Rebuilding Charlie

Charlie has been providing our power here for the past 5 years , has weathered many a bad storm. Its great, each time we look up at the tower and see him spinning away. Lately we have noticed that he has been producing less power so it's time to give him an overhaul..

Bad news

First thing to do is check each phase with a voltage meter, and we notice one phase is only giving half the voltage of the other two, not so good . We check out the wiring and the slip rings all is ok. So that only leaves the generator itself..

Out with the tools and soon the cause of the problem is obvious ..some of the coils have shorted out ..this means we have two options

1......send the turbine away to be rewound

2..... Build a new turbine using the body and parts from the old one..

We have noticed before that the quality of the engineering on the turbine was very bad ,bearing holders off center, bad casting etc. Its probarbly not worth the money to get it rewound, so we opt to build our own. For many years i have wanted to build one of Hugh Piggots designs and now is the time. There is plenty of information on the internet about building turbines and Hughs website and otherpower. com in the usa..

Our original turbine was a 3 meter diameter so i have decided to build Hugh Piggots 3 meter design, so we can use the same blades.

First step making the copper coils.

First thing is to make the coil winder, good quality plywood is best for the job. You need to be accurate with the spacer and the four bolts that the coil is formed on. i used a piece of solid plastic and treaded bolts with wing nuts for holding the two halves together. Take the time with this part as its important all the coils are the same size at the end to fit the stator.

Now time to wind the copper

This was an easy one for me as i have an old AVO transformer winding machine. The copper comes on a 5 kg roll. For this turbine the wire is 1.6 mm diameter and quite difficult to handle . The amount of turns etc. is all in the book, again take care to have all the coils the same size, we checked them by weighing each one after completion.

Time to build the stator

Again plywood is used to make the mould required for casting the stator,the thickness is the same as the coil thickness. We used polyvinyl resin and talcum powder as in hughs plans. My first time working with it ,a bit scary alright.

You have to work fast as it sets fairly quickly, so its important to have everything measured out and ready to go.. Eg. have the resin measured out in batches and the hardener and talc weighed and ready to add when required..

On the left is a picture of the nine coils spaced and wired up in the star three phase configuration. We used resin and fiberglass cloth patches to hold it all together. It's set out on an exact drawing of the stator to keep everything aligned.This ensures that the magnets align with the coils at the right time when the turbine is spinning.

On the right the stator mould is visable with the coils positioned .

Use plenty of release agent ,in this case Vaseline ..to keep everything from sticking together when the resin sets.

Also use plenty of screws to keep the lid firm and to compress everything which leads to a uniform stator thickness...

On the left here we are casting the stator. Moving steady and quickly, not forgetting to grease the center island well.

Room temperature here is over twenty degrees so it wont take long to harden ,but we will leave it for a few days over the weekend, just to be sure. 

On opening the moulds the top and bottom timber parted easily .

The center island need a little tapping to remove, but it all came apart as expected..

Next we cast the rotor magnet using the same technique and running the resin just over the edges of the magnets. It keeps them waterproof and helps them to stay attached to the rotor when its spinning. We used an electric sander to vibrate the resin in all the castings, its a great way to remove air pockets and bubbles from the resin.

Here is the completed hub attached to one rotor, the magnets are 42 grade and very strong and great care is needed handling them, they will easily pull any tool from your hand.

The threaded bars and nuts are stainless steel and we used loctite on them in case vibration would loosen them. Also in the picture you can see the three stainless steel bars that will position the stator, between the two magnet rotor disks. These have been attached to the original generator body.

I used spacers to position the stator exactly over the magnet disks and then welded the brackets to the generator body, it ensures that they are in the correct position.

Here the brackets are seen, and next thing is a few coats of rust proof paint The nice thing about the old genny body is that we can use the slip ring assembly .

 Now its time to erect the body on the pole and assemble the generator up there. Our pole is very strong and in a very exposed site , Its not as high as it could be for maximum power but its ok for our needs here.

On assembly we notice that the stator bolts are slightly too long and are snagging the blades so its out with the grinder.

Paper towelling was wraped around the rotor disks to keep metal filings from getting in between them and the stator..Now its time to adjust the Rotors distance from the stator, some 1.5mm spacers and a calipers makes easy work of this..

The blades and hub are assembled on the ground making sure all is evenly spaced.

Loctite on the bolts is a good idea

We took the opportunity to touch up the blades when we had them down, the leading edges had chips out of them we used fibrelass to do the repairs Its probarbly a good idea to check the blades for wear a few times a year..These blades are the original ones and now five years old but plenty of life left in them yet...just as well as carving a set of them is a job for another day.

The hub goes on handy over the four stainless steel bars, which only leaves the tail to go on..

We have increased the tail size to double its original, this should help to keep charlie facing the wind at lower speeds, The furling is another thing we will have to address, after some testing. The tail on this turbine is not offset very much and the tail itself is fairly heavy, but thats for another day.

So charlie lives again  Splendid in his new coat of green. 

So  we have to be carefull now for a while and keep an eye on how hes working, The Furling is happening too late we have got over 1 kw out in a gust not very strong It is certainly generating power in lower winds than the original chinese one also there is a little imbalance to be sorted out . not too bad..