My 17 Footer is ready to fly

[mitcamp]

I purchased the 32 mags 3 x 1 1/2 x 3/4 from our host, and used a 18 in.  1/2 thick disc as Dan said the mags were a little too close together on his model. I used West Epoxy on the 2 rotor disc



My stator is wired for  24 volts and Dan did his for 48 volts. The stator is cast in fiberglas.





I took Dan,s advise and used a 6400 lb axle and spindle



This is where I started to add a few of my own idea,s.  I use 3 sliprings on this model and will take 3 cables of 2/0 160 feet to my 24 volt array. This is a top view of my slipring and brush assembly.





I am using 3 brushes on each slipring for a total of 9 brushes. This machine will be putting double the amperage as Dan,s because his was 48 v and mine is 24 v  Somewhere I came across a discussion and was said Dan,s was puting out 83 amps. So at 160 amps divided by 9 brushes, would be 17 amps per brush. These are starter brushes and are rated for 600 amps. Should be an easy life even if my calculations are off.





This is a rear view of my Dual Rotor with the rear panel off. This machine is covered as we get all kinds of weather in the Northeast. I used the buckets that the wire came in to cover the sliprings, brushes and my Yaw bearing. The buckets are slightly larger than 5 gallon cans





I am using 6 stud rectifiers in a homemade heatsink with fans and could be modified with larger heatsinks if they show any sign of overheating.





I have made a knife switch to control this machine and will probably rig up a load to short it into instead of the stator taking the heat.





Seen a post a week or two ago about a similar sized machine with a homemade braking system. So I,m giving it some thought.May add a brake too. Hey I had one of these get away in 72 mph gale and I nearly had a heart attack watching it. Used up a considerable amount of toilet tissue too. If it ever happened again, well I,m leaving home and let the wife look after it.  

I want thank you guys for the help you all give me, last 2 years  Flux,Dan B, Shadow, Wilbur, Dave and everyone else. I would not be raising this 17 ft.Dual Rotor machine if it were not for you.    Mitcamp

[Dave B]

Mitcamp,

  Looks very nice, keep us posted on it's performance. It may have been my manual brake you mention. I know what you mean about a run away being a very stressful situation. Case in point : my previous 12' single rotor self started completely shorted and accelerated to a (frequency measured) 800 rpm sounding just like a jet ! Winds topped out gusting to 65 plus mph and remained well above 35 mph for hours. I had hoped for complete furling at around 400 rpm but did not have enough offset and it actually sought the wind instead. A few coils finally loosened and scraped the magnets limiting the rpm to still nearly 400 rpm making a sound I'd rather forget. Nights like that you are glad that you design everything twice as strong as you think it will ever encounter and then build it twice as strong as that besides. Incredibly all parts remained together and my 85' tower didn't bat an eye. Anyone who has experienced this helpless feeling before knows how special a manual brake could be and I will never put one up again without one. Just a story I wanted to share that may save someone's genny and or tower sometime. Dave B.  

 

[willib]

Nice slip rings

Thats an awesome effort

got any output data?

much luck with it

william  

[DanB]

Looks very nice Mitcamp - I hope it works well for you...

One comment - for teh stop switch you have basically a triple pole double throw switch.  You only need a double pole single throw - although since you have it there I'd use triple pole single throw.  What you have now has 3 positions - down is braked, up is 'on' and in the middle is 'self destruct'.  If you only have two positions (open  - which would be on - and braked) it would be a bit safe in case anyone ever decided to mess with the switch.  Just a thought...  you have 9 leads on there - it be safer if you only had 6.

[mitcamp]

 Dan, on all the other machines I built from 4 foot to 12 foot I used my rectifiers at the top. This 17 foot is the first for rectfiers at the batterys. For some reason I could see the switch before the rectifiers, and never considered swich after the rectifiers. You could call it being narrow minded. Wife would say Pigheaded.

