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Member postings for Marcus Bowman

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

Thread: Arduino Uno Programming Assistance Request
04/01/2018 08:32:07

Here’s a thought which interrupted my beauty sleep at 5AM.

It’s a bit broad-brush, but the application is at the end.

It is interesting to reflect that this problem has been solved quite effectively already, in a mechanical clock. As I am sure you know better than me, a clock has two distinct parts – time, and strike (or bong, as we are calling it). The time side does just what the name says. If we ignore, for the moment, the arrangements for ‘warning’ (i.e. the just-before-the-strike arrangements preparing for the first strike in a particular sequence to be delivered swiftly) at the appropriate moment (quarters or hours), the time side trips the strike sequence. While the strike sequence is doing its thing, the time side carries on. There is also no possibility that a second strike sequence can be triggered during striking. After the trigger event, the strike does its job independently, including using a rack or a count wheel to determine how many strikes of the bell take place. When the strike sequence has finished, everything is reset, and the strike side waits for the next trigger.

One clear demonstration of this kind of signalling by the time mechanism to an independent strike mechanism is in a musical clock with lots of bells. Generally speaking, the whole of the musical side can be removed independently, leaving the time side just doing its own thing.

So; in the Arduino system, the RTC provides the time, and the Arduino can work out what that is in seconds, minutes, hours and so on, using an interrupt.

Perhaps that same method can be used to control an independent electronic strike ‘mechanism’.

One way is to try to have the Arduino fetch the time, decide when to trigger the bongs by looking for an appropriate time, and control the timing within the bong sequence. That’s a combined effort, but the time and strike ‘mechanisms’ are separate functions. It is true they run using just one processor, but that’s a convenience allowed by software. It does lead to the kinds of problems you (and we) have been experiencing, because we humans have to work out how t interleave what are actually separate functions hanging off just one processor.

A second way would be for the Arduino to fetch the time, decide when to trigger the bongs by looking for an appropriate time, then signal the number of bongs to another device which will sound the bongs and deal with their timing. The Arduino takes nothing to do with that, and just carried on dealing with the time. That’s pretty similar to what a mechanical clock does. You may say that is inefficient, but in a nod to established mechanical solutions, it can be implemented at low cost. Add a Nano or something similar, to handle the strikes.

Then, the Arduino repeatedly reads the time from the RTC and decides when, and how many, bongs should sound. It makes available a sound_the_bongs flag, and a number_of_bongs.

The second device does a somewhat similar job to the Arduino, to deal with bong number and duration. It waits for an interrupt generated by the Arduino sound_the_bongs flag, reads the number_of_bongs, and deals with the timing of signals to relays etc.

So the time and strike ‘mechanisms’ are essentially separate, and function much as in a mechanical clock.

The elements of most of the code required has already appeared in earlier posts.

If you have an Arduino and it is connected to an LCD display, for example, the LCD display essentially handles turning data into visible characters. The Arduino doesn’t do that part. All the Arduino does is trigger an update and make data available to the chip on the display. It’s the same in most computer systems, with the CPU passing signals to a graphics or sound or network card.

In theory, cunning programming should allow a single Arduino to handle both time and strike functions (see earlier post commenting on co-processing). In practice, I wonder if it is not simpler to separate them and use two processors.

Alternatively, fetch the time using an interrupt, then control the timing of the bonging using an internal timer on the same Arduino. That makes it appear as though the Arduino is doing two things at once. The wonder of speedy execution and juggling of electrons. It’s a mixture of hardware interrupts and software timers.

Then I fell asleep again, until I was interrupted by the alarm.

Marcus

04/01/2018 07:45:04

James,

Ah, but that was work...

I thought for a moment you were going to say you used to go to a gym and could bench press 500Kg, but then you stopped and haven't gone for years. Now you find you can only do a bit, and you have forgotten how.

Welcome back to mental gymnastics...?

Marcus

02/01/2018 08:21:12

James,

Looking again at snippet 1, and working on the basis that it is always useful to know why something has gone wrong, I can't see where you do a LOW digitalWrite. Surely once the led is turned on, it needs to be turned off again after a period of time. Otherwise, it will stay on until you go around the loop again and turn it on again....and then it will never be off.

