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BarkyJ
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Posted: 07 August 2018 at 10:04pm | IP Logged Quote BarkyJ

Thanks Fillm,

That's a scary picture you posted there.
We don't get winds like that at all where I am, however fully taking what you (and others) have said on board.

The failure on your hub though seems to be at the end of where the blade would be, like its been levering at that line where the inner clamps have been.
Mine has the long plates running under the round hub to the point of the inner CSK bolts, which also has 16mm thick blades running up to that point, and then another thinner plate on the windward side. I'm looking at what I have and would be surprised if it manages to break through all that - but you guys are the experts, not me.

As mentioned, it is not just 1x 6mm round plate I have, it is 2 of them. But I have it like this so I can remove the whole blade assembly off the windmill, leaving the 2nd plate attached still which is attached to the generator.

I have always been contemplating adding a smaller plate on the windward side, which ties the blades together there, but I originally thought that was going to be overkill.

Anyway, tomorrow I am putting the blades on as is, just for a low wind test, we are only expecting like 6-20km/h winds, so nothing extreme at all, but I just want to get them on and see if it spins ok unloaded, and see if the controller is registering all the bits correctly, as its hard to simulate spinning motion while adjusting load - my drills just aren't up to more than about 30s of running.

I will be taking it down again the same day.

Edited by BarkyJ on 07 August 2018 at 10:05pm



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BarkyJ
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Posted: 07 August 2018 at 10:39pm | IP Logged Quote BarkyJ

Question. What's the recommended practice for the stator and weather. Do you need to do anything to protect them like circuit board lacquer or something, or are they fine as is?
Thanks
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Posted: 08 August 2018 at 10:23am | IP Logged Quote Warpspeed

I don't see this as an ultimate strength problem, but as a metal fatigue problem.

The hub is definitely going to see some very high cyclic stresses that very slightly flex it first in one direction, then in the opposite direction. Fine cracks may begin to appear at the surface at the highest stress points, usually where there are dramatic sudden changes in cross sectional area.
Corrosion in these fine cracks may add to your woes, as moisture wicks into the cracks and remains there.

Then one day in a fairly stiff breeze that it has already survived countless times it will unexpectedly fail, go out of balance, and then completely self destruct.

What you really need at the hub is very high stiffness, which material thickness alone will not usually provide.
Gussets, ribs, rolled edges or whatever to make the hub really stiff without being unnecessarily heavy should be the aim.


Edited by Warpspeed on 08 August 2018 at 10:25am


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gpalterpower
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Posted: 08 August 2018 at 3:29pm | IP Logged Quote gpalterpower

Hey Barky,
Nice build you got going on there buddy. Im liking the nacelle and stepper motor arrangement. Im just asking how you are going to attach the hub to the shaft. Its just that it just looks like a 12mm hole in the centre! Im assuming then youll be placing it on to the 12mm metric thread on one the end of the shaft. Am I correct in saying that, or do you have something else in mind. Thinking you may need a boss to strengthen the attachment point otherwise you may get some serious flexing on that thread!

I built a dual bout 5 years ago and I wanted to make sure that it was going to stay together during heavy wind gusts and storms. The good thing is its still flying and it has been thru some horific gale force winds in its time.

Marcus

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Jarbar
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Posted: 08 August 2018 at 6:24pm | IP Logged Quote Jarbar

As a rare contributor due to Ill health, but a long time frequent observer I'll chance my hand at the cause of the fatigue cracks on phillm hub disk.On a previous build for karlj the RHS that Phil used for the nacelle had the side torn out of it in an upward direction.This destruction was caused by the gyroscopic force of the spinning blades needing to go somewhere. Caused by the constant and sometimes violent changing of direction of the mill head by the tail trying to track the wind.And the amount of overhang in front of the pole.(longer lever)

This causes the mill head rotating around the pole and the gyroscopic forces of the spinning blades to try inducing swinging up as it furls. This can be seen and felt if you spin a bicycle wheel whilst holding each end of the axle and then trying to turn it left or right.In one direction it will swing up and in the other direction down.

