Author Topic: 16 Footer fails to furl (Read 21574 times)

galeforce jones · « **Reply #33 on:** January 22, 2010, 12:32:55 PM »

I think its well understood that in sudden gust the furling doesn't react fast enough and you will see very high amps, this situation should only last a few seconds. You say you ran to the window and discribed seeing the tail in its fully furled position, I would suggest by now the amps are well under control.

ghurd · « **Reply #34 on:** January 22, 2010, 12:41:39 PM »

Looking at my genuine state-of-the-art (ebay) setup,

Looks like the open part of the hinge pipe "could" jack itself up onto the weld bead.

And if it did that with enough force, I could see it binding...

But I don't see how it would un-furl in low winds, if it was binding to the point of doing what yours did.

Just another thought.

Mine doesn't fit that tight.

G-

David HK · « **Reply #35 on:** January 22, 2010, 01:05:41 PM »

Just out of curiosity, which way does your 'prop' turn when you stand facing the machine from up wind?

David in HK

Hilltopgrange · « **Reply #36 on:** January 22, 2010, 01:33:44 PM »

Hi Bob, I normally shut down the 16 and 12 foot machines when very high winds are forecast but I let the 10 footer fly through it, if it blows up its no big loss as it is now fairly old and probably overdue a rebuild.

I'm still undecided as to the best overall solution but I suspect it is most likely to be pitch control, with a little luck the solution that flux suggested will keep it ticking over.

I need to do a lot more research and get the drawing board out again!

These little things are sent to try us!

Russell

Hilltopgrange · « **Reply #37 on:** January 22, 2010, 01:55:51 PM »

Hi Ghurd I have a positive stop for both positions of the tailthat stops it well short of the weld. This pic shows it best

http://www.otherpower.com/images/scimages/7813/6.JPG

for some reason I cant post a pic? so heres a link.

Russell

Hilltopgrange · « **Reply #38 on:** January 22, 2010, 02:03:58 PM »

Hi normally when this machine furls the power drops after an initial peak, this time was very much different though, the output of 96A was sustained until the gust started to drop. My charge controller etc is located in the workshop so I was able to see the turbine and ammeter from this position. It most definitely failed to turn out of the wind.

Russell

Hilltopgrange · « **Reply #39 on:** January 22, 2010, 02:07:29 PM »

Hi David The rotation from upwind is clockwise.

Russell

fabricator · « **Reply #40 on:** January 22, 2010, 02:48:36 PM »

I'm really starting to think I need to come up with an automatic mechanical breaking system before I fly my seventeen footer, there definitely seems to be a pattern here.

I've been spending some time looking at my alternator assembly and thinking about a ring gear from a car flywheel mounted to the back of the rear rotor, then driving a pinion that uses something like a governor like they used to use on steam engines that would activate a mechanical brake, activation deactivation would obviously be the trick here, and remember all this is still just a bunch of bits and pieces floating around in my largely empty cranium.

ghurd · « **Reply #41 on:** January 22, 2010, 02:54:56 PM »

Again, just a stray thought... But I think a Really good one this time!

Looks like the bottom hits before the top? (probably just the pic)

If the top and bottom strut don't hit the stop at the same time?

A thin flat blade exhibits (tiny amounts of) lift.

Could it be the cloth tail pushed out enough to be a better airfoil?

I think I can see that happening, and the lift would try to hold the tail up. Much the same as lift from a blade tries to turn the prop.

So.

Blow that cloth out like the wings on the Wright Bros plane,

include the pipe at the outside of the cloth,

look at the vector forces causing lift on the blades,

And the tail lift could push it to stay up there.

Much like Ed's 1-hour conduit and cloth HAWT blades,

http://www.windstuffnow.com/main/one_hour_projects.htm

G-

Hilltopgrange · « **Reply #42 on:** January 22, 2010, 02:56:19 PM »

Hi Bill, very interesting its going to take a while to read and digest.

