simply because I'm too lazy(and probbably wouldn't have an clue what to look for) I would like to now about starteres/getnerators/altrenators. First, I know that whenever a motor is turned it generates electricity, so I believe that in a most(or all?) cars the starter is used to generate electricity? Or is there a starter motor witch doesn't generate electricity when the engine is running, and another motor (generator) to make electricity when the motor is running?

Logan

 

the starter uses electricity in the battery to crank the motor over, after it has done this then the alternator starts to spin which creates an electric charge through the use of magnetic fields and windings inside the alternator. Once this has begun the battery is being recharged.

 

In most gasoline powered golf carts the starter is a combination unit. It starts the cart then makes juice to charge the battery.

1990 F-150 4.9l 5speed 4x4

 

When you pass electricity through a conductor, it generates a magnetic field. Coil the conductor, and you have a larger magnetic field. Now, pass a seperate conductor through that field, and it induces current (electricity) in this seperate conductor.
So, in a starter, electricity from the battery flows through the 'field coils' generating a magnetic field. The armature of the starter produces magnetic fields matching those of the field coils; alike magnetic fields repel each other, so the armature moves the only way it can, circularly. This spins the flywheel, in turn rotating the engine. As soon as the engine starts turning the starter, it disengages from the flywheel, and stops spinning as soon as you let off the key. NOT GENERATING ELECTRICITY.
In an alternater, the armature is turned mechanically, by a belt running off the crankshaft. When the armature rotates through the magnetic fields of the field coils, a current is induced through the windings of the armature; which is regulated and sent to charge the battery, which, in turn, runs anything electrical on your truck.


-Andrew (Semi-Electrical Guru, in training.)
f250_64(No Email Addresses In Posts!)

Nothing, and I mean nothing, stirs the soul, saying I'm a bad **** like lettin'em rip with a window shaking, fuel gulpin, carbon monoxide belchin, attention gettin, V-oh my LORD!-8!

 

I have seen riding lawn mowers have a combination type unit. Starter/alternator. Several older tractors also. It mounts up like an alternator and does charge the battery when the engine is running and it will turn the engine over when starting.

Jakegypsum // Ford fleet, soup to nuts.

 

The starter/generator combination sounds like a nice weight saving idea, but I assume high rpms of an automobile engine would be too much for this application and would burn it out, whereas the lawn mower and golf cart probably turn low rpms. I recently read that an electric motor actually does generate some electricity that feeds back along the power lines and that this happens because an electric motor is basically a generator run backwards or vice versa.

 

just to be more spcific, I took one of my small DC motors, put a tester on it, turned the out-put shaft by hand and it did generate electricity. To me it seems kinda while, stupid that there is a starter and altrenator, because I'm quite sure that if the the starter were left in contact with the fly-wheel it would be able to charge the battery. The weirdest part to me is that the starter is a one pole motor. But I'm not sure what that kind of motor could be rated for, so I guess that a starter could be burned out by the high RPM the egnien produces. But unless the insides are compelty different, the altrenator shouldturn like a normall motor if power is supplied to it's poles.

Logan

 

Yes, but, the alternator is designed for the higher RPM's, as well as the heat. The starter is designed for generating super-high torque at slow RPM's, not for higher RPM's.
The heat generated by cranking the starter for slightly over 30 sec. will melt the solder holding the windings of the coils together. You can see the problems that could be created by spinning the starter at 4000 RPM for several miles would cause. ;-)

-Andrew
f250_64(No Email Addresses In Posts!), same for yahoo messenger

Nothing, and I mean nothing, stirs the soul, saying I'm a bad **** like lettin'em rip with a window shaking, fuel gulpin, carbon monoxide belchin, attention gettin, V-oh my LORD!-8!

 

Let's see, the flywheel is probably about 14" diameter, so about 44 inches circumference, and the starter gear has a circumference of say 3 inches. So if the starter stays engaged it will turn about 15 times faster than the engine. Cruising at 2000 RPM will cause the starter to turn at 30,000 RPM and I would expect it would blow up if it first didn't burn up.