Redid the earlier test - results seemed inconsistent.  Battery used was an older one with lower charge (1.2V) and a DMM is not highly accurate measuring resistance of small OHMS.  So in this test I also did amp measurement in circuit and R=V/I for resistance with a fresh battery.

12' : .88v / .74a / 1.19 ohms : 0.6512w
6' x 2 : .46v / 1.44a / .319 ohms : 0.6624w

12' : 40T x .74a = 29.6AT  :  29.6AT / .6512w = 45.45 AT/w
6' x 2 : 40T x 1.44a = 57.6AT  :  57.6AT / .6624w = 86.95 AT/w
Edit: or is it 6' x 2 :((20T x .72a) x 2) = 28.8AT ?? This is the question??

191% increase in AT/w with parallel winding.

Additional testing/results/observations/comments requested !!!

- - -
TK -

"measure the current using a voltage-regulated power supply that won't sag the way a small battery does."

As resistance decreases, amps increases, and voltage decreases.

If you are powering your EM with a small battery, then this is a 'real-world' test of the operating conditions.

What is your take on the parallel winding? (2 wires that are 1/2 the length each of the original wire wound '2-in-hand')

Would you conclude that it will increase the efficiency of the EM by increasing the ampturns per watt?

What WOULD you conclude?

tx

Tineskota,

of course it is done, the so called multilayer-wires. They are used for fast-power-puls-applications. See my last post.

Another user posted an american supplier of square-wire :

http://www.mwswire.com/square.htm

@xaverius : Can we agree on this : two coils on one core - where each coil has 10 windings - switched in parallell will enter the formula with  10 Turnes and no more. It resembles the mulitlayer-wires I posted above.
If you use a multilayer-wire ( 100 thin wires in parallel)  of the above spec you will not increase the Turns by 10 times 100 but only the Amperes by reducing the resistance depending of the 100 parallell inner resistance - let say by 50 % - therefore the result of the formula : Ampere x Turns = 10 Turns  x double Amperage because of 50 % less inner resistance.

LOL but I like this discussion. Yes we have to test it, , no way.

Regards

Kator01

So I have one long wire. I sever it in two lengthwise. Now I have 2 long wires, each with half the cross-sectional area of the original wire. Now I join the ends back together. And I have, magically, created a wire with less resistance than the original wire.

Sorry, there must be something I'm missing.

Not severed lengthwise, crosswise.  ex:  100 feet of wire would become 50 feet.

Yes, I got that now, thanks, in fact I got it a page or two ago.
So there are the same number of turns, half with one strand and half with the other, just more current because of the lessened resistance.
So why not do it again, split that wire into 4, or even 8 short lengths, heck, just use a single turn of 16 tiny short wires in parallel!! Heck, just wind the armature with multi-stranded wire...

I wonder why they don't.
I think there's a tradeoff there somewhere...

That's right, why stop there, you can use as many wires in parallel as you desire.  Not only will you reduce resistance but you will also reduce reactance which is much greater than resistance in an AC application, that is if you are using and AC power source, or pulsating DC.  Of course if you are using ferrite or laminated steel the reactance in not an issue.

@ TinselKoala, Kator, gyasulun and CapnHook, I owe an apology.  I believe my examples are becoming confusing.

In the wiring scheme, consider this.  10 V,  1 lenghth of wire 80 feet @ 4 ohms.  Number of turns = 100.  Amperes = 10/4=2.5A.  10 x 2.5=25W

Ampere-turns=250

If another 80 feet lenght of wire is coiled on top of the first wire and connected to the first wire in parallel, the total resistance now becomes 1 divided by 1/4 + 1/4=2.  10V/2=5A and number of turns is NOW 200.  10 x 5=50W

Ampere-turns=1000

250AT/25W=10AT/W    1000AT/50W=20AT/W

You could look at it like you have one 160 feet wire to start with, divide it in two and wind two coils on top of each other, wire them in parallel but that is a harder way to understand it.

So in your example, you propose AT/W is 2x.

But is it really?  If total amp draw is 5A and you have to wires in parallel, that means the 5A will be split between the two wires meaning 2.5A on each?
AT = (100x2.5)x2 = 500 AT
500AT/50W= 10AT/W  - the SAME AT/W as the 1 coil
??

So again, muti-wire coils/multiple coils will increase AT for a given coil dimension.
But it will NOT increase AT/W........
(double the AT but double the watts)

??
- - - -
If not: (if my above point is shown incorrect)

How might the winding of the 2 lengths of wire differ?  Which would be preferred?

#1: Should it be wound 1 full coil, then the 2nd coil over top of that?
#2: Wound as 1 coil with 2 wires in hand at the same time.
#3: 1 full coil 1/2 the length of core then 2nd coil the 2nd half length of core.

#1. the 2nd coil is futher from the core thus the ampturns are less effective, reducing the actual ampturns of the 2nd coil by x%, meaning the total AT/w boost is not 200% but only x%?

#2. the width of separation of between turns of each individual wire turn is now 2x, so the density of amps per turn of each wire is less meaning AT is reduced by x%?  Might the field of each wire interact with each other?

#3. Coil 2 is going to be way less effective as it is so far away from the 'active' end of the EM?

Or none of the above apply, it's all relative.  But the preferred winding style would be: #1 or #2? (I vote #2)

Might some of these possible 'issues' mean there is a practical limit to the number of wires/coils used?  What might be the limiting factor of the number of wires used?  Why?

