Winding a strong electromagnet

[mondrasek]

Hi mondrasek!  Yes - that online coil simulator is awesome.  I've used it often to determine wire length and resistance of coils of certain dimensions - works fine for cored-coils in that sence.
Have you done anything more on your gravity/latch wheel?

Capthook, no, I have not done anything more with the gravity/latch wheel that uses PM stators.  Once I found the flaw in my logic I realized that I had nothing new and was therefore bound by the laws that show a pure gravity powered machine is impossible (barring the invention/introduction/generation of anti-gravity).  Until finding that mistake I had to assume that something unknown or untried with the magnet arrangement was supplying something more.  I was/am fairly ignorant about magnetics.  But that lead me to thinking more about them and the possabilities for using electromagnetic stators.  I've researched that a bit as you have seen, but only so far.  Since what I've seen so far supports that magnetic fields are, like gravity, a conservative field of force, I've little hope for that route either. 

But I am still intrigued with the relationship of magnetism and electricity, as this has been harnessed successfully to do work in many forms, including the electric motor.  I have no ideas how to design anything that can produce work without consuming or wasting more input electricity than it outputs (so far), but I've built and played with a couple Imohtep/Bedini fans and a Tesla switch while learning more about some of the different electromagnetic phenomenon that I hoped had potential.  The Tesla switch had me looking at electrical resonance as well.  Nothing has shown me OU potential.

The one thing that I still have in the back of my mind is the testing where I learned that a PM being accelerated away from an EM/solenoid induces a current in the EM/solenoid that appears to assist the acceleration and not oppose it.  This is still very interesting to me.

I had hoped Clanzer might find the desire to finish the "Mondrasek wheel" he started, just to see how close to unity he could come.  Maybe I will try that myself some day if I ever have the extra resources.

Nice to see Xaverius adding more EM info on this thread.  Spider's reference to Brooks coils also sent me back to the coilgun.info sim to do some testing.  I'd like to build a high self inductance, low resistance EM that does not have a core that is attracted by a PM, but I don't think that is possible.

M.

[TinselKoala]

I've had good results using soft iron wire (available cheaply at local hardware stores) for EM cores. The wire can be straightened by clamping an end in a vise and pulling the other end; individual pieces can be insulated with heatshrink, and a bunch of straight, insulated pieces bundled together or stuffed into a tube makes a very nice core.
Ferrites or other smooth cores can be held securely in compression fixtures that can be easily fabricated from plastic stock.

[capthook]

I've had good results using soft iron wire (available cheaply at local hardware stores) for EM cores. The wire can be straightened by clamping an end in a vise and pulling the other end; individual pieces can be insulated with heatshrink, and a bunch of straight, insulated pieces bundled together or stuffed into a tube makes a very nice core.
Ferrites or other smooth cores can be held securely in compression fixtures that can be easily fabricated from plastic stock.

Iron wire is similar to the Bendini design using welding rods.  The problem is the airgap between the individual pieces, resulting in less total material and thus a less effective core.
For mounting - I have considered something along the lines of adjustable hose clamps.

- - -
A few other design notes:

For traction magnets - a slightly rounded, convex  core end will actually have stronger holding power than a flat face.

And as to adding a permanent magnet to the far end of the EM to give the core an initial starting polarity as mentioned earlier - consider this:
"If we have a certain number of magnetic lines, N, the pull is proportional to N(squared).
So the more powerful the pull to begin with, the greater is the change of pull when you produce a small change in the number of magnetic lines."

I'd like to build a high self inductance, low resistance EM that does not have a core that is attracted by a PM, but I don't think that is possible.
M.

And adding this magnet - in  repulsion to the PM, at the far end of the EM will negate the PM attraction to the core IF the airgap is sufficiently large and the end magnet is of sufficient strength (the airgap/end magnet strength/PM are relative)
- - -
A good (long) read is the following book, courtesy of Google scanned books project.  Though written in 1892, it is still valid in (most of) it's principles.

http://books.google.com/books/pdf/The_Electromagnet__and_Electromagnetic_M.pdf?id=CLmFTg_j0pwC&output=pdf&sig=ACfU3U3SDSRbaHhRwpQzx6pb7kwk3pCBuA

- - -
And I ordered some ferrite rods today for testing as cores (https://www.amidoncorp.com/categories/6) ... .5" x 3" 800u....should be here early next week...

As to breaking the windings down into smaller segments to reduce resistance:
This seems a huge idea - why isn't it the norm and why is X's mention of it (apparently) the first I can find mention of it anywhere?  Multiply the available amps, and thus amp-turns, seems HUGE!

However - for my particular application - I am pulsing the EM with a small capacitor.  As such, to increase the capacitor discharge time constant, I actually need some resistance in the circuit.

And the EM I'm using is a polarized (permanent magnet on armature/rotor) electromagnet in repulsion over an air-gap.  Once again - information/data on this style of EM is in short supply.

Any and all comments, thoughts and links would be of great assistance!

[Xaverius]

@ CaptHook, how is it going.  I can totally relate to your frustration on finding high permeabilty materials.  You're right pure iron is very expensive.  You might try ScientificAlloys.net.  They have a variety of materials and their sales personnel can provide information.  Have you tried Stormwise.com?  That's where I got my ferrite.

I'm not sure about cold rolled steel?  Could you provide more information about it?  The permeabilty is most important.  Another route you might try is to solicit a supplier for a sample. Usually it's free, you'll have to pay shipping and consult with a salesman.

I tried using GIron before.  It is similar to MuMetal, it has a permeabilty of 100,000 and is used in magnetic shielding.  Cost me $40.00 for a piece of foil one foot square.  I cut the foil into strips, stacked them together, wound tape around it and then wound it with wire.  A total dud!!!  No magnetic strength whatsoever.

I think the best material is silicon electrical steel which is very common but manufacturers will only sell to buyers with LARGE orders.  If you can salvage the cores from used transformers or inductors you could obtain the material, but I'm not sure how to do this.

@ TinselKoala, what is soft iron wire, is it picture hanging wire?  What is it normally used for and what should I ask the salesman for?  I've heard that welding rods bunched together make good magnetic material, but I haven't verified it.

[Xaverius]

As to breaking the windings down into smaller segments to reduce resistance:
This seems a huge idea - why isn't it the norm and why is X's mention of it (apparently) the first I can find mention of it anywhere?  Multiply the available amps, and thus amp-turns, seems HUGE!

Why isn't it the norm?  Why indeed!  In the century and a half that motor/generators have been in existence this concept has been known, yet ignored.  Manufacturers/engineers are only concerned with practical applications of electrical equipment. Since the prime mover provides power to a generator the input energy is considered no object.  Since the generator provides power to the motor the energy used by the motor is no object.  Where innovation enters the picture is where for reasons of size reduction and energy conservation higher permeabity(electrical steel) materials are used.

It was not the aim of the original industrialists to produce overunity, their aim was(and is) providing products(motors) and services(electrical generation).  Modern capitalism is based on this premise, energy operates the world.  Without it, the modern world as we know it would not exist.  The only thing that will crush the power of the bankers/corporations is the implementation of free energy.