Author Topic: Monday Jan 31 (Read 3033 times)

DanB · « **on:** January 31, 2006, 04:12:33 PM »

We had a pretty productive day. Rich came up again to work on his 7' machine. Again, this will be a single rotor machine using big round (2" diameter x 1/2" thick) magnets. It's for 12 V, we wound the stator with 50 windings of #13 wire. It is fairly resistive, I doubt we'll see much over 500 watts from it, but it should do OK in low winds and we'll set it up to furl early. With a single rotor were not making best use of magnets here, but the idea is to keep it simple - avoid the complexities of two rotors, jacking screws etc. Pictured above Rich is drilling out the stators mounting holes.

We cut out plywood disks for the centers of my big magnet rotors. The 'islands' are 14.75" in diameter. We caulked the bottoms of them and stuck them down, and dammed up the outside with tape. We used West system epoxy and mixed in chopped fiberglass strands in hopes that it would stay together better than the polyester did on my 17' machine. Speaking of my 17' machine (which had problems last week).. we repaired it last thursday. We repoured the magnet rotors with west system epoxy/fiberglass strands. We also opened the airgap slightly. The bearing was still fine - we adjusted it and raised it last Thursday. It works fine now - actually somewhat better in high winds (it makes more power and runs slightly faster). Hopefully it will last a while this time!

We put Rich's 7' machine together several times in different configurations and tested some things. Again - his stator is wound with 9 coils, each has 50 windings of #13 wire. The first test was with a single magnet rotor which has 12 of the 1" x 2" x 1/2" blocks, grade 35. We hit 12V DC at 284 rpm in that configuration.

The next test used the same magnet rotor, but we ran a blank steel disk on the other side of the stator. This got us 12VDC at 207 rpm. This would be reasonable for a 7' blade set.

The next test (and final configuration for Rich's machine) has a single magnet rotor (no blank rotor) using 12 of the 2" dia x 1/2" thick magnets. This got us 12VDC @ 196 rpm. Interesting... there was some discussion last week about how these coils would be not be ideal with these magnets, and how we had these magnets too close to each other on these disks. Using the same stator, and 2" x 1" blocks (1 cubic inch of magnetic material) with 1 rotor only, we had 12VDC @ 284 rpm. Using the 2" disks (about 1.5 cubic inches of magnetic material), crowded as they are, we get 12VDC at 196 rpm. Interesting how our magnets are 50% more massive and were getting almost 50% lower cutin speed here. At 196 rpm were about dead on for a 7' blade assuming it cuts in at 6mph with a TSR of 8 (these tend to cutin at a higher than designed TSR because the blade is under no load at cutin - after cutin the TSR will fall some). So - while I wouldn't expect lots of power from this in high winds, I think it will do nicely in lower winds and we'll furl early so that we dont burnup hopefully. Unlike DanF's single rotor machine, this one will have the magnet rotor on the back so that wind can help cool the stator. It also makes certain we'll not have any magnetic attraction to the stator bracket.

Pictured above is Rich's alternator finished (except for paint).

Shop Safety...

Always offer ear protection to guests when grinding in the shop.

This fellow accidently was moving his magnet rotor too near a box of razor blades! Keep all ferrous items clear of magnet rotors...

This fellow has forgotten about the can of gasoline and the open container of laquer thinner and he's preparing to weld...

Before grinding or welding, be sure the area is free from flamable items.

This fellow got his long hair stuck in the flat belt...

Always keep hair tied back and be careful around belts.

Don't wear necklaces while operating the drill press.

Scott started his magnet rotors for the 'wincharger' project. Again - this machine will sport an antique 11' 2 bladed wincharger blade and it's airbrake. We used wedge shaped magnets for this one. These magnets are such that 24 fit together to form a ring 12" OD and 8" ID, they are pretty much perfect for 12" rotors.

He also got all his coils done. We did this one with two strands of #14 in hand, and 36 windings per coils.

Here's one of my magnet rotors being mounted to the hub. We're using 5/8" threaded rod for this one. The holes in the hub (after we knocked the studs out) were just under 5/8", so we had to drill that out.

George and I are lowering the top rotor on. We have nuts on the studs so it won't go down far.

Scott got his coils wired up. We used copper tubing as a 'connector' between the coils so we could crimp and solder it. It's a nice way to connect coils when you have multiple strands. Then we insulate the connection with heat shrink tubing.

Next Monday we'll be ready to cast Scotts stator and magnet rotors - short of paint, and drilling out the old blade and airbrake - his will be finished.

