Here is a list of all the postings Andy Ash has made in our forums. Click on a thread name to jump to the thread.
|Thread: Audi recall|
It used to be BMW's but I think the Audi has had "special status" for a while now.
I guess it's a combination of the BMW looking quite flabby these days, and Audi being on a sales drive.
The thing that didn't change was the mindset of the drivers.
Edited By Andy Ash on 24/09/2016 17:20:24
|Thread: using milling cutters|
Hopefully I won't be criticised for grandmothers and sucking eggs, but;
You could always remove the worst of it with a hacksaw.
Using some low-tech to do the worst of it, will save on the expense of a high-tech cutter. Plus, of course, when you convert all of your material to shavings, the bits you don't need can't be used for something else in future.
|Thread: Myford ML4 ?|
I'm pretty sure your machine has been modified Mike.
Normally the handle is on a shaft that passes through the apron. On the other side of the apron, on the same shaft is the pinion that directly engages with the rack.
Most lathes the saddle traverse operates in the other direction to the normal ML 1/2/3/4.
If you're working close to the chuck, you're used to a normal lathe and you forget; it can be nasty.
This is especially true when you finish a job and want to just wind the saddle back.
Many people modify them with an extra gear to reverse the direction of travel and avoid the accidental crash.
Edited By Andy Ash on 06/09/2016 20:51:27
|Thread: Hinkley C|
I am not of the view that renewables can provide the balance of energy that we need to keep going.
Core energy supply has to come from somewhere. Especially here in England, at our latitude. We will always need a way to get through the cold winters. We often get them. At a gentle extreme there is staying warm and comfortable. At a more harsh one, there is the need to keep sanitation - nee life support - for our cities going. In extremis they represent a burden for the nation, irrespective of our future willingness to feed them with energy.
I remain a supporter of coal, of which there are still considerable reserves. Coal will not run out in your grandchildren's lifetime. Obviously CO2 is an issue with fossil fuels. Although carbon sequestration is being explored it is not easy or cheap.
We should expect to pay more for our energy; This is not so that some Oligarch can extend his yacht.
Nuclear fuel is readily recycled and reprocessed. Although high grade waste is intensely toxic, unlike CO2 it doesn't escape you. It hangs around. I find it absurd that people see this as a bad thing. Indeed it makes the problem of our hunger for energy manageable. To my mind nuclear energy is ideal. It is honest.
It seems to be a part of the human condition to betray responsibility for our environmental impact. With Nuclear energy it is impossible to hide that impact of energy use without a structured, methodical approach to storage of waste.
I personally do not relish the Chinese input to the work being carried out at Hinkley. To my mind Chinese quality control, and indeed outright integrity, is not satisfactory for the standard of work we require in a flagship Nuclear reactor. If Hinkley as it stands today does not complete I will not be sad.
What I am sad about is that we know we need nuclear power. Indeed we need nuclear engineering. We need nuclear engineers. We have chosen not to invest in nuclear technology. Yet again in the UK we have failed to manage the pipeline of expertise and preserve capability, underwritten by integrity and quality.
Stupidly, we now expect other nations to provide excellent solutions to intensely difficult problems. At the same time, we expect those nations to deliver at the level of integrity and quality that we always did in the past. It isn't really surprising that they fail to meet expectations.
"If a job is worth doing, it is worth doing well."
"If you want it done well, you'd better do it yourself."
Edited By Andy Ash on 03/09/2016 20:27:50
|Thread: Tidal power getting going in the UK|
I always thought that the Boris Island airport would be a good candidate for tidal power.
Use the tide to lift it up.
Have the weight of the thing generate electricity whilst it gradually falls.
|Thread: Myford ML4 ?|
That last point from Neil is really critical.
Those pinch bolts are easy to abuse. Once abused, it's really hard to get it back again.
I apologise for not being very attentive, I've been a little busy this weekend.
I recently had a fair bit of dialogue with Wayne from Staffs. A whole load of ML4 type stuff (including the pinch bolts) came up. You might find that thread interesting......
Edited By Andy Ash on 29/08/2016 11:04:55
I think I know the holes you mean.
I don't think I ever had any screws fitted in there. One hole is full of paint.
The other is clear to the bottom, and I can see the shell, and then a hole through to the spindle.
If you rotate the spindle you can see it moving at the bottom of the hole.
