Trimmer Engine Generator

   Hello Instructables community.
   I was thinking of making a 12 volt battery charger with a trimmer engine (pictured) connected to a scraped car alternator (I found several on eBay). But I have a few questions: 1. Would such a combination work as shown in the illustration?  2. Would it be best if I directly connected the engine to the alternator with no drive belts or chains, or would the high gear of the large engine gear and small generator gear be worth the extra trouble.  3. What is the best way to connect the two? And 4. Where should I remove the engine from the "trimming part". Any answers will be appreciated.
                                                                                                                 Confused DIYer

Picture of Trimmer Engine Generator
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maalikm911 (author) 1 year ago

Hello Instructables Community

Me and my dad have made a succesful generator. it may be crude but it does produce over 12 volts.

Snapshot 1 (28-07-2016 3-03 PM).png

Make an Instructable out of it ;)

maalikm911 (author)  Downunder35m1 year ago

I was planning to do that, but the process may be different for someone else due to different engine and parts, and I have neglected to take photos of building it.

im going to be a negative nancy, but those trimmer heads dont have a whole lot of torque to spin a alternator/generator, especially if you put an electrical load on the system.

maalikm911 (author)  thematthatter1 year ago

I didn't consider that, If it doesn't work by connecting the two parts together, I will use a gearing system to produce more torque.

I have done some of these "generators" back in the day for camping use.
Long before real generators became quite and cheap enough.
The key is the right speed for what you need for the alternator.
For example:
In a car the alternator is able to produce quite good amps already at around 2000rpm - for the engine.
But just to charge a battery anything above 1000rpm should do fine.
Your motor will be slower, so a bigger pulley on the motor and a smaller pulley on the alternator would be a good start.
I doubt you will have problems with the engine torque so unless the alternator is not giing out enough you won't need extreme speeds.

maalikm911 (author)  Downunder35m1 year ago

How fast is the engine? I looked online and didn't get good results. Some say around 5000 rpm and others 8000 rpm. I don't believe it's that fast. You guys know? It's a Ryobi 725r trimmer.

I've ridden a bike powered by one of those little engines. It was fast(for a bicycle). So u oughta hav enuf power one way or another, methinkst.

maalikm911 (author) 1 year ago

I found a new problem: do I have to buy an external regulator and if so, how do I wire it to the alternator and battery?

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Get a cheap car alternator with regulator build in ;)
Most actually are designed this way as the generator provides AC, so the regulator is usually included with the rectifier.
As for the coupling I think the best option is to use pulleys and belt.
Far easier than mechanical coupling directly on the axle and easier to work with if you need to repair things.

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