Creating large DC Motor for Funzies. Won't work.

NascentOxygen

Yes, the lamp is a convenient resistor. I suggested that you use it so it limits the current through the strand of thin wire. If you just connect a piece of wire across a car battery there will be a big spark, the wire will glow red hot and melt, thus ending the experiment. But with the lamp in series, the lamp will limit the current to a safer level. The wire may still get hot and start smoking, but the experiment will have served its purpose: do you see instant movement in that strand of wire or not?

You must take the eggbeater out of the circuit for this single wire test so it doesn't steal the current from the piece of wire. Use a strand of wire that is flexible and hang it so it is free to move a bit, so that you can watch for movement. Because if you observe that the single strand does not move, then sure as anything neither will your eggbeater rotor!

Averagesupernova

You really need a commutator. Suppose with a single loop of wire the current is split evenly through the upper and lower loop. In order for the rotor to turn the upper wire has to move in the opposite direction of the lower wire. One wire will fight the other. Remember the right hand rule when it comes to magnetism and current flow? The reason your single loop worked at all is because the field was small enough on the top compared to the bottom so the lower 'outpulled' the upper.

NascentOxygen

I think you mean "it rotated a few degrees then stopped" don't you? It surely didn't keep turning and turning endlessly?
So it melted the plastic-coated wires from the battery, or did it melt the egg-beater wires? (They look so thick that I'm surprised the 12v supply survived. Your eggbeater is no different from a short circuit.)
Even if it is theoretically possible to get your homemade rotor to operate, it will first have to be modified a bit to give it commutator action. But I'm not suggesting you do that until we establish whether it stands any chance of working.

Flyingwing12

I got the small single wound job to spin continuously yes.

It has to be possible for this thing to spin.

I think I just need a very strong magnet.

And how would this commutator work? This keeps being mentioned and yet no one says how I should hook it up?

try using MS paint to make a diagram or something like that. They help out a lot.

Flyingwing12

And electric motors of this scale are basically short circuits right?

I thought the huge coils of non conductive wire are for resistance?

Please elaborate.

NascentOxygen

Well, "short circuit" is a relative term. To a 12v car battery, your eggbeater with its heavy gauge copper wire is getting close to a short circuit. Connected directly to the battery terminals I'd expect the wires to glow red hot and melt, that is, if the battery didn't explode under the strain.
It's called "insulated copper wire" because the outside is covered with an insulating layer, either enamel varnish, or coloured plastic. Motors use lots of coils to produce strong magnetic fields.

NascentOxygen

Great! Then why not settle for that as your demo motor? It's so unusual that most people will be mystified to see it spinning, telling you it can't be happening—it won't spin without a commutator.

If you go to youtube.com and search for "simple motor" you will see plenty of DIY motors. You might get ideas from there. But I really think you should stay with the simple one that spins once you have got it going!

I once salvaged the electric motor from the windshield wiper assembly I found in an old car dump on the edge of a wood. The assembly was mounted at the top of the windshield, and the armature of the rotor projected through the case (as a brass rod) so it was within reach of the driver. You see, the motor was a design that isn't always self-starting, so it was sometimes necessary to twirl that rod to get the wiper's motor to start spinning!

dlgoff

edit: removed emoticon link

Anyway,

I_am_learning

dlgoff, I don't think Commuter is needed for a half-turn configuration in a non-uniform Magnetic field. (The OP's setup.)
The videos and documents you are discussing refers to a regular DC motor with uniform fields and integral no. of turns, which surely does need commutator.

I_am_learning

To prove my concept, I tried to do this quick and dirty experiment, but it failed.


My guess was,
While the wire is in lower half of its imaginary rotation-circle, the torque will be produced in one direction and when it is in top half, torque will be in opposite direction.
But since the average Magnetic field strength on top half is lower than in bottom half, during each complete rotation torque should be +ve and hence, the rotation should have continued indefinitely.

I think, the inertia (due to torque in bottom half) isn't being able to overcome -ve torque + friction during the top half. i.e. I think the reason for failure is mechanical problems.

If I have some serious theory flaw, please let me know.

P.S: I do believe that coil design with commutator would surely give the best result (an order of magnitude more torque), but I am just trying to verify if other method could work* or not.
*Although for demonstration purpose only

dlgoff

You are correct however giving the OP a little more info about motors could help his/her learning.

Flyingwing12

I had a car battery charger hooked to the motor and was only getting 9 volts out of it. This was until I moved the motor and it made contact, in which the wires were instantly fried!

What caused the voltage to be 9 volts across the pos/neg wires?

NascentOxygen

I guess you are implying it to be a 12 volt charger? Possibly the charger is not much more than a transformer with a full wave rectifier. Suppose you supplied a full wave rectifier with a 14v (peak) sinewave.... neglecting losses, the output would be a series of half-sinusoids of peak amplitude 14v. If you use calculus (or a good ol' moving-coil meter), you will discover that the average of this rectified sinusoid is 9 volts. For a short time around the peaks a 14v sinusoid overcomes the car battery voltage, and forces charging current into the battery in short bursts.

I suggest that you continue to use a headlight globe in series with the charger during your experiments. This should protect the charger from damage due to overload. If your experimental motor shows no sign of working when the charger has a globe in series with it, then it's a safe bet it won't have worked had you overloaded the charger.

NascentOxygen

Which wires melted? The wires coming from the charger, or the wires you soldered together to make the eggbeater?

NascentOxygen

By failed do you mean there was no observable movement? What is the material in that catenary? It looks a lot like polycarbonate string.

Are you doing the test that I suggested OP should try?

I_am_learning

its working now. http://www.youtube.com/watch?v=D1Gpg...e_gdata_player

NascentOxygen

Well done, I_am_learning! That's a convincing demonstration.

If you soldered (or twisted) another semicircular piece onto that, to complete the ring, it should spin faster and more smoothly. Current drain will go up, though.