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.

.

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.

.

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.

.

[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.

.

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.

.

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.

.

[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.

.

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.

[Michael GilliganParticipant @michaelgilligan61133]

A quick bump for this potentially useful thread

Experimenters might be interested in this ebay offering:

https://www.ebay.co.uk/itm/276719767514

[various sellers & various prices]

.

Unique design with an original secondary coil for conducting experiments on lenz’s law of electromagnetic induction.

.

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

Quick update, my sounder project temporarily diverted into the software side – the ESP8266 code that translates text, translates it into Morse, and the drives the sounder.   Works well but needs more testing.

I’ve put a little effort into designing the mechanical sounder, and received help from Duncan Webster who supplied a PO Relay as a source of soft iron, and an anonymous friend who sent me this excellent link on PO Relays – most informative!

Wishing to design an electromagnet that provides a known force from a given voltage (6V), I’ve been collecting the formula that needed to do the sums.

Assuming the sounder should produce an audio click of about 1W, and the click-arm is fitted with a return spring of force N:

• How much electromotive force should the electromagnet deliver?
• How many watts are needed to power the electromagnet at 6V.  (Calculate current)
• Therefore to what resistance does the coil have to be wound?
• Given the physical dimensions of the proposed coils (2 in series), how many turns of what gauge magnet wire are required.
• What length and weight of Copper wire of the required gauge has to be ordered.

Data so far, which may help others treading the same route, extracted from my design document:

The project is educational, attempting a design that meets a specification, not experimental.  Wrapping magnet wire round a couple of 6″ nails and hoping for the best is a poor option when a couple of thousand turns are needed, and the coils have to fit into a given space.  A sounder that works is easy enough if the builder is prepared to alter volts and amps to suit, and doesn’t care if the on and off clicks are unequal.  Building an optimised sounder that doesn’t make Morse hard work by mangling the timing is trickier than I first thought.

I think building a sure-fire IMLEC winning loco would present similar challenges.   Matching firebox to fuel, matching tubes to firebox, identifying optimum speed and tow-bar pull relative to cylinder volume and piston stroke, matching steam pressure and capacity to the pistons, and identifying optimum timing are all a balancing act.   Existing IMLEC competitors all appear to be rule-of-thumb designs, nothing wrong with that for general purpose running, but unlikely to squeeze out all possible micro-efficiencies.    May not be worth the effort.  It’s interesting that full-size 60631 Tornado has similar performance stats to the original A1 locos despite benefitting from modern design methods. It certainly doesn’t leave them in the dust!

Dave

 

[Michael GilliganParticipant @michaelgilligan61133]

News:

That nice Mr Ali has a lot of sellers offering Tau 5030 Solenoids, at prices bearing little resemblance to Amazon’s

But, as we don’t do links to the aforementioned … here’s Amazon:

https://www.amazon.co.uk/Electromagnet-TAU-0530-TAU-0530B-Solenoid-Keepping/dp/B0CF86CFM7

MichaelG.

[SillyOldDuffer]

On SillyOldDuffer Said:
Quick update, my sounder project temporarily diverted […]

Wishing to design an electromagnet that provides a known force from a given voltage (6V), I’ve been collecting …

Very interesting post, thanks  Dave

Just an  ‘idle curiosity’ question:

Was the 6 Volt level that you mention “standard” for Telegraphs … and if so, what was the tolerance ?

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

On SillyOldDuffer Said:
Quick update, my sounder project temporarily diverted […]

Wishing to design an electromagnet that provides a known force from a given voltage (6V), I’ve been collecting …

…
Was the 6 Volt level that you mention “standard” for Telegraphs … and if so, what was the tolerance ?

MichaelG.

Sort of.   I’ve read a number of old books and they tend to be a bit vague!  Also apparent that back then the different telegraph and railway companies did their own thing – very little standardisation. Early telegrams were mostly handled by the railway companies.  They needed telegraphy for operational reasons, and were pleased to recoup the cost by allowing the public to send messages.  Later the GPO got in the act, and there were commercial and technical shenanigans when their network was connected to the railway systems.    Different operating voltages were part of the problem.  US and British books don’t agree either.

Seems most telegraph systems signalled at about 70V, and sometimes sounders were directly connected to the line.  More usual though for the line to operate a relay, and for the sounder and other equipment to be driven by a local battery, often a group of Zinc/Copper Crows Foot cells:

More detail here.  Quite elaborate!  “The electrolyte is derived from a blue vitriol and water solution. The blue vitriol must completely cover the copper element, and sufficient water must be added to cover the zinc element. A teaspoonful of sulphuric acid is added to this solution to give the best results. In order to prevent creeping of the electrolytic salts, the top of the jar is generally dipped into hot paraffine. Best results are obtained by pouring a layer of pure mineral oil over the top of the electrolyte, because it prevents evaporation as well as the creeping of salts. To put the battery into service after these steps have been taken, it is necessary only to place the cell an a short circuit for about 24 hours. This action produces a light liquid called sulphate of zinc, which forms around the zinc element and protects it. The copper sulphate solution, which remains at the lower end of the jar, is the heavier liquid. Very little care is required for the maintenance of gravity cells, because all they require is an abundant supply of blue vitriol and water. The best results are obtained when both liquids meet at a point midway between the zinc and copper elements. When the blue line falls too low, that is, on the level with or below the top of the copper element, blue vitriol and water should be added. When the copper sulphate begins to fade in color to a light blue, it indicates that blue vitriol should be added. Care must be taken that the blue vitriol crystals fall to the bottom and do not rest on the zinc crowfoot. The blue line should never be permitted to reach the zinc element. If the line rises anywhere near the zinc, the copper sulphate should be siphoned out by means of a hydrometer syringe, or the cell placed on a short circuit. As long as the cell continues in action, the quantity of sulphate of zinc increases. When this becomes too dense, or above 1.15 specific gravity, the top of the liquid should be siphoned out and water added to the remainder.”

About 1.1V based on Zinc having a standard potential of -0.76V on the electrochemical series, and Copper being +0.34V

Not difficult to make a replica.  If only I had time.

Doesn’t look as if tolerances were tight, and I’ve not found mention of anything as sophisticated as a voltmeter!

A later book mentions the battery being a 6V accumulator, and I went with that because 6V batteries and PSUs are readily available today.  Thought about 5V from a USB wall-wart too, but dropping the voltage reduces an electromagnets response time.

Trying to build up the enthusiasm necessary to tackle some magnet maths today and find I would much rather take a nap!

Dave

 

 

[Author]

Posts