By continuing to use this site, you agree to our use of cookies. Find out more

Member postings for Tony Jeffree

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

Thread: Radio controlled clocks
12/06/2021 17:39:36

That would work! Actually, the BBC Micro:bit processor that I am using in my current clock is capable of broadcasting to other Micro:bit processors so that might be a simple thing to achieve - not sure about range though, I suspect it is similar to the range of Bluetooth so may not be good for the whole house.

12/06/2021 17:30:58

I have 3 wall clocks dotted around the house which used to contain "standard" Quartz clock movements, but a couple of weeks ago I remembered that I had three MSF radio controlled clock movements squirreled away doing nothing, and have replaced the "vanilla" Quartz movements with them. For the benefit of those that are not familiar, these movements use the radio time signal from Anthorn in the Lakes (broadcast at 60 KHz) to keep the clock accurate, and they revert to a conventional Quartz movement if they lose radio signal for any reason. The great advantage of these movements is that they are always accurate and automatically compensate for GMT and British Summer Time changes, so you fit and forget.

So far, so dull. However, given my recent experiments with a free pendulum clock where I used a gutted Quartz movement as a cheap means of providing motion work (see https://www.model-engineer.co.uk/forums/postings.asp?th=171748 ), it occurred to me that these movements could be useful in other projects, given that it should be possible to extract useful pulses from the drive system. The movements I have here seem to have separate drives for the minute/hour hands (pulsed every 15 seconds) and the second hand (pulsed every second), and these could be used to drive other things, for example:

- Use the 1-second pulse in place of a pendulum to drive more conventional and visually interesting motion work;

- Use the 1-second pulse to drive a hit-and-miss synchroniser to accurately synchronise a mechanical pendulum & associated motion work;

- etc.

There are also receivers/decoders around that can extract the whole of the data stream transmitted by Anthorn, which includes year, month, day of the month, day of the week as well as time of day, so potentially one could produce a mechanical clock with perpetual calendar, taking the data from the radio signal.

Anyone ventured down these (or similar) paths?

Thread: A prototype Lavet stepper motor
07/06/2021 09:59:48
Posted by John Haine on 07/06/2021 09:12:36:

I was thinking further about the bounce problem, I think if one could ramp the current to the solenoids, up and down, so the "holding" magnet ramps down while the "next" magnet ramps up, it should be possible to get smoother motion, even quasi-continuous. A 2-phase version might use a standard stepper driver with microstepping to do this; otherwise I wonder if an Arduino could do it using its PWM "analogue" outputs?

You can certainly do that - apply two sinusoids, 90 degrees out of phase, to the two coils of a conventional stepper and it should give you continuous motion or near enough. In effect that is what happens in a brushless motor.

07/06/2021 09:57:53
Posted by duncan webster on 07/06/2021 04:15:27:

I bought the book eventually, very good. He refers to #37 Magnet Wire. As it is an American book do I assume AWG? This would be 0.00445" diameter, which is near enough 41 SWG

I bought the book too - makes an interesting read!

27/04/2021 21:34:37

Talking of resonances, we have a long case clock that occasionally strikes a "duff" note - never the first of a strike sequence, and never more than a couple of times when (for example) striking 12. Nothing wrong with the striking mechanism as far as I can tell; I eventually concluded that sometimes the hammer strikes the bell at just the right point in its oscillation for the movement of the bell and the hammer to effectively cancel each other out.

27/04/2021 21:30:07
Posted by Michael Gilligan on 26/04/2021 18:16:36:

This one is even bouncier : **LINK**

https://youtu.be/zxVp0c2aFzw

MichaelG.

Ugh - that one's a bit rough to say the least - some nasty resonances interacting by the look of it. Definitely in need of some damping somewhere. There's an awful lot of inertia in that drive system which isn't helping.

26/04/2021 10:34:53
Posted by Michael Gilligan on 25/04/2021 22:33:21:
Posted by John Haine on 25/04/2021 10:44:48:

Sorry, lost a bit at the start of last post! I should have said that this chap, Weston Bye who writes in the Digital Machinist mag, has designed an interesting stepper that could be a better bet than the Lavet type.

.

Brief video here: **LINK**

https://youtu.be/B5S9yRCJkyY

... seems to have rather a lot of recoil [bounce] on that seconds hand.

MichaelG.

You could probably improve that somewhat by reducing the rotor mass and increasing the coil current...

25/04/2021 18:36:54
Posted by John Haine on 25/04/2021 10:44:48:

Sorry, lost a bit at the start of last post! I should have said that this chap, Weston Bye who writes in the Digital Machinist mag, has designed an interesting stepper that could be a better bet than the Lavet type.

Interesting - thanks. I had already started experimenting with magnetic gears...

Thread: DeskCNC resurrection - USB to serial adapter
10/04/2021 11:02:59

yes

09/04/2021 14:27:13

I converted my Taig CNC mill some years ago to make use of DeskCNC as the controller software/hardware (writeups were in MEW at the time). The mill has been gathering dust since we moved to Scotland in 2014 and I have only recently been resurrecting the PC side - the original laptop that I used had a serial (COM) port, which is long gone from modern spec PCs, so a major hurdle was to find a suitable USB-to-serial adapter that would do the job. I had 2 of these lying around that I spent much time & effort on, unsuccessfully - mostly due to hardware in the adapters that was too old to have any drivers that would run on Windows 10. So, after much frustrating effort, including managing to get one of the adapters to sort-of work with an old driver, I bit the bullet and bought a new adapter, one of these:

<USB adapter>

Which seems to work nicely with the in-built driver options that Win10 provides. I thought it would be worth mentioning in case others have come across a similar problem.

Now to see if I can remember how to run the mill and cut a few parts...

Thread: A prototype Lavet stepper motor
05/04/2021 19:24:49

There may be a short (or long!) delay while I get my Taig CNC Mill back up and running - looks like I will need to do some major surgery on the controller side as my Desk CNC software/hardware doesn't seem to want to play with a modern-spec PC. So currently looking at alternatives...

Thread: Greenwood Tools
02/04/2021 22:47:22

That is very sad.

Thread: A prototype Lavet stepper motor
29/03/2021 18:37:08
Posted by Michael Gilligan on 29/03/2021 18:33:47:

Posted by Tony Jeffree on 29/03/2021 18:26:16:

.

Hmmm...still not seeing where you are going with this...

.

Just that it’s a very simple milling job

Oh well ... probably best if I stop intruding.

MichaelG.

Ah...yes indeed. Mind you, my head tends to take me in the direction of CNC for that kind of milling, so much less of an issue.

29/03/2021 18:26:16
Posted by Michael Gilligan on 29/03/2021 18:04:57:
Posted by Tony Jeffree on 29/03/2021 11:17:23:
Posted by Michael Gilligan on 29/03/2021 08:22:06:

[…]

I will leave you guessing for a while devil

MichaelG.

What a tease, Michael smiley c'mon...spit it out!

.

angel ... it’s sheer poetry :

.661be963-b47b-4f13-a355-5e894037f4e5.jpeg

.

MichaelG.

.

Edit: Just noticed that I cropped a little too much off the bottom of the screen-shot

... The purple radius line starts at the 6 o’clock point.

Edited By Michael Gilligan on 29/03/2021 18:23:35

Hmmm...still not seeing where you are going with this...

29/03/2021 18:24:12
Posted by John Haine on 29/03/2021 17:58:17:

Nice! What is the diameter of the shaft please? It looks like about 2mm. Is the shaft silver steel?

I've ordered some of the magnets of the same size. I was wondering, if the shaft was the same nominal size as the hole, would it "short out" some or all of the flux? Can you tell if there is significant flux in the hole?

I'm thinking of trying the configuration where the stator is a solid strip, with a pair of "notches" in its periphery at 45 degrees, as in the wikipedia illustration (and patent I think).

How many turns on the coil? I've gone back to the coil winder project, have to get that working to make the coil.

Now where did I leave that bucket that needed mending.

The shaft is 1.5mm diameter and is the plain part of a 1.5mm twist drill. The bearings had an ID of 1.5mm and I happened to have a pack of cheap drills to hand so that was the obvious solution.

There is certainly some flux in the hole, but I suspect it wouldn't make much difference to the peripheral flux - might actually increase it. Worth some experimentation there.

I'm also considering the solid-strip-with-holes-at-45-degrees variant for the next (final) attempt as it is potentially easier to make.

The coil is 20mm long wound on a piece of 3/8" steel bar. The OD of the winding is a gnats less than 14mm but I couldn't tell you how many turns. The wire is 38 SWG. I'm planning to try a slightly different configuration for the magnet - I have 4 plastic sewing machine bobbins that I wound with rather thinner wire (50 SWG I believe) for another project that never completed; the bobbins are around 6mm ID. One or possibly two of those may be about right to drive a rather scaled down motor. We'll see.

Edited By Tony Jeffree on 29/03/2021 18:34:50

29/03/2021 17:00:01

I've made a new rotor for the motor. The original rotor looked like this:

The magnet (in the middle) is 6mm diameter 4mm long. Had to be made in 3 sections because the magnet is a solid cylinder. The new rotor:

The magnet is 6mm OD, 3mm ID, 1mm thick and the brass bobbin that it is mounted on can therefore be machined in one piece. Short video of the motor with its new rotor:

The motor runs much quieter than with the original rotor, as the magnet is significantly lower power. Next stage will be to re-make the electromagnet/armatures/pole pieces to scale them down to a more reasonable size.
29/03/2021 11:17:23
Posted by Michael Gilligan on 29/03/2021 08:22:06:

Update:

I may be wrong [ it has been known! ] ... but :

I think I now understand the elegant geometry of the tapered ‘horns’ on those rotor-arms

Although it looks like the production items might have been stamped from sheet; it should be a relatively simple matter to machine them from solid.

I will leave you guessing for a while devil

MichaelG.

Edited By Michael Gilligan on 29/03/2021 08:32:36

What a tease, Michael smiley c'mon...spit it out!

28/03/2021 14:15:20

The tapering is all about ensuring that the rotor's rest (un-energised) position is as shown in Fig 2. That is important so that when the next polarity reversal happens, the tapered horns are attracted to the next stator pole, and the rotor will rotate. It controls the direction of rotation of the rotor. If they weren't tapered (or bent inwards to create more clearance at the tips, which would have the same effect), the rest position would be somewhere more nearly half-way along the rotor poles, and it would be uncertain as to which direction the rotor would move on the polarity reversal.

You could achieve the same effect by keeping the thickness constant and the clearance between the rotor and stator poles constant, but making the "flying" part of the rotor poles taper to a point in the axial direction.

28/03/2021 12:10:07
Posted by Michael Gilligan on 28/03/2021 11:22:44:
Posted by John Haine on 28/03/2021 10:47:15:

A sketch for the purposes of explanation, as implied I think in p2 line 85. I suspect that in manufacture the rotor polepieces were stamped from flat plate then bent in two places, then finally milled to form the tapered circular forms on the actual poles.

.

Yes, I agree regarding the purpose, John ... but I’m trying to comprehend the three dimensional shape, which [regardless of the actual manufacturing method], appears to be rather like something you might cut from a ferrous equivalent of the plumber’s ‘stop-end’

**LINK**

https://www.jewson.co.uk/p/altech-end-feed-stop-end-22mm-copper-ALTEF068

MichaelG.

.

Hopefully: one of the 3D CAD wizards might come to my rescue, or Duncan might be able to provide a close-up photo [unfortunately, the photo that you grabbed doesn’t quite do it].

.

2d37a5bf-3eaa-44a9-bb06-a7c7dc60528e.jpeg

Edited By Michael Gilligan on 28/03/2021 11:30:36

Michael -

I found Figure 2 from the patent was the best one for visualising what is going on. You are right - the two pole pieces (10 and 11) are best visualised as being cut from a steel version of one of your plumbers' stop-ends. If you look at part 10 in fig 2 and attempt to screen out the "noise", the top surface of 10 looks very much like the profile shown in Fig 4, with the cylindrical portion of the part (which appears from the photo to be essentially rectangular if you were to cut it away and flatten it) has been thinned, so it is full thickness at the end nearest the electromagnet's pole pieces and tapers to almost nothing at the tips. The tips therefore clear the pole pieces of the electromagnet by the minimum clearance plus almost the thickness of the metal. The effect of this is that in its un-energised state (as shown in Fig 2), the permanent magnet will align the rotor so as to minimise the gap between the rotor's pole piece and the electromagnet's pole piece (which is the state shown in Fig 2). However, the thinner tail of the rotor's pole piece is near enough to the next electromagnet pole piece to ensure that when the electromagnet is next energised, with the reverse polarity, the rotor will rotate in the direction of the next pole.

27/03/2021 16:47:04
Posted by duncan webster on 27/03/2021 16:40:55:

But that would mean that at 5 to 3 (for instance) the hour hand would be resolutely pointing to 2. Better to build 2 off 60 step motors and only pulse the hour one once every 5 minutes.

It might actually be easier to make a 2 phase stepper with 60 notches per rev, the only extra is another coil I think, and the rotor is simpler, just cylindrical rather than the snail shape

No necessity to use hands, of course, you could use a digital style HH MM SS display.

Edited By Tony Jeffree on 27/03/2021 16:59:58

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Support Our Partners
emcomachinetools
Eccentric July 5 2018
cowells
ChesterUK
Warco
JD Metals
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest