45 Gallon Drum

I shortened the air gap by stacking another row of magnets on the ones in the bottom cone. This improved the balance, but I didn't have enough magnets for both cones. Next I made new rings with a smaller diameter to obtain about a 1/2" air gap. I found that my rings weren't perfectly round. Two bicycle rims would be better (as Tracy told me).

I burned up the rheostat because all the tests made were at "maximum speed." The entire frame shook when the cones were wobbling, so the structure must be improved. The motor used is loud, so I need a new one.

As you can see, too many difficulties to resolve, but I'm still going on. I did not take anymore pictures at this time.

Then something unexpected occurred. When using my finger to rotate the cone, I noticed two sounds. The first was the cone's aluminum wrap vibrating at a low frequency (brrrrrrr) which disappeared when the aluminum wrap was removed. The other was high pitched and very similar to a car disk brake's noise. When the cone wrap was removed, this sound became quieter, but was still there. I believe the cone wrap was "amplifying" the sound produced by the nail (needle point bearing) in the notch (the same physical principle used in those old-fashioned phonographs). I filled the notch with WD40 for lubrication and eliminated that noise. I believe the sound's source was difficult to determine because the entire cone emitted it.

Later, I rotated the cone again without the aluminum wrap and with the notch filled with WD40. I noticed a deep hum (actually, it sounds like "hummmmmmm"). This sound appeared to be coming from the magnets. I discovered that if the cone was spinning quickly (about 120rpm), but centered and not tilting, the humming wasn't produced, but if there was an off axis deviation or a tilting induced by hand powered motion, the sound was easy to obtain. I believe this is the same effect Justin obtained with his machine.