Up and running, turbulence question

[Dutch John]

OK. Got her up and running. Everything seems to be fine. No stalling. I do not have a windspeed meter and a DC amp meter yet, so I don't know about cut in speed nor amps at furling. Turbulence was to be expected, because of the limited allowed height and trees in the neighbourhood. What would be best. Let the turbine swing or have this dampened?









Regards,
DJ

[hayfarmer]

wow.very creative tower design,Does it go up and down easy? and can you top any trees to fix the dreaded Turbulence" that's thinking out side the box with the gin pole/
hayfarmer

[Dutch John]

Yes, very easy to lower the turbine. The only difficult part is to climb in the 90 degree wooden post.
Hmm. Topping trees. There are hundreds in the neighbourhood and most of them not mine.... I could use the wood, however...   On windgusts, the turbine sometimes makes a 90 degree swing and needs only a second for that. Should I worry? Looks quite scary. It also partly furls on these occasions.

Few more pics:





Not sure if the box and batteries remain at the tower. The shed nearby is rather moist, no better than the ventilated box. Both batteries and box will get shade from a few solar panels in the future.

Regards,
DJ

[hayfarmer]

very impressive set up you have there. I am under the impression only trees 200-250 feet from mill are a problem,so those baby's are at my mercy.

it looks like you get some serious power out of it. mine when it gets cranking it turns right out of the wind and takes another minute to cut in speed again,at

modest wind speeds it stays in the wind but not much power to speak of.

hayfarmer

[gsw999]

Thats a nice looking setup , how tall is the tower ?, how close are the neighbours ?, looks like you did a good job!!!

[Dutch John]

The tower is a bit above the allowed 10 metres. Neighbours are 125 metres away. Our home is south of the turbine and only 40 metres away. I do not expect much power from winds between south and east. Most wind is from south-west to north.

I had some trouble with local authorities about possible noise and they first didn't want to give me allowance, because I couldn't show them numbers. But the turbine is amazingly silent. A whispering sound when the blades are accellerating or decellerating, but no more than a ceiling fan at speed. Then there is the generator hum at cut-in speed. It can only be heard at the base of the tower, because it resonates by the big box. Really, the two 2 watt fans and the controller dumping power are better to be heard. Probably also because of resonation.

Regards,
DJ

[gsw999]

I despise the authorities here and havent asked for planning permission for my 35 foot turbine  ( I rent a property and have asked my landlord and he is fine ) , if more people told the govt to go xxxx themselves then they would interfere less in our lives. What really gets me annoyed is the way that they will happily allow mobile phone towers to be put up next to schools etc but start talking about a 30 foot wind turbine and everyone starts getting upset.

A new law is being processed at present which allows the erection of a turbine up to 23m with no minimum distance from neighbours, anything over that (23m+) and the minimum distance starts at 1000ft from nearest residence and obviously increases with the height of the turbine.

your workmanship looks very good and looks like you live in a very nice area, I agree about the winds from the north and north west are very strong here , I am lucky and have a good clear mile from that direction.

Keep up the good work.

[Dutch John]

Turbulence was to be expected, because of the limited allowed height and trees in the neighbourhood. What would be best. Let the turbine swing or have this dampened?

Suggestion anyone? In my opinion less swing would be better. Less gyroscopic forces.

Regards,
DJ

[ghurd]

"Anyone"?  Hey, that's me!   

If it "hunts" too much the power will go down.

The general consensus, as I understand it, is bearings allow too much hunt movement.

Pipe on pipe (greased), or pipe on plastic on pipe (all greased), create enough drag to limit excessive hunting, while allowing enough freedom to get facing the wind.

On my tiny stuff, a fast 20(?) degree turn drops the output to maybe half or less for a second.
I expect the big ones would not generally turn as fast, but the output reduction would last longer.

There is no real power to be harvested in gusts.  I see no reason to slow the blades while chasing a short lived 5 degree change in wind direction.

My suggestion based on far smaller units is to let it turn free enough to face the wind at about 4 or 5MPH, and certainly before 6MPH.
Facing the wind before 4MPH is just that much more wear for no gain.
G-

[SparWeb]

I thought someone would have answered that by now, too.  (oops Ghurd posted 10 seconds before me).
Gyroscopic forces get larger as the RPM gets higher, as well as the rate of yaw, which for you seems high, but it's nothing I haven't seen on my machine, either!