Snippet One
void Strike_the_Hour () {
unsigned long Present_Each_Hour_Strike_Time = millis(); // Sets the present time
Elapsed_Each_Hour_Strike_Time = Present_Each_Hour_Strike_Time - Previous_Each_Hour_Strike_Millis; // Calculates length of time that has passed since last event


while(number_of_strikes < 5){

State_of_Hours_Activator_LED = HIGH; // Activates the solenoid.
digitalWrite(Hours_Activator, State_of_Hours_Activator_LED);

:::::::so this turns it ON, but for how long? And where is it turned OFF again before you go around the loop again?

Even if it did go off, it will go on and off so quickly you will not see the off states.

SOD's program sets a specific delay time for that purpose, so that's one way of sorting the problem.

number_of_strikes ++;
}
}

01/01/2018 19:33:01

Just a thought. What has been proposed so far are good workable bits of code.

You mentioned earlier that your were reading the time from an RTC module. Does it, by any chance, make use of an interrupt on the Arduino? I ask because the interrupt will interfere with the millis() function. At the very least a long ISR will interfere with the count required for the value returned by millis().

Which library, if any, are you using with the RTC module?

Marcus

Thread: Condensation
30/10/2017 21:53:04

I have a friend who has just solved the roof element of this problem. His workshop is in a detached single garage with a cenent/asbestos type of roof (as mentioned by HowardT). It dripped badly and the whole place was a rust-generating environment. He has just replaced the roof with a proprietary product consisting of panels which have a ribbed metal outer skin, a thick foam layer, then a ribbed metal inner panel. The roof is now leak-free and doesn't drip. Instead of insulating the walls, he runs a small tubular heater all the time. Seems to work. One benefit being that the workshop is never chillingly cold. The roof was replaced in a day or so, and the panels seem easy to work with. They look the same as the panels used on many newish industrial buildings. Not cheap, but good things seldom are.

If it was my workshop, I would insulate the walls. Speaking from experience of two previous detached workshops, insulating the walls and ceiling (or roof) makes a huge difference. I had a large garage-sized wooden workshop which was lined and insulated with Celotex. Then I had a small detached single-brick outbuilding which I strapped and lined, insulating with rock wool. I also installed a night storage heater in that one, and I could run down the garden and stand in my workshop at any time of the day or night, with the temperature at a constant 64 degrees. Not even a hint of rust. Joy.

Marcus

Thread: Milling - How to get a good finishing cut?
29/10/2017 23:34:07

If it was me, I would use a polished, uncoated single-flute carbide cutter with an aggressive geometry designed specifically for machining aluminium. If possible, I would avoid using long small diameter cutters,

Speeds and feeds are pretty important. Spindle speed shold be basded on around 100metres/minute, so a 3mm cutter should be turning at somewhere around 10,000rpm. I'm guessing you are not running your spindle at that speed. A 10mm cutter should spin at around 3000rpm, which is achievable on many small mills, so that's a good go-to size for starters. Won't work for tight corners, of course, but ,as JasonB says, you may be able to deal with those by drilling, or by machining separately.

Rough out, leaving 0.2mm to finish. Climb cut the finishing cut. High speed, but a slower linear feed may help.

I have had decent results with a long series 2 flute cutter on 50mm deep finishing cuts, but it was a 10mm cutter, not a 3mm matchstick. Roughing at 3000rpm, and up to 500mm/min, taking cuts of 15, 15 and 20mm down the face, finisihing with a single climb cut pass at full depth, 3000rpm and 120mm/min. Material was grade 6082 (HE30).

Marcus


Thread: Soft Alumninium
29/10/2017 23:16:48

I have sheets of aluminium 1050 and it is officially specified as soft, with poor machinability (see: http://www.aalco.co.uk/datasheets/?gId=1). The 1050A is grade 'O' which is the softest, and I also have grade 'H' which is tempered. You do need to be quite careful when specifying which grade you need when you buy it. Grade O is easy to bend and shape, while grade H14 has a bit more stiffness. 1050 is lovely stuff, but only for forming, bending, etc.

At the risk of offering a counsel of perfection, I would punch holes in sheet up to about 2mm and would not normally attempt to drill it. I consider 3mm and over to be plate. The Q-Cut cutters work ok on the thin sheet, but they need to be sharp. They do, however, produce a nice curve into the hole, on one side of the sheet. At a pinch, you can use woodworking techniques, and I have seen, and tried, some simple techniques like using a woodworking gouge or chisel to punch a hole, then using a shaped fibre or plastic punch to finish the edges with a flare. It may seem like butchery, but produces lovely finished work. I have a Metalman 'corking tool' which is a chisel-style punch with various heads for that kind of job, and its a handy tool.

