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new rotors
By electronbaby, Section Homebrewed Electricity Posted on Tue Mar 16th, 2004 at 09:19:31 AM MST
I started on these yesterday...

and today i will finish them up. I have to drill and tap lowering bolts and then sandblast it. then comes the fun part of gluing my magnets on. These rotors are 14" in diameter and are 1/2 steel. They are heavy,.. but its what i had lying around. I doubt I will see any flux leakage on the backside of the rotors by using 1/2" steel. This machine will get the wedge shaped neos DanB used in his 14' machine. Im thinking of going a bit bigger on the prop for this one though.. possibly 16'. This machine will use a 24V stator. The spindle I have clamped in the vise might end up being the one I use for the machine because I too have run out of volvo parts hehe. To the right in one of the pics you can see the hub I made up to allow me to spin these on the lathe and balance them. I basically transfered the lug pattern and bolt them on. If you dont have a shop to cut them for you and you have to end up doing it yourself (like I did) I found it much easier to cut them out with a torch and stack them on top of each other and tack weld them together. If you do this in the beginning,... there is no reason why they wont come out identical in the end. The welds can always be cut off in the lathe when you make the final outer edge cut. Im having a blast!!

-RoyR

new rotors | 10 comments (10 topical, 0 editorial)

Re: new rotors (none / 0) (#1)
by xeroid (centurion27@lycos.com) on Tue Mar 16th, 2004 at 10:38:35 AM MST
(User Info)

Whoa! That's a BIG, HONKIN' machine!

Nice work. Can't wait to hear how it performs.
Regards, XEROID.

Re: new rotors (none / 0) (#2)
by devoncloud on Tue Mar 16th, 2004 at 04:57:56 PM MST
(User Info)

hey, what did you use to smooth out your edges when you put it ont the lathe? it looks pretty smooth for a disk sander (which is what I am thinking of using), and I am doing about the same thing that you are for my rotors. Also, is the sandblasting that important?

Re: new rotors (none / 0) (#3)
by electronbaby (roy<at>windsine.org) on Tue Mar 16th, 2004 at 07:07:16 PM MST
(User Info) http://www.windsine.org

devoncloud, i only used a disc sander to de-burr the edges so i wouldnt cut myself up... that wouldnt be the first time thats happened :-) they are pretty sharp when they come out of the lathe. the smooth edges you are looking at is the direct result of a straight cut with the lathe right through both discs simultaneously (to take off the rough edges from the torch cut). sandblasting probably is probably not that important, but i always want to make sure the magnets get glued down good and it helps to glue to a semi porous surface. also the paint will stick really good and its just a nice way to clean them up. :-)
Have Fun!! RoyR KB2UHF
[ Parent ]

Re: new rotors (none / 0) (#4)
by paulpic on Wed Mar 17th, 2004 at 03:07:37 AM MST
(User Info)

Just looking at pictures here i would advise you to drill and tap threads on discs for a puller,this to remove the discs when go to set the air gap.

Paul

[ Parent ]

Re: new rotors (none / 0) (#5)
by DanB (danb@*no spam*otherpower.com) on Wed Mar 17th, 2004 at 07:13:58 AM MST
(User Info) http://www.otherpower.com/

Excellent... it looks like lots of fun!

I think the magnet arrangment, and the 14" disks would be very appropriate for a 16' machine... (maybe the stator will melt but well find out!). On mine, when I thought I got the stator right I still had to open up the airgap to 7/8" (and the stator is 1/2" thick) to keep the blades from stalling. (mine has 14' dia blades) It's been a good machine so far, it's changed our power situation in a drastic way.

And well be right on your tail on this one Roy... I believe today well be starting an almost identical machine with plans for a 16' prop to be installed at my brothers cabin up here.

Re: new rotors (none / 0) (#6)
by electronbaby (roy<at>windsine.org) on Wed Mar 17th, 2004 at 07:27:39 AM MST
(User Info) http://www.windsine.org

Very cool Dan. we need to keep in touch to trade secrets :-) The coils for these 14" diameter rotor machines are quite large and there is lots of room for the coils. Im keeping in mind your experience with the 7/8" airgap and my stator probably will come out 1/2" thick also. im thinking I can get away with using 14AWG wire. Its gonna be for 24V so the internal resistance will be a bit higher than Im used to seeing with the 12V stators. The idea behind the 1/2" thick steel rotors was kinda to eliminate or cut down on the flux leakage between discs except where there was a magnet. Maybe this will give a cleaner flux pattern between mags and make for a very clean waveform. Its really too soon to tell. Im gonna fimish up the rotors by the end on the week and get them in the lathe so I can play around with matching up an appropriate coil design. Im gonna cast a couple single coils and run some tests at different RPMs. you know the deal :-) Ill be sure to take pics and post a write up. The 24V thing is new to me so its alot of experimenting but TONS of fun!! -RoyR
Have Fun!! RoyR KB2UHF
[ Parent ]

Re: new rotors (none / 0) (#7)
by DanB (danb@*no spam*otherpower.com) on Wed Mar 17th, 2004 at 09:05:31 AM MST
(User Info) http://www.otherpower.com/

Hi Roy -
just for your referance...
my machine has 9 coils (12 magnets) presumably like yours will.

