Pulley Ratio

Worm gears are theoretically less efficient than other forms of drive, though they can have useful applications where there is a substantial reduction in shaft speed required together with a 90deg change in shaft alignment.

In an application like wind energy capture, a worm gear is likely to prove uneconomic; it would be better to use a set of bevel gears instead.

Belt drive is suitable when the two shafts are parallel, as suggested above, in which case the worm drive is not applicable.

The chain system used in the modern safety bicycle is one of the most efficient transmission methods available for parallel shafts, and may be more applicable in wind energy harvesting than belts, frankly.

Thank you for your comment.I kind of thought worm gears wouldn't be to good.But dosen't hurt to ask.

tks again.

I think u can use chain drive or bevel gear drive.More convenient is gear drive in which u can use compound gear system.I u r not worried about torque the u can use compoud gear drive for this u can use speed of last follower/speed of first driver =product of teeth on driver/that on followers

A worm gear is one of the few gearbox types which does not work for stepping up speed. A double belt drive (or double chain and sprocket) could work: two 10" to 2" sets would give you a total 1:25 step up.

Bear in mind that if you double the speed, the voltage will double, but the current will halve -- in other words, the power (the product of amps and volts) will remain the same.

You mention "About 4 rmp, it will produce...". If rmp means rpm, this would be an extraordinarily slow windmill. That would mean that your alternator would be turning at about 37 rpm, or once every two seconds, with your current ratio.

tks Blink, your right in the RPM. it is very slow. I made the coils in the alternator to get it the out put at about24- 27 rpm to produce about 12 volts.The coils have 200 windings each of #16 magnet wire.I have it in a poor spot for wind for in the summer with the trees having leaves on them. But its alot of fun building and fooling around with it.I would have to admit that for me,Solar pannels are produce the most.Well for my area.My vawt is only 30 ft high. it has three blades,each is 7 1/2 ft tall and 30 inches wide.

tks

john

I personally cannot see any reason for the current to be half if the speed is doubled.....

If you have a fixed resistor as a load and you get say 5 amps at 12 volts and you double the speed of the generator, I feel (ignoring efficiences for the moment) that if the voltage doubles, the current will also double and the power will therefore quadruple......

Simple Ohm's Law I feel......

Can anyone show me an error in my thinking?

I see no error in your thinking...

More speed will produce higher voltage, and higher vlotage will produce more current.

If he is trying to charge a battery (presumably through a diode), I believe the battery will act as a voltage limiter, making the current go up faster with increased voltage than would be the case into a pure resistance.

To the OP: Since you have made your own alternator, yes: more poles in the alternator will work better at low speeds. Low speed motors have many poles, and low speed alternators should also. If you are getting 4 Amps at that speed, you must have done a few things right! In my limited experience, the greatest weaknesses in home-made alternators are in the design of the pole pieces on which the windings are placed, and especially the gaps between the coil pole pieces and the actual magnets or their pole pieces. It takes careful design, precision machining, and careful assembly to get the gaps down and consistent. Magnetic field strength weakens rapidly with increased gap.

Assuming the poles are spaced as close together as possible, adding more poles of the same general design will mean a larger diameter for the pole contact region, and larger diameter means higher relative pole speed for a given RPM, and again higher speed means more voltage and therefore more current.

As others have said: show us some pictures, and maybe we can make more specific recommendations.

Hi Andy,

I'm making the assumption that the reason the windmill runs so slowly is that its speed is limited by the available wind power -- otherwise, it would have to be a very large machine, to be designed to rotate at 4 rpm.

So then, if the limit on power is the wind speed, gearing won't change the power. With a permanent magnet machine, doubling rpm will double voltage, and to keep power no greater than the input limit would require that the the amperage (related directly to torque) would have to drop by half.

Raising the wind speed to 16 mph would help a lot. He'd get 64 times the power, so his roughly 40 watts would go to 2560.

I don't think there is an error in your thinking, at least in the sense that your numbers seem correct. My sense is that, unless this machine is huge, the 4 rpm comes about from being overloaded (i.e., wind power limited): (unless the turbine is very large diameter) that rpm would mean peripheral speed is a fraction of wind speed, which is not the usual operating condition.

