Author Topic: saw blade mill design  (Read 2757 times)

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richhagen

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saw blade mill design
« on: September 10, 2004, 02:50:51 AM »
This is an evolving design that I decided to try and come up with.  I will update this as more components are finished.


Goals:  


functional small mill for battery charging made from readily available parts

minimize cost

minimize fabrication time

maximize reliability

interchangable, reproducible components


Since the dual axle brake drum designs seem to work so well, I figured I would start by scaling that down to saw blade size rotors.  Since schedule 40 pipe is readily available, I decided to build the frame of the genny from that.


Rotor:  I have a stack of old 7 1/4" saw blades.  I started by drilling 6 holes in a 2 1/8" circular pattern in a couple of blades.  I have a bunch of 1" diameter 1/4" thick circular magnets. I arranged 16 of them on a blade leaving about a quarter inch between each magnet.  If I can devise a decent design, I'll probably switch to Neodymium magnets as they would give much better performance.





I didn't have a deck of cards, so I marked the magnet positions on the rotor with a protractor and compas.


Stator:  I made a wedge shape as previous work was done by DANB and others arrive at and I didn't have the time to do that much research about the optimal coil at this point.  I made a wedge of 1/2" plywood 1/2" at the bottom and 5/8" at the top.  I wound a coil of 100 turns of about #30 or so magnet wire for testing.  I mounted one of the rotors with magnets stuck, but not glued, onto a piece of 5/16" threaded rod and loaded that on my drill press which was set for 280 rpm.  I only generated about a 3rd of a volt.  Figuring that I needed to generate at least a volt or so per coil and that for a single phase machine. I wound a coil of 300 turns and generated about .91 volts with it.  I wound up 16 coils of 300 turns each, made a stator mold out of some 1/2" ply wood and some spare boards, marked up the slots, greased the form, placed the coils, and cast the stator with 'Bondo' as it was the only polyester resin I had available at the time. I noticed when I removed the stator that some of the coils had shifted slightly, probably from

the thick bondo and the clamping of the mold, I'll order some polyester resin and hardner on line for future models.  I tested the coils on the drill press and made the interconnections for a single phase stator.  I was able to generate 20 - 21 volts from the stator.  I expect it will perform better with the second magnet rotor.  I wasn't able to measure the amps as that function on the meter I had with me was broken.  Most of the time the wind speeds around here are slow so I will be looking for an early cut in speed.






This was the mold for the stator.






Here is an image of the stator at this point.






Another image of the stator and mold, showing the shifted coil positions. I think I need to glaze this side of the stator with a little more 'Bondo' to protect the coils.

« Last Edit: September 10, 2004, 02:50:51 AM by (unknown) »
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hiker

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Re: saw blade mill design
« Reply #1 on: September 11, 2004, 10:29:11 PM »
you might want to try and double or triple up  on your mags--sure helped out on my ceramic mag alt..

 looks great..
« Last Edit: September 11, 2004, 10:29:11 PM by hiker »
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hiker

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Re: saw blade mill design
« Reply #2 on: September 11, 2004, 10:30:53 PM »
you might want to try and double or triple up  on your mags--sure helped out on my ceramic mag alt..

 looks great..

« Last Edit: September 11, 2004, 10:30:53 PM by hiker »
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richhagen

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Re: saw blade mill design
« Reply #3 on: September 11, 2004, 11:43:25 PM »
Sounds like a good idea and like in my response to your post, I'm not afraid to copy good ideas.  I'm thinking maybe I'll make a wooden frame for the magnet rotors, like you did for your stator and stack/glue two or three magnets in that frame.  As soon as I get back to the shop (term used charitably), I'll try and measure the voltage difference with two magnets.  I suspect that even as it is I will be able to divide the stator in half and still generate enough voltage to charge 12 volts, however if I can divide it by 4 then I'll be able to generate significantly more amps, providing I can carve blades to match the alternator power requirements.  Just having fun, Rich Hagen
« Last Edit: September 11, 2004, 11:43:25 PM by richhagen »
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richhagen

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Re: saw blade mill design
« Reply #4 on: September 12, 2004, 03:56:30 PM »
Doubled up the magnets and saw only a little over a volt increase in the output.  I'm going to look back at some of the other projects in the archive as the amps out is really low for this stator.  I have a one to one ratio of coils to magnets, and it is single phase.  My coils as described above have thin wire and lots of turns.  I speculate that the internal resistance of the coils is holding the amperage down.  Also, some of the coils shifted during casting and are slightly out of position.  Basically, I think at this point I'm going to research a little and build some coils and test them.  Once I have a designe with enough voltage and amperage I will build another stator.  Just having fun, Rich







rotor and stator on drill press set to 280 rpm with meter showing rectified DC output.

« Last Edit: September 12, 2004, 03:56:30 PM by richhagen »
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