This upward or downward force is what I believe has fatigued the hub disk. If it is made thicker then the force is transferred to the next weakest point which was the RHS on Phil's karlj mill.A thicker walled tube was used in the replacement and boxed in. I can't seem to find the photo's that were on this site to show the torn metal.But that could just be my lack of investigation.

On a mill I made that was designed to tilt up out of the wind it would spiral madly around the pole trying to dissipate this force in a figure 8 pattern, and after many experiments,I designed a better furling method.

As BarkJ has a motorized furling system in place to track the wind,I imagine the forces will be less immediate and violent by providing a smoother transition in directional change but not entirely eliminating them.I do agree that a second plate on the opposite side of the blades so that the above mentioned forces are transmitted to the shaft further back than the 12mm threaded section and onto the main shaft diameter other than through the plastic magnet hub.

Its been a great project to follow so far and your skills and willingness to present them here are greatly appreciated.Keep up the great work.

Lets see if my arm survives!!

Edited by Jarbar on 08 August 2018 at 6:30pm


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BarkyJ
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Posted: 08 August 2018 at 8:51pm | IP Logged Quote BarkyJ

Hi Marcus

Cheers - trying to put something into practice, but unsure if I am winning or if it will be a complete disaster yet. Time will tell :)

So the single 'old style' male-male shaft connects the two rotors together, and they are on the splines of the shaft, so locked in at both ends. The nacelle and bearing arrangement I have posted about already, determines the spacings and I designed it as such to utilise the correct parts of the shafts, so no cutting or welding of the shafts was needed at all. One end has the longer threaded male end, and this locks to the 2x 6mm plates I have. The other end basically has a flat waster on it and lock nut, and just stops the rotor 'coming off, that end, and pulls the rotor and bearings etc all nice and tight.

The first plate has 5x 10mm 'buffered' fingers which go through the peanut shaped openings on the rotor. There are 10 peanut openings on the black rotors, and I have 5 fingers which go through these openings. So as the prop turns, its linked directly to the outer plate, which is bolted to the inner plate, which has fingers which push on the rotor in 5 places, which turns the rotor, turning the shaft, turning the 2nd rotor. Basically.
When I say 'buffered', its basically just a pressed on plastic tube over 10mm solid welded in studs into the 6mm round plate. (Ive not pictured this plate to date in my posts). It is a hand pressed in neat fit, so it basically makes the rotor and first plate, one piece, once tied to the centre shaft. There is a 3D printed solid piece which sits between the rotor and this metal plate, which essentially fills in the gap, as the rotor has a stepped section right by the shaft output, and this is not at the same level as the ribs of the rotor, or the edge of the rotor. So I modelled this and printed a plate which levels everything out basically. The 5 metal pins which go from the first plate through the peanut shaped holes of the rotor, pass through this 3D printed plate also.

So this plate with the fingers, threads over the 12mm thread on the main shaft, and bolts to the 2nd plate around the edge, but also goes over the centre 12mm shaft too. So no power is directly applied to the spline of the shaft from the prop plate, as both spines have rotors on them.

It's a little interesting and makes you go 'hmmmm' a bit, but when you think about it, it's solid as, totally sandwiched and nothing can 'go' anywhere, and should translate the prop power through to the dual rotors nicely. Hopefully. :)

Hey, if someone didn't try it, who would, right...
I came up with this solution after looking at all the washing machine pieces I had, and started threading bits on to each other, and soon realised that I didn't need to weld any shafts to achieve a dual rotor, and the input of power into the system could be achieved indirectly through the rotor, as long as the pieces were solid in contact and essentially became a single piece. So that is what I set out to achieve and I think I have done so, but we shall see. It might explode but I somehow dont think it will.
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BarkyJ
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Posted: 08 August 2018 at 8:55pm | IP Logged Quote BarkyJ

Hi Jarbar,

Thanks for taking the time to post. Sorry to hear about the poor health, I hope things are going alright.

