Member postings for Macolm

Here is a puzzling computer episode. I have a five year old PC running Windows 10. It has a M.2 SSD for the operating system only, a SATA HDD for main data storage and a second SATA HDD used as part of a backup scheme. There is also a DVD writer, and a memory card reader utilising USB3. The problem started when the card reader failed to recognise a camera SD card.

Thinking this might be due to poor contact, I removed the card reader, which looked in good order apart from some dust. I cleaned the various sockets with switch cleaner, and put it back. But switching on, the PC hung, and my heart sank when the blue screen "Attempting Automatic Repair” appeared. I have had little success with Windows repair! However, there was no hard drive activity whatsoever, and after a few minutes it needed a forced switch off. Retrying, the BIOS setup did not reveal anything, indeed all voltages were in spec and all drives shown as present, but the failure to start remained.

An intermittent short circuit or similar hardware fault seemed possible so I proceeded cautiously, disconnecting the card reader, but still the hang. I then disconnected all the SATA drives, and now the PC operated normally with the M.2 drive, with system file checker not indicating any damage.

Replacing the SATA drives one by one, both HDDs operated normally. Reconnecting the DVD writer caused the boot failure, but disconnecting the power cable with the data wire still connected, the fault was gone. The DVD writer was removed, inspected for shorts or damage and powered up from a spare supply with no suggestion of fault. Replacing it with only the power cable connected, the PC worked.

Had that SATA channel failed or been damaged? With some trepidation I transferred the SATA cable to the second HDD, and the fault returned. Back to the original connection, but with a new SATA data cable to the DVD writer, and all was well. A faulty data cable! Yet checking the cable for shorts and continuity, no fault was found.

It is surprising that a SATA malfunction on a secondary channel could hang the whole PC. Certainly the DVD writer is first in boot order, but the second non bootable HDD showed the same malfunction.

One further Windows irritation. The card reader did not initially show up in Explorer, then I remembered that this happens if no drive letter is assigned - I had initiated reinstall. Catch 22! You need a non M$ utility to give the drive a letter. All was then well.

You do get used to the peculiar choice of cross slide dial increments. It starts well enough - one turn is 10mm on the diameter, and whole millimetres are numbered 10, 20 etc. Then it goes wrong with each millimetre divided into five major then five minor graduations, presumably somehow conceived to be as near as possible to traditional British units. After a bit it is OK, and does keep you on your toes!

It may be related to the power cross feed which is half the rate of the along axis. This may have dictated the two start cross lead screw, whereas a single start would be more satisfactory for precise setting, allow better dial increments, but would need a higher geared apron power feed.

Another thing to watch is projection of the plastic sleeve at the negative end. Intemittent problems with replacement AAA rechargables in out Panasonic phones were due to poor contact due to this. They are now fine after trimming flush with a razer blade.

The following website has interesting information and opinions about a huge range of domestic appliances. It can be useful to find what brands share a common design. Some of the information can be not particularly up to date.

https://www.ukwhitegoods.co.uk/help/about-the-appliance-industry/manufacturer-information

Repost:- edited to clarify.

A method I have not got round to trying for making a through hole is to mount the ball concentrically in the headstock, and use a Dremel or similar with a diamond point. The axis of the Dremel needs to be offset so that the point OD just overlaps the spindle centreline to provide good cutting velocity over all the area of the desired hole.

Finesse will be needed and of course progress will be slow, but it may work. Either finish to diameter with additional passes of the point, or locktite in an insert.

A method I have not got round to trying to make a through hole is to mount the ball concentrically in the headstock, and use a Dremel or similar with a diamond point. The axis of the point rotation needs to be offset to just overlap the spindle centreline so that there is good cutting velocity over all the area of the desired hole.

Finesse will be needed and of course progress will be slow, but it may work. Either finish to diameter with additional passes of the point, or locktite in an insert.

If you handle your own backup regime, just a recomendation for "Free File Sync". It is open source, allows filter criteria to be set and the setups saved, very quick, and so far has been entirely foolproof. It always seems to find the network paths OK even when Windows 10 is having a bad day with this.

I have a 80mm diameter circular slide rule that I still use occasionally.

Hydrogen as vehicle fuel is a new thing and there would be a learning curve which would include developing safety procedures, but it all looks manageable. It is widely used in industry and mostly treated with respect because it does have two tricky properties. Leakages can spontaneously combust, and it can burn with a nearly invisible flame.

Incidentally, the BOC safety advice is not to extinguish burning hydrogen leakage unless the leak can be totally stopped.

It would be necessary to use "zero carbon" energy to make it. Production from fossil fuel is likely to be less efficient than just burning that fuel directly. As with electric cars in the UK, for the next ten years it will be remote CO2 emissions, not zero emissions.

