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Old 01-22-2010, 09:22 PM
yachtwork yachtwork is offline
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Default How to belt drive just about anything from any engine - DIY

This is a link to a system of belt driving just about any PTO device, like a pump, air compressor, extra alternator (for fast charging), or hydraulics from just about any engine.

It could be a good system for adding some fun to a go kart.

The article also give three methods of adding a second pulley to the front of any engine including a DIY method of adding a pulley in just about any bush location.

There is also a DIY method of perfectly marking where to drill the holes to match the engine without having to measure.

The article was originally written for boats, but it's the same for any engine.

The link is-
http://www.tongacharter.com/report-alternator.htm



Hope it helps someones project.

Scott
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Old 01-23-2010, 04:05 PM
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but where would you mount it on a small engine, to work on an industrial engine it would have to be an electric start only engine then you might be able to mount it to the flywheel bolt
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Old 01-24-2010, 10:56 AM
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It wouldn't have to be electric start... a pull start motor could run an alternator to charge a small battery and run lights or whatever else you wanted. If you mounted the alternator to a kart chassis, you could mount a pulley in front of or behind a centrifugal clutch (get creative and find a way... don't be a nay-sayer on this forum for the f--k of it) and belt drive it. If you kept the engine pulley a bit smaller and ran the alternator slower, you might not get full amps out of the alternator, but you'd take a lot of load of the engine and as long as you were a ways above idle, you'd charge just fine. It'd be fun to try if you had some fab skils and weren't afraid to TRY things...
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Old 01-24-2010, 01:00 PM
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FIY:
Delco 12si alternators like the one pictured above usualy have a max output rating somewhere between 65 to 100+ amps and usualy require 3 to 5hp. from your engines avalible power to spin them up to full output. For an installation on the average 6.5 hp powered go kart, selecting an alternator with a much lower max power rating (like a 20 or 30-amp model) would probably be a good idea so the engine would have some power left over to still drive the kart... These lower output alternators would also come with the added benefit of requiring lower belt tension levels that would put less strain on your cranks support bearings/bushings.
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Old 01-24-2010, 02:10 PM
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Quote:
Originally Posted by nerfo View Post
you could mount a pulley in front of or behind a centrifugal clutch
i have actually suggested this but many people say it wont fit because the crankshaft on most motors isn't long enough for a clutch and pulley
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Old 01-24-2010, 05:08 PM
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The length of the shaft is where "getting creative" comes into play. Make a bushing that fits inside a pulley, and that a 5/16" bolt fits through, use a big washer under the head of the bolt to hold the pulley on, then use the pulley as both a chain guide/clutch retainer! That's one possible idea. Of course it wont work on EVERY engine/clutch out there, but a guy who really wanted it to work could probably get something like that going on anything if he really wanted to.
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Old 01-27-2010, 08:53 PM
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my dad picked up a metal model 't' gokart yesterday, $250. original motor, original wheels, etc. it has a double pulley on the crank, and a wood or asbestos disc attached to the transmission pulley. i was wondering why that would be there, the guy showed me it had reverse because of it. the disc rode in the extra pulley groove to gain a reverse gear. talk about stupid simple. problem is no clutch.
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Old 01-28-2010, 10:34 AM
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You can drive automotive alternators with a pull-start engine. You still need the battery to provide the field voltage as the alternator is "excited" while it speeds up. Once at a certain, minimum speed the alternator then charges the battery as it does in a car, truck or boat. If you remove the battery while the alternator is providing current, you can easily overheat and damage the alternator windings as well as the internal current regulator. The battery, and it's resistance, is integral to the current regulation circuit.

http://www.alternatorparts.com/under...lternators.htm

Automotive engines typically do about 2500-2700 rpms for highway speed, so alternators are pulleyed to about a 3:1 or 4:1 ratio. For a gasoline engine that produces it's peak horsepower close or at it's redline of 3500 RPM, you could gear things a little closer. For durability you'd want to increase the pulley diameters but keep the ratio the same, so that more belt surface touches the pulley. This will compensate a bit for the conditions that homemade systems of this kind must endure - like sitting in the freezing garage for six months allowing the belt to get a "memory" of it's shape.

