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A Blast from the Past...


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You all remember the post about a cheap generator I guess? The one using a lawn mower motor driving an alternator with a voltage meter, charging a battery? Well here's the youtube video of it again. But as you watch the video below, he's only getting 14 volts because that what a car alternator should put out. And I guess that's fine if you just want to charge 12v batteries. But what if you want to do more?

What i'm getting at is this. If you need more volts then 14, find a junk treadmill setting out by the curb on big item trash days. Most treadmills (for your home) use DC motors (unless they are very old). And I can almost bet you the motor is not at fault on these junkers. The point is, if you use a treadmill DC motor instead of an alternator, you can generate much more voltage. If the motor spec plate says 120 volts/5000 rpms, you need to drive that motor at 5000 rpms for you to generate 120 volts. So all you would need to do is figure out what pulley size's you would need to make the DC motor run at 5000 rpm in this scenario. Keep in mind these types of motors come in all kinds of spec ranges. Also you will need to beef the frame up a bit because these motors are usually a little bit larger then an alternator out of a car.

Now if you really want to be cheap, figure out a way to drive the motor using a stream or a windmill.. :idea:

Rim

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I think you are gonna find that when you gear your treadmill motor to generate 120 volts you are going to need some serious horsepower to turn it. A lot more than the lawn mower engine. And things will make a pantload of noise and stress out that little motor really quick.

Low voltage high amperage is a lot better unless you have some serious horsepower on hand. Even that alternator will load up the lawnmower engine pretty good, or vice versa.

Check it out...Hook a 12 volt light bulb up to a drill motor power cord and turn the shaft...now pull the trigger. Can you make the bulb glow? Can you make it burn out? Hook up a flashlight bulb and try it. Now a 120V. light bulb. This experiment will show you in your hands how much twist it takes to make a motor generate. You will almost tear the handle off that drill before you can get the chuck to turn and glow that 120v. bulb!

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You can bypass the Regulator on the Alternator.

You can by pass the Diodes and the things will weld.

There's a number of options to play with..

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Bob,

I don't think you would have any probs cranking the briggs up as long as you put an on/off switch in line so you don't have something down line instantly wanting to draw current. And if you do have probs cranking the motor i'd suggest using flywheel style pulleys which come in different weights and sizes to add a little centrifical force to the situation.

As far as gearing goes there's really not much gearing to it. If you get lucky and find a motor rated at 3600 rpm then you won't need any gearing since briggs motors are hp rated at 3600 rpm.

I use to light up several 100 watts worth of light bulbs on our bench test at the production plant I use to work at. We would use the bulbs to create the current draws for the motor controllers and motors we wanted to test. But the motor driving the light bulbs was never a test subject. It was being driven by the motor we were testing.

Rim

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Home most of our motors were rated for 15 amps current draw since that's what most houses have installed in the breaker panel. Plus we had a 15 amp breaker installed on the in-line side to act as a back-up in case the house breaker didn't trip.

Rim

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One horsepower is equal to 746 watts. No matter how you cut it up and splice it, you are going to have to put at least that much in to get that much out. The voltage/wattage formula is easy so you can do some simple math and figure out exactly how much (theoretically) you can generate with that lawnmower engine before you stall it.

You are going to find that low voltage/high amperage is a bunch more efficient for small generation unless you have a large engine and a good dynamo, like on a welding machine. Sit down with a calculator and see for yourself.

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I appreciate what you guys are doin I love buildin stuff BUT,........

Look for the coupon for the Harbor Freight 800/900 watt 2 stroke gen Got mine for 80 bucks on sale goin on the 2nd year of use no problems.

I watch T.V. run an elec drip coffee maker an charge the house batts on the trailer.

Its Quiet an dependable power so far. an I don't have to figure anything out, what a break that is for this ol timer !!!!!

Got myself another coupon an I'm gonna get another one an keep it in the box unopened for backup.

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Now I hate to get off of apples and go to oranges. But this dude talking about building a wind turbine. Now look at his motor recommendation. Read the last paragraph. Would a small turbine put out the needed torque to turn that motor?

http://powerplans.ne...ine-generators/

Rim

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Like Bob said the more current you trye to pull from them the more Torque you will need (Larger Blades).

You can limit the current being drawn from the Gen with little trouble.

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Well I think a 5 hp gas motor puts out about 10-12 ft/lbs of torque at 3200 rpm. So how much more torque are we talking about to drive a 1.5-2 hp DC motor? Ballpark will do.

Rim

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Doing it on paper your talking a butt load of math.

What are the Veriables?

You need to know Pully Size.

Reduction rates.

..........................................

The motor has a Torque rating on it. I would just use that as a starting point.

http://www.physicsforums.com/showthread.php?t=540966

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Ballpark on the Briggs would be a 2 inch pulley and maybe 1.5 inch on the motor like this motor. That will get it close enuf. But i'm not sure where the max torgue curve is on this leeson.

post-26159-0-90566500-1347408988_thumb.j

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Have Fun!