Bosch produce sheet metal hole saws with very fine teeth, and those may work on 1050, but they are expensive.

I also use some of the 6000 grade bars, plate and flats (6082, 6060, etc) and cast tooling plate. 6032 was formerly called HE30 and it machines quite well. The cast tooling plate is a joy. I would not use a standard milling cutter, though. In my opinion, the only cutter you should use is one produced with a geometry specifically to suit aluminium --- carbide with a single tooth and very aggressive angles. Accupro (sold by MSC Industrial) work very well indeed, but are very expensive. The finish is like chrome, even when machining dry. Use a high spindle speed and feed rate. Lathe tools are the same - you really must use a polished carbide, uncoated tipped tool for good results.

Its a lovely metal to work with, though.

Marcus

Thread: Medding MF4 drill pulley
09/10/2017 07:54:45

Is there a grub screw hiding in the groove of the pulley? My MF4 has grub screws as well as tapered keys in both pulleys. I'm not convinced its a tapered bush. I think it is a parallel shaft.

Meddings would tell you.

Great drills. I have had mine since 1975 and use it a lot.

Marcus

Thread: BSF and Whitworth "Across the flats " sizes.
09/10/2017 07:47:32

Once upon a time, MEW or ME published a table showing equivalences across W, BSF and Metric bolt heads, Sadly, I can't recall the issue.

Marcus

Thread: Milling Vice
01/10/2017 22:30:23

I use a couple of Vertex K4 vices, bought from Chronos, I think. They have worked well for me. Jaws are plain, with no grooves. I use sets of parallels almost every time I use the vices, so I'd recommend those, if you don't already have them. I don't see them on Chronos ay more, but Warco do them. I also see vee jaws for sale on Chronos, for the K4.

I took off the swivelling bases and fixed each vice to a plate of 16mm steel which has through holes to suit my tee slot spacing.

Marcus

Thread: A ghastly bodge
30/09/2017 07:35:40

Is there room to make a short adapter?

Marcus

Thread: Parting Off With an Interrupted Cut - Is it a daft idea?
19/09/2017 22:18:44

If you are worried, part off with by parting the major (continuous) diameter section of the bar, with the edge of the tool just at the intersection of the continuous section and the milled section. Any clean up or bringing to final finished width can be done using a 4 jaw chuck.

Marcus

Thread: Help Wanted
19/09/2017 21:45:04

Can you post some photos in an album?

Marcus

Thread: Drilling Tapping and cutter sharpening etc
19/09/2017 21:40:32

I seem to remember that an individual is allowed to make a single instance of a patented device, for personal use or study, but not for resale. Patents are, as you say, Michael, public documents.

Marcus

18/09/2017 22:34:43

Oh Dear! I bought and paid for a paper copy some time ago. However; I can confirm this is a jolly useful publication. I must say I prefer reading the paper copy in bed, rather than the electronic copy. The paper copy does a soft landing on the floor when I fall asleep...

Marcus

Thread: Looking for a supplier of tool grinding wheels.
18/09/2017 20:27:25

I have used AbTec for several wheels for surface grinding and for tool & cutter grinding, in recent times, and have had a happy experience.

www.abtec4abrasives.com

Marcus

Thread: Boring large diameter hole in aluminium bar
05/09/2017 19:05:20

Although 8 and 12mm bars are useful, I made an additional larger diameter bar with an HSS tip for finishing cuts on larger bores. It's 25mm diameter and much more rigid than the smaller bars. Although the tip is an inserted bar of HSS, it is fine for 2 or 3 fine finishing passes (all of the same depth of cut). It is a bit of a chore having to remove the 4-way toolpost and mount the big bar, but I have found it pays dividends. One of these days, I will make a similar bar which takes a polished tip insert. As you probably know, those polished inserts are available with different tip radii, and the slightly larger radii are ideal for smooth finishing cuts.

I have bought nice inserts and bars, and other tooling, from www.shop-apt.co.uk (with whom I have no connection).

Marcus

Thread: LBSC's Designs
05/09/2017 15:41:24

LBSC's magazine articles did that, of course. His subsequent books did the same thing for individual designs. In modern times, the equivalent is the ARM1G design, the book for which is shown here: http://www.g1mra.com/shop/

and its predecessors (Project and Dee), although ARM1G is designed to accomplish just what you describe, including lots of parts which can be bought from trade sources, such as frames, complete cylinder assemblies etc, so that the entry level can be tailored to an individual's pocket, capabilities and resources.