Also know that temperature of the alternator windings and casing impacts the amount of current you can draw. The colder it is, the more you can draw. This is why automotive alternators have an integrated fan, and hope that the car is moving more than it is idling. I'll give you a tip - large case alternators generally can provide more current than small frame alternators earlier in the RPM range for a given temperature. If you can get a large frame alternator that's generally better however whatever you get at a junkyard, you can drive with a lawnmower engine no problem.
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Old 01-29-2010, 09:01 AM
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I'd like to add... keep in mind all you're going to be running are a couple lights and maintaining the charge on a small battery. We don't have to run windshield wipers, heater fan, air conditioning, radio, power windows... etc. If you have a go kart with a 50 amp alternators and it's putting out 50 amps... take a picture of that ghetto bomber and get it on here!
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Old 01-29-2010, 09:43 AM
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Quote:
Originally Posted by frederic View Post
You can drive automotive alternators with a pull-start engine. You still need the battery to provide the field voltage as the alternator is "excited" while it speeds up. Once at a certain, minimum speed the alternator then charges the battery as it does in a car, truck or boat. If you remove the battery while the alternator is providing current, you can easily overheat and damage the alternator windings as well as the internal current regulator. The battery, and it's resistance, is integral to the current regulation circuit.

http://www.alternatorparts.com/under...lternators.htm

Automotive engines typically do about 2500-2700 rpms for highway speed, so alternators are pulleyed to about a 3:1 or 4:1 ratio. For a gasoline engine that produces it's peak horsepower close or at it's redline of 3500 RPM, you could gear things a little closer. For durability you'd want to increase the pulley diameters but keep the ratio the same, so that more belt surface touches the pulley. This will compensate a bit for the conditions that homemade systems of this kind must endure - like sitting in the freezing garage for six months allowing the belt to get a "memory" of it's shape.

Also know that temperature of the alternator windings and casing impacts the amount of current you can draw. The colder it is, the more you can draw. This is why automotive alternators have an integrated fan, and hope that the car is moving more than it is idling. I'll give you a tip - large case alternators generally can provide more current than small frame alternators earlier in the RPM range for a given temperature. If you can get a large frame alternator that's generally better however whatever you get at a junkyard, you can drive with a lawnmower engine no problem.
+1, excellent info frederic. (and nerfo)

I spent serveral years rebuilding/bench testing Alternators. We had 2 test-benches, one had a 3hp and the other a larger 5hp electric motor to spin up the Alternators. I found the lower powered test bench did not have the necessary power to spin Alternators over around 70-amps up to full output. While our 5-hp bench tester could easly spin up Alternators with max outputs of up to 150+ amps.

While I agree that the type of large case/frame Alternators (like 70's/80's Police cars came with) usualy produced higher output at lower RPM's, I just wanted to point out that any Alternator with over about a 30 amp max output would most likely end up being overkill for most any go kart and take way too much of the small engines avalible power away from driving the kart.

A go karts limited electrical demands wouldnt necessarily cause any Alternator to charge at full tilt all the time, but a partly discharged battery could for awhile...

If I were to choose an automotive Alternator to instal on a go kart, I'd probably go with a Delco 10SI (Lester part #7127) rebuilt to a lower max-output level. This Alternator model is inexpensive, reliable, easy to repair and have a built in regulator. There are Self-energising regulators avalible for these and when used the alternator simply needs 1 (10-gauge) wire ran to the battery's positive post to function. Most of these 10SI alternators are commonly rebuilt to around a 65 amp (or so) max-output level, but if you deal directly with a rebuild shop they can usualy equip it with a lighter duty Stator (and even Rotor) to lower its max output level closer to 30-amps and leave more of the engines avalible power to actualy drive the kart.
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