Stepper motor for wind!

[melder215]

stepper

I have made a few wind generators from stepper motors. not hard. other parts of it are harder than just making electricity. VAWT . i have a case of 1n4004 if anyone gets a hold of me via yahoo you can have some. will work for 1n4001 or any 1n400? I have having rotors machined for them, and i salvage lots of them.

 

[bryan1]

Well guys last night it there must of been some decent wind as my 550ah battery bank was on 28.4 volts where 2 days ago they were on 24.9 volts. now my small stepper motor genny finally bit the dust. 3 sets of blades later all destroyed so with the last hub i made an ali one and fixed it real good on the stepper output shaft. today i found the blades about 50 metres away still intact and the stepper shaft was sheared off about 1/4" from the stepper body. So it's did proove my lastest hub worked a trick and it just goes to show stepper motor gennies are only toys and when a real strong wind comes around they will bite the dust everytime.

Cheers Bryan

 

[Silversolar]

I will quote what I posted before "it is one thing to make it work, it's another thing to keep it working. "

Vertical axis wind turbines are difficult to control and protect during high winds. I saw one design that the blades are intended to fly away to protect the rest of the parts, for some design - this happens natually. Down wind horizontal axis design may make sense.

 

[duffy]

Another thing that bothers me about vertical axis designs is they don't seem to be spinning as much or as often as the horizontal axis designs. Anyone else notice this?

 

[tcmtech]

I have looked at the vertical axis designs before and I think that they are best suited to small usage and power applications. there size to power ratios are rather poor in my opinion. a honest rated 1 Kw is about 6 feet across and 20 feet high! A 1 KW horizontal three blade is much smaller lighter and simpler to build.

a simple rule I learned a long time ago relating to horizontal type generator shafts is that they should be at least 1/8 inch in dia per foot of blade dia in order to keep from failing. And keep the rotor as close as possible to the generator.

I have had good luck with that ratio all the years I have been building home made units. I have never had a shaft failure yet!

 

[Jules_Theone]

I think the main advantage with vertical axis wt is that they work in gusty winds from any direction a lot better than horizontal. Where I live, in the middle of a city, this would be better. I've made a three cup flappy wind turbine which works pretty well from the gusts between houses. I have mine trickle charging a large battery bank - I figure if I can get enough random generators charging it, it will be good. I think that many small generators on house roofs etc are less intrusive than massive wind turbines which can be seen from miles away. Nano power is the way to go!

 

[tcmtech]

Nano power is the way to go!

I dont know. I would rather have 3 10 Kw on the hill behind my house rather than 10000 3 watt units every where on my property!
Personally I favor the middle ground sized units that the average person can afford to own and operate. That being anything from 50 watt to 500 KW.
As for type, us what ever works best in your situation. I have large open areas of wind driven prairies so I personally prefer big and visible for miles myself!

 

[Wond3rboy]

The advantage of Vertical Axis design is that it gives you more chance of a rotation i-e wind direction is not so important(with oin certain limits). Also when blades of horizontal designs are thin then it may lead to less rotation.

Wind turbine - Wikipedia, the free encyclopedia

As far as Nano power is concerned it is only good for remote areas. Like tcmtech said i would rather have one battery powering my appliances then a battery for each. Less maintainance!

 

[Silversolar]

The power you can get from the wind depends on the sweep area exposed to the wind covered by the turbine blade (either vertical or horizontal), the densitry of the air (dependent on the altitude of the place, temperature and humidity), and the cube of the wind velocity. Velocity is the main element of wind power.

Vertical axis (savonius, darius, drum type) rotors spin slower because the blades only work half of the time (180 out of the 360 degrees) while horizontal axis rotors work all the time because they are exposed to the wind throughout their rotational axis.

For a simple twisted blade shape for horizontal axis rotors, smaller rotors will spin faster than larger rotors. This is why gear boxes are needed for large turbines to translate the sharft speed to 1800 or so to reach the dynamo RPM requirement.

Multibladed turbines (farm wind pumps) will start spinning at low wind speeds because of its high solidity compared to two to three bladed turbines for electricity generation. However, multibladed rotors will only reach a certain RPM and not spin faster because the blades will be "shadowing" each other at this speed, but with high torque. Few-bladed rotors will require a higher starting wind speed but will spin faster than the multi bladed rotor at hight wind speeds. This is ideal for direct-drive wind electric generators with low torque requirements.

Wind in urban areas are turbulent (constantly changing direction and velocity) and vertical axis turbine seems to have higher tolerance than horizontal turbines. Ideally, turbulent places are not good for wind turbines because they produce a lot of mechanical stresses to the wind turbine. Minimun turbineshaft-blade Diameter ratio is 1/10, but safer for 1/8.

Making small wind turbines in a DIY way is like kite flying. You do it because you like doing it, but you don't do it all the time. So, enjoy kite flying ... or making small turbines.

 

[Mr RB]

...
3 sets of blades later all destroyed so with the last hub i made an ali one and fixed it real good on the stepper output shaft. today i found the blades about 50 metres away still intact and the stepper shaft was sheared off about 1/4" from the stepper body. So it's did proove my lastest hub worked a trick and it just goes to show stepper motor gennies are only toys and when a real strong wind comes around they will bite the dust everytime.
...