Fingers crossed that my motorised implementation does remove some of this violence you speak about, which comes about from the furling. I am certainly looking into the plate on the windward side to tie things together more. The main issue is I likely won't have shaft thread left at this length away, due to how think the blades are etc, but I am thinking of a solution to this and might have something in mind.

Cheers for the support. Fingers crossed things work out OK.
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BarkyJ
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Posted: 08 August 2018 at 9:15pm | IP Logged Quote BarkyJ

So today I took a few hours and did some more work on the windmill with my old man.
We bolted the prop and outer plate onto the windmill, and started checking clearances, and soon discovered a major issue which was just a stupid oversight.
The props do not clear the turret motor, so the pictures I have put up previously are going to change again, as I need to move the motor to the side of the pole.

Not a huge issue, but just a pain in the bum.

We put a piece of box section on the side of the pole, which is what the motor was bolted to, to turn the turret around. But what I didn't consider is how far it sticks out, and when the windmill turns around to be on the motor side, just how little (or no) clearance there actually was. The box section was added for ease of bolting on the motor, but turns out its the cause of the clearance issue.

So what I did today was start off the mounting again, but I put the motor on the side of the box section, rather than on the top, so we gain 40mm of clearance. I will finish this off tomorrow hopefully, weather permitting. I then need to design new brackets for the Encoder and the Home position sensor (grrrrr), as the chain length has to change again, and so the encoder can't go where it was, yadda yadda....
Back to the drawing board for those, but all will be fine. Just some days of work lost. stomped on. plans ruined. world is ending... you get the idea :)
I should have it sorted by Saturday though.

So after that was discovered, we decided to just try out the winch system after all the weight is now installed. Well, another issue was found.

The winch setup we have is a laminated plank, fixed to the ground about 1m from the base of the mast, which stands vertically, but slightly leaning towards the mast. It is about 4.2m in length, so ends above the hinge in the masts pole.
The board has 2 steel cables going off to anchors, which are positioned behind the plank, away from the mast, allowing it to sit leaning slightly towards the mast, but supported by the cables, and the ground.
We then have a hand winch on the plank, the cable goes up into a pulley, out to one of the Eyes where the 3rd guy wire cable attaches to which secures the mast when erected, into a hook with a pulley on it, then back to the top of the plank into an anchor.
As you crank on the handle, it pulls the cable through the pulleys and pulls the mast up. When the mast is up, its bolted at the hinge, the guy wires are tensioned, and the plank/pulley/winge arrangement can then be moved out of the way and stored, leaving the mast with its guy wires in place.

Well, the issue is the plank isn't strong enough. It started bending too much, so before it busted we took it down, and bolted on a 4x2 to the back of it, and tried again. Still not strong enough. So we brought some 50x50x6mm angle iron, and bolted that to the back of it, pinned back into the 4x2 also, and now it's good and strong (but weights a stupid amount and is a bit of a mission to handle now - grr). So now the plank is strong enough, tested again now show an issue with one of the anchors which support the guy wires into the plank, one started to remove itself from the ground. It was not as robust as the 3 which support the mast guy wires we never intended it to have so much strain on it, but it appears this is a heavy sucker! So we post hole bored in a new one, deeper and bigger, and now that all seems fine. But now the eye bolts we used, started opening up. They were a non welded type, 8mm galv. Not good enough now with all this weight. Again, this is just the winch stuff, not the main mast equipment, that was well over spec'ed. So tomorrow I need to get some bigger ones, welded type, and replace them.

Sigh - all a bit heavier than I was expecting I guess, and it just the initial lift which is the heaviest. Once it gets beyond about 120 degrees the weight comes right off.

So instead of today with our 4m/s wind having a little test of all the systems, turned out to be issue fixing and getting wet in the rain, and still a few steps behind.

Oh well, all part of the learning. Luckily nothing broke, issues were found and are being rectified.