Your motor puts out 1.62HP @ 5190 RPM

TORQUE = HP x 5252 ÷ RPM

1.62 * 5252 / 5169 = FtLb Torque

The following examples illustrate several different values of TORQUE which produce 300 HP.

Example 1: How much TORQUE is required to produce 300 HP at 2700 RPM?

since HP = TORQUE x RPM ÷ 5252

then by rearranging the equation:

TORQUE = HP x 5252 ÷ RPM

Answer: TORQUE = 300 x 5252 ÷ 2700 = 584 lb-ft.

Example 2: How much TORQUE is required to produce 300 HP at 4600 RPM?

Answer: TORQUE = 300 x 5252 ÷ 4600 = 343 lb-ft.

Example 3: How much TORQUE is required to produce 300 HP at 8000 RPM?

Answer: TORQUE = 300 x 5252 ÷ 8000 = 197 lb-ft.

Example 4: How much TORQUE does the 41,000 RPM turbine section of a 300 HP gas turbine engine produce?

Answer: TORQUE = 300 x 5252 ÷ 41,000 = 38.4 lb-ft.

Example 5: The output shaft of the gearbox of the engine in Example 4 above turns at 1591 RPM. How much TORQUE is available on that shaft?

Answer: TORQUE = 300 x 5252 ÷ 1591 = 991 lb-ft.

(ignoring losses in the gearbox, of course).

The point to be taken from those numbers is that a given amount of horsepower can be made from an infinite number of combinations of torque and RPM.

Think of it another way: In cars of equal weight, a 2-liter twin-cam engine that makes 300 HP at 8000 RPM (197 lb-ft) and 400 HP at 10,000 RPM (210 lb-ft) will get you out of a corner just as well as a 5-liter engine that makes 300 HP at 4000 RPM (394 lb-ft) and 400 HP at 5000 RPM (420 lb-ft). In fact, in cars of equal weight, the smaller engine will probably race BETTER because it's much lighter, therefore puts less weight on the front end. AND, in reality, the car with the lighter 2-liter engine will likely weigh less than the big V8-powered car, so will be a better race car for several reasons.

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Gotta luv this place,talk about ask and ye shall receive :brows: I never use a generator,trailors,rvs and the ilk as I camp to get away from civalization and noise,like it rough and it's good enough for me. My aunt bought a monster RV bus style and used to make me laugh like crazy :ROFL: when she'd complain about ROUGHING IT in her $300,000 rv-John

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HJ you would be right at home the way we camp here.....

At this spot we had to rake the cow turds and horse poop and leaves to make a clean place to

post-300-0-73115500-1347472310_thumb.jpg put our sleeping quarters...Andrea uses a hammack and

I use my tentpost-300-0-44126200-1347472391_thumb.jpg about 50' past the back of the corral is the

river where my dredge is parkedpost-300-0-73521400-1347472471_thumb.jpgwe got a little gold

from there...post-300-0-85126300-1347472529_thumb.jpgat night I could shine my maglite out

across the water and count 8 sets of eyes of crocs....post-300-0-32564400-1347472681_thumb.jpg

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Everything was fantastic G till ya mentioned them 8 sets a eyes :th: I had a REAL close call in Costa Rica and I do NOT play with toothy big lizards no mo' thank you very much-nice cool lookn' camp though-thanx for great pics-John

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Hey John

Yup, we are one of those kind of "campers" now. We bought one of those buses and I am in heaven after many years of much more simple camping. Unlike many that have these beasts I am not afraid of manzanita pinstripes and will take it on some questionable roads. Sure does make for a very comphy camp. I still do most of the cooking, eating etc outside but now have unlimited ice, a real freezer and fridge (nice chilly beers even after 10 days), a queen bed for the old bones and a way to watch "Treasure of the Sierra Madre" on occasion. Also makes for a great guest room when at home.

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Whatever floats your boat El D,glad to hear ya are so happy,just not for me as 4 X 4s barely make it to my rough claims as 3 creek crossings,steep vertical cliffs with miniscule roads, and tons a mud make it fun fun fun. I'd do anything for my privacy and solitude. I'm just saying not for me till I get old-John

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  • 10 months later...

Mines a 7500 watt generator from Costco, with electric start. Will run the whole house if I want it too. Grubstake

I got a 6000w Diesel... Was wanting to be able to hook it up to power the house... What do I need to do? Have not really looked into it, but your post got me thinking, I am sure some sort of chord is made made for this, so find that first, Installing the proper outlet for the chord end, wired back into a new 15a fuse... Then if power goes out, flip the main off, and fire up the generator, then flip my generator fuse on... Would this work safely or do I need something more?

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Google MANUAL TRANSFER SWITCHES. you will find your answer there. One will allow you to set different circuits that are breaker protected for the house at the same time it will prevent power feeding back into the grid, a safety concern for the power company.

You can't run much on one 15 amp circuit..........

Edited by El Dorado
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