You have very valid points.  I guess I am getting ahead of myself.  Your reference to "AT/W" I distorted somewhat.  Actually the example of 1000AT/50W or 500AT/50W is related to the Magnetic Field Strength which grows the magnetic force geometrically according to wattage.  As the wattage increases, H (magnetic field strength) produces more magnetic force with the square of the increase.

250AT/25W has 1 unit of magnetic force.  500AT/50W has 4 units of force, yet the amount of input has doubled. (25W to 50W)  And yes, the AT/W ratio is the same @ 10.

You're right the two parallel wires reduce to 250AT each for a total of 500AT, 1000AT simply relates to the total input, NOT the effective input.

I think method #2 would probably be most effective as the two wires would have equal spacing from the core.  The distance away from the core reduces the amount of flux influence.

Method #3 would be like two small EMs back to back so would only have half the magnetic flux.

I'd say there is a practical limit as to the number of wires used, mainly the distance of the windings from the core.  Too many wires, too much distance so you would have to carefully balance the number of wires, number of windings, wire thickness and so on.

AT/W may stay the same and total power used may increase but total magnetic force would increase even more.  This would be advantageous with a solenoid or a motor pole where a large amount of force is needed to overcome the resistance of a generator in order to produce the needed wattage.

the AT/W ratio is the same @ 10.

Xaverius - thanks so much for the clarification!  I had been scratching my head the last few days over that.

As TK points out - fewer turns of thicker wire reduces resistance and increases amps that increases EM strength at the cost of more power consumed.
Winding 2-in-hand further reduces resistance and increases amps that increases strength at the cost of more power consumed.
Two excellent methods for increasing AT per meter.

However, if the goal is OU, the more power you consume the more power you must produce.  Catch-22.
This has been the reason for my focus on the AT/watt.
You may have noticed on my excel spreadsheet the power input of .5 watts.

The last wind I did was:
#22 AWG : 140' : 3/8" x 3" core : 1" OD  x 1 7/8" L coil : 781 turns : 2.3 ohms
1.06V x .461A = .488W : 360 AT : 1/2 lb. of holding power.

So with under 1/2 watt of input, I'm getting what appears to be a sufficient EM strength for my application.
However, thanks to the discussion here, winding it 2-in-hand will increase the EM strength relative to the power draw.  (ie. 50% more power but 75% more strength -)  The same AT/W but a relative larger flux - a larger % of domains aligned.
As such, designing for larger device output to accommodate the larger EM power draw should result in a net system gain.

Another thing I noticed this last week:
A larger core diameter will perform poorly over a smaller diameter at low  input power.
The 3/8" core works better at .5W than the 1/2" core.
My thinking is that the low input can only align a small % of domains.
With a smaller core, that % of alignment is greater than the % of the larger core meaning greater EM strength.

Hi CapNHook,

               Sorry for making you scratch your head so much, my technical writing skills are not the best in the world but I'm getting better day by day, LOL!
Also, the math as you can see will sometimes throw you off.  I've been working with electronics and physics for many years and I can easilty get confused when the numbers start flowing, which they most certainly will with these two topics, LOL!

                 That being said, you made a good observation with regard to low power input and a narrow cross-sectional core.  I think you're right, at low power less domains are capable of alignment, also I might note that the same thing happens with shorter cores.  I've had the experience that at low power inputs, shorter cores yield less magnetic force, probably because the domains are squeezed together longitudinally and can't align efficiently.  In other words, a longer core allows the domains to "stretch" lengthwise and align properly.

                  One thing you may know by now, when you DOUBLE the magnetic field strength(H), you QUADRUPLE the magnetic force.  So in your examples, when you DOUBLE the AMPERAGE, you also DOUBLE the WATTAGE, however the AT/W remains the SAME, but the MAGNETIC FORCE QUADRUPLES.

                   In your application you are using repulsion, in mine I am using attraction.  If BOTH modes are used with a pulsating DC power source you are effectively DOUBLING your output.  Attraction and repulsion are used in AC motors, but to no overunity effect because when the cycle changes directions the attraction or repulsion is negated gradually.  With pulsating DC that problem is eliminated.  Also if you use BOTH POLES of the EM you double your output again.  Double the amperage, double the modes(attraction/repulsion), double the poles(N/S), you will increase your output by 16X.

                    BTW, have you achieved any result with 1006?  Good luck.

Thought I would add this here as equations can get lost in the shuffle and might not be easily 'translated':

Question: I want to duplicate the 2000 Gauss strength in an electromagnet with a 3/4 inch diameter, 2 inch length solid metal core.

Answer:
A rough approximation:

(1) H in Oersted= (.4 x 3.14 x N x I)/coil length in cm

(2) B in Gauss = (H x (core permeability x 0.00000125664)) x 10000

So if 2,000 Gauss needed with core permeability of 800u:

H= 2000/10.05312 = 199
(rearrangement of  (2))

H = (.4 x 3.14 x N x I) / 5.08 = 199

N x I = (199 x 5.08) / 1.256 = 805 ampturns

So you could use:

N x I = 805 turns x 1 amp = 805 ampturns

805 turns of #22 AWG = 8.3 ohms
I=V/R : 9volts / 8.3 ohms ~ 1

So 805 turns of #22 AWG at 9 volts on a 800u permeability core (1010 steel) will achieve a rough approximation of around 2000 Gauss.