Author Topic: More progress on my 17 (Read 3342 times)

fabricator · « **on:** May 31, 2009, 07:02:31 PM »

I got the tail put together this weekend, I went in a little different direction, try as I might I just cannot do steel on steel, it goes against 30 years of steel fabrication experience, I have a twenty four inch piece of 1.5 inch sched 40 with UHMW bushings, the tail is attached with a full length pin with safety pins in it on each end.

fabricator · « **Reply #1 on:** May 31, 2009, 01:04:42 PM »

Here are some pics.

Boss · « **Reply #2 on:** May 31, 2009, 02:37:31 PM »

What's the idea behind the extra tail bearing shaft?

halfcrazy · « **Reply #3 on:** May 31, 2009, 03:22:48 PM »

I like it. what did you do for the main turbine yaw bearing? We are getting geared up to build 3 of the 17ft machines and i would like to add bearings to it as well.

pepa · « **Reply #4 on:** May 31, 2009, 03:31:05 PM »

hi Fabricator, nice looking job, will look even better wnen she is flying, pepa

RobC · « **Reply #5 on:** May 31, 2009, 05:30:12 PM »

The first windmill I built had uhmw bearings all the way around and it worked great. However the second time I was in a hurry and went steel on steel with a roller trust bearing on top to carry the weight of the mill and it also works great. I think the added friction doesn't hurt a thing. The down side is that once a year I have to take it down and grease everything. Still I have yet to see any real wear. However on my next mill I plan to put Delrin bushings on the tail boom. RobC

fabricator · « **Reply #6 on:** May 31, 2009, 06:36:45 PM »

It is just the simplest way to put it all together.

fabricator · « **Reply #7 on:** May 31, 2009, 06:39:39 PM »

The tower stub has two UHMW bushings about 24 inches apart, and there is a large tapered roller bearing on the top to support the weight, there are bushings or bearings everywhere no steel on steel.

projectpower · « **Reply #8 on:** May 31, 2009, 06:41:02 PM »

wdyasq · « **Reply #9 on:** May 31, 2009, 07:08:08 PM »

For those who don't know about the plastics, UHMW is a great bearing material noted for its' wear properties and low friction in contact with steel. It is softer than Delrin/Acetal and can be machined in a wood lathe (I suspect a good turner could machine Delrin in a wood lathe also.)

Nice work fabricator.

Ron

fabricator · « **Reply #10 on:** May 31, 2009, 07:30:09 PM »

UHMW is extremely easy to machine, the one thing that bugs me is, when you turn it on a lathe under power feed the chip comes off as a single piece of UHMW string and it is very hard to break, it has a tendency to wrap around the work piece and generally make a big flailing mess, I try to get hold of the end at the beginning of a cut and pull it into a coil as it comes off.

wdyasq · « **Reply #11 on:** May 31, 2009, 08:40:44 PM »

UHMW and Nylon have both been known to build long strands and wrap up in machines. lathes have been broken as well as machinists hurt from these materials fine qualities.

Ron

windy · « **Reply #12 on:** May 31, 2009, 08:58:12 PM »

Nice looking project!

Not sure if this is much of a concern, but with your double tail shaft is that going to change the furling response? You are getting out further from the center of the mill and that could change things. Any other comments on this?

windy

Top of the Hill · « **Reply #13 on:** May 31, 2009, 11:15:25 PM »

Very Nice, fabricator.

Can you give me a ETA on my 20 ft that your making for me ? Also be sure to paint mine ok.

oztules · « **Reply #14 on:** June 01, 2009, 01:03:05 AM »

Looks the goods, but 2 things.

1. I don't see any preload bias stop. The notch on the Dans and Piggot style, does two things. One way it stops the tail hitting the blades in furl, and the other it holds the tail just off straight with a pre load from the gravity. Otherwise it will hang way out to the side, and hurt low wind performance. (blades will be facing well off the wind until the wind starts to get strong enough to load the head bias against the tail bias and it all starts to straighten up

2. The floor is too too clean

SparWeb · « **Reply #15 on:** June 01, 2009, 08:32:56 AM »

I stop the feed, just for a moment, to break the chip. Then continue. I'm holding the long chip as it comes off. That doesn't work on the finishing pass, of course.