We got the airgap on mine set about perfectly, so hopefully later this week we can design the coil shape and run a test coil in there. The airgap is set to .85" and the stator will be .625" thick.

willib · « **Reply #1 on:** January 31, 2006, 09:41:20 AM »

The second photo from the top shows how massive those rotors are !!

oh Man !!

electronbaby · « **Reply #2 on:** January 31, 2006, 11:09:43 AM »

whats she weigh in at so far Dan?? lol

pretty scary.

good luck !! :-P

RoyR

KB2UHF

DanB · « **Reply #3 on:** January 31, 2006, 11:17:59 AM »

It's around 170-180 pounds right now. I expect the stator will weigh around 35 or so, and the rest of the 'body' around 40. I expect it'll be about 250 pounds not counting blades or tail.

willib · « **Reply #4 on:** January 31, 2006, 11:34:40 AM »

here is a possible coil shape.

you should have 0.75" around the outside of your coils, maybe a tad less..

The rectangle in the center is your 3" x 1.5" x 0.75" magnets , wow also massive..

The circles are 1.5" dia , 0.75 Radius.

your coil is bounded by 9 degrees top and bottom .

In my opinion you can save on resistance , by not making the coils fill the entire 18 degrees around the perimeter of the stator, as shown by the position of the two rightmost circles.which are instead centered on the 1.5" width of your magnets..

The two leftmost circles are centered 1" apart , and is a compromise to get them to fit in the spot allotted to them.

The two center circles are spaced 1.5" apart ..

http://www.otherpower.com/images/scimages/2965/DanB_coil.GIF

This is two coils spaced 24 degrees apart..

Note: to others, this is just the stator, the magnets are spaced 18 degrees apart.

http://www.otherpower.com/images/scimages/2965/DanB_2.GIF

DanB · « **Reply #5 on:** January 31, 2006, 02:16:28 PM »

Interesting and thankyou!

I might try one like that.... My inclination is to make them a bit wider with about the same hole you've described in the middle. My thinking could be off though...

richhagen · « **Reply #6 on:** January 31, 2006, 04:43:52 PM »

I had noticed the post on the 17 foot turbine that the magnet rotors had rubbed on the stator which had become warped as a result of the lightning strike that shorted the rectifiers. In my thinking this is likely the only reason that the magnets came loose on the 17 foot one.

It relied on the adhesion of the cyanoacrylate glue on the bottom and the polyester resin on the side, in addition to the magnetic attraction to hold the magnets in place. Cyanoacrylate doesn't have that great of shear strength from what I have read, and I suspect that the polyester resin, the steel backing, and the magnets all expand at different rates with temperature change.

I noticed in the past that you made a rotor for a 10 or 11 foot machine in which you put a wrapping of fiberglass cloth around the outside of the magnets, and I believe on that one you had cleaned it up with a lathe really nicely. It seems to me that this would be a stronger design. Even with the current design leaving the magnets embedding incomplete to leave room for air circulation. A wrap around the steel plate of the epoxy, along with a wrap of fiberglass would add a lot of strength to oppose movement of the magnets. It's so large though I don't think you could pretty it up on the lathe, and the thought of all those magnets near a large metal tool seems a little scary to me anyway.

I don't think you will have any problems though unless the stator actually contacts the rotors though. It is a neat and interesting project. Rich Hagen

Ding123 · « **Reply #7 on:** January 31, 2006, 08:21:58 PM »

Hi DanB.... the little woman says to say Hi too....she thinks the stuff that you do is great!I wish I had it that easy,LOL!!!!

I looked at all the one-sided machines and your comments were really easy to understand .This is good...for us new guys!

You don't speak in numbers,this is also good!When you show your pics and explain what you're doing it is easy to picture ourselves..sitting on the couch with the dog.

Maybe next Monday you could tell me what you think of putting a thin disk made of lead on the opposite side of the rotor to sort of keep the flux in....or does that make sense?

Ding123

wooferhound · « **Reply #8 on:** January 31, 2006, 08:32:05 PM »

Regarding the welding with gasoline and laquer thinner in the area. At least the Liquer Bottle was empty , , ,

ghurd · « **Reply #9 on:** January 31, 2006, 08:49:34 PM »

I keep going back to using a couple brass or S.S. pins at the outside of the magnets, where the extra fiberglass cloth was. The buggers couldn't get loose with pins holding the outside edge?

Around here, we call something that big a neighborhood.

G-

DanB · « **Reply #10 on:** January 31, 2006, 08:54:24 PM »

"Maybe next Monday you could tell me what you think of putting a thin disk made of lead on the opposite side of the rotor to sort of keep the flux in....or does that make sense?"

um... no ;~)

lead wont have any affect except to keep the powers of kryptonite hidden from superman.

