Question for the Electric Motor Wizards - Motor Direction

[moronic_kaos]

Yes this is a GAS MOTOR question, please don't mistake it and move it to the electric motor section.

What exactly specifies the direction in which a motor will turn? And for that matter, if using the motor as a generator, must the motor spin in the same direction, the opposite direction, or either direction?

Trying to plan out the creation of a double-use motor. That is, an electric starter (by extending the shaft for the magneto, running a pully or sprocket and connecting the electric motor in front of or above the gas motor) & electric generator. Cub Cadet made it work (though they say it takes quite awhile to charge a battery), so why can't we?

I know a 12v cordless drill will turn over a 20-30ish cc motor as that's how I used to start my weed whacker. Thinking about picking up a junk cordless at the flea market on Sunday to attempt this with, but I don't know how it will fare with a motor of this compression.

Any thoughts?

EDIT: Thought of an even more stupid question. Can a cordless drill charge itself? (given that something else, in this case a gas motor, rotates its engine & some other circuity is involved).

 

[professor]

The old -time small tractors used a starter/generator which was not efficient at either but did do the job if the compression on the engine was low enough (compression release or small engine). They got away from them when engine mfg.s went to generating juice at the crankshaft. These units are quite heavy for the small amount of output they give.
Fast forward to today, does anyone use this style combo anymore?

How long do you think that cordless drill would last as a generator?

 

[moronic_kaos]

How long do you think that cordless drill would last as a generator?

Why wouldn't it? I've seen cordless drills last for 10+ years as a drill under heavy use (with the occasional battery replacement), why wouldn't it work as a generator for a year or two?

EDIT: Not trying to challenge you or anything, I'm just trying to learn the whole "generator effect thing", what works, what doesn't, and why.

 

[Happy Jack]

Aircraft can use a starter generator.
Some old Cushmans' ran them ,so did old small Kawasaki's.

The "general" idea you really need to first study is the difference between DC and AC motors (like this Electric Motor - body, used, water, life, law, plants, energy, system, air, cause, primary, waves, basic, change, part, principle

Then you need to look at how complicated a starter generators can be for small MB's >>> Dan's Motorcycle Generator/Electric Starter (Dynamo)

That will tell you that it may be better just to find on old starter/generator to adapt to your MB for your experiment.
(they do rob a bit of engine power as they do drag on your performance)

A battery drill does not like spinning at high rpms for a long sustained periods of time, it will wear out the mechanical parts pretty quick (gears, bearings, etc). The starting rpms required for your MB motor to be spun by the electric drill are pretty low and the hi-torque applied is only for a brief time. The "generation" of electricity (AC or DC) will take some circuitry to use the higher Motorbike RPMs (to charge a battery, or run a light) AND some "switching" to get the juice to flow in the direction you want.

Can an electric motor be used as both a starter and generator? Sure, have been used for 100+ years. BUT when used as such a hermaphrodite they are a bit half-arsed in both functions; cause you don't get something for nothing.

Short answer: If you get a used electric drill, a simple manual hand tachometer like this cheapie electronic one like >>> Digital Contact Tachometer OR this deluxe one Digital Photo Sensor Tachometerand a Volt/Ohm/Meter you can play with the drills rpms and the volts/amps/ohms output that you get and see for yourself. That simple test will broaden your understanding tremendously. Well worth the effort.

Good luck.