Member postings for Muzzer

Truly immaculate!!

BTW, the text shown in the link differs from the page address it takes you to.

This is what you want for the blog: **LINK**

Murray

A few years back. my QNAP NAS (mirrored drive) failed and bricked both HDDs so I lost everything on them. Luckily I had periodically backed it up but I was still well pissed off. The root cause was the external PSU going West, corrupting the HDDs and/or controller as it gradually failed.

No excuse for not backing up. These days it is often just a case of plugging an external (pocket) drive in and it will do the rest automatically.

Murray

Gray - PM me your email address.

BTW, if you can get a rotary table with the same number of slots as you have cams on your Camlock, it makes the design a lot easier. However like me, you may already have bought the RT....

Murray

It says " no reserve" but closed without bids at $4250?? I must be missing something - perhaps it's an Anitipodean thing.

Murray

I've got the official ISO spec for the Camlock system. Just emailed it to you....

You can see a couple of glimpses here.

Murray

Edited By Muzzer on 10/09/2018 10:56:10

BTW, there seems to be a flatbed Drummond(?) up for grabs on homeworkshop ATM - "Small lathe and pillar drill" 25 quid near Doncaster.

Murray

Yes, that wins the prize!!

Get yourself a modern insert / holder system such as the AP** which have much better geometry and are supported with a vast range of modern insert materials, coatings, chipbreaker geometries and applications. There are many reasons why TP** inserts are essentially obsolete today. Ironically, AP** inserts are more suited to older and less rigid machines than TP**, as they generate lower cutting forces.

You can get yourself a 12mm AP** holder for 20 quid and matching inserts for under £3. If you are happy to take your chances on Banggood, AliExpress, ebay etc you can do even better but you need to have an idea what you are buying.

As mentioned, that insert has no obvious parentage, so could be made of sugar or flint. Whatever you do, get inserts of known / decent origin before you get too baffled at what you are finding.

Murray

Quite an interesting article from Misumi on anodising. Always been fascinated by the "sort of hexagonal" structure of the oxide cells that are formed. These are electrically insulating of course and can actually form a fairly effective insulation layer.

In a previous company, we found various instances where the primary insulator (typically Mylar film) on some mains equipment had been punctured by swarf or other particles but the anodisation layer had been able to withstand the test and / or operating voltage. Not something you should rely on and not something that would be approved but almost certainly prevented quite a few field failures.

Must try the process myself some time....

Murray

No sorry, your logic is back to front.You will only dissipate heat ("real" power) if the impedance has a resistive element to it. Or put another way, if the VAs have a "real" component, in phase with the voltage.

Remember that we are talking about measured values here. If there is no mechanical shaft power involved, all of the real / resistive part of the VA is dissipated as heat.

In the example I have, you could have a large VA and zero power factor ie zero dissipation.

Murray

On this side of the world there are requirements for efficiency. Good summery here Std efficiency (IE1) motors should be about 70-80% at full load. Obviously they will be 0% at zero shaft load but even if the losses remained constant across the range, that would be 20-30% of the full power.

More likely that he didn't take account of the power factor. If you measure voltage and current and simply multiply them you might be overlooking the fact that the current will be substantially inductive (lagging) ie out of phase with the voltage. He might actually be seeing 300VA, not 300W. With a theoretically perfect inductive load, you could actually draw a large lagging current / reactive power but dissipate zero real power (aka heat).

Can only guess, as not much to go on.

Murray

Aha, thought so but the different registered addresses etc puzzled me. Yes, the prices were very slightly cheaper. That parting kit at £98 (blade and 10 inserts) was a significant reduction over the individual prices for blade and inserts - blades are usually about £80 and inserts around a tenner each. Simpy wouldn't be prepared to cough up for that.

Murray

Had an industrial placement at English Electric Valve Co's Lincoln factory around 1984, working on microwave duplexer production and test. These were for pulsed radar with peak power in the 10s of kW - but average power much less than that. If I switched on the duplexer leakage tester I was developing without remembering to insert a duplexer, you could smell the ozone. Radar / microwave doesn't do anything insidious like sterilise you or give you the Big C on the sly - if anything you'd wonder why your skin was getting hot. I never noticed anything beyond the ozone smell.

It could have been a factory making plumbing fittings, as most of the materials were copper, brass, ceramics etc and processes were induction brazing, spot welding etc. The biggest valves they made then were giant thyratrons the size of hot water cylinders. IIRC, they also made parts that went into the Exocet missiles the Frogs had sold to the Argies.

A couple of years before this when I was at school, the Falklands War was going on and a friend and I constructed a 1kW linear amp for 2m band using a couple of valves rather like the finned one shown above. Power was 1kV and they lit up when you transmitted. Despite coupling this up to a large Yagi beam on a rotator, we failed in our quest to contact a family friend on a RN ship down there. Would have been something to talk about but it came to nowt. Quite possibly we would have miscalculated the transmission time but the distance was perhaps a bit ambitious.

Another valve we played with was one of those "acorn" valves. These were tiny by valve standards but we failed to prevent it from hooting uncontrollably at something like 500MHz. Transistors were a lot simpler to use!

Murray

Stung into action by several months of forced separation from my workshop, I suffered another serious accident involving a mouse. On this occasion it resulted in the delivery of a 3mm version of the Iscar TGFH parting tool kit from Zoro (see post above) and 5 of the uncoated inserts for loominum cutting.

Found myself back home and in the workshop this afternoon due to impending leave, so it would have seemed rude not to have done some initial tests.

