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11-28-2008, 11:03 PM #1
Any ideas for converting a windmill?
I've taken on a new project involving the conversion of a windmill. We'd like to convert an old Aermotor windmill to generate some small amount of electricity. Were hoping to maybe be able to run some small lighting or something non critical of that nature. The windmill has a 6' blade and is currently capable of approx. 125 rpm, with a vertical stroke of approx. 6" and is capable of up to 32 strokes per minute.
Our goal is to keep as much of the original look as possible, so my goal is the convert the vertical stroke to a circular motion. At which point I expect to do some experimentation into how much horsepower it is capable of producing. And then I have several ideas as to how to connect it to any number of different generators. We are not attempting this to make the most efficient wind powered turbine the planet has ever scene, only to attempt to generate some small token of energy so we can claim the windmill is being used.
Now for the conversion question. Does anyone have a reliable method or idea as to how I can convert the vertical stroke to a circular motion?
11-28-2008, 11:15 PM #2
Eny set of bevel gears I would assume?
And you could use them to go up 100%, same, or down 50% in speed while your at it to git to where you wanna be.
Think Snow Eh!
11-28-2008, 11:54 PM #3
If you're looking for just a token, the simplest thing is a gear rack and a pinion on the generator shaft. The generator will be reversing every stroke, but a bridge rectifier will give you a pulsating DC output that can charge a battery. Not efficient, but simple. You'd need a generator that would put out something at 300 RPM equivalent, which is about what you'd get. Next would be a flywheel. A geared flywheel would easily get you up to 2K RPM on the gen shaft. I don't know how heavy it would need to be. 25 or 50 pounds maybe?
11-29-2008, 12:36 AM #4
The conventional way to convert a stroking motion to rotational motion is with a crankshaft, which is probably the same way the windmill is converting its rotational motion to a stroking motion.
11-29-2008, 12:46 AM #5
There is more than one way to do what you want.
Use the vertical motion to stroke an air cylinder. Put one way valves on each end of the cylinder so it will suck air into the cylinder through 1 valve then pump it out into an air tank through the second valve. The horse power of the wind mill will determine how much air pressure you can pump into the air tank. Use the compressed air to power a small steam engine. Use the steam engine to turn a 12 volt DC generator to charge several car batteries. Buy a DC to AC inverter on ebay I bought a 1200 Watt Inverter for $78.00 on ebay.
I have a 300 watt DC to AC inverter, 750 watt DC to AC inverter and a 1200 Watt DC to AC inverter. I turn on the inverter that I need to power the item that I want. It is a waste of power to use the 1200 watt inverter to power a tiny 100 watt light bulb. Idle current on the 1200 watt unit is a lot more than idle current on the 300 watt unit.
It would be much more efficient if you use the rotary motion of the wind mill to turn a generator. If you want the wind mill to keep it original appearance as much as possible a 1000 watt perment magnet generator is about the same physical size as a 1 hp electric motor. Mount the motor on top next to the rotating shaft it won't be very noticable.
I can run a table saw, coffee maker, refrigerator, drill press, router, skill saw, electric drill and several other items inverters using power from the storage batteries. I can turn on 1 or all 3 inverters.
If you wire several batteries in parallel they will run them self dead they try to charge the other batteries that they are connected to. You have to use diodes in each positive and negative wire of each battery so they can not run them self dead trying to charge each other. You also have to use diodes between the generator and batteries. If you use just one very large very high amp battery then you don't have to deal the diodes. Don't use a battery less than 1000 amps.
If you have 1 battery that is rated 12 volts DC at 1000 cold cranking amps that equals 12000 watts. Amps x volts = watts. If the battery is rated 1000 amps for 1 hour and you use 1000 amps in 1 hour then the battery will be dead after 1 hour. You can run a 100 watt light bulb for 120 hours (12000/100=120). You can run a 600 watt refrigerator for 20 hours but remember a refrigerator cycles ON/OFF automatically you can probably run it for 4 times longer or about 80 hours. As long as the generator keeps up with recharging the battery everything is fine.
You can buy perment magnet generators on ebay and also WW Grainger.
11-29-2008, 12:51 AM #6
your numbers do not compute. you say it spins at 132 rpm which would be 132 strokes per minute. then you say it is 32 strokes per minute. Easy conversion would be to mount a magnet on the pump rod. Then a hollow coil of wire that the magnet goes up and down inside of. Like the shake flashlights.
or you could mount magnets on the back of each sail and have one or more fixed pickup coils
I tried something like that and fed the output into a step up transformner to make a neon bulb flash in time with the rpm.
11-29-2008, 01:07 AM #7
The speed and the strokes per minute were taken from an original data chart on the windmill, though I have not verified the model to be absolutely sure. Unfortunately that will either involve climbing the tower, or the more likely outcome of contracting a bucket truck to put me up there.
But at least there are a lot of really good ideas here.
11-29-2008, 01:19 AM #8
Despite the suggestions that would make Rube Goldberg blush.....
.....the SIMPLEST way to generate electricity with the thing is to mount a small pulley on the shaft behind the blade.......then get a small permanent magnet DC motor of maybe 12 volts, and run that with a belt from the main shaft. Probably 2 timing pulleys and a belt from Martin Gear would work fine......probably want to over speed the DC motor to get around/at least 1000 RPM on the motor shaft....your power and torque available will determine the best ratio. It won't make much power.....20-50-100?? watts perhaps.......depending on which hurricane is in the neighborhood that day.....