Not at all. What size stepper motor was it? What size shaft? What diameter and weight/mass of blades? I really would like more info, even pictures too if you have them.

The most likely deduction was that the stepper "generator" was destroyed by using much too large/heavy/unbalanced a rotor blade diameter for the shaft strength and/or that faulty blade design caused one or more blades to fail which was then the cause of the motor shaft failure.

I had a stepper genny with 1/4" shaft and just under 3 foot diameter 3 blade aluminium rotor in my parents backyard for about 15 years, and it was still spinning fine when they sold the house some 10 years ago. There was no appreciable wear on the bearings and of course with no brushes to wear out it was working as good as new.

 

[bryan1]

Hi Roman,
The stepper was a 5 volt 1 amp bipolar I got from jaycar years ago. Just last weekend I took the genny down and thru it in the bin. Well for me it was fun building it years ago and my 2hp motor conversion is still going well. My next wind genny will be for the house and I'm deciding between another motor conversion or a dual axial flux.

Regards Bryan

 

[Mr RB]

Thanks for the info. I was curious about the stepper type, because in that common size 23 (5v 1A) they have 2 types, one is cast alloy casings, great close tolerance ball bearing races and hardened stainless steel 1/4" high quality shaft. The other type is a "pancake" or "can" style, these are cheap crap; bronze simple bearings, pressed thin steel casings, and usually have a tiny 1/8" (3mm) shaft made from some type of cheese.

Have you looked at the fisher&paykel washing machine motors for your next mill? Or is that what you are saying with the "motor conversion"?

They have good bearings, perm magnets, strong shafts and they dont need rewinding, just reconfiguring the coil connections. From what i've seen there are a few people using them for home wind bacause of their large diameter (excellent low speed power output) and brushless design etc.

 

[bryan1]

Hi Roman,
I have made a couple of F&P wind gennies before but I found the cutin speed was too high for my location, it took near 300 rpm to cutin.

My 2hp motor conversion which i'm currently using cut in around 100 rpm and is much better performer.Here is a link to my diary post on the FL forum **broken link removed**


Regards Bryan

 

[Mr RB]

Very interesting. I never would have considered that type of motor/gen for a windmill even with the magnet mod.

Are you shaping your own blades? I had an idea a while back to put a "wingtip" on the outer edge of the blades, similar to the new wingtips they have on 747s etc, to increase laminar airflow over the airfoil and reduce spilloff from the tip into vortexing and drag etc.

As far as i know nobody's ever thought of doing it with windmill blades before, just aircraft. Just another one of those things I'd like to play with but are too darn busy!

 

[tcmtech]

Nice motor mod I have a 7.5 hp 875 RPM motor I am going to do that to as well. I may have to join your forum over there as well!

The AE section here is too nit picky and over pompous for me to be willing to show off my more creative engineering concepts.

Those blades you have look similar to the windmax ones I tried a while back. I see you have a block of something attached to the back of you hub. I assume its for balancing purposes?
I ran into that problem with my last set of wind max blades they were badly mis matched from the factory.
Have you had any problem with the offset furling setup developing a bad oscillation in high winds? I did one many years ago and had horrible results from it. I have yet to retry that design again.

 

[be80be]

bryan1 That windmill is to sweet Good job.

 

[thigiru]

Again the speeds that you drive your generator matters alot.

 

[Mikebits]

Well guys last night it there must of been some decent wind as my 550ah battery bank was on 28.4 volts where 2 days ago they were on 24.9 volts. now my small stepper motor genny finally bit the dust. 3 sets of blades later all destroyed so with the last hub i made an ali one and fixed it real good on the stepper output shaft. today i found the blades about 50 metres away still intact and the stepper shaft was sheared off about 1/4" from the stepper body. So it's did proove my lastest hub worked a trick and it just goes to show stepper motor gennies are only toys and when a real strong wind comes around they will bite the dust everytime.

Cheers Bryan

Steppers were never design to be generators as you have found out.
I would think friction would be inherent in a stepper motor.

 

[duffy]

Does the tail on that thing automatically feather in high winds? You have the offset mount, but I don't see a spring or anything in there...

 

[Mr RB]

Steppers were never design to be generators as you have found out.
I would think friction would be inherent in a stepper motor.

They are fantastic generators!

Massively powerful permanent magnets (some of the stringest in the business), heaps of poles so they start generating at low revs, really high quality hardened stainless steel shafts, expensive precision ball bearings rated for high radial and axial loads, large cast alloy end plates designed to be heatsunk into the mounting bracket, and NO moving parts (brushes etc) aside from the rotor itself.

You can't really ask for much better in a generator. They have a fairly high "detent torque" due to the magnetic poles that makes them SEEM hard to turn by hand. But that magnetic force acts like an efficient spring, so once it is spinning with a flywheel mass like a blade assembly the detent torque is largely recovered and does not cause the drag you would expect.

They are just about the best generator package you can get in that size and wattage. Just don't expect to connect a 7 watt stepper motor with a 6mm shaft to a 2 meter diameter windmill! Any rotor that is within the stepper motor specs for shaft loadings will work reliably for many years.