Working Magnetic Motor on you tube??

[MeggerMan]

Hi all,
To test the strength of two magnets you can make a tube from flexible plastic wrapped around the rod magnets.
Then hold the tube veritcal and measure the repulsion distance.
Al confirms this distance for the stator magnets to be 30.5mm
My N42 magnets repel a distance of 31.5mm
You could do the same with the rotor magnets, except you need to tape the ring into its own tube then slide this into another tube.
Effectivly making the ring into a rod with the poles facing straight down the tube.

Someone asked about the IceBreaker board, I bought it from Magenta 2000 in the UK.
http://www.magenta2000.co.uk/kits/900.htm
The stepper motor circuit is just a set of 4 transistors coming off the PIC chip I/O pins, I think I have the circuit diagram somewhere.

Interesting comments about the stator inertia, maybe we need to fine tune how much flywheeling there is.

The only way to reduce the inertia would be to use smaller bearings, like these:
http://www.technobots.co.uk/acatalog/Online_Catalogue_Miniature_Ball_Bearings_384.html
I was thinking that two bearings, one either side of the magnet and use a brass shaft turned to fit the stator centre and the bearing centres.
Two smaller bearings should help reduce the friction as I suspect one bearing on its own with suffer a lot of twisting forces.

Shame I do not have a lathe.....Sean, I'm stuck.....

Test showing rotor magnets in repulsion, "sorry about the poor lighting".



Regards
Rob

[Omnibus]

@MeggerMan,

For now I think we should stay with the bearings proposed by @alsetalokin. Don't think the problem is in them. The magnets, the fields they produce, finding magnets with matching fields, knowing what the mutual strength between rotor and stator is etc. these are the main problems, not the mechanical construction, I think.

[Craigy]

@ All

From the Steorn Forum.

       MeggerMan:
        @Al, one question/test for you, if you stack two of the rotor magnets in a plastic tube in repulsion, what is the gap that seperates them?
        I know the gap from a N42 1/4"x1/2" rod.

        Regards
        Rob


Al:
    I would really like to know the answer to that one also.

Good test.
Almost exactly 3 cm, maybe a rch more, like 3.05 or so.
Of course, density is unknown.

Meggerman:
Hi Al,
Thanks ... 30.5mm sounds very close to the results for a N42:
http://i100.photobucket.com/albums/m25/kingrs/DSCN5262.jpg

31.5mm by bouncing the magnets and looking at the average.
The tube is Kapton, so its difficult to see through.

Perhaps its N40?
[edit] by adding another 1/4" x 1/4" rod (total = 1/4" dia x 3/4") to the bottom magnet increases this to about 33mm [/edit]

Regards
Rob

Al:
@Rob--maybe, I just don't know. I don't think so though, they certainly don't seem as strong as the 834DIA stators.

(I have highlighted the important points that I see.)

Figure this out and we will have working replications.  IMHO.

Cheers,

Bruce

Seems liek the ones me and clanzer have then

[Omnibus]

@Craigy,

So, your rotor magnets seem stronger than what's needed for the motor to spin. Mine are also stronger in the setup I have now with me. The other setup isn't with me right now and don't know what's there in terms of magnet strength--anyway the rotor magnets are rectangular there and I think they are also N42. Can you check what you stator magnets are compared to the rotor ones?

Just ordered N38 1/4" x 1/2" cylinder magnets. We'll see if that'll improve the performance. If you know where to get even weaker ones would appreciate letting me know.

[MeggerMan]

Hi Omni,

I hear what you are saying and yes we should go with what Al is using, but we need to be sure that bearings we are using are very similar magnetic wise.  From some of the tests I have done, the proximity of the stator magnet to the bearing causes a huge amount of friction.  It was just a suggested test.

So I wonder if Al has stumbled upon some stainless steel bearing made from high quality low magnetic SS.
I think we need to get him to perform another test for us.

Test1:
With the rotor removed from the baseplate, using a single rotor magnet, measure how far away from stator you need to be to be able the move the stator magnet using repulsion force.  With a heavily magnetic bearing I expect this distance to be very small because of the large amount of friction.
From the ease with which Al seems to be able to spin the stators I suspect he has some very non-magnetic
bearings.

Test2:
Using a piece of plastic tube slide the magnet and bearing onto it and measure the maximum gap before the bearing falls off from its own weight overcoming the attraction force.

Test2 is probably better than Test1, I will see what he says, its a test we can all do then to compare our bearings magnetic wise and friction wise.

[Edit] Hey Craigy, get those magnets straight, that sloppy angle will give you bad results... [/edit]

Regards
Rob