centrifugal clutch for vawt

[captainward]

I live in a light wind area in so cal that has gusts up to 20 mph.  My wind turbine
would benefit greatly if i had a centrifugal clutch connected to it. Is there a clutch already made that I can buy that would kick in at low rpms say 30 rpms ?
Anyone have an idea to modify an existing centrifugal clutch ie gokart clutch? your help is much appreciated!

[electrondady1]

never heard of anyone putting a clutch on one
how are you loading the mill?
usually they free wheel up until they reach cut in speed

[Harold in CR]

 Mighty nice mill. Care to tell us more about it, as in Dimensions, expected output, etc. 

Thanks, Harold

[captainward]

Welcome and Hello Thanks for responding.

The VAWT Lenzs 2 wing here has a 48" length is covered with aluminum sheeting over pine ribs.
It has a small pmg from windzilla  puts out 12 Amps at 300 rpm.
Because of the light winds and the stopping and starting I feel a clutch would be a better idea.
you can see the video of it on youtube  "my vertical axis wind turbine" pts 1-4
I also have solar power for the rest of the year.
any suggestions for the centrifugal clutch would be helpful  Thanks and as always
 Thanks for L@@king.  CaptWard

[SparWeb]

Hey I haven't seen a Lenz machine on the forum for a while.  Thanks for putting up the pictures.

Does the windzilla have any "cogging" feel when you turn it by hand?  If this is interfering with start-up then you likely have a bad choice of generator (don't know anything about the windzilla myself - I make my own PMA's) even though the specs of the generator do sound like it would work.

It could be just as easy to build yourself an axial-flux PMA than to set up a clutch.  Fitting to the shaft, added bearings, tuning the counter-weight, there's such a long shopping list of things you would have to do to make that clutch work...  so I recommend you just build a PMA that will free-wheel up to cut-in speed and eliminate the problem entirely.

Maybe another member of the forum has successfully mated a Lenz turbine to a windzilla (or similar) PM generator, so stay tuned; they might have another solution, but I doubt it.

Oh, and welcome aboard, captain.   

[captainward]

Hi SparWeb  The motor spins very ease but in light winds it won't let the turbine go round that is why I want a clutch so even in the summer months when  the winds are light it can still rotate and not just sit there because of not enough wind velocity.

[Frank S]

It sounds to me like you are wishing to have a rotating piece of yard art not trying to produce any energy in very light winds but when the velocity reaches a certain level it begins to produce. Also with the blades already spinning when the clutch engages there would already be some kinetic energy built up.
 Does that sound about right?
 What is your gear up ratio?
  A go-kart clutch type could be an option like you mentioned.
 There are many low inertia centrifugal clutches out there, some even over center lockable. ranging from fractional HP through 100s of HP

[sean_ork]

rather than a clutch use a voltage controlled relay or a SS alternative - wired to take the load out of circuit until it's spinning and producing a usable output - when the output drops below a usable amount the relay drops out

automotive relays tend to drop in/out at around 9v - using the volts drop across a diode (or 2) allows the actual drop in to be adjusted

[electrondady1]

that's got iron core written all over it.
the wind must be strong enough to pull the mags past the iron.

[captainward]

Hello FrankS, Yes you have hit it on the head I simply love to watch the turbine go round in light winds but still be useful when the winds are strong enough. the gear ratio is 5 to 1 thats a 10 inch pulley to a 1 3/4 inch pulley.  or one rotation each second= 60x5.5 = 330 rpms = 5 or 6 amps@12vdc.

Sean-Ork, The problem is maniacal as the weight of the shaft and wings add drag until the wind reaches about 2 mph but it must get to 5 mph before it will turn the generator plus a small amount of friction will engage the shaft much better than one big torque grab.

Also I am wondering if the generator is at say 6 volts is it still charging the battery's some?

[captainward]

FrankS, so where  are these centrifugal clutches that might work, that I can look at?
I have looked on the internet but to no avail. I have a feeling I will have to get one close to what I need and cut down the weights until I get the friction I need at about 5 mph sound about right? My lathe has a rpm meter on it.  As for building a new PMA not going to happen too much $. My fingers don't like magnets that strong.

[Harold in CR]

 A centrifugal clutch has springs that hold the shoes away from the drive part. You will need to change to a lighter tension spring on the shoes, so it will engage at a slower RPM. Do not to anything to the shoes, themselves. Clutches are available on ebay, among other places. Do a Google search, then, click on images on the upper left part f the page. You should get exploded views in some of the images.

 Like your turbine. Is it about 4' tall wings ?