11-29-2008, 02:48 AM #9
The common Aermotor windmill is, in the parlance of the American windmill industry, "back geared", which means that the fan shaft drives twp pinions meshing with larger gears, each carrying a crankpin. The gear ratio will change a bit with the fan size and gearbox model, but is typically between 3 : 1 and 3 1/2 : 1. The ratio Harley cites, 125 : 32, is close enough that I'd call it "in family".
11-29-2008, 02:51 AM #10
12 volt testing
It came with a 2 3/4" pulley and if my calc's were right based on the 125 rpm wheel speed I could step up the speed to 954 rpm using a 21" pulley on the on the shaft behind the wheel. My first thought was that it wouldn't be hard to fabricate an offset mount to put the alternator right next to the windmotor. However this creates another problem of how do I keep the wiring from being rapped around the windmill as the wind changes. And I was told that the idea would not fit with the original plan to keep it original looking. So I'm hoping to still use a similar idea on the ground after converting the stroke from the original shaft back to a circular motion.
11-29-2008, 02:59 AM #11
John Garner you wouldn't happen to know where I can find a reference showing how that gearing is layed out.... would you? I wonder if it could be reverse engineered to convert the stroke back to circular motion?
11-29-2008, 03:25 AM #12
Sure do: www.vintagewindmills.com
On the left side of the screen is the Web Site Index; click on Resources, then Library, then Manufacturers, and finally Aermotor. A couple of the .pdf documents there include "exploded view" or "general arrangement" drawings of the Aermotor gearbox.
11-29-2008, 03:46 AM #13
11-29-2008, 05:31 AM #14For an extensive discussion on the differences between windmills and wind turbines, please investigate the wide variety of excellent resources available on the Internet, including wikipedia.org's entry for "windmill" at: http://en.wikipedia.org/wiki/Windmill
So what is the difference between windmill and wind turbine and why can't one use a windmill for electrical power generation?
11-29-2008, 09:57 AM #15
The windmill is made to pull a rod up (pulling up water), and gravity the rod back down. If you must use the original design and can't mount an alternator on the gear head, I would mount it at the bottom.
I would use a rack on the pull rod to turn a pinion. I would put a sprag clutch on the pinion. The pull rod will require a weight or spring to make it return properly. Use a compound jackshaft and a heavy flywheel to get the rotational speed up. I would couple the jackshafts with narrow serpentine belts. Then use a GM alternator to make your electricty.
I favor the GM alternators as they are cheap. Alternators have a much wider range of speeds than generators.
11-29-2008, 10:55 AM #16
You should consider removing all the mechanism, leaving the turbine. Then, for the alternator. An automotive alternator probably won't do it: check the avarage wind speed for your site, and try for a cut-in speed of half of that, also, the amount of power available from the wind will determine alternator size. If an automotive alternator will work, don't worry about using battery power to get things started, there's usually enough residual magnetism in the iron to tickle the field. Good luck.
Try this site for alternator info:
11-29-2008, 11:01 AM #17
Rube Goldberg indeed ! At the risk of repeating myself, why in the world don't you just look up at the windmill shaft and see what they did to convert rotational motion to stroking motion in the first place, and then duplicate the idea on the ground to convert the stroking motion back to rotational motion ? Most such windmills designed to pump water simply use a crankshaft ( or crankpin if you prefer) , which is the simple and energy efficient way to accomplish this without spending time up in the air, which you've stated you don't care to do. It could be as simple as a metal disc with a pin on it, mounted on the generator shaft , with the pump rod connected to it. You may have to use a pulley drive and jackshaft to step up the rpm , depending on what generator you use.
11-29-2008, 12:41 PM #18
Why not use the windmill to pump water uphill into a holding tank? Then use a water turbine to generate electricity. This will provide some electricity on demand even if the wind isn't blowing. You store potential energy anytime the winds blows and use it as needed.
11-29-2008, 01:53 PM #19
Windmills are designed to be low speed, high torque devices. They need to have a lot of force to pump water or grind grain. They also need to pump at low wind speeds. Unfortunately electricity has other ideas. An efficient motor or generator needs, normally, to be run at high speed. They have managed to make efficient lower speed generators and motors but these are usually high pole count. This means lots of magnets or poles.
A windmill can deliver instantaneous efficiencies up to 15 to 20 percent but normal operating efficiency is only 4 to 8 percent. They are known as "drag" devices. Regular wind turbines are 30 to 40 percent efficient.
11-29-2008, 02:04 PM #20
The closer the rotating electrical machinery is located to the blade shaft the better.
Gears, shafts, bearings, cranks, pistons, air pumps, water pumps - they all induce
a parasitic drag.
If you are serious about the conversion then disconnect as much rotating machinery
from the shaft that carries the blades, and mount a generator or alternator directly
on that shaft if possible. If you need to increase speed to get to the sweet spot
of an alternator rpm, a small toothed gilmer belt is pretty low loss.
You can leave all the rest of the 'stuff' in place to retain that old timey look.