The nearby oil holes look to be much the same if you remove the oiler.
Hope it helps.
That link is superb.
The A4 sheet that Myford sent me was obviously taken from that information.
It was the picture at the beginning and the Whitworth / Metric screw-cutting table in the middle.
I imagine they didn't send me the descriptions and part numbers so I didn't try to make an order!!!
I don't know if it helps, but you should find that the standard Myford vertical slide will fit on the machine.
In some ways the ML4 is better with the vertical slide then the ML / Super 7. The dovetail bed is better at dealing with forces upwards and away from the bed. Obviously the vertical shears on the seven rely on the retaining plates and the accuracy of the shims for upwards forces.
I remember being quite disappointed about that last point when I got my Super 7.
Edited By Andy Ash on 28/08/2016 10:55:56
I don't think your topslide is original, so I can't say what your grub screws do. It appears to have the ML7 dials by the look and these didn't come along for a good few years after the machine was made.
It's probably not a bad thing, the original had 12tpi screws, which are a little like a chocolate teapot.
I remember writing to real Myford back in the eighties when I got mine (as a teenager). I asked for a manual, but they said there wasn't one. The sent me a photocopy of the picture (IIRC) linked on Brian's profile. It was pretty grainy. Then at the bottom of the A4 sheet was the original screw cutting chart for the change wheels.
I don't know what I did with it. But it's long gone now.
Edited By Andy Ash on 27/08/2016 20:11:16
I think you might have some missing there.
Not including the ones that are part of the tumbler, I have;
2 x 20
25 - 65 in steps of five
Eleven in total.
If you look at my albums, you will see pictures of the back-gear assembly on the ML4. They weren't taken to show that detail, rather the actual headstock bearings. Irrespective you can see how the assembly works.
There is a lever to control the position of the back-gear on its eccentric peg. There is another lever to lock the eccentric peg in place. The lock mechanism works the same way as the tail-stock barrel lock. On the tail-stock the lock works to prevent sliding motion, on the back-gear the same scheme locks rotary motion.
There is no detent for the back-gear lever. Each time you engage it you have to carefully monitor the degree of mesh before locking the position.
There is a cast iron guard that covers the back-gear and a thin piece of sheet metal that screws to the guard casting to close the back-gear fully in.
Mine has a vee pulley now but it originally had flat belt. They came from Myford with either as a customer option, but early ones were sold as default with flat belt and later ones with vee pulleys.
I doubt you will want to paint it its original colour, which was a rather hideous shade of green. Not the modern soft green, but a vicious shade of malachite. I think it had a bit of yellow in it. I have seen flakes of it in areas of mine that have never properly been cleaned.
Edited By Andy Ash on 26/08/2016 10:57:08
|Thread: Charlie Dockstader' Simulator Program|
This one is even more belated!!!
I'm fairly sure you will have moved on from this now. I still don't know the actual answer to your question, but I do remember you asking it. I also remember thinking that the trouble with the Dockstader software is that it isn't very interactive. IF it has a layout for the gear you are interested in, then it can give SOME help.
I've been attempting analysis of valve gear on an engine and searching for new (free) software to simulate 2D kinematics. I've come across this software for "Windoze" called "Linkage"......
This version has not been out long, and I've never seen it before. It has been designed to do any system of links, slides, pivots, gears and pulleys. I've found some situations where it can't calculate a geometry which ought to be physically possible. Generally though it's much more usable than the Dockstader software.
It has a bunch of examples built into it, and one of them is Stephenson's gear. Most of the examples are simplistic, or weird things like marble launchers.
The only thing I think that the Docstader software has over it, is steam diagrams and plots of the valve events. I'm still experimenting, but you might find inventive ways to achieve the same ends. In any case if you want to experiment with the overall geometry of a valve gear this is certainly worth a look.
Hope the O2 is going well...... (I guess you probably finished it by now!)
|Thread: is this motor suitable for a milling machine|
From what you show it seems correct, but my meter probes won't reach your motor from here. Unfortunately I can't say you won't burn your house down!
Edited By Andy Ash on 03/08/2016 22:30:26
|Thread: CE marking and Brexit|
I must add to this by suggesting that even if the meaning were an actual directive (and not just FAQ), that this kind of intent will always be heavily flouted anyhow. I am unwilling to cite examples here because of the public and hostile nature of the discussion, but I witness it every day.