Andy,

Both you and the guest at post 9 are correct. This is why they have peak power tracking systems. We have dealt with this before. Basically if the turbine is way oversize for the alternator then your argument stands but in all likelyhood the turbine and the alternator are more or less matched then if the gearing is too high then the rotor will slow down, as there is a finite energy that can be extracted from a given wind speed and turbine.

regards

Chas

We have received so little infos that its difficult to make any comment. I thought that he had given the size of the VAWT, but it must have been another blog....

So actually, until we get better/accurate infos, we are all correct!!

But I do understand and fully agree with your comments.....

See post #8. To put things into context we're talking about something about twice the height of a house with four average doors at the business end producing about enough power to light four incandescent bulbs during the evening (assuming good storage/conversion efficiency).

I would have thought that such a large VAWT could have turned at least a car alternator over some gearing at a reasonable speed.....with a reasonable wind around of course....

I read somewhere that on average a windmill only works efficiently about 28% of the time, wind wise that is....the rest of the time there is simply not enough wind........

Thanks for pointing out the size details......

The crucial points to getting more power out of this device is the swept area of the turbine blades and wind velocity, the bigger the better.......

Worm gears, with a few exceptions, actually work in only one direction. Mostly that direction is a reducing speed direction......not what you want!!! You need a higher speed output......

Pulleys I find personally good, toothed belts may be better.....less turning resistance. Gears may be even better, though I do not personally think so.....

Can you post some pix?

What efficiency and performance (durability) is concerned the order would be:

Gears: Most efficient, highest performance, highest (initial!) cost but relatively low maintenance (if designed well)

Chain/teethed belts (although I would be inclined to put teethed belts in between chains and belts): efficient, relatively high performance, intermediate (initial) cost but more maintenance costs expected relative to gears

Belt: Not very efficient, relatively low performance, relatively low (initial) cost but relatively high maintenance costs

I am a little confused by your post. It appears that you are increasing the alternator shaft speed by 9.3 to 1 as compared to the shaft of the wind turbine. If you have light winds and are getting low rpm from the wind turbine, gearing the the alternator up puts more load on a wind turbine that is already underpowered. Nothing is free, more output from the alternator, more load on the wind turbine. Higher gearing of the alternator will put more load on the wind turbine, necessitating a more efficient turbine. How about a chain and sprocket assembly from a multi-speed bicycle? This would allow you several choices of shaft ratio speeds to choose from.

To hook up a set of bike gears would be very hard and much work.and to have them switch gears automaticly would be also hard.I was thinking or asking is a 2 shaft gear box would be better them just a 1 shaft gear box. same as what better 2 pullies or 4 pullies that come out with the SAME ratio.

A SINGLE REDUCTION CHAIN DRIVE WOULD PROBABLY BE THE MOST EFFICIENT WAY TO GO. GEARS ABSORB ENERGY, SO USING TWO GEAR REDUCTIONS WOULD DOUBLE THE LOSS. CHAIN DRIVES ARE VERY EFFICIENT. AS FAR AS MAINTAINANCE GOES, MODERN MOTORCYCLES HAVE OVER A HUNDRED HORSEPOWER AND GET SURPRISING LIFE OUT OF GOOD QUALITY CHAINS WITH CLEANING AND LUBING ON A REGULAR BASIS. SINCE YOU'RE ARRANGEMENT WILL BE UP IN THE AIR AWAY FROM ROAD DUST, SAND ETC. YOU SHOULDN'T HAVE MUCH MAINTAINANCE IF YOU USE A QUALITY CHAIN AND GOOD CHAIN LUBE. OF COURSE AN OILBATH WOULD BE IDEAL, BUT I THINK THE ADDED COMPLICATION WOULD BE UNNECCESARY IN YOU'RE APPLICATION CONSIDERING THE OUTPUT OF THE TURBINE. WORM GEARS ARE HIGH REDUCTION DRIVES AND TRANSMIT A LOT OF TORQUE BUT YOU CAN'T DRIVE THEM BACKWARDS. I.E. TURN THE SPUR TO DRIVE THE WORM.

thank you all for the comments.I guess that I have it all figured out with all the input.

Thank you all again.

John

Dear Jak,

please don't SHOUT quite so much......

Thanks.