My first Neman motor

[detrix42]

Hi, I am another person trying to replicate a Newman motor.  I have a vidoe posted on youtube.

http://www.youtube.com/watch?v=eZxStFSnpp8

this works for about 30-50 seconds.  I need some help understanding what I am doing wrong.

Build info:
Coil - 3285ft of 30AWG magnet wire; Resistance is at 430 ohms.

A calculated number of windings at 2788.39 Battery Pack - 12 9V in series currently reading at 93.2V

Commutator - 6in diameter, copper segments are approximately 30 degrees with 30 degrees in between.

Magnets - 1" x 7/8" dia. Neodimium (96lbs of force at the surfaces); with a couple of smaller neodimium magnets for extra kick.

Ask me if I missed anything.

I tried to post a picture but there was a server error... I will try again later.

[detrix42]

with 93.2v and 430ohms this calculates to .2167amps (216mA). So it should be under 100mA when running with the momentary contacts. But I am not sure what it actually is. I do not have any analog meters.

The calculated number of windings is probably more like 2600. I did not initially consider that the diameter of the coil was getting larger.   .  Anyways, I would like some help understanding why it slows down and stops.

Thanks

[gyulasun]

Hi,

One possible explanation for the stop is that one of the 9V batteries out of the 12  'gives up' in the series bank.  Have you checked how many volts remain from the 93.2V by the time it stops? Would be wise to check all the 9Vs individually while the motor is running. IT is possible that only one or two of them is the weakest and inreases too much the inner resistance of the total battery bank.

Other notice: I think that you would get better RPM if you placed the shaft from the top of the coil to the centerline of the coil so that the magnets should not protrude out at the top but would be fully immersed inside the coil --- much better induction could take place. I know you would have to care of the safeness of the wire enamel insulation, the shaft would come out in the center of the coil windings diametrically on both sides. Perhaps using a short plastic cylinder on both sides with a correct inner diameter could solve this problem, serving as a kind of "bearing" for the horizontal shaft.

rgds, Gyula

[detrix42]

I have another tube for another coil, but will have to wait until I can afford more wire.  I am wondering why it slows when at first I get good rpm/rotation.  So When I can afford the wire I will have a top coil.

[gyulasun]

...
I am wondering why it slows when at first I get good rpm/rotation. 
...

Have you checked the batteries, as I wrote, while operating?

Another good check would be to run the motor from, say, 6 series batteries only and see how it goes.

By the way your batteries seem to be used up pretty well already because 9 times 12 gives 108V and you measured 93.2V, right?  so an average voltage of 1.2V is "missing" from each 9V battery. Unfortunately, the inner resistances of such batteries are pretty high in themselves, and connecting them further in series gives further dissipation loss.

IF your motor could run on 6  9V batteries (i.e. on 54V) then you could connect the other remaining 6 batteries also in series, then this series bank in PARALLEL with the previous 6, to double the total current capacity.

rgds, Gyula