Thanks for the link

Russell

HaroldCR · « **Reply #43 on:** January 22, 2010, 03:04:46 PM »

Russell

I found a photo of what I was trying to describe. Send me your email address at hm in cr at gmail dot com

Hilltopgrange · « **Reply #44 on:** January 22, 2010, 03:16:22 PM »

Hi ghurd your certainly flexing the grey matter lol!

The tail was tied up for the pic and is not right on the stop but it does make contact on both the top and bottom strut together, that angle is what determined the angle of the stop. Another stop was also added after this pic was taken for the normal tail position I think it is shown in one of the other pics of the build.

The aerofoil theory may be a valid point, I don't know to be honest, I would have thought as it was facing the wind that it would have tried to push it to the unfurled position.

Russell

Hilltopgrange · « **Reply #45 on:** January 22, 2010, 03:31:30 PM »

I don't think a mechanical brake would have helped in this situation, by the time you would get to it the event would be over, and you could do more harm than good throwing on a brake at that power level. Come to think of it this may well have happened before when I wasn't on hand to witness it. It was just pure chance that I was there at the time, computer logging of the output and rpm would be the only way to know. Hindsight and all that lol

You should change your sig line to

I aint skeered a nuthin ......except a big gust

Russell

Hilltopgrange · « **Reply #46 on:** January 22, 2010, 03:36:36 PM »

Harold you should have mail! if not my address is hilltopgrange at tesco dot net

Russell

TomW · « **Reply #47 on:** January 22, 2010, 03:39:29 PM »

Thinking on braking these bigger units I keep coming back to old style semi truck or trailer drum brake as an emergency / parking brake. Fitting back over the hub activated like any brake pad type. Maybe get away with one pad too? Just seems an easy upgrade with a bit longer hub support tube spacing forward of the yaw assembly. If they can stop a 40 ton truck on a grade they should handle a big prop when slowed by a short or good load.

I am no builder but thats where I see this leading

Seems the drum could bolt to the rear of the rear rotor to give a good braking surface?

Seem to recall those drums are 20" diameter or so so should maybe fit. Stator mounting may need to be reconfigured.

From there you can activate with air or hydraulics or even a mechanical activator.

Just ideas.

Tom

ghurd · « **Reply #48 on:** January 22, 2010, 04:08:21 PM »

"I would have thought as it was facing the wind that it would have tried to push it to the unfurled position."

Me too!

But something held the tail there, and if it was facing the wind, and not binding itself, then I think the answer has to be in the tail's lift properties and related to crazy-fast wind speeds.

I can not believe it is simply the prop's seeking force alone.

I wondered about the tail causing these types of issues since I saw a TV show about "Rods" (A mythical creature like a pencil with maybe 8 pairs of wings). These 'rods' were photographed while parachuting into a vertical cave. The program had a few groups looking into different possibilities.

The math Geeks did wind tunnel tests showing a flat plate had lift, and a lot more than they thought. And more than they could calculate at the time (IIRC).

My first thought was lift in the tail could screw up furling calculations. More so based on straight level wind, not moving like threads on a screw.

I thought the concept would be compounded depending on blade efficiency and direction of rotation because they would greatly alter the angle of attack seen by the tail.

Obviously the left/right side offset.

Next was if the tail was connected to the left/right side of the tail boom.

The wind sees (| or |), not ||.

(I still think thats worth considering when you can't sleep)

I stopped thinking about it because my gray matter was blowing fuses.

(today, mind-numbing piece-work gets the gray matter stimulated)

Before the end of the program (by accident?) the camera Geeks pretty much proved "Rods" were moths photographed with a digital camera.

Same crazy stuff happened in the cameras as when taking a pic of a fast moving windmill.

G-

Hilltopgrange · « **Reply #49 on:** January 22, 2010, 04:25:18 PM »

My 10ft machine was built almost as you describe only with a Renault car drum and brake, snag is it tends to rust and fail when you need it or as happened with mine the rust builds up on the inside of the drum and starts draging and make some strange noises.

When a machine losses load and runs away so do I, about 100m upwind is a good spot to watch from cause thats about all you can do.

