Winding a strong electromagnet

[capthook]

The larger the area for a given flux density then the greater the amount of MAGNETIC FLUX.  The more magnetic flux then the greater the MAGNETIC FORCE.  DOUBLE the AREA, you will DOUBLE the MAGNETIC FORCE.

Magnetic force is what I was referring to rather than density - I should have used the proper term to convey my meaning.

So in the calculations you gave: ??

B= flux density in Tesla: (from the H and B calculations in the earlier post)  ?
A= cross sectional area of core (in meters: pi x r²) ?

N= Newtons ?
1N = 1kg x m â,, s2 : (how did you translate into lbs/kgs - what value for m(meters) and s(seconds) ?

So you calculate B (as in earlier post) and then do this futher calculation for F ?
- - -

Also have the following equation that hasn't been listed/mentioned:

Force between electromagnets
For electromagnets (or permanent magnets) with well defined 'poles' where the field lines emerge from the core, the force between two electromagnets can be found using the 'Gilbert model' which assumes the magnetic field is produced by fictitious 'magnetic charges' on the surface of the poles, with pole strength m. Magnetic pole strength of electromagnets can be found from:

m= (N x I x A)/L

The force between two poles is:

F= (u0 x m1 xm2)/ (4 x 3.1459) x (r x r)  (is the F here also Newtons?)

A= meters squared (cross section area of core)
L= length in meters
u0= .000001257
- - -

The 1010 - if my tests on the 1006 vs. the 1018 (both cold rolled rounds of 1/2"D x 3"L)are any indication: the 1010 would be (slightly) better than a bolt from Lowes but would basically the same as 1006 and 1018?
Have you tried something other than the ferrite?

[capthook]

And 3 points that haven't been addressed from the original post:

1. Core length vs. diameter:  the preferred core length is at least 5x the diameter

2. Winding length:  a winding length of at least 2x the  winding diameter is preferred.

3. Winding diameter: the windings beyond 1/2" from the core will increasingly contribute more to resistance than to the flux.  See the attached picture posted by Honk in another thread.

[Xaverius]

Magnetic force is what I was referring to rather than density - I should have used the proper term to convey my meaning.

So in the calculations you gave: ??

B= flux density in Tesla: (from the H and B calculations in the earlier post)  ?
A= cross sectional area of core (in meters: pi x r²) ?

N= Newtons ?
1N = 1kg x m â,, s2 : (how did you translate into lbs/kgs - what value for m(meters) and s(seconds) ?

So you calculate B (as in earlier post) and then do this futher calculation for F ?
- - -

Also have the following equation that hasn't been listed/mentioned:

Force between electromagnets
For electromagnets (or permanent magnets) with well defined 'poles' where the field lines emerge from the core, the force between two electromagnets can be found using the 'Gilbert model' which assumes the magnetic field is produced by fictitious 'magnetic charges' on the surface of the poles, with pole strength m. Magnetic pole strength of electromagnets can be found from:

m= (N x I x A)/L

The force between two poles is:

F= (u0 x m1 xm2)/ (4 x 3.1459) x (r x r)  (is the F here also Newtons?)

A= meters squared (cross section area of core)
L= length in meters
u0= .000001257
- - -

The 1010 - if my tests on the 1006 vs. the 1018 (both cold rolled rounds of 1/2"D x 3"L)are any indication: the 1010 would be (slightly) better than a bolt from Lowes but would basically the same as 1006 and 1018?
Have you tried something other than the ferrite?

??  B=Tesla,  A=pi x r^2 in meters   N=Newtons  1 pound=4.4N

Yes, after you calculate H(AT/m), you then multiply by ur and obtain B in Tesla and further calculate F in Newtons.

Then it seems like 1010 is a loser as well as 1006 and 1018 unless we can find a foundry that can provide annealing at a reasonable price.

Other than ferrite the only thing I've tried is GIron which is similar to MuMetal but cheaper in cost, with a ur of around 100,000.  I obtained it as a type of foil which I cut into strips with tin snips and laminated them together into a bar.  No magnetic force whatsoever.  I think it is like ferrite, it only reacts to high frequency magnetic fields as in radio circuits.

I am somewhat familiar with the EM force formula but don't use it too much.  The force calculation in this formula is also in Newtons.

[Xaverius]

And 3 points that haven't been addressed from the original post:

1. Core length vs. diameter:  the preferred core length is at least 5x the diameter

2. Winding length:  a winding length of at least 2x the  winding diameter is preferred.

3. Winding diameter: the windings beyond 1/2" from the core will increasingly contribute more to resistance than to the flux.  See the attached picture posted by Honk in another thread.

Could you tell me how you arrived at these conclusions?  @ #2 a winding length would be pi x diameter which is 3.1416 x diameter, not 2x?

[capthook]

All 3 are 'rule of thumb' conclusions offered in a number of text books ( I spent 8 hours at the University library reading recent and detailed texts), a number of Ebooks, and websites read over the last few months.

1. Some B/H curves state the B applies IF a given core is length 5x diameter.

2. Winding length:  a winding length of at least 2x the  winding diameter is preferred.
The physical dimensions of the coil.  ie. 1/2" OD mean at least 1" length (depth) of coil.
(not feet of wire)
Guess I should have said it more clearly as 'winding length' sounds more like 'wire length' rather than the physical dimensions of the coil.