Mine is currently setup for 12 volts, although I intend someday to upgrade to 24, that will mean a new stator.

On mine, each coil has 24 windings and I wound it with a bundle of 4 strands of #14 wire. The stator is in Star. 4 strands of #14 is equal to #9. And keep in mind, with a 14' prop mine stalls unless I open the airgap up extra wide! As it is, it's doing reasonably well I think, about 200 watts @ 10 mph and perhaps 1.3KW around 22 - at which point it starts furling. At 25 mph its partly furled and it peaks around 1.5 KW. On rare occasion Ill see a bit over 2KW from it - but its not supposed to do that.

If I were building a 24 volt machine, I'd use #11 wire - or 2 strands of #14 and perhaps 50 windings for the 16' prop?? (thats what Ill try first on this next one which will also be for a 24 volt system)

[ Parent ]

Re: new rotors (none / 0) (#8)
by electronbaby (roy<at>windsine.org) on Wed Mar 17th, 2004 at 09:27:07 AM MST
(User Info) http://www.windsine.org

ok,.. well that gives me a starting point.. :-) thanks... ill make sure to make up one of those coils (2 strands of 14 @ 50 windings) and test it also. My stator will be wired in star also and im probably going to look for the cut in RPM and shoot for an open voltage of 29V at a slightly higher RPM (not much). (divide by three) and you have voltage of one coil. between 8V and 9.6 should get me in the ball park. Im going to do my coil testing with both mag rotors installed in their normal position on the lathe. This should eliminate alot of guess work. On the new 16' machine your starting, are you going to still maintain a 1/2" stator? I know its hard to fit all those windings in there. Im wondering now since Im using 1/2" steel discs (alot more steel density than the 3/8" you used) if the flux pattern will become weakened and allow for a smaller airgap (below 7/8")?? I cant imagine it would.:-) Ill keep you posted. Thanks Dan!! -RoyR
Have Fun!! RoyR KB2UHF
[ Parent ]

Re: new rotors (none / 0) (#9)
by DanB (danb@*no spam*otherpower.com) on Wed Mar 17th, 2004 at 09:45:20 AM MST
(User Info) http://www.otherpower.com/

Hi Roy -
just in response to your comment, and perhaps an expert can get in here and correct me if Im wrong...
"My stator will be wired in star also and im probably going to look for the cut in RPM and shoot for an open voltage of 29V at a slightly higher RPM (not much). (divide by three) and you have voltage of one coil. between 8V and 9.6 should get me in the ball park. "

You would divide by 3 if you're in Delta, but in star youd divide by 3 and then multiply by something like 1.7. So youll be looking for lower voltage than what 8 I think from a single coil at cutin speed. And if your reading AC RMS voltage, then you figure the peak voltage is somewhere around 40% higher than that - so your cutin speed might come in surprisingly low (and the resistance too high) if you don't keep that in mind. Then there's the drop in the rectifiers....

My bet is, with a half inch stator,and a 16' prop, and a 5/8" airgap - itll be right about 50 windings per coil if you're in star. I am intending a 1/2" airgap on this next machine. Yours may be slightly different, since the rotors are thicker, but I think it will be almost identical. My rotors only had the slightest magnetic field on the back side...

[ Parent ]

Re: new rotors (none / 0) (#10)
by electronbaby (roy<at>windsine.org) on Wed Mar 17th, 2004 at 11:45:47 AM MST
(User Info) http://www.windsine.org

Dan, i have to correct myself. :-) When the stator is wired in star (wye) only two legs are in series at any given time for each phase (120 degrees) Therefore, you must divide by two. BUT, since there will be 9 coils this means that each leg of the wye will have three coils in series. Two legs are in series for every 120 degrees of rotation, For a total of 6 coils in series every 120 degrees of rotation. SO,... to find the appropriate voltage for a single coil, you must take the RMS voltage from two legs and divide by 2, then divide again by three to find the voltage for a single coil. So for instance, you wanted 24V RMS for a cut in voltage. This would mean that every 120 degrees, you would have two legs producing 24V RMS. Each leg would be producing 12V RMS. This means that each coils in each leg would be producing 4V RMS. Its better to do all the voltage calculations and measurements using the RMS value. Even with the alternator connected to a battery bank, current will start to flow even before it reaches the bank voltage (which really means cut in is actually below the set bank voltage).
Have Fun!! RoyR KB2UHF
[ Parent ]

new rotors | 10 comments (10 topical, 0 editorial)

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