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I suspect we all have the idea of that part now, so here is a finished raw cut. The finish is the same as a fence paling, or a weatherboard. So very happy with the finish, 2 minutes with the planer and the leading face was virtually complete. From start cutting to finished cut and plane, was only about 10 minutes. This beats the hell out of half a day or more doing it with the saw and chisel.
Here is the remains from a few cuts. Thats a lot of timber I don't have to remove by hand.
The three blades and all the angle cutting is finished. It took an hour or so do make the jigs and guides, an hour to cut all the blade blanks. This is the fastest way I know of cutting blades of this size. If I had built the jig a bit less flimsy, you could pump out blades all day long.
Things to know.
- Do sharpen the blades before you use them.
- Do tighten the chain more than is usual, we don't want too much slop, else you will have to leave more error wood to compensate.
- I elected to saw on the back of the blade (see photo's). This allowed me to have good vision of the cutting process as the chips get thrown away from you.
- If you do 3, then be careful of backlash.
A second jig does the rear of the blade (airfoil side) and is every bit as quick.
And now just have to plane the camber for the airfoil side. May make a jig for that too, but the planer will probably be fast as well as there is not lots to get rid of. The hard part is done.
Posted: 11 August 2008
Well today was the day the chainsawn blades took to the air.
It was on a small 3.5m tower just for testing and trimming the turbine.
They worked unbelievably well. As is customary when you raise these things in the air, there was barely a breath of wind anywhere... in the roaring forties in winter.. no wind.
The breeze was so low that I could barely feel it on my face, so I estimate about... 3mph.
With the blades not balanced, they would not even rotate. After balancing (with some magnets and spanners magnetically glued to the front plate), it slowly started to spin up. I could barely detect any air movement. Quite suddenly they gripped whatever air was there and you could hear them cut the breeze, even though I could barely feel it.
Here is the test site, the trees are about half a kilometer away from the mill.
I was dumbfounded, with almost no detectable air movement, the damn things were trying to cut my head off. They were putting out 27v in virtually no wind.... no power mind you, but I would not have suspected that they would even spin under their own power.
I didn't have any batteries on hand, but I did bring a 415v 3kw induction motor .. just to put a load on the alternator .... on the off chance a gust came along and it became unruly.... and it did
A gentle 5-10 mph gust came through, lasting about 40 seconds at best, and it took off and drove the big 3 ph motor at a very respectable pace.
So I was right, these are high TSR blades, too fast I think for this alternator, as it is very electrically stiff for battery charging. They make a slight swish noise from front and rear, but eerie silence out either side.. very odd... no detectable sound at all out the sides.
I have not been face to face with blades of this diameter on a basically frictionless alternator before, but is all a little bit scary when you are both at ground level.
Here it is a bit closer.
Anyway, the chainsaw blades are very impressive performers on their first windless day out.... and no I haven't built the tail yet.
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