Matter of fact I will take your advise and put the switch after the rectifiers. It would be less confusing for my wife to shut it down when I was away.

Do you think I need more heatsink for the stud diodes. If you think I would be better off with 2 or even 4 of your heatsinks I will have you send them to me. I would rather over build the heatsinks, than have a problem. Thanks  Mitcamp

[Flux]

Now that you have the choice, put the switch before the rectifier. breaking dc with a knife switch with no flickers is a messy business.

If you do it before the rectifier there is no feedback from the battery so you can just short the 3 ac incoming leads. Minimum requirement 2 pole single throw, 3 pole single throw is nice. No need for any change over.

Flux

[mitcamp]

Dave B,  I printed a picture of your brake system and have been pondering over it for hours. Have you or anyone else considered mounting a seperate disc on the extreme rear of the hub. (I see Dan B mounts his rear rotor in this fashion.) Now...with this mounted, could we then use a set of mechanical calipers on this steel disc to help slow it down in a emergency.

It could be activated the same way you have yours setup, by pulling a cable that is inside your tower at ground level.  In my case I would run a solid plastic cord up my pipe that supports my sliprings. Like the stuff used with large weedeater. Its orange in colour and you can,t break that stuff. By using the plastic cord in the pipe, it would never short-out the power cables.

I,m actually putting off my installation until I figure this brake thing out.  Mitcamp

[mitcamp]

Hi Flux, I was expecting to hear from you. I will continue with my plan and put the switch before the rectifiers.

 I wanted your opinion on what I just posted to Dave B regarding a optional brake system. We were answering at the same time.

If I remember correctly,reading in one of your post, you said you had devised several braking systems for your own generators. So you are familiar with the problem.

Dave B and I are in the experimental mood. Can you point us in the right direction. I,m old enough to handle a few slaps upside the head.  Mitcamp

[Dave B]

Mitcamp,

  Yes, I considered adding another smaller disk behind the rear rotor so a caliper arrangement could be used. As you can see I left room for this and I considered a go cart disk brake arrangement or possibly a light weight motorcycle set up. Figuring that my rotors are 1/2" I felt comfortable that used as a parking brake I could keep it simple and utilize the rear rotor. It is mounted on the back side of the hub with all thread and nuts securing it independent of the other front and back. Between my disks are machined aluminum spacers that allow a large surface area for mounting the front rotor so there is very little chance of the rotor flexing or bending the all thread which I think possibly has happened to some in the past with large heavy blades and relying on hanging the rotors and blades off the allthread with just stand off nuts between. A close airgap can go away, magnets can scrape, heat builds up, stators melt and coils open and then overspeed with self destruction. A little off track there but it all goes back to wanting to shut down the mill when high winds are expected or any other time you just don't want to think about it turning. My cable through the top tower section is a bicycle brake cable adjacent to the power cable, the remaining cable is joined to this and just hangs down the inside of the tower.  Good to hear you're working on a manual stop, you've been bit before also. Keep us posted,  Dave B.

[ghurd]

I have a feeling many people put too much faith in safety devices, often cutting important corners feeling "It's OK because it has this safety device!"

Gun people never trust a safety or anything else mechanical.

Weed Whacker line gets weak.  Faster than you'd think.  I bought a giant spool of name brand orange-size line and maybe used 50'.  Now it breaks before full speed even if it did not hit a weed.  It was not exposed to sun light, high heat, strange fumes, etc.

So I'd trust tiny 1/8" braided nylon far more.

G-

[Dave B]

Ghurd,

  I agree that there may be a better choice for the (cable down the tower) mine is galvanized wire rope rated at hundreds of pounds. I also believe that any additional safety device is better than none at all. There are many ways to set up a manual brake which is just one of several different ideas depending on what your intent is. My specific application is a parking brake, not a speed control nor a drag brake to slow the mill but rather a means to avoid start up and is to be engaged with the rotor stopped or very nearly so. I also have the option of actuating this in reverse to my current set up where by the extension spring tension on the cable dis-engages the brake so if this cable or means to secure it ever fails the brake will be engaged (actuator bar weighted so gravity is always the force trying to actuate the brake). I've got furling, shorting and now the mechanical brake besides, I will feel much more comfortable when the big winds are on their way.  Dave B.