Found a piece of 2" dia mystery steel and mounted the tool up in the holder. Being an industry standard parting blade size, I was able to swap out my existing Korloy "Saw Man" blade for this one quite simply.

The parameters for the (steel cutting) IC808 inserts are 4-10 thou per rev and 80-180 m/min (sorry for mixing units but my Bantam has an imperial feed gearbox). That translates to about 700rpm min surface speed.

Started out using girly settings ie 250rpm or so with tentative hand feed and the whole machine almost shook itself apart. Quite alarming and surely not good for anything.

Then upped the speed to 700rpm and took a more serious cut. Job done - no juddering and a nice curly ribbon of swarf. Juddering only started when the tool approached the centre, at which point the surface speed was obviously quite a bit lower. Engaged the feed (about 3 thou per rev) at 7000rpm and it cut like a good 'un.

No photos but a took a quick video for Seasick Neil.

Edited By Muzzer on 06/09/2018 18:01:05

EA Technologies used to be one of those myriad government funded industry research groups that were all flogged off to private owners or management buyouts. The waybackmachine from year 2000 says

The company became fully independent in October, 1997, with a management and employee buy-out. It is now owned by its staff of more than 240 people and new entrants to the company are offered share options after a qualifying period.

The company was originally formed as the research and development arm of the UK electricity industry in the 1960's. It became semi-independent in the early 1990's and has rapidly developed a culture which focuses on delivering technological solutions which are commercially practicable and valuable, whilst maintaining the highest standards of intellectual endeavour.

It's now a "consultancy" and I've encountered them on a professional basis on various occasions since around 2000, the latest being a (short!!) period of employment as head of engineering at one of their spinoffs which ended when I figured out what was going on, confronted the CEO and agreed to part ways amicably.

IIRC, the Capenhurst site (where I briefly worked) was the site of one of the first experimental nuclear reactors. Unlike any of its commercial cousins, this one was actually decommissioned although there are now various ongoing nuclear businesses there including Urenco (fuel enrichment) which seems to be putting up loads of new real estate there. Confusingly, AEA Technology also used to have a presence there although I see they went bust and are now part of Ricardo.

Murray

BTW - why does the forum says my message is "35535 characters too long" when it has less than 1600??? I pasted plain text in. Go figure....

Edited By Muzzer on 05/09/2018 17:27:46

To answer the question in the header - yes in general if you force the motor to spin faster than the no-load speed, the back EMF will exceed the supply voltage and the motor will generate. This applies to all of the above, including the various brushless motors - as well as"normal" AC induction motors.

There's a lot of ambiguity in motor descriptions but what is usually described as "brushless DC" is driven by 3 trapezoidal ie flat topped phase voltages ("6 step" control). If you drive the motor and observe the waveforms, they will look sort of flat topped. In contrast, an "AC brushless" will generate something approximating to a sinusoid. Both are synchronous machines with permanent magnet rotors and need to be commutated by some form of electronics.

You can commutate brushless motors without absolute position indicators (such as hall sensors, resolvers etc), based on the back EMF but the challenge comes when you wish to start the thing moving. Without movement you have no back EMF, so can't determine where the rotor is. In some applications you can just ramp the speed up and let it follow open loop but for loads with high starting torque or where positioning is critical this doesn't work so well.

Joseph - if you look at the phase voltages between your motors, you'd probably understand why they might have difficulty synchronising. I think you'll find they are a long way from either trapezoidal or sinusoidal.

Werner suggested using a PM motor as a generator but the voltage will vary proportional to speed. If you are driving with a variable speed (eg engine), this may be a problem! With a claw pole alternator ("Lundell" machine) that has a wound rotor, you can change the voltage constant by varying the rotor current, otherwise it behaves in a very similar fashion. That's what the alternator regulator does of course.

Murray

There should be a pin at right angles to the cam to hold it in place. On my Bantam D1-3 spindle there are 3 cams and 3 slotted screws. Remove these to have a closer look. Presumably one of them has been broken.

This thread shows some drawings from the standard that defines the dimensions etc.

Murray

One conclusion you can come to fairly early on is that fluorescent strips cost pretty much the same to run as their LED cousins - the cost in terms of W per Lumen works out very similar. The difference comes in other metrics such as warm up time, noise, ageing mechanism (flickering?), size, weight etc. LEDs lose light output as they age but a decent quality one should at least make it to the end of its natural life.

The biggest problem I've had with LED lighting has been premature failure due to crappy quality solder joints and internal components failing catastrophically. Almost all of the dozen or so "Luceco" candle bulbs I bought from Maplin (remember them?) have now failed due to dodgy solder joints going intermittent. less than a year after purchase and well within the claimed lifetime. I think many of these "lifetime" figures have simply been pulled out of their ass. Worth going for a semi reputable brand and keeping the receipts (buy online, click and collect etc keeps an electronic copy) so you can go back to them and play pop if necessary.

Murray

There are 2 versions of the sticky LED strips - the "IP66" version is allegedly proof against dust and liquid. Seem to cost pretty much the same but better suited to use within coolant-rich enclosures. These strips are pretty much a generic product now and available from any number of outlets. Being 12VDC powered, they are relatively safe.

Murray

We've all got our own bacon to fry and I won't tell you how to do yours. But if you think about it, with a closed loop stepper you don't need such big motors and drivers to be reasonably certain of getting the performance you need. So instead of climbing into a large, crude tractor so you feel certain of getting up the hill, you could do the same job using a Micra with traction control. If you must use that analogy.

Murray