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Old 01-12-2018, 07:17 PM
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Default Alt-Drive Charging

So this may be beating a dead horse after thousands of questions on this subject but say if one added an actual alternator but not connect it to the axle but to the engine output itself. I was thinking about it and other than the added resistance what if someone ran a TC setup via jackshaft (mounted to frame) and used a similar duo-drive system like a snowblower. But one sprocket drives the jackshaft and TC an the other connected to the alternator/generator. The mounting is just a matter of measure, drill, stick. Yes I understand that you can get charge coil kits but if someone wanted to run something a lil more peppy...

I'm getting stupider ideas off the sauce than I was on it.
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Old 01-12-2018, 07:40 PM
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There's no reason you couldn't run it off a jackshaft. It would make far more sense than running it off the axle.

Alternators like to spin 5k-6k rpms to make any decent amperage, and will easily handle 10k. That's why your alt pulley is much smaller than your crank pulley in your car. Trying to achieve this off the axle would require such a massive pulley driving it, it would be bigger than your wheels.

Running on a governed engine, supposing your alternator pulley is 2", you'd want around a 4" pulley driving it off the jackshaft so the alternator is happy at partial throttle. To achieve this off the axle, you'd need like a 24" pulley. (Gear ratios multiply. For the alt to spin twice the engine speed, you'd have to have double your drive reduction ratio when running off the axle, for maximum alternator output.

Also, there's no sense running anything bigger than about a 60a alternator at the very most. Parasitic power loss will become a problem. Either you are somehow managing to USE that much power, and it's using up precious hp to spin it, or a larger alternator will have significant enough rotating mass that just spinning it up will hurt your acceleration.
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Old 01-12-2018, 08:19 PM
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I have a few GL1500 alternators lying around. One has a 1.5" 3/8 pulley on it. At half mash would be turning it at about 5200 and smashing it would easily bump it up to about 8k. (3" driver, 1.5" driven. Pulley calculator. No one's stupid enough to have a chain driven alternator) My modded GX390 can crank at 4130 at WOT so speed isn't an issue. Just a matter of resistance and location. Magnums don't offer the most play room.

Next best thing I thought of is taking a 10hp briggs with a shortie shaft (dumnut who cut the shaft because he thought that's how you fit a CC) and rob the alternator drive setup off the Goldwing and use that sytem at the end of the jackshaft. Only then would the alternator would be more of a power wh... but things would be more compact. On the flipside that's ripping apart a perfectly good engine that can be used for stupid crazy swaps.
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