Fingers crossed for something spinning as a test early next week.
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BarkyJ
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Posted: 09 August 2018 at 8:20pm | IP Logged Quote BarkyJ

Rectified the motor and sensor placement issue today.

Motor is now mounted, encoder and home position sensor managed to utilise their existing brackets with only a tiny modification to the encoder bracket. These are installed again and working correctly.

Winch issue is partially resolved, got some M12 stainless welded eye bolts and installed them into the anchors for the winch system now, so I will finish this off on the weekend and hopefully get things back on track for a test run.
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fillm
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Posted: 09 August 2018 at 8:42pm | IP Logged Quote fillm

Jarbar wrote:
As a rare contributor due to Ill health, but a long time frequent observer I'll chance my hand at the cause of the fatigue cracks on phillm hub disk.On a previous build for karlj the RHS that Phil used for the nacelle had the side torn out of it in an upward direction.This destruction was caused by the gyroscopic force of the spinning blades needing to go somewhere. Caused by the constant and sometimes violent changing of direction of the mill head by the tail trying to track the wind.And the amount of overhang in front of the pole.(longer lever)

This causes the mill head rotating around the pole and the gyroscopic forces of the spinning blades to try inducing swinging up as it furls. This can be seen and felt if you spin a bicycle wheel whilst holding each end of the axle and then trying to turn it left or right.In one direction it will swing up and in the other direction down.

This upward or downward force is what I believe has fatigued the hub disk. If it is made thicker then the force is transferred to the next weakest point which was the RHS on Phil's karlj mill.A thicker walled tube was used in the replacement and boxed in. I can't seem to find the photo's that were on this site to show the torn metal.But that could just be my lack of investigation.

On a mill I made that was designed to tilt up out of the wind it would spiral madly around the pole trying to dissipate this force in a figure 8 pattern, and after many experiments,I designed a better furling method.

Lets see if my arm survives!!


I have got no idea what that has to do with this thread ... really , it is like 10 years ago, and FYI it had nothing to do with gyroscopic forces I welded the yaw pivot shaft to the heavy walled RHS and in high wind it flexed, the flexing caused it to eventually the crack fatigued on the weld line and then let go and allowed the turbine to go vertical, it was repaired by putting the The yaw shaft completely through the 100mm RHS and it never skipped a beat until the tower collapsed.

Same with the hub ... flexing will eventually find the weak spot..

Maybe the hand on the arm should give another person their dues, rather than point at me??



Edited by fillm on 09 August 2018 at 8:52pm


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gpalterpower
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Posted: 09 August 2018 at 9:39pm | IP Logged Quote gpalterpower

Hi barky, so the hub is pressed directly against the rotor and drives via the fingers which line up with the
Peanuts holes in the rotor. Is that right? Do you have any photos of that? Like to see them. I'm just wondering hour much push and shove those rotors can take. I know they are pretty rigid but if they flex a little they would cause a poling effect on the stator and burn out. There's only a very small air gap between the two. Just a thought.
On my mill, I moved the front rotor back a little which gave me additional room to mount the hub directly on to a 25mm section of the shaft
I had a 50 mm diameter boss welded onto the hub to take the full weight therefore leaving the rotor completely free to do its job.

Marcus

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BarkyJ
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Posted: 09 August 2018 at 9:51pm | IP Logged Quote BarkyJ

Hi Marcus

Ill try and get some more pictures tomorrow/Saturday and post them.

yep, the hub is pressed against the rotor, and drives the rotor around with the fingers.
Not really any different to the spline turning the rotor really, in fact it might actually be better. The rotor cant warp or distort from this direction of movement from what I can tell, as the fingers are locked into the peanut holes. For the rotor to distort, things need to go inward or outward, but this is purely rotational, and fixed to the metal plate. If anything, it would prevent distortion of the rotor. I cant foresee issues with this, but as mentioned its still very experimental, but hopefully it works well.



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