Simple audio amp design

The simplest lathe is the portable bodger's device; just a couple of pointy steel bits that can be fixed to a timber. Poke one point into end A of the workpiece, the other point into end B, and wrap a cord around the workpiece. Reciprocating mechanism (pedals, springs, counterweights, or somesuch) turns the work.

A traditional bodger would disappear into a wood with a few bits of steel, and come back at the end of the day with a few bits of steel and a packload of chair spindles, or table legs, or spokes...having cut trees and processed the wood.

A grain mill (water powered) could be built from wood and stone, of course. And until steam and electricity got convenient, iron mills were all on watercourses too. They made iron bars, and any smithy could turn those into pointy bits, thus making a lathe with hammers and tongs.

Not to mention the electric motor, the pulleys, the belts, and the electric power plant out there somewhere, some of which required lathes to build.

mandag den 27. december 2021 kl. 01.22.07 UTC+1 skrev Cursitor Doom:

once you build a bad lathe by hand you use that to make a better lathe .. earliest know castings is more than 5000 years old you can make gears with a file,

Mechanical averaging is a very powerful way to generate accurate motion.

With patience, you can lap three surfaces against each other pairwise to generate almost atomically-flat surfaces. Cleaving crystals is even better, if you have a single crystal handy.

Before interferometric control was developed around 1950, diffraction gratings were ruled using lead screws and very long split nuts. The two were lapped together over many cycles to smooth out the irregularities.

Once you have things that are very flat and straight, you can do a lot via geometry.

A good read is "Foundations of Mechanical Accuracy" by Wayne Moore, which is big bucks in the used market, but can be downloaded from archive.org.

Cheers

Phil Hobbs

three plates lapped together demonstrated here:

mandag den 27. december 2021 kl. 21.43.01 UTC+1 skrev Lasse Langwadt Christensen:

The Clickspring youtube channel shows a lot of ancient layout and toolmaking techniques in the process of making a Antikythera replica

Mica, split with an x-acto knife, is reported to have sub-nm RMS roughness. But I guess not very flat.

Yes.

It appears there are many different versions, so getting the specific one you had as a kid might require trial and error.

Interesting, thanks.

Cheers

Phil Hobbs

I know. I've done it myself. My big old Harrison lathe came without a threading dial which needs to mesh with the leadscrew, so I created one myself out of nylon using a needle file. Nylon was ideal to work with and since this application was close to zero load, practical as well. Dab of grease and job done. Of course any metal you can file will work every bit as well as the machinable plastics and may well be preferable in certain circs.

For somebody who claims to believe in evolution, John Larkin is remarkably unwilling to accept that today's lathes were developed from earlier technology by an incremental process - one that we could certainly emulate, if we had to. It might take a while.

On a sunny day (Mon, 27 Dec 2021 05:10:50 -0800) it happened snipped-for-privacy@highlandsniptechnology.com wrote in snipped-for-privacy@4ax.com:

Is not all ye need a 3D metal printer ?

There are places in the world where I think they never stopped making tubes. How's your Chinese?

I think the cathode coatings were the magical parts.

The quality of my Chinese (and Russian) is about the same as the quality of a lot of their electron tubes-not very good at all ...(some from my own experience, and feedback from ppl in other groups I interact with (e.g. audiophile and ham radio)).

That is what I have gleaned from my readings as well. I don't have the indepth physics background to understand the details or the chemistry behind it.

did you not watch it? His expermient showed about 50% atmospheric pressure in the crude valve / lightbulb.

Pressure is not the only issue, IIUC it depends on gas composition too. Air is not good in that respect, N2 is.

Ordinary incandescents have a low-pressure argon fill. Nitrogen is way too reactive at > 2500 K.

Cheers

Phil Hobbs

Some linear amplifier tubes had deliberate gas fill, which increased gain somehow. But it made them slow.

Thyratrons and VR and T/R and krytron tubes of course used inert gas.

Does anyone know what this is?