My 5 watt air core alternator attempt.

[gotwind2]

Continuing from my original posting.

http://www.fieldlines.com/story/2008/2/10/115511/907

I used a piece of plumbing tube with pieces of Lego (it just happened to be the correct size) glued to its diameter with super glue.

A 20mm x 20mm (3/4"x3/4") diametrically magnetised Neo magnet (2poles) and a single bearing were used.

I wound 300 turns of No 28 wire (150 per side).

Output was quite surprising 1 amp@2000 rpm - 7 volts@2000rpm(open circuit).

The main problem was the Neo magnet was being attracted to the steel bearing race and this added quite a lot of drag - I bought a stainless bearing hoping it would be non magnetic, however it is not possible to buy a non magnetised stainless bearing race apparently - something to do with the hardness needed for bearings, does not allow for the softer non magnetic stainless.

Ed, how did you overcome this problem?

Video here - illuminating a 5w Luxeon LED/driver package.

http://www.youtube.com/watch?v=sXuAjf7f-EM

Cheers

Ben.

[feral air]

Bearings like these ought to work a bit better. (not affiliated)

I wouldn't mind getting a couple so if anyone gets a package and wants to part with any, let me know. take it easy

[gotwind2]

Thanks for the offer Feral air.

They look very expensive - I think a sintered bronze bearing may be a cheaper solution.

Sintered bronze bearings are self lubricating.

Alternatively a hard plastic bearing, Nylon maybe?

Ben.

[Jeff]

Delrin would be better than Nylon, and only slightly more $$. It also comes in rounds (lengths of whatever diameter you need).

[feral air]

I get $44.84 shipped...$5.60 each. That's 8 "meals" at a fast food joint I guess.

Got any links to cheaper bearings? I'm stuck on dialup so it takes me forever to find anything. take it easy

[windstuffnow]

  That came out pretty nice Ben !  Pretty ingenious.  The smallest one I made didn't use bearings, the nylon ends served as a bearing.  The 4 pole unit didn't have any negative effects with the bearings, could be the flux is fairly well contained within the 1x1 block of steel the magnets are mounted to.

   I think even my small one is a bit larger than yours and since there is no steel in it, except the bearings the flux is attracted to them.  A longer tube spacing them out a bit might help, also a non magnetic shaft.

Great work!  

.