Unfortunately there are definite practical constraints that make such rules impractical. Often there is a choice to do no business, or to work around the book.
Edited By Andy Ash on 03/08/2016 21:53:37
I usually am wrong, but in the case you cite, it is the shop that is listed and not the panel. Unfortunately you cannot self certify your own shop.
Obviously your particular cited scheme only applies in the US anyway, but with reference to my own comments UL reserve and confer special meaning to the words "listed" and "recognised". These meanings hold throughout the world, as far as I can see.
Some of this just doesn't sound right to me.
My understanding is that a mark like UL recognised or UL listed can only be used if a UL test house has directly evaluated a product for compliance.
By contrast, a CE mark can in many cases be self certified. No independent test authority required to mark the product.
If one were to gain a UL type approval, for example, it would likely be a significant basis for justifying self certified CE marking with little other work. Equally one could quite properly and justifiably self certify for CE without a UL type approval.
Is is notable that a self certified CE marking would likely be ignored by a UL authority, unless it was unjustifiably applied. Indeed you would probably expect them to "dob you in" to someone, somewhere who might actually care.
What is even more interesting about the CE marking is that different product classifications have differing levels of standard. The Underwriters Labs are pretty strict as I understand it. Given that they are a commercial entity they have to be. The quality and reputation of their mark depends on them upholding good standards, wherever is it displayed. The authority protecting the CE mark has no such concerns - in most cases.
Actually, an interesting area of concern for the European authorities is pressure vessels. The CE mark is still self certified, but where pressure vessels are the subject of international trade, they must carry those marks, or be impounded.
I don't think there is any requirement that any goods be sold with any kind of mark anywhere in the world (except probably North Korea). I do find it interesting though that the EU specifically reserve the right to impound pressure vessels that cannot be traceably linked to a manufacturer.
|Thread: Electronic ignorance|
I found Solid state electronics particularly hard to get a handle on, but you have to treat it like the Romans would have.
Divide and conquer.
A discrete transistor is a special case of the solid state chip. It only has one transistor. Unlike a vacuum triode, you will be hard pressed to make a transistor at home. The vacuum triode was a British invention, and it is not surprising that it is better understood in Britain than the American transistor. Personally I think it is a sad reflection on our nation that if you can't make one in a shed then it can't be a British invention. It does seem to me that it is the case - I digress.
There are layers of thinking in a typical IC and you have to separate them and understand them individually.
At the lowest level you have the transistors and other passive circuit elements. One layer up you have the circuit techniques, things like current mirrors, differential amplifiers and logic cells. Two layers up is functional objects like whole memories, analogue signal conditioning, analogue to digital conversion and arithmetic logic unit functions. Typically these functions are glued together and sequenced with a special kind of functional object, the state machine. Where the state machine is externally programmable, the world of software dawns.
Together, these functions can be seen as modern wealth of VLSI architectures, video codecs, baseband digital tx/rx chipsets and so on.
Just try to deal with the one transistor first. There are different types. FET's aren't very different from thermionic valves. In a similar way that the grid potential intercepts charges in the vacuum triode, biasing the gate voltage of an FET varies the availability of charge carriers in the channel of the FET, by attraction/repulsion of an electric field.
Bipolar transistors are even easier to think about if you don't care about the accuracy of your model. If a semiconductor diode is a non return valve, then a transistor is a non return valve where the flow in the pilot controls the possibility for flow in the main valve. In both cases the most obvious effect is force needed to push the spring behind the valve and lift it from the seat.
Mathematically the way to predict transistor behaviour is through a model something like Ebers-Moll. Although it is a good model, actual transistors vary wildly. The model will never predict any particular transistor very well. By looking at the maths for the model you will see why quite quickly. One parameter is very small, but in an exponential relationship tiny changes dominate the behaviour.
Very few people have a need to model individual transistors. They naturally vary so much, there is no point. As has previously been described by others, you aggregate them and bring them under control in feedback loops. In the feedback loops passive components, which can be made accurately, tame and linearise the transistor parasitic effects.
Single transistors are good for power handling, but they usually have poor gain. Small transistors consume power in their own right, but can be much faster. You can always get enough gain by cascading amplifier stages. The only way to make higher frequency circuits is to use smaller transistors. Very small transistors are hard to package individually. High frequency circuits usually are packaged into VLSI chips with other parts.