Neither is it on a weight basis if you include the mass of the storage container. Remember that the configuration of even 400 bar storage is likely to be an assembly of small diameter tubes to fit the space, rather than a single container which would necessarily be either spherical or large diameter cylindrical. Fancy any of this under the seats of your car?

Hydrogen cannot be liquified except at cryogenic temperatures. The critical temperature is -240C, so only 33 degrees from absolute zero. The boiling point at one atmosphere is -253C, so unless pressurised AND cooled, it can only be liquified for temperatures within 20C of absolute zero.

Practicable bulk storage has of necessity to use very high pressures, and thus energy per overall unit weight is less than for petroleum fuels.

The design of varifocal lenses is always a compromise between the desired gradation of optical power, and the inevitable distortions that result. The latter are the reason for the "swimming" effects, which for those lucky enough are completely corrected in the brain, and which for a minority are never tolerated. Designs have improved greatly over the years, but often minimised distortion results in perceived peripheral soft focus.

Most of the more expensive makes give some form of money back guarantee on the lenses, though mounting costs will probably not be covered.

Carbide needs to be kept in compression. Setting the tip slightly high (in a front toolpost) helps ensures this, even if there is a dig in; if the tip is low, there is a good chance the cutting edge will be pulled off.

I doubt if earthing the lighting will make much difference. This sort of susceptibility is common with high impedance logic circuits. If the capacitive scale is like most others, the positive of its battery is already connected to the metalwork of the scale. What is happening here is that the “operator” is an aerial receiving radiation from the lighting. The capacitance between his finger and a susceptible point in the scale circuitry is sufficient to induce a big enough "signal" to cause malfunction. If he “earths” himself to the mill metalwork, the unwanted signal is bypassed and its magnitude much reduced.

I doubt if it would matter whether the mill is earthed or not. There is plenty of signal path at the relevant frequencies to the mains wiring via stray capacitances.

Prevention would need an earthed screen, probably impractical in this case.

Edited By Macolm on 03/04/2021 15:20:22

Edited By Macolm on 03/04/2021 15:23:47

I should have mentioned, if the arbour has a drawbar thread, a "slide hammer" technique will work with screwed rod, a nut and a sliding weight. Someone recently reported success with this technique. A sufficiently robust drawbar would also do, but many just have a hex sleeve retained by a small pin rather than an integral bolt head.

Treated with care, keyless chucks are excellent to use. Do not attempt to drill or hammer in the centre recess. The actuation thread occupies the central core.

Not difficult if you follow the Albrecht instructions. The main problem is to undo the two halves of the main body. Well fitting half clamps to hold it in the vice and a chain wrench is best, but other means to grip it can be Jubilee clips or exhaust clamps, Protect the chuck with thin aluminium sheet. Dismantle over a tray!

Once dismantled, there is through access to knock out the arbour.

Edited By Macolm on 27/03/2021 12:47:53

Edited By Macolm on 27/03/2021 12:48:35

If the box was a standard single electrical box, Toolstation have good quality metal boxes complete with lid. It looks as if the board might mount on the long screws without the live connections shorting.

See Product code: 15062 - Axiom Metal Clad Blank Plate 1 Gang + Back Box

There are also similar boxes in other sizes. The website is frustrating though, and not everything they stock is necessarily displayed, but may be found with different search text.

If using Windows, for managing and processing images, Faststone Image Viewer is free, very easy to use, versatile and powerful. Navigation is similar to Windows Explorer, but double clicking an image brings it up in full screen. Then hover the cursor at an edge, and editing menus appear. To convert to jpg (or whatever) just use “Save as” to select saved image type.

Advanced features include batch processing and renaming, and very straightforward tools to move (sort) images to one of several folders.

There are a number of similar free image applications, but of these, I find Faststone the easiest and most comprehensive to use.

Agreed that the brush resistance is (necessarily) very low. However, the brushes inevitably short circuit the commutator segments as they bridge them, though there should be very little back emf between them at the point of commutation. Choice of brush material is thus a compromise between the series resistance introduced in the main current path, and the losses due to any residual circulating short circuit current (which higher brush resistance would reduce).

If the motor were rewound for, say, half the supply voltage, the current would double for the same power, and the back emf, per above, would half. Thus the optimal brush material resistance would need to be four times less for the losses to remain the same.

Perhaps I should have made it clearer – “The choice of brush material resistivity is mainly a function of the supply voltage”. To make it clearer yet, it is down to how it affects allowable current density in the brushes, so for similar size motors, the current will increase as the supply voltage decreases. This is why battery tools will usually have copper loaded graphite brushes, whereas small mains universal motors will use straight carbon/graphite.

In practice, choice of best brush composition is much more complicated. There is plenty on the Internet about this, but mostly oriented towards large machines rather than typical diy motors. If cutting down brushes to a smaller size, selecting them with the same supply voltage is a way to reduce the risk of problems.