Spacing of magnet on the rim

[lis_wang]

I found there might have some mistake in the beginner's handbook pg 55 about the spacing between the magnet on the rim. If the rim is 22inch (mine is 22.44in), then the circu
the circumference should be 3.14x22=69.08in, 24 magnet will have 24 intervals, then the spacing of the magnet should be 69.08/24-1 (width of magbet)=1.8in.

How can we have 3 inch spaing as stated in the book last paragraph of pg 55? Can anybody clarify for me? Thank you very much

I remember somebody said in the forum, the spacing should be able to put 3 to 5 magnet. But with outside diameter at 22in and magnet size
20mm x 50mm x 10mm (in the book, stated the magnet size is 1in x 2in x 0.5in, I just bought the closest one as I cannot find the exact size), It seems
impossible to put 24 magnet.

Could anyone here help me?

Thanks

[Retep]

Magnet Spacing

Dear lis_wang,

Thank you for your question. You can see on page 55 that there ARE 24 magnets on that wheel! So, no mistake! As you build your own model, the exact number of magnets around the wheel is NOT important. If 24 won't fit, then use 22 or 20. Usually, the fewer the magnets you have, the faster the wheel will turn because there is more time for the discharge process to happen in-between. But at a certain point, you have too few, and the wheel starts to run slower again.

Also, having exactly 3 inches between the magnets is not critical either. Uniform spacing is preferred, but some models in the early days did not have very precise spacing and still worked. The important thing here is to BUILD SOMETHING and test it! Once it is working, you can change one thing at a time, like fewer or more magnets on the wheel, and see how that changes how the machine runs.

The magnets are not exactly 1" x 2" x .5" anymore. They are slightly smaller then that in all dimensions. The link in the book goes to a page where the correct type of magnet is sold. Look at the specifications of that magnet and get something similar wherever you can.

Hope that helps.

Peter

I found there might have some mistake in the beginner's handbook pg 55 about the spacing between the magnet on the rim. If the rim is 22inch (mine is 22.44in), then the circu
the circumference should be 3.14x22=69.08in, 24 magnet will have 24 intervals, then the spacing of the magnet should be 69.08/24-1 (width of magbet)=1.8in.

How can we have 3 inch spaing as stated in the book last paragraph of pg 55? Can anybody clarify for me? Thank you very much

I remember somebody said in the forum, the spacing should be able to put 3 to 5 magnet. But with outside diameter at 22in and magnet size
20mm x 50mm x 10mm (in the book, stated the magnet size is 1in x 2in x 0.5in, I just bought the closest one as I cannot find the exact size), It seems
impossible to put 24 magnet.

Could anyone here help me?

Thanks

[Tom C]

Lis,

equidistant magnet spacing IS critical from a resonance standpoint, if you can get them exactly equidistant, the coil and the rotor will go into resonance... take the time to get them right, its something you wont have to do later.
Tom C

[lis_wang]

Dear lis_wang,

Thank you for your question. You can see on page 55 that there ARE 24 magnets on that wheel! So, no mistake! As you build your own model, the exact number of magnets around the wheel is NOT important. If 24 won't fit, then use 22 or 20. Usually, the fewer the magnets you have, the faster the wheel will turn because there is more time for the discharge process to happen in-between. But at a certain point, you have too few, and the wheel starts to run slower again.

Hope that helps.

Peter

Dear Peter

Thanks for your reply. Maybe I need to change the numbers of magnet based on the spacing of magnets. Do you think what is the preferred spacing? My rim OD is 570mm, and magnet is 20mm x 50 mm x 10mm. As I am going to use permanent super glue to fix the magnet on the rim, after I fix, it is not easy to take out. So I want to get it right at the beginning.

[D Rhodes]

No mistake with John's wheel in the book as far as I can work it out. 22 inch diameter gives 69.11 inch circumference. He had 24 x 1" wide magnets. 69" divided by 3" = 23. Put a line on rim every 3 inches. I had some fun with a diagram. And by the way, I stock the 2" x 1"x 0.5" magnets..they are much better than the 40mm variety I reckon.

[Lannister]

Just an FYI for reference, I just finished my first SSG last night and used a 22" bike wheel and 12 Ceramic Magnets and it works fine. They line up perfectly to the spokes so no measurement was even needed. Magnet, 2 spokes, then another magnet on the 3rd spoke, then another 2 spokes, and so on all the way around. It comes out perfect for those wanting to use a 20" Wheel.

Pic for reference: http://img.photobucket.com/albums/v1...ps84f7f31b.jpg

Just an option for those wanting an easy job of it.

[Tom C]

Just an FYI for reference, I just finished my first SSG last night and used a 22" bike wheel and 12 Ceramic Magnets and it works fine. They line up perfectly to the spokes so no measurement was even needed. Magnet, 2 spokes, then another magnet on the 3rd spoke, then another 2 spokes, and so on all the way around. It comes out perfect for those wanting to use a 20" Wheel.

Pic for reference: http://img.photobucket.com/albums/v1...ps84f7f31b.jpg

Just an option for those wanting an easy job of it.

you need to double your magnets if you want better performance.

Tom C