I'll take another look at your photos, in case there are details that need a fix.  Generally this isn't the death of turbines, so 2nd priority, maybe.
Have you been measuring RPM and wind speed?

later.... (editing my own posting)



Is there an "UP" stop on the tail when it's fully furled?
How deep are the angles that support the spindle?
The picture perspective is impossible to judge.  If the spindle is supported only by the plate across the angle legs, then there may *may* be enough flexibility for rapid yaw motions to cause the rotor disk to contact the stator.

Bear in mind that yaw motions that cause gyroscopic precession are actually "torque" that wants to nod the rotor up or down.  Since that torque is twisting the spindle mount, I'd recommend a tube or building up a box for stiffness.  None of that means you are going to have a problem with what you did.  I can only offer a "perfect world" kind of suggestion.

Ghurd already said what I could say about performance.  Turbulence always sucks. 

[fabricator]

My fix would be to wait till the interest in the new turbine dies down then add 20-30 feet to it, the local NAZI's will never notice.

[Dutch John]

SparWeb,

There is an up-stop, but on the pic it is hidden behind one of the tail beams. I am not afraid that the spindle support wil bend. I took Hugh's design, but added more material and welding to it in order to make it very stiff. But I do need to reinforce the towers upper part. It is not really idle bending of the post that scares me, it is the turbulence frequency of bending-straightening-bending that could causes hair cracks.

Ghurd,

The yaw bearing is very well greased and smooth, despite pipe in pipe. Slowing it down by friction is not the way to go, because it is difficult to obtain constant friction. I made some thoughts about dampening, but that would add extra material like pulleys and a V-belt. Damper could be a visco coupling from a cars cooling fan.

Anyone who made a more simple construction?

Regards,
DJ

[Flux]

Congratulations, nice machine.

Turbulence is always a problem on poor sites and does reduce performance. In general it doesn't cause much other problems with small machines as long as you don't get a blade strike on the tower. I agree that you may be better off stiffening up the top part of the tower if there is obvious bending but I suspect there is not much more bending from gyro forces than there is from thrust, it just shows more obviously.

Rotary damping is not easy and I seriously doubt that it is even worth trying. As others have said, friction from pipe on pipe bearings does tend to reduce tail wag compared with low friction yaw bearings but this is not the same as violent yaws that you may see on a turbulent site. it will take a lot of damping to stop that happening.

For small machines even on turbulent sites it seems easiest to just live with it.

I am sure the only real solution is to use servo yaw but then you need pitch control or some other method of power limiting and it becomes far too complicated.

Flux

[gsw999]

Might help if you stuck a video up?? it wouldnt help me because Im not knowlegable enough but might help others.

[freejuice]

In general it doesn't cause much other problems with small machines as long as you don't get a blade strike on the tower. I agree that you may be better off stiffening up the top part of the tower if there is obvious bending but I suspect there is not much more bending from gyro forces than there is from thrust, it just shows more obviously.

Flux

I will parrot what Flux is saying here.

My personal experience...I would see my 11 footer often try to bend the tower ( 60ft 4inch sch 40 pipe) while the turbine  was pointed straight into the wind. From a very, very layman's point of view: Unless the site is so turbulent is can swat that mill back and forth, like a Chinese ping pong match, gyro should not be too much of an issue.

I have a thrust bearing on my tower stub and the mill can turn even if I stare at it hard enough and some strong winds have pushed it around....But thurst from a straight on wind has on more than one occassion had my rear-end probably so tight you couldn't shove a pin up it! Not that I would want a pin or anything like that....
 All the best,
 Gavin

[Dutch John]

I guess I need to observe for a longer time, because today we had wind from south-east, blowing past nearby trees almost as high as the turbine. Very little hunting and still power being delivered. Must have been very rough wind and windgusts earlier this week.

Probably it is more a psychologic problem. You know, having spent so much time on building, you do not want to get your baby hurt..... I am a pessimist by nature. But pessimists never get disappointed...

Regards,
DJ