There is a case for 3D modelling of LBSC's designs, as a project in its own right.

There is another case for updating those designs, by converting sympathetically to metric dimensions (which would get my vote) to make them accessible for younger or newer builders (say under 70), and/or by updating the designs comprehensively to modern standards and practices, including modifications in the light of previous builders' experiences.

There is also a case for preserving the 'words and music' of text and drawings from the magazine articles. Those preserve an important aspect of his success, which is the 'can do' spirit. I agree with earlier comments about LBSC's intentions, and his ability to describe how to do the job with limited resources. It would not, however, be my approach now, as I think that although it may (and I do say 'may' lead to success, there is a danger that it fosters an attitude which rather devalues the depth of understanding and sheer skill which can be developed by deliberately pushing oneself to develop the appropriate workshop resources and associated skills to do the job in a more precise, and often more effective, way. This is, if you like, the difference between the approaches of LBSC and G. H. Thomas [I will stop here, as I notice a hobby horse preparing to gallop]. This is important, though, as it impinges on the discussion of whether to simply preserve the LBSC designs in their original state, or whether to comprehensively update them.

Drawings re-drawn by the magazine staff would be M.E. copyright, of course, as would the page layouts, but the words and original illustrations and drawings belong to LBSC's estate. Which takes us full circle, I think...

Marcus

Thread: Boring large diameter hole in aluminium bar
05/09/2017 08:07:34

RPM = cutting speed (metres/min) / circumference (metres)

Aluminium has by far the highest recommended cutting speed of all the common materials in our workshops, at 75 to 105 metres/min for HSS tools and 900 to 2200 metres/min with an uncoated polished insert.

At the lower end, on a 50mm diameter bore, that translates to 500 - 668rpm for HSS and 5732 - 14102rpm for a tipped tool. Two limiting factors have already been mentioned: lathe top speed and chuck rating.

So; run the lathe at top speed, but expect the carriage feed rate to be slow. The tipped tool rpm are well outside the Myford/Boxford/mini-lathe speeds, but that will not prevent the tips working reasonably well. I certainly would not be inclined to attempt this job with HSS tools, but opinions (and results) vary. I machine aluminium frequently on the lathe and the mill and have found the tipped tools or polished carbide cutters ground with cutting angles specifically designed for aluminium to be the answer to the clogging and sticking problem. Flood coolant helps too, of course, if you can stand the mess. WD40 stinks too much for me. Carnauba wax works too, but is too laborious to apply, and too expensive. Neat cutting oil works, as does water-soluble cutting oil. Application by toothbrush is too much effort, on a time-consuming job like this.

Some manual lathes (Hardinge, for example) can run at 5000rpm, and suitably rated chucks are available at a price.

The smaller diameter stages of drilling and initial boring will work best at correspondingly higher rpm.

In the end, we do what we can with what we have, and a 50mm hole is perfectly achievable without too much difficulty (except, as previously noted, for the copious swarf).

Despite the higher recommended speeds, I would simply use top speed and be content with the chrome-like finish on the final finishing cuts. Wondrous to behold.

Two other points:

The work needs to be gripped in such a way that there is clearance behind the work for the cutter to pass through without hitting chuck or faceplate, at maximum cut diameter.

The boring bar for the final stages needs to be stiff and/or of large diameter, to prevent 'ringing', and to provide sufficient rigidity for the finishing cuts. It depends on the finish you need on the job.

Marcus

04/09/2017 08:11:21

I have recently done much the same thing, for several workpieces. In aluminium, machining speeds are so high this is not a terribly lengthy job using large drills then a boring bar, compared to the same thing (also recently undertaken) in steel.

I mounted my AL in the chuck, drilled to 19mm, then used a toolpost-mounted boring bar and power carriage feed.

I used a tipped tool with an insert designed for AL (mirror polished, and with an aggressive rake). You have little chance without that, as an HSS tool will clog in seconds, especially at higher speeds without a lubricant. Using the insert, I machined the work dry, although flood coolant would be better. Coolant will also help prevent HSS tools clogging, but not for long.

I also changed the speeds as the diameter of the bore increased, to stay within the efficient cutting speed range.

The grade of AL also makes a huge difference. I used 6082 (HE30). 7000 grades are even better, but much more expensive.

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