I think I made the world's longest run-on sentence. Anyway here goes again (admin if you could delete the other post - thanks)
Hi All,
I read bill541's post about ferrous cores and that got me thinking... Since I don't have a lathe, but I do have a few B&S motors lying around I developed a twin rotor alternator to use for testing. It's small - only 7" in diameter.
It has 8 magnets total. 4 on each rotor. The magnets are also small - 1" x .125" disks. (Neo) I guess that makes this thing a 4 pole machine. The gap between the faces of the magnets is .405".
Here's what I tried so far:
First I wound up a sort of "standard" wedge shaped air core coil with 100 turns. The hole in the center is just a shade over 1".
Then I wound up another coil with a ferrous core. This one is round, also 100 turns. I started out by using some .030 body metal. I put a piece of masking tape down one side (for insulation), and cut a strip .375" wide and about 15" long. I coiled that up so it has an outer diameter of a shade over 1". The ID is about .375".
It was pretty easy to make, since I just shoved the coiled steel in between the cheeks of my coil winder and wound right on top of it. After winding I slathered it with epoxy, and attached a stick to it for mounting. I folded some 6 mil poly over it so it wouldn't stick, clamped it between my bench and a 2 x 4 to make sure it didn't grow any. Here's a blurry pic of it:
Here's the test results (sorry about the high rpm - like I said no lathe!!):
Both coils are .375" thick and there's a gap of .015" on each side of the coil to the magnet.
Air core coil:
RPM 1,800, Hz 60, Volts 4.8
RPM 2,100, Hz 70, Volts 5.7
RPM 2,400, Hz 80, Volts 6.5
RPM 2,700, Hz 90, Volts 7.3
RPM 3,000, Hz 100, Volts 8.1
Ferrous core coil:
RPM 1,800, Hz 60, Volts 8.7
RPM 2,100, Hz 70, Volts 10.2
RPM 2,400, Hz 80, Volts 11.6
RPM 2,700, Hz 90, Volts 13.0
RPM 3,000, Hz 100, Volts 14.2
Looks like the ferrous core thing is interesting. All tests performed while loaded with a 25 watt, 12 volt light bulb.
Next up I am going to try putting some laminates right in with the windings, sort of like: ({({({o})})})
For example, wind 30 wraps, and put in one "(" and one ")" on either side of the circle like brackets. Then wind another 30, and put in more steel. I figure if they're distributed a bit like this then there won't be much cogging.
I'll post the results of that test if I get up early enough to do it tomorrow. And if I don't run out of aspirin!!
Happy new year everybody,
Ted.