The insert image tab no longer works for me for some reason

http://www.otherpower.com/images/scimages/7813/pic5h.JPG

Russell

Hilltopgrange · « **Reply #50 on:** January 22, 2010, 04:43:32 PM »

It maybe that the machine was turned a few degrees out of the wind it would be difficult to say exactly even as much 10 deg would not be distinguishable from the ground even with the streamer maybe that would account for the tail staying up.

I seen that program about the "flying rods" some where convinced they where micro ufos lol

My grey matter is no longer grey I have reserved that shade for my hair, the little I still have! which is significantly less than yesterday I may add!

Russell

Volvo farmer · « **Reply #51 on:** January 22, 2010, 06:30:58 PM »

That thread is over three years old. Why not share your successful design of your yaw controller, with the electronic bits and ham radio antenna rotator, rather than link to a three year old thread? Surely it would be more helpful to share your experience with yaw control than link to a three year old discussion of some vaporware.

TomW · « **Reply #52 on:** January 22, 2010, 06:43:23 PM »

Ungrounded Lightning Rod · « **Reply #53 on:** January 22, 2010, 07:32:59 PM »

If you're going to use a mechanical brake you have to actuate it under load occasionally to keep the drum/disk clear of rust and dust and the pads clean.

Downside to using drum brakes is that the self-adjusting for wear takes place when you apply them with the shaft turning in reverse. This doesn't happen on wind turbines (unless you lasso the tail and turn them to face downwind or motor them backward.) Probably not a problem though: You won't be stopping the mill with them often enough to wear them down into needing adjustment.

fabricator · « **Reply #54 on:** January 23, 2010, 05:00:11 AM »

Now I'm wondering why not just just set up a wind speed actuated relay that shorts the phases above a preset wind speed? Say, above 45 mph the mill is shut down, the chances of severe damage are greater than the worth of the power generated for the duration of the extreme wind conditions anyway.

bobshau · « **Reply #55 on:** January 23, 2010, 11:06:44 AM »

Three weeks ago, I lowered my 20' diameter windmill (shown here: http://www.fieldlines.com/story/2009/3/2/171331/4786) after loosing a phase resulting in uncontrolled overspeeding that burned out the stator. As a result, I'm installing an electrically actuated trailer brake that looks much like the one in Russel's photo above. It uses the commercially available controller that allows for manually adjusting the brake torque for an acceptable coastdown. It will be actuated by a circuit designed to trip on a preset overspeed. My intent is to shut down in high winds from any lack of furling or loss of a phase, etc. Shutdown will remain until the trip circuit is reset. I plan to post photos and a description after I finish the modification and get some operational experience.

Blessings and peace.

Bob

galeforce jones · « **Reply #56 on:** January 23, 2010, 01:49:21 PM »

Hi,

I have seen a situation where the tail is in the fully furled position with the blades still facing into the wind. This can happen when the wind is coming from 2 directions at once. It can happen because of the contours of the land or to do with the position of a turbine in relation to a large house. Not sure if this is clearly explained

The breezy 5.5 does not use any furling, it relies on blade design.

fabricator · « **Reply #57 on:** January 23, 2010, 06:24:41 PM »

bobshau, that sounds like something that could work, relying completely on the regular furling set up is obviously not working on the larger machines, would it be even remotely possible to just y branch off the stator rectify it there, step it down to 12 volts and do everything at the alternator instead of running wire and controling it from the ground?

scoraigwind · « **Reply #58 on:** January 24, 2010, 06:21:48 AM »

Wow what a lot has been said about this event, and I can't claim to have read every detail.

I can say that we have a couple of 16 foot machines here with 12 inch offsets and this has never happened to us. Not yet, after ten years.

I am very puzzled by the following bit: "I ...was able to see the blades where pointing straight into the wind with the tail completely folded to the furled position."