[Bruce S]

There are clutches you can adjust.
Try looking into the pull-rope units for Briggs & Stratton 5 - 9 HP engines. These can be opened and different weights ( steel balls ) changed.
Also the newer 49 - 250cc Scooters use a type of clutch that is based on weights, there are different weights than can be used to tweak to cut-in , but it will be trial/error.
I would look for the pull-rope lawnmower type, they'll be set for Vertical use, where the scooter type will not be.
Nice looking unit, inquiring minds want to know more :-).
Cheers
Bruce S

[Frank S]

Try this to get you started
http://www.abssac.co.uk/uploads/products/cat_b7hir_Clutch%201.jpg


he NLS® centrifugal

clutch reduces motor acceleration time and power requirements in a variety of power transmission applications. Offering a low initial starting torque, the NLS clutch provides soft starts and reduced starting current. Because motors achieve running speed almost immediately, motor current and motor heating are reduced.

No-load start
Cushion for high inertia starting loads
Dampens shock starts
System overload protection
No slippage at running speed
Inner shoes
High energy capacity

[fabricator]

Since you are really not getting anything useful out of the thing for a large percentage of the time, why not just remove the generator and buy more solar instead of a clutch, then you will have more usable power and yard art at the same time.

[Frank S]

One thing to consider though witha clutch like you are considering.
 your machine  runs at such low RPMs that the inertia will be very low the clutch may need to be an overrunning sprag that physically locks up at a given RPM instead of relying on fly-weighted   friction pads

[midwoud1]

Or a type of clutch that activates the airco pump in our cars .
Seems to be friction free in off position.

[Frank S]

Or a type of clutch that activates the airco pump in our cars .
Seems to be friction free in off position.

 Yes but the current draw may be higher than the output of the VAWT

[captainward]

to fabiacator, because i get 30 days a year with clouds and rain that bring in wind. solar is no help that 30 days.
So far the spring clutches are not adjustable can't cut the spring down. problem not solved.

[fabricator]

It takes 12 vdc to hold a compressor clutch in at probably half an amp or so and it would need that the entire time the thing is running, very likely more than the thing is producing.

[SparWeb]

Hey look: more pictures from captainward:  http://www.fieldlines.com/index.php/topic,148024.0.html



Now I see the 5:1 gear-up that you mentioned.

Your problem may be the resistance in the sprocket drive and the PM generator, which have been given a 5x torque advantage over the VAWT.  No clutch would solve that.

Don't worry too much about light winds, there is NO power in it. 

[Mary B]

Be easy enough to design a voltage controlled solid state relay(or fet) that kicks in at x volts as a chopper to start getting output and kicks in fully once the rpms are up enough. Sort of a crude MPPT

[captainward]

to MaryAlana, Thanks for your input I am not sure how your answer would solve my problem? how  would that work?

[Bruce S]

At what wind speed does it start turning at 30RPMs ?
If you're looking to get something in a wind at less than say 7mph , it may not be worth the extra trouble.

[fabricator]

No matter what you do it probably won't overcome the mechanical advantage that is weighted toward the generator side right now, until it sees higher wind speeds

[electrondady1]

the best solution is  more lenz2 units,
 stacked up or running in tandem forming a wind wall.

 

[Frank S]

 I think Fab hit it right on the nose.
 No amount of elaborate or even simple controlling of the electrical output will solve the low energy potential of low velocity winds as long as the gear train and generator are in circuit with the turbine.
 2 simple tests can be preformed to show exactly where the blades will start to turn .
 disconnect the wires from the generator preventing any current flow, note at what point the blades begin to turn.
 Next remove the chain from the sprockets leaving only the turbine's resistance to low wind start up, note the wind velocity of this.
 He is probably going to need a clutch that is controlled by a combination of things mounted directly to the the turbine shaft which would remove even the gear train. this will require a larger clutch because of the mechanical disadvantage of the 1 to 5 ratio..
 I doubt if the simple spring controlled friction fly weights will ever accomplish this. But there may be another way with a mechanically applied clutch connected to a fly weight governor 
 more than likely anything used will have to be highly modified to work in this application 

[captainward]

Well Thanks for all the input I can now think about it and make a decision as to what to do.
all the comments were very good THANK ALL OF YOU SO MUCH A PLEASURE HEARING YOUR OPINIONS.

MERRY CHRISTMAS & HAPPY NEW YEAR.   CAP.

[Mary B]

I would use an arduino, monitor rpms, simple fet switch... requires electronics knowledge and programming.

[just-doug]

if you are doing your own machine work,a simple sliding dog clutch,or possibly a sinkerow ring like manuel transmission uses.shift it in with a air door.