I've come across some types of steel that start doing that, and the continuous chip is a vicious springy spiral, razor sharp, and 500F hot. ouch!

fabricator · « **Reply #16 on:** June 01, 2009, 03:01:00 PM »

The last time I had to get stitches it was from a HOT, SHARP chip off my lathe.

fabricator · « **Reply #17 on:** June 01, 2009, 03:02:02 PM »

It only moved out four inches, I don't think it is an issue.

fabricator · « **Reply #18 on:** June 01, 2009, 03:09:49 PM »

That is a good catch, I plan on adding the stop but did not know quite where it should go, if you are standing behind the alternator with the tail to your left should it be somewhere around 95 degrees off the alternator plane?

An BTW OZ I have been devouring ever thing you have to say about carving blades with a chain saw, I'm gonna be all over that when blade carving time come around, I'm not dreading it at all any more.

Also, the floor is only clean because before taking the pics I blew it out with my leaf blower, I do that ever six months or so whether it needs it or not.

oztules · « **Reply #19 on:** June 01, 2009, 05:14:47 PM »

I,m not the best person to respond to this, as I have had mixed reviews with my testing of the right spot. I feel 5-10 degrees off straight (drooping side of head)is about right, but I have tried all kinds of angles, and it is hard to tell which is the best. If you have low winds, this will be more easily determined, my winds are rarely mild, so it's hard to pick.

Imsmooth has done a video and comprehensive bunch of pages on blade carving with a chainsaw. http://www.mindchallenger.com/wind/bladecarving.html

I would recommend you view that as well. I still think that straight twist and taper is the best compromise for these kinds of alternators (Imsmooth thinks otherwise)... and the chainsaw likes it better too.

But seriously, an average blade I think does better at mixed TSR, rather than designing for a peaky TSR (perfect calculated blade)... and never running at it. I suspect (but don't know for sure) that the peaky blade will drop off efficiency faster as it moves further from design TSR (the straight twist and taper blades we chainsaw built for the AWP seems to back this up.... performed better than the fancy originals)

If you intend to use these things in partial stall operation as the Dans do, this should be more true. (which is why they do so well with this design parameter perhaps)

I would use their description of blade dimensions from their book/online story as the basis of my blades.

If you intend to use mmpt, then proper blade design would be an advantage..... if you could live with the high RPM.

.............oztules

fabricator · « **Reply #20 on:** June 01, 2009, 06:30:19 PM »

I'm still new enough to all this stuff I have a hard time getting my head around the whole straight twist and taper as opposed to the calculated blade thing, is there somewhere that explains this stuff ion depth?

Also I've watched imsmooths videos and read his site.

oztules · « **Reply #21 on:** June 02, 2009, 12:49:44 AM »

Here is a very good how to from the FAQ section; http://www.fieldlines.com/story/2007/3/8/13649/79230

Note, when you get down to the part where he puts in all the cuts and then chisels them out..... this part is done with a chainsaw in about 4-5 mins for a 2m blade (4meter set). All the measuring etc is the same. The jig just needs to follow these straight lines. Once the jig is set, really just need to place the blanks into it and saw.. no marking either.

For the first one, lines give you some confidence that you were correct in the jig making.

...........oztules

fabricator · « **Reply #22 on:** June 02, 2009, 04:24:22 AM »

Thanks Oz good stuff.

Ungrounded Lightning Rod · « **Reply #23 on:** June 02, 2009, 05:52:15 PM »

Here's a thought on the preload bias stop:

- Use a rubber foot on a long screw (with a couple locknuts) so you can adjust it.

- Tie a piece of ribbon to the hub to be blown backward by the wind, so you can see whether your mill is flying at right angles to the (departing) air or not.

Then you can adjust the stop until it flys the way you want under preload.

If the mill was loaded to maintain a constant TSR in varying winds it would fly at a constant angle to the wind for any wind speed where the tail was still on the stop. It isn't loaded that way, of course. So there will still be some variation in the flight direction with wind speed while the tail is on the stop.

You'll want to adjust it so it flies facing straight into the wind for some wind speed between cutin and start of furling - say for your commonest windspeed.

Note that aiming errors cause the power collection to fall off by a cosine law, and cosine is close to flat for the first 10 degrees or so. So don't sweat it if you're not quite facing the wind dead-on for some wind speeds - you won't lose much.

fabricator · « **Reply #24 on:** June 02, 2009, 07:51:55 PM »

I like that idea a lot, it'll be a simple thing to add an adjustable stop with a rubber bumper, with a max angle of about 10 degrees over 90.

fabricator · « **Reply #25 on:** August 13, 2009, 06:40:05 PM »

I had some progress on the stator this week, I might cast it this weekend, then all I need is blades and a tower and I'll be flyin! Well, maybe concrete anchors.......a winch........a hilo battery.......just some balance of system stuff.....yikes!

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Author Topic: More progress on my 17 (Read 3342 times)