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Member postings for Calum Galleitch

Here is a list of all the postings Calum Galleitch has made in our forums. Click on a thread name to jump to the thread.

Thread: New highway code rule.
23/01/2022 14:22:18

The photograph in question is a stock image, meaning it has nothing to do with the article; a harassed subeditor typed in "car door cyclist" to a stock image library and selected the first image that came up. Since so few of us pay for our journalism nowadays, these things are hardly a surprise.

As for looking in a mirror, I am surprised and concerned that so many posters have forgotten or never learned what a blind spot is.

Thread: Music on TV Programmes.
17/01/2022 15:35:26

An awful lot of the issues discussed are down to the simple fact that much television is now being made very cheaply. For most of broadcasting's history, the equipment was simple but high quality and maintained and used by highly trained engineers and operators who were given the time and resources to get the best from it.

Nowadays, a spotty youth can operate a black box and get adequate results. Once a programme is made, all these adequate results are mixed together by another underpaid spotty youth with too much to do and not enough time, with inadequate supervision, and the result is broadcast, mumbles and all.

Of course progress has done great things: the BBC offers many more services than they did, and I don't think many of us would want to return to the days of two, three, or four television channels.

Thread: That Strange Calculator Again
17/01/2022 15:24:11
Posted by Nigel Graham 2 on 17/01/2022 10:47:56:

Yes = I think the larger, blind holes are simply to take a finger-tip or the back end of a pencil, as in the old rotary telephone dials.

They certainly look like it, but I am still a bit sceptical - how many other circular slide rules of any function have this type of design? It's quite a lot of effort to go to to stamp and deburr twenty holes on a disc that could have been flat and turned with a finger. Rotary telephone dials required a positive stop and a bit of effort to turn, so the through hole design made sense.

15/01/2022 18:16:08

Probably worth saying, since it's been mentioned again - I'm quite sure this has nothing to do with music in any way; none of the numbers bear any resemblance to acoustic physics.

The thing that puzzles me still is the holes in the two dials. The holes in the inner dial are clearly a detent, but the ring of larger holes doesn't seem a sensible way of making a dial that would just be rotated about as in a circular slide rule. So was something inserted in those holes, or was something visible through the holes?

13/01/2022 22:59:54

Sector 1: 1/15 - 1/240 = 1/16, as does 1/12-1/48

So why the plus sign? Since some of the fractions given are improper, I think the point is to take an input from a process, which may arrive as an uncancelled fraction (say 6/8) and use that as an input to this device.

Since the plus and minus signs appear to be reversed, perhaps the purpose of this device is to generate some sort of correction.

Whatever it is, it seems to be a fundamentally mathematical process, based around sixteenths.

Lastly: there seems to be a sort of symmetrical correspondance, sectors 2 and 14, sectors 3 and 13, and sectors 12 and 4. But it doesn't continue, at least obviously. Why are sectors 7, 11, and 15-18 blank? Why is there no sector 19?

I don't think it is to do with Troy weights: one Troy pound is 12 Troy ounces, made of 20 pennyweights, consisting of 24 grains.

Thread: Internet Speed ?
04/01/2022 18:10:43

The CE website in its current incarnation is really struggling. It doesn't work at all on Firefox (for me at least) and only grudgingly on Chrome. I wouldn't attempt to order from it as it stands - if I needed something only they carry I'd ring them for it!

Thread: Headphones - any other deaf folk out there?
06/11/2021 22:25:16
Posted by Robin Graham on 06/11/2021 00:03:13:

The idea of getting internet connectivity in the cellars by powerline is attractive - but would it work given that the cellar electrics are on different circuits from the rest of the house?

For what it's worth, my powerline network here runs well from my office through the rather dodgy domestic wiring, through the domestic meter, into the main spike and back out through the three phase meter for the farm, down yet more dodgy three phase wiring that splits out somewhere I haven't even been able to find, and finally into my workshop. I'm lucky I guess that the domestic supply is on the same leg as the one split from the three phase on the other side. Anyway, point being it's a fair old distance and doesn't seem to struggle at all.

Thread: Antikythera Mechanism
02/11/2021 16:43:20

That's a rather different meaning of sparse - from the statistician's point of view, our Antikythera problem here has an abundance of data, we just don't like the answer. Sparse is more like (to continue the car insurance analogy) knowing age for some, gender for others, make of models for some, and not having a full set of factors for most of your datapoint.

One of the problems with statistics in general is that it's a very new subject (Akaike himself died only in 2009) and beyond the basics, it gets fearsomely mathematical very quickly. Moreover, in many domains it's a skill that is called on infrequently. I have a fairly solid grounding in conventional and Bayesian statistics, but I'm still hesitant to weigh in on this problem.

01/11/2021 22:40:18

Akaike, not Akaite. AIC is for selecting between different statistical models where there are many different possible factors that a particular model may use. For example, a model that assesses your risk of crashing a car (for insurance purposes, say...) could use your age, gender, hair colour, location, car type, engine size, and so on and so on and so on. However, the more factors you use, the more your model is just a complicated representation of your original data. AIC is used when you have a selection of similar models and want to select between them.

Thread: Moving and Storing a Workshop
29/10/2021 00:49:31

I wonder if it might be worth calling one of the workshop clearance guys and ask if they could handle it for you - doubt it would be cheap but then I doubt it'll be cheap however you do it, tbh.

