Adding a Generator to a Small Engine

Yes.

Output of lawn mower should match to the input requirement of flywheel generator.

i only have a mageto. what do i need for the change over?

The magneto provides the spark to ignite the fuel. What does the magneto have to do with attaching a 12 generator (alternator) to a lawn mower engine?

thank for the info. great answer

I'm with you on this. All of the flywheel alternators that I have seen have very low power output. And the cost to buy the flywheel, stator set, and voltage regulator would cost more than buying a group 31 battery, and just recharging it when home again. There are some small low drag alternators that are out there. Mount a pulley to one end, and fab a bracket. Drive it with a belt. The small alternators that are used on a small GM or Ford product should be cheap in the junk yards. The Alt can require a bit of power to generate high power, so get a low power unit, and try to not load it too much when the engine is being asked to do other work. Or, is the only purpose of the engine to run the alternator? In that case, you can get up over 100 amps with that Tecumseh. Good luck.

i'm thinking of using a starter from a small lawn mower engine along with a regulator to use as a generator. do you think it will work? @ what rpm? the motor rpm will be approx.800-3200rpm and driven from the crank. what size pulley should i use on the starter?

6.5 hp is about 4800 watts. Now you will get 6.5 hp out of the shaft of this motor only at one optimum speed with a matched mechanical load. Most of the time the motor will be providing less than this optimum value but still likely more than the alternator can safely translate. My point is that the design of the alternator and how it gets mechanically connected to the motor shaft will likely be the limiting factor for the electrical power you will get out of this combination. From what you've given us I suspect that the RPM on the alternator shaft must be increased for efficient operation. Think about the alternator pulley diameter in a car and the drive shaft diameter. Your voltage regulator will modulate the amount of mechanical power that will be translated to electrical to maintain 12V out as motor speed changes and electrical load changes. I've digressed again, my point is that there is not enough information to answer your question. We do not know the electric load, the other mechanical loads on the motor, the coupling between alternator and motor, the alternator model itself or even how the motor throttle will be controlled.

Ah, finally found it - http://theepicenter.com/tow02077.html

I agree with redfred - if your primary goal is to make 12 volt DC power, use a car alternator with regulator. Not sure of the new ones, but some of the older GM alternators have the regulator built in - just connect a couple of wires. They used to be pretty cheap in the junk yard. The site above has some good info, including how to make a mounting plate. They'll even sell you one.

Your starter will last about an hour or two before the brushes and bushings go to pieces if you are lucky. They are high current short duration motors.

Get a common Delco 10Si or 12SI size alternator off of a GM vehicle (1970 - 2000+ models) at the salvage yard for around $20 - $30 or new at a any auto parts store for around $50 - 80 and run it with a belt drive on a 1:1.5 - 1:2 gear up ratio.

They are rated to put out around 60 - 100 amps at 3600 RPM and higher and you can also buy them aftermarket with whats referred to as a 'one wire' design where they are self exciting above 2500 - 3000 RPM and you only need to connect one wire from the output lug to your battery to make them work opposed to the normal three wire type that need an exciter wire and voltage reference wire connection plus the main output lead.

New at most auto part supply stores for around $80 - $120.