High frequency discrete transistors can be made, but they are usually made in more exotic materials like Gallium Arsenide, where higher electron mobilities can be exploited.
New fields include superconducting technologies where electromagnetism can be used to control conductivity. Indeed, in some cases new types of sensor are possible using exotic physical techniques (Yttrium barium copper oxide for SQUIDS and high temp superconductors, Camium Telluride for x-ray detectors, and Indium Phosphide for millimeter wave.)
If you need high power and high frequency, it might just be that vacuum tube technology is what you actually need. In the end the Tevatron and LHC are just enormous vacuum tubes. I'm pretty sure they are still used fairly widely in high power applications like broadcast transmitters, industrial RF heaters and nuclear research.
Not only is it the case that no-one knows it all, no-one can think about all the things they know at once.
It's just divide and conquer, and that is all.
Electronics is not "obvious" in the way that mechanics are. That makes it harder to learn. You have to be able to do some maths to be able to figure out what it happening. Somehow you have to trust that your understanding, with the maths applied, really is what is happening.
If you get that bit wrong, then you won't figure out why it doesn't work without trial and error, which is going to be slow. Trial and error can sometimes be the answer, but without the maths you don't know how big the error was. The consequence is that you have no idea what to try next.
I've heard it called "stabbing in the dark". It is why electronics is difficult.
Mechanical engineering is not the same. There are things you have to know, but if the widget isn't long enough to reach, then you have to make another which is longer. If it keeps breaking, then it has to be thicker or made of a stronger material.
Mechanics and electronics are different beasts. Mechanics can be the art of making things to someone else's design. Hobby mechanics can simply be development of the skill and knowledge required to make something that looks nice and works well, from raw materials.
Electronics is different. By comparison there isn't much art in making a radio to someone else's design. It is enough for some people, but you can make the radio and it looks terrible, but works just as well as an immaculately constructed one.
The "art of electronics" is understanding and optimising what is happening. If you don't want to understand it, then there isn't much art to it.
I wouldn't recommend reading "The Art" from cover to cover. It's not that sort of book. The whole point of it, is that you get an electronics cookbook. If you want you can buy your own cookbook with circuits that you like, or want to explore. When you have built your circuit and it doesn't work, or you just don't understand why it does work, then "The Art", will explain why.
It probably won't answer your question directly, but if you use your brain, it will help you to realise the answer for yourself.
To those that don't like the book, I suspect it's because you've not tried hard enough.
You need to get hold of a book called "The Art of Electronics" by Paul Horowitz and Winfield Hill.
If you try hard you might find a free PDF which you can use on your tablet PC, but I would always recommend purchasing an original copy, obviously.
It's an unofficial "standard text" for most EE undergraduate courses.
|Thread: is this motor suitable for a milling machine|
I would have thought that although it is rated with dual voltages, it could still be used with an inverter.
It is common for three phase motors to be capable of being wired either star or delta. The impedance of the winding is different in either configuration. The rating plate should say if the rating is star or delta. If it does not, you would probably assume that the rating is for delta. This is how larger/older motor rating plates work, to allow for star/delta starters.
In your case the label inside the connection cover implies that the two voltages on the rating plate are for delta and star respectively. I'd say that you can use that motor with either a three phase or a single phase input inverter.
It does depend very much on what inverter you obtain to use with it. Generally an inverter with a single phase input will only have a fairly small output voltage rating. A three phase to three phase inverter would normally have a much higher output voltage rating. This is not a rule, just an observation.
To compensate and get broadly equivalent ratings from a motor at different voltages you would wire 240V delta and say 415 star. If you just want the maximum from the motor, wire delta whatever the supply. If you want efficiency and/or low inrush wire star.
There is absolutely no reason not to use a motor like yours with an inverter. You should do some simple experiments however. Get a current clamp and verify the rating plate data. You can also get thermistor protection relay packages from people like ABB automation. These can act to stop the motor in thermal overload conditions. That might be quite important with a fully sealed motor, like this. Obviously it must have poor airflow.
The connections you will have to buzz out. It looks to me like someone has written the terminal numbers on the wires. Check them obviously, but there is no reason not to use 10A marathon/choc block inside the box to make connections.
You should expect it to work out such that low voltage is the delta connection and high voltage is star connection. If it doesn't something is up.
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