DanB · « **Reply #11 on:** January 31, 2006, 08:57:23 PM »

I think epoxy will be fine. For one - this will turn pretty slowly. For two... epoxy really bonds nicely to these magnets- nothing like polyester (which doesnt stick very well at all). Also the magnets have a chamfer on teh edge and the epoxy is on that, so unless the fiberglass reinforced epoxy breaks - and all the bonding comes loose from the magnets, these wont go anywhere.

but yes - pins, or a band - or like zubbly is doing (bolt them down) - all are great ideas.

force9BOAT · « **Reply #12 on:** January 31, 2006, 11:42:14 PM »

West epoxy is what I used on my stator and also for many years of boat building. That stuff is really great and strong. I use the 10-hour hardener. It actually takes about a week to fully harden but when it does its hard as a rock.

Rob

mlz · « **Reply #13 on:** February 01, 2006, 12:33:02 AM »

Woof, what do you think is in the red cup in the necklace picture?

Hmmm....

Frank06 · « **Reply #14 on:** February 01, 2006, 04:32:46 AM »

Great stuff - I really appreciate the time and effort it takes to post these updates. I plan to use West on my project (got my magnets yesterday - thank you!); it IS strong stuff! I generally use some of their filler but will also mix with f-glass strands to add tensile strength. We build a lot of cold molded boats around here with it.

Wish I understood some of the details better but I'm sure that will come with time and experience.

wooferhound · « **Reply #15 on:** February 01, 2006, 07:44:03 AM »

Yes your right. At least he did'nt spill it in that accident.

Ding123 · « **Reply #16 on:** February 01, 2006, 08:09:07 AM »

You made HER day!!!lol.....ding123

jackforeman · « **Reply #17 on:** February 01, 2006, 03:48:28 PM »

I really liked the images, very impressive, but the picture of your dog with the ear protection gear is the best. And it is actually a real message, I wish I had worn ear protection more often myself.

picmacmillan · « **Reply #18 on:** February 02, 2006, 01:45:52 PM »

i learned a new tip from the boys in the south again today. ...use some copper pipe to hold the multy strands of wire for soldering...very good idea...and as they say, take one and leave one, so here is a little thing i do for placing magnets..i use a plastic door stop and slide the magnets on to the plates nice and gentle..ease the doorstop out(they are angled), and viola! (speeled bad on perpose) good job..pickster

willib · « **Reply #19 on:** February 11, 2006, 02:43:44 AM »

" Using the same stator, and 2" x 1" blocks (1 cubic inch of magnetic material) with 1 rotor only, we had 12VDC @ 284 rpm. Using the 2" disks (about 1.5 cubic inches of magnetic material), crowded as they are, we get 12VDC at 196 rpm. Interesting how our magnets are 50% more massive and were getting almost 50% lower cutin speed here. "

Pi(r)^2(height)= 3.14 cubic inches of magnetic material vs. 1 cubic inch of magnetic material , not only that , the 2"dia Magnets , are 1 inch thick!!

I've inquired around , but no one seems to know how to relate energy product , to pole strength , to the thickness of a magnet..

other than the stated ' pulling force' that i see in ads for magnets..

which is interresting BTW..

I've got some magnets in transit , should be here tuesday , which will hopefully confirm a suspicion i have , which was sort of confirmed by Dan with his lower cut in from the 1 inch thick magnets..

That is, the thicker a magnet is the more power it will produce leading to lower cut in speed..

the magnets i have on order are 7/8"dia. by 1" thick ,which are twice as thick as the ones i have on my test bed now , so i can make a direct comparison of the two..

the 7/8"dia. x 1/2" have a pulling force of 37lbs , where the 7/8"dia x 1" have a pulling force of 74 lbs..

i also have several different coils wound for the 7/8" magnets , 1 is 17 ga, another is 20 ga, and a double wound 20 ga, a triple wound 20ga, and lastly my 10ga coil

it should be interesting

willib · « **Reply #20 on:** February 11, 2006, 01:05:54 PM »

sorry Dan i thought they were 1" thick you were right about the 1.57 cubic inch of magnetic material..

DanB · « **Reply #21 on:** February 12, 2006, 09:03:54 AM »

yes, that's right, they are .5" thick. To fit coils in with magnets packed this tightly we need a smaller hole, the same size that we use for the 1" x 2" blocks is reasonable I think. In the end resistance isnt changing but voltage is almost 50% more (than it is with the block magnets) so I think we're doing OK here.

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Author Topic: Monday Jan 31 (Read 3033 times)