I have on a couple of occasions seen a machine go into the downwind position from the fully furled, and then go berserk on overspeed with the tail in the fully furled position and the wind pushing it up against its stop. It's such a weird thing that its hard to describe it even. The blades swing themselves downwind and continue to run in the same direction (with reverse pitch) and manage to push the tail round at right angles to the wind. I just wonder if this is what you saw. I can't make sense of the tail being furled up in any other way! The tail does not lift itself against its weight and against the wind's pressure.

The 16 footers here on Scoraig have very simple band brakes that work well, and they have a minimum of moving parts. The brake bands hang below a big drum and are operated by wires down the inside of the tower that pull down one end of a rocker. The other end of the rocker lifts the end of the band brake.

I am considering fitting a furling winch system like the ones on Bergey Excel turbines for my new 18 footer that I am slowly finishing. At this stage in a new design I tend to dream up automatic systems that shut the machine down on overspeed etc but I doubt if that will happen.

bobshau · « **Reply #59 on:** January 24, 2010, 06:49:55 AM »

Thanks for the comments; you got me thinking. If I put the controls on the ground, I'll need two #10's to power the brake and possibly a speed signal (#14) comming down the center of the tower along with the windmill power cable. This gives me the ability to set the brake drag from the ground and make any corrections for brake wear, etc. If I design the brake power supply and controls so they remain at the top with the generator, I would loose this feature. My thought is to bring the #10's down the tower, at lease until experience shows that frequent adjustments are not necessary.

Thanks again for your comments. Blessings and peace.

Bob

fabricator · « **Reply #60 on:** January 24, 2010, 08:53:40 AM »

Ok, I see the what you are saying Bob, it sounds like a good plan.

imsmooth · « **Reply #61 on:** January 24, 2010, 09:28:38 AM »

Could the wind be powerful enough that it is moving the blades like water moves a waterwheel? The tail would be fully furled and the blade rotation would be perpendicular to the wind direction. The wind would interact with the side profile of the blades. I guess the only way to tell is in a wind tunnel and see if the blades would rotate at high speed in this direction with high winds.

imsmooth · « **Reply #62 on:** January 24, 2010, 09:30:46 AM »

What about remote control? Have a small sublevel station below your turbine with a small battery, trickle charged by the turbine. Have a remote control to work the actuator.

Question: do you have specfic pictures and details of how you cast your fiberglass blades? I have never done this and wondered where you learned this, and what was needed for someone to do it.

scoraigwind · « **Reply #63 on:** January 24, 2010, 10:12:34 AM »

It seems as if the blades can get into a state at very high revs where the tip speed ratio is so high that they work well in negative pitch (wind from the back) and the whole rotor disk becomes like a big wing and the centre of lift on that wing is way forward from teh hub, and this pulls it round until it's nearly flat on to the wind, even though it has to drag the tail right around with it.

It's a remarkable sight, and the noise is also something. First time I saw it was on a Dutch LMW turbine 5 metres diameter (16 footer) and way overspeeding. It's not so common with axial flux alternators because they usually have good torque and are less prone to runaway so long as you are driving them well within their capabilities. And it's a freak event in wild conditions with a dash of turbulence thrown in. Should never happen if the tail is properly set up and the machine is furling right. The solution is to make the tail lighter. Or indeed to shut down in high winds although that option never appeals to me at all and I never actually do it. It's probably preferable to buying new trousers, but then my windmills tend to behave quite politely in storms.

Hilltopgrange · « **Reply #64 on:** January 24, 2010, 10:16:52 AM »

Hi ulr sorry for the delayed response, my internet connection has been playing up.

When I built the 10 footer with the brake my intention was to use it regular as you suggest to keep it working and clean, didn't happen though and the bearings went so I just rebuilt it without a brake.

Russell

Hilltopgrange · « **Reply #65 on:** January 24, 2010, 10:29:34 AM »

The snag I see with a relay shorting the phases is this would happen at peak power, it would some how need to wait for a lull in the wind and a drop in power. Not saying it couldn't be done though!

Russell

News:

Author Topic: 16 Footer fails to furl (Read 21574 times)