[Flux]

I have never played with brakes. Parking brakes should present little problem but stopping a machine in full flight with a failed alternator ( no electric braking) would be a lot more demanding. It is a wet and fairly nasty climate here and it would need a lot of effort to make any form of brake that would remain operational for long without lots of maintenance but I have no doubt that it can be done. In dry climates there may be little problem.

I have always stopped things by moving the tail at right angles to the normal position.

Again such mechanisms need occasional greasing but seem not to be much trouble.

These mechanisms are easy if you have slip rings and can bring the control cable down the centre. With the power cables down the centre things are somewhat messy and I have generally used control schemes similar to the Freelite with the manual furling working via a sliding sleeve over the outside of the yaw tube (this is the bit that needs greasing). You have to be certain that you have enough tail area to overcome the prop seeking torque. I saw somewhere that a Bergey failed to stop with the tail at right angles. Something strange about how Bergey manage with such small alternator offsets but I wouldn't have suspected that the tail was too small. Nothing is really certain with all this stuff.

I have built one machine with slip rings. The tail pivot is reversed ( it forces it to furled position. A control rope passing down the centre with a weight attached keeps it into the wind via pulleys and a drum on the tail rod concentric with the pivot.

The heavier the weight the higher the furling speed. Was it worth the hassle of making slip rings? probably not but it is a nice control scheme.

I suppose a parking brake is better than nothing but not my choice.

Flux

[jimjjnn]

Weedeater cord does deteriorate over time. Don't know why. It gets very brittle and wont cut weeds cause it cant run at the speed anymore as Ghurd stated

[jimjjnn]

Put the switch BEFORE the rectifiers as shorted batteries get VERY NASTY!!!!!!

[Ungrounded Lightning Rod]

For some reason I could see the switch before the rectifiers, and never considered swich after the rectifiers. ...

Matter of fact I will take your advise and put the switch after the rectifiers. It would be less confusing for my wife to shut it down when I was away.

With that arrangement I think she would become very confused when she first disconnects the switch from the "generator on" position and the mill speeds up and starts to shake itself apart, then she shoves the switch into the "brake on" position and sparks fly, the switch welds, the diodes explode or pop internally, then either the wires become red hot, the insulation starts smoking, and the genny catches fire or the mill continues to runaway and finishes destroying itself, throwing huge chunks of blade around the yard at about a quarter the speed of sound.

= = =

NEVER put the brake switch after the rectifiers.  Presuming you're disconnecting the battery properly, when you turn the switch on the momentum of the blades keeps the generated voltage from dropping until they have been slowed down.  With a short across the output the current climbs drastically, limited only by the voltage drop in the diodes and resistance of the wire.  Result:  Fried diodes and (if they fail open) a runaway mill.  (If you're NOT disconnecting the battery properly you melt the wiring into slag, set the shed on fire, and/or explode the battery and spray the vicinity with boiling sulphuric acid.)

= = =

You use a double-pole switch on the 3-phase side of the diodes.  Tie X to one pole, Y to another.  Tie Z to the opposite end of BOTH poles.  Label it "electric brake".

Off:  Normal operation.

On:   Three-phase is shorted on the AC side of the diodes:  Brake are on.

There is no third setting to foul up with (or confuse the wife).

[Countryboy]

You may want to look at trailer brakes, like on trailers pulled behind a pickup truck.  These are electrically controlled brakes.

You could set a relay that engages the brakes when voltage/amps get too high - a way to shut it down prior to frying the stator or the mill running away from you.  (and set it up so you can manually shut down the mill with it if necessaary.)