Thread: Reproduction ivory look hand grips
14/10/2021 17:06:59

The GPS material Jason mentioned handles very like ivory, but lacks the crosshatching effect of real ivory. There is a rather cheaper material called Arvorin, which is made of resin and available in all sorts of shapes and sizes. It's a bit brittle so needs to be worked with care but does have a more realistic (though clearly not real) effect. White delrin can be baked in an oven and with a little care will scorch to a nice cream tone that can be polished. There is also the Guitar Parts stuff, which now includes Elforyn - they're pretty expensive but very nice and some of their grades are uncannily realistic.

Bone requires a lot of processing to degrease it, and if you don't do it properly it looks fine and then starts sweating fat a few days later.

You can still get actual mammoth ivory, although it's much more expensive and not particularly great quality these days. And if you search popular trading sites for "natural material", you can often find old and ugly bits of sculpture and carving that the world would not miss if they were recycled.

Thread: SKY abandoning their satellite customers
10/10/2021 19:15:17
Posted by Ady1 on 10/10/2021 17:57:37:

sat has got to be the future because they cant wire up the whole world, which would be daft anyway

The interweb consumes vast amounts of energy and resources

Satellite is ideal for broadcast, but less so for internet. My day job involves talking to a webcam all day, and it would be intolerable routed over satellite: you can't do much about the speed of light.

Thread: Indexing Plate
29/09/2021 15:29:41

The photo and drawing linked on this page show pretty clearly how a forked detent works in principle:

http://homews.co.uk/page541.html

You can apply the same logic to your plate.

Thread: Converting fractions to decimals
27/09/2021 23:06:59

Not at all - I have a little app on my phone that reproduces a complete slide rule, with my own choice of scales on it (Infinirule, it's called, for the curious). I even use it every once in a while.

Thread: Heatshrink sleeving as a heat insulator for valve handles?
26/09/2021 13:21:20

Two wee points about heatshrink: one, it only shrinks to about 50% of its size, so it needs to be carefully sized for the part. Second, over time it will lose the inherent tension it has when shrunk, and can slip if it's not mechanically secure.

I'd give the silicon tube serious consideration - it's easy to find in various sizes and colours and should be ideal, I would think.

Thread: The most complex clock built in our lifetime
25/09/2021 14:31:25

In the context of hobby engineering, the question "why" is not a valid one.

Thread: Myford ML7 accuracy
13/09/2021 23:47:20

Cal, it's probably worth saying that cheap Chinese made specialist equipment and cheap Chinese made lathes are not quite the same quality of thing. A lathe is fundamentally a machine that can make machines, and as such it can be altered, updated, improved, in a way that (say) a polishing tumbler or a ring engraver can't. You can with a little effort acquire a very bad Chinese lathe, though these days you'd have to make an effort to do so, but it would be capable of improvement in a way the ring engraver isn't. Many are based on the same fundamental design and they've been making them for thirty odd years.

That said, I think I'd agree about a Taig or Cowells: we often say "you can make small parts on a big lathe", but the truth is it can be a pain and there's an ideal machine size for a given part. Those lathes will be far better machines than the smallest/cheapest Chinese lathes.

Thread: Lathe Vertical Milling Slide
10/09/2021 13:12:44

I think Ade's one is from Warco, and is similar to the ones you see all over eBay, etc.

I've been looking at the topic a little myself, as I'm not really keen on buying a small mill that I will still want to upgrade in any case. There seem to be three routes:

  • bodge
  • buy
  • build

Bodge: I was considering simply bolting an angle plate to my cross-slide, and my compound to that. Unfortunately my compound has a fairly fixed post in the middle of it, the removal of which would be more of a pest than I think it's worth. Acquiring a surplus compound from eBay or the like would seem to make sense, but people want surprising amounts of money for them.

Buy: there are quite a lot of not very good devices out there, all of which I'd need to make an adapter plate for. Obviously a vertical slide is a compromise but I kind of feel all these are a compromise too far.

Build: there have been (at least) two builds in MEW, one recently in 305 and 306, and a bigger, more robust one in 205/6/7. I haven't had a proper look at this last one but just from scanning it looks like a solid machine. I was thinking of modelling it up in OnShape to see how it looks. Other suggestions warmly welcomed!

Thread: I need to cut chamfers into x64 pieces of mild steel - any advice?
03/09/2021 14:49:31

Can you make a jig to be held on the cross-slide, and take it off with a milling cutter held in the lathe? Once you have everything lined up, it should be pretty quick - lock the carriage and away you go.

Thread: Protractors scaled in Radians
26/08/2021 19:16:23
Posted by Bazyle on 26/08/2021 18:20:53:

I've never understood why Excel does trig functions in radians making for an extra calculation instead of providing a straight-up degree option. It must waste millions of man-hours per year around the world.

Well, I suspect the answer is that most of the people designing software in the early days were mathematicians, and so it made sense to make your software that does mathematics do it in a mathematical way. Or, probably more likely, those functions were imported in from a Fortran library, long, long ago and now can't be updated, or everything would break. As an aside, trig functions are calculated in radians, so if you enter anything else it must be converted under the hood anyway.

This may be egg-sucking territory, but Excel has a "named range" functionality, where you can give a grid of cells a name. This grid can be 1x1, and it functions like a programming variable. It is useful for constants like this: you can name a cell "to_radians", say, and then enter your formula as =SIN(90*to_radians).

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