Hey Jerry,
Darn I had a very long detailed explaination typed up here and when I went to hit the number 1 key when putting in some numbers I slipped and hit the Esc key and it erased it all. So I will start over with a breifer explaination and since you haver alot of experience and knowledge in this, it will likely be enough.
The Prestolite automobile alt which produced the numbers in the original article is an 8 pole (4N & 4S) 3 phase alt. I rewound it using 46T per coil, 4 coils per phase of #20 wire using the coil alignmet scheme of each coil in a phase is aligned with all N polls at onec or all S poles at once. 24 slot stator each coil in a given phase has 2 empty slots inside it and then 2 empty slots before the next coil starts. