Electromagnets (Split From Stuart Dynamo)

[duncan webster 1Participant @duncanwebster1]

It occurs to me that delayed release on Dave’s clacker thing could be sorted by incorporating a permanent magnet in the moving bit. Then an opposite polarity pulse through the electromagnet would repel the clacker. I think that’s how old style phone bells worked

[Michael GilliganParticipant @michaelgilligan61133]

Baseline: 1851

https://www.rigb.org/explore-science/explore/collection/michael-faradays-iron-filings

MichaelG.

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Edit: __ and here [1] is the entrance to that Rabbit-hole:

https://epsilon.ac.uk/view/faraday/letters/Faraday2485

[Michael GilliganParticipant @michaelgilligan61133]

http://faradaysdiary.com/ws3/faraday.pdf

Note: site is ‘not secure’ … but seems fine

apparently just a pre-publication PDF

… I took the risk … you might choose to avoid it.

[noel shelleyParticipant @noelshelley55608]

Michael, bearing in mind the original title of ME I would think that there will be designs for a simple coil winder to be found in amongst it’s pages , especially the early volumes ? If I remember later I will have a look. Noel.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, Noel … despite the obvious attractions of modern solutions, that would certainly be interesting.

Much appreciated

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

For general info.

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My order from Philip Harris arrived safely this morning

[ the obvious choice of supplier for anyone of my generation who did Science at school ]

https://www.philipharris.co.uk/

More anon, but at first sight it looks like my £19.50 was well-spent !

MichaelG.

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[Michael GilliganParticipant @michaelgilligan61133]

[John HaineParticipant @johnhaine32865]

…but similar to mine in concept which just uses mdf-like material, M8 studding, and a few other materials.

If you did decide on the CNC approach Michael, I can recommend a little program called Gcoil which takes the particulars of the coil needed and spits out gcode.  The original download is lost in the mists of time but can be found

here

(today at least!), and I have a copy I could share.

[Michael GilliganParticipant @michaelgilligan61133]

Excellent, John … thanks again

[ you have my eMail address ]

I have some bits & pieces of MakeBlock which will probably do nicely for most of the mechanicals.

MichaelG.

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Edit: __ their current website is a nightmare to navigate, so I’m sharing this page:

https://forum.makeblock.com/t/part-for-simple-linear-motion/28

[Nicholas FarrParticipant @nicholasfarr14254]

Hi MichaelG, I’ve never seen that Philip Harris website, some handy gear on there, and it looks like they might get some of my money, as they have a M1 500k calibration weight for not too much money. Thanks for pointing us to them.

Regards Nick.

[Michael GilliganParticipant @michaelgilligan61133]

Before embarking upon any attempt to measure the “magnetic softness” of our Iron with the devices at our disposal … I thought it useful to check what the Experts say.

This document https://www.nationalgrid.com/sites/default/files/documents/13791-Electric%20and%20Magnetic%20Fields%20-%20The%20facts.pdfc

cearly states:

Natural Sources

The earth’s magnetic field, which everybody is constantly exposed to, is around 50 microteslas in the UK.

and [ignoring any linguistic pedantry about the plural] that’s good enough for me.

It gives a reasonable calibration-point for the sensor in my iPhone, which is presently reading around 46 microtesla using the Magnetometer in the excellent Physics Toolbox. … At a rough guess, therefore, these sensors are within +/- 10%

Anything much better than that is likely to be very expensive, and high-maintenance.

I offer this only as a quick & dirty ‘reality-check’

MichaelG.

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P.S. __ The readings on my iPad and iPhone match to within a couple of units

[Michael GilliganParticipant @michaelgilligan61133]

Without wishing to take us off-topic, I would just mention that I am very impressed by Vieyra Software:

https://www.vieyrasoftware.net/

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

The presentation is bonkers … but there is a lot of good information in this:

https://youtu.be/FYZBmNxV9N4?feature=shared

MichaelG.

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[Les TParticipant @lest]

Philip Harris do 12 mm X 200 mm soft iron for electromagnets. I’m using this for a replica

Murday clock.

https://www.philipharris.co.uk/product/physics/electricity-and-electromagnetism/magnetism/soft-iron-rod/b8h26291

 

Les

[Les T]

On Les T Said:

[…] Philip Harris do 12 mm X 200 mm soft iron for electromagnets. […]

🙂

… as per the delivery note which I posted yesterday.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

To the best of my very limited understanding … the ‘Sounder’ that S.O.D. is proposing to replicate is covered by Bunnell’s patent 627,799 of 1899

… I have put a copy of this in my ‘Documents’ Gallery.

 

The significant point being that the patent really covers acoustic improvement of a device already well-known to those practiced-in-the-art

So does anyone have details of the first ‘design-concept’ ??

… any assistance in support of my searching would be appreciated.

MichaelG.

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Edit: __ Wikipedia to the rescue

https://en.wikipedia.org/wiki/Alfred_Vail

[Michael GilliganParticipant @michaelgilligan61133]

[Michael GilliganParticipant @michaelgilligan61133]

[ UPDATE ]

… despite which; I think this is the seminal patent

.

.

 

… I will be back !

MichaelG.

[duncan webster 1]

On duncan webster 1 Said:

It occurs to me that delayed release on Dave’s clacker thing could be sorted by incorporating a permanent magnet in the moving bit. Then an opposite polarity pulse through the electromagnet would repel the clacker. …

The main objection to Duncan’s idea in a Sounder application is the need to provide an opposite polarity pulse.  At the moment I intend to use a coil spring to provide the return, represented by a cylinder below.  It’s tensioned by the adjuster on the right:

To show the spring I’ve hidden one of the axle supports and a magnet!  This is the full view:

Food for thought though.  An alternative is a pair of opposed super-magnets, which take up a lot less space!

In terms of optimising the design, there’s a balance between the electromotive force applied by the electromagnet, the strength of the return spring and the lever action & mass of the top bar.  To give the mass of the top bar more time to build energy whilst accelerating, I’m pretty sure the electromagnet should be moved closer to the axle, but how close depends on the diameter of the magnet coils, which depends on the number of turns needed to operate at a particular voltage and current.  (I guess 1W will generate a sufficiently loud click, which means winding a coil for 6V @ 170mA)

Dave

[duncan webster 1Participant @duncanwebster1]

Negative going pulse is dead easy, you can get a chip with 2 H bridges, it even has built in flywheel diodes.

I can’t help thinking that simply mounting a decent size relay on a sound board would give you what you need, but it wouldn’t look good.

[Author]

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