Member postings for Nick Clarke 3

Are the tips on your soldering plier removable or replaceable?

If so could you make two fine pointed tips to be applied applied to the larger piece, on one side of the joint? This would need to be held in contact with the smaller one of course.

Single sided spotwelding is sometime done in car repair, but at far higher temperatures of course.

And this is also useful if you are looking for sample electronic components - many manufacturers will go out of their way to support designers.

True, but the OP's question was "Is it possible in theory to add a lens or lens combo to increase the depth of field to the existing lens?"

Posted by Michael Gilligan on 09/10/2019 08:56:10:

To the best of my knowledge, Nick ... an additional positive lens will reduce the focal length of the prime lens.

If I am missing your point, then would you kindly explain.

MichaelG.

Apologies Michael - got my positives and negatives the wrong way round - but my post was about the practicalities of changing focal length so this is the corrected version:-

In theory it is possible to change the focal length of a lens, but only at the expense of changing all of the optical properties of the device.

The (approximate) depth of field of a lens is inversely proportional to the focal length squared, so by adding a second lens the DOF will be changed as the focal length changes. Adding a negative lens will increase the focal length and so decrease the DOF. If you add a second positive lens you will decrease the focal length and hence increase the DOF, but the magnification and the whole geometry of the setup will change. Almost certainly not worth it.

The classic work I use in a photographic context is Photographic Optics by Cox

The formula concerned is 1/Focal length 1 + 1/Focal length 2 = 1/Focal length 1+2

I hate inverse formulae!!

Take care, Nick

In theory it is possible to change the focal length of a lens, but only at the expense of changing all of the optical properties of the device.

The (approximate) depth of field of a lens is inversely proportional to the focal length squared, so by adding a second lens the DOF will be changed as the focal length changes. Adding a second positive lens will increase the focal length and so decrease the DOF. If you add a negative lens you will increase the DOF, but the magnification and the whole geometry of the setup will change. Almost certainly not worth it.

The classic work I use in a photographic context is Photographic Optics by Cox

I can recommend a good ointment!

Jason's video -

"Pressure on the outside of the can is over 3000 lb" - a bit high and by quoting the force on the can as a whole as pressure misleading to say the least!!

If a valve were fitted to the feed line and the boiler allowed to cool completely then there would be low pressure in the boiler. The minimum this could ever be would be an absolute vacuum - and in real life it won't be that low.

if the valve is now opened the pressure of the atmosphere in would be 14.7 lb/sq in hence this would be the biggest differential pressure. The 85psi pressure would be pushing out, not sucking in.

The need for exact standard sections becomes less of an issue if the design process is thought through. Where size is not needed to be exact many designers appear to have said 'chuck a piece of 5/32" bronze bar etc when what they needed was a piece of metal large enough to finish to the desired size, more or less. Also with older designs I suspect designers did not want to inflict unnecessary machining down to size on hobbyists with limited machining facilities. To the end of his life LBSC wrote about 'those lucky enough to have a milling machine' when today far more people either possess one or have access to one through a club.

What I am trying to envisage is the designer thinking of 1.2" but making it 1 1/8" for simplicity and today needing to use 30mm for convenience. Neither of the two alternatives are accurate to the original idea, but both work and if you want accurate - today you can mill it!.

One interesting thought about measurements is regarding copper sheet. It used to be thought that 10g, for example, was a replacement for 1/8" being a few thou thicker. 3mm is about 10 thou thinner than 10swg But US 10g (B&S) is thinner again. If we are buying copper sheet or tube with our import streams focused more across the Atlantic than into Europe which will we be getting in the future??

All will probably be within any reasonable safety factor, but several published boilers with 'grandfather rights' as established designs have been questioned in today's world and I don't think this will help.

I also agree - I use XP, Win7 and Win10 here along with different types of *nix and Mac OS - however being a computer nerd I get often asked questions along the lines of 'I use XP and my new printer won't work' or 'I have a new PC that came with Windows *** and now my old software won't work'.

Keeping old systems running depends upon you being able to freeze them in their entirety - as soon as you need to replace one part you can start to get issues.

But this isn't just a Windows issue. Apple upgrade as often and while their systems may seem to stay more stable they don't have to deal with the huge number of independent third party hardware and software suppliers that Microsoft do. To go onto the App store compatibility is checked - it is not at all like that on a PC! - and it doesn't last forever - I have a Mac Mini that is PPC based and won't run OSX 10.5 or later and a Classic Mac SE30 that is restricted to MacOS 7. Both still work fine with their own software and hardware many years after they were superseded.

By the look of it the front section of the lens does not rotate so a ring there connected to the tripod screw on the camera by a bar with a tripod screw at the centre of gravity may be the only way to go.

LBSC in December 1956 published a design 'For the kiddies' of a steam hammer to crack nuts.

Don't find the need myself but …….

If it is a wrong thread perhaps something left hand used in obscure Eastern European machine tools for a short period only in the 1920s??

On decimal day morning, just after opening time I went into a pub (not quite legally, I have to admit) bought a bottle of Guinness for the sake of spending my first decimal money. After a lot of '2.4 pence is a penny' and 'a shilling is 5p' and 'there are a hundred p in a pound' sort of discussions between the two bar staff I was given my change from a pound note.

Counting it up a bit later for the novelty value of seeing the decimal coins I found I had more than a pound in change ………..!

Michael

Can't find it using LTM or Leica as search terms on this site - have you a reference?

Edited By Nick Clarke 3 on 26/09/2019 18:28:48

Just been reminded of a weird thread - Leica Screw Mount lenses (LSM) were 39mm dia x 26tpi whitform - now theres an odd mix if ever there was one.

The USSR simplified it to 39mm dia x 1mm pitch - 23 thou of a mm larger pitch which presumably takes account of any minor threadform variations.

Leica lenses will screw into Russian cameras and Russian lenses into a Leica - I have both here - but there can be other differences as well.

Edited By Nick Clarke 3 on 26/09/2019 18:14:24

I can't ever visualise me being either14st or 89kg again

Yes - not in the rotational sense so much as fore and aft with every stroke.

One useful conversion is 750W is approximately 1HP - as older machinery is equipped with fractional horsepower motors while the smaller new stuff is measured in Watts.

Or didn't bother measuring it at all on the assumption no one else would either?