter, as is the heat. You may have to adjust the exposure value, and beware of condensation on the lens.

Geoff

I have a question. I know of the Doppler Effect, where the pitch of an approaching train horn or whistle rises, then falls as it passes and recedes. I have, however noticed that the whine of a jet aircraft, whether the Vulcan or the local police helicopter, appears to rise in pitch as it recedes. Any idea why this is?

Geoff

Great! Brooklands is fabulous! I went last year.

Geoff

NASA publication:

http://file.lasersaur.com/docs-thirdparty/Fastener_Design_Manual.pdf

Geoff

Titanium 'squeaks' when nuts and bolts are assembled, so Molybdenum Disulphide is used to lubricate them. Silver is also used as a solid lubricant, but may be a little expensive...

Regards

Geoff

I watched, and photographed it with my small camera, as it has a more powerful zoom, although the definition is a bit 'soft' at maximum. Left on Automatic, it focused on infinity, and got the colour very well. (It also used the flash, but strangely enough this had no effect!) I also discovered a few 'dead' pixels in the sensor. They look like stars on the LCD screen, but do not move with the sky, and do not appear on the image.

Regards

Geoff

No-one seems to have mentioned Patternmakers' rules.

Geoff

A little, the turntable motor, a few microswitches, the mains plug. But BEWARE of the high voltage capacitor near the magnetron, a two terminal device which can kill you with an electric shock if not discharged first by shorting with a heavily insulated screwdriver.

Geoff

This should liven up the thread...

http://www.shapeways.com/blog/archives/1952-revealing-dita-von-teese-in-a-fully-articulated-3d-printed-gown.html

http://www.shapeways.com/blog/archives/1952-revealing-dita-von-teese-in-a-fully-articulated-3d-printed-gown.html

Regards

Geoff

Clickable link added.

Edited By John Stevenson on 27/03/2015 12:43:25

It's not rocket science!

All the best engineers tell you to change the oil in your car engine every 6000 miles. It will last a lot longer if you do, whatever the manufacturers' or oil companies tell you.

Regards

Geoff

When I worked in satellite communications, we often used coaxial cables and had to fit connectors on the ends. The connectors were several pounds each, but much cheaper as a crimped version. The correct tool for crimping them on was about £125. However, my chief engineer didn't approve, he said he couldn't take them apart to see how well they had been assembled!

Geoff

>Big issue with these is that sooner or later you will attach the probes and put something more than a >few volts straight into the audio card and ...

The biggest issue I had was when constructing my radio telescope, I found a few volts coming 'out' of the sound card, which confused my satellite finder meter!

Sorry, M G Scroggie.

Geoff

Also, Foundations of Wireless and Electronics, William Scroggie. It has run to many editions.

Geoff

Gordon,

the industry standard is by Horowitz & Hill, The Art of Electronics, but it's expensive. The monthly magazine Everyday Practical Electronics is good at explaining how circuits work.

Geoff

Depends what you wish to measure. You can get virtual oscilloscopes and other test gear that work at audio level (Up to maybe 20 kHz) which you can download from t'internet, some free, some not, and beware of viruses!

Geoff

I bought the cabinet for a WM180 and stood it on that. I didn't bolt it down, and I have not needed yet to make long items, so the ultimate in parallel turning has not been required to date.

Geoff

Once on the Welsh Highland Railway, I was labouring for the stonemason when he was building a reception chamber for the trackside drains, and he had it nicely completed when a passing dumper truck driver asked innocently whether the drain pipes ought to be incorporated into it...

I had a Gat once, great fun it was. The muzzle velocity was so low you could watch the pellet in flight, and the way gravity caused the trajectory to droop at longer ranges. I have a couple of Airsoft replicas firing plastic pellets, they are better, a Glock 17 and a Luger. One of them is very inaccurate, but the other is quite good. My brother has Dad's .177" air rifle, I think its a Diana. The first time he taught us to shoot with it, he took along a plywood backing so we didn't endanger any sheep in the distance. Then we found out that the pellets were bouncing off it and coming back at us too close for comfort! We therefore tilted it back a little so they bounced off higher into the air, just as 'stealth' techniques are used to hide warplanes and warships from radar.

Geoff

As another radio amateur I can confirm that. the cheap ones are the worst, as the manufacturers leave out the interference suppression components (sometimes even the safety bits) after the things have been CE tested, or even just mark them CE without authority, as there is no regulation on the use of the mark. Good ones might be OK, but a quality manufacturer will be able to show you the test results. Well-known names in the industry might be OK, but check, and be prepared to pay!

Geoff