[harrie]

looks like a lot of good work Mitcamp, Its surprising how many hours one can log up building a turbine, Its almost as good as chasing women, ha. Well at my age, its alot better. I think sooner or later, someone will come up with a good way of brakeing, I think with my way of turning the turbine out of the wind, works quite well, at least you can short it out at low RPMS. I have sence installed a cable operated spring loaded heavy duty pin that will slip into the spokes of the large gear and hold it out of the wind. The high tourqe low RPM motor I have at the top, did not hold up, the weight of the turbine simply destroyed one of the small gears in the motor. I have sence installed a rubber gear on the motor,which just is pressured against the large gear, and still will turn the turbine out of the wind, so all is well with that. Great pictures, and thanks for sharing.

[DanB]

I feel like the brake shouldn't be required so long as the alternator is stiff enough to shut down by shorting.  Both mine will shut down in any wind (that I've seen) and stay that way even by shorting 1 phase - which means any 1 wire can break and it's still good.  When the stators fail they always seem to short internally (or the stator becomes a potatoe chip/brake pad all by itself) and stop.

But - the brake certainly doesn't hurt and its interesting.  I have trouble imagining how to deal with the cable running down the tower/not getting twisted up with the wires.  Slip rings simplifies that but I prefer to avoid that step.

One possibility I've been thinking about would be to build half the braking gear onto the tower top, with a heavy cable running down the outside of the tower  (away from the lines that might be twisting up). To turn the brake on and off, you would use the cable to raise/lower the wind turbine and the weight of the turbine would apply pressure to the brake.    This all isn't probably very clear and I've not put in many details - there would be different ways to make this work... I've just been pondering ways to do this in a simple way with out needing slip rings.

[Dave B]

Hi Dan,

  Interesting thought on the brake idea and just a quick comment also. You have the resources and is now an efficient process for you to build these machines. I wish I had this testing type luxury but do not so I'm trying to keep things safe and so for me my parking brake will be a great stress reliever, not a cure all but a great option. It is and continues to be a tremendous resource of information with your posts of failures and successes and I really appreciate you guys pushing the envelope at times to find the limits of the design so we can all learn what may or may not work with our own machines. I think most will agree we would be struggling far more without all the help you provide. Thank you for sharing the Bergey non shut down story also, Murphy's Law at it's best. Thanks Dan,  Dave B.  

[mitcamp]

Lightning Rod, Many things was happening that day and I was taken away from the computer several times while I was on this post. Lets just say I was on 3 channels at the same time.

Dan B did not advise me to put the switch after the rectifiers, so the following statement was my mistake.

"Matter of fact I will take your advise and put the switch after the rectifiers. It would be less confusing for my wife to shut it down when I was away."

I will read it next time before I post it.Mitcamp

[mitcamp]

Hi harrie,  Well after hearing Dan B saying the alternator should be stiff enough to stop with 1 phase shorted and that his 17 foot and 20 foot has seen some good stiff winds, that did make me feel better.

I did have some butterflies in my stomach last november watching my 18 footer floundering for 4 hours until the stator burned up,then it stopped. That was all my fault, because I built the rotors with 2 x 1 x 1/2 magnets. lesson learned.

I will still work on a braking system and I would like to have the added insurance of another way to control it. It is ready to go up now, but I,m going to hold off for a few weeks just in case I come up with something. Its going to be up a 100 feet and  a big job to remove blades, rotors and stators at that height, for modifications.

Keep up the good work and someone of us will stumble on to something.      Mitcamp

[Dave B]

Mitcamp,

  Glad to hear you are still planning on a brake arrangement, at 100' (mine will be 85') you and I both know how nice it will be to shut down the machine. I just lowered my tower yesterday in preperation for setting up the new machine. Keep us posted on your progress, I hope to have mine up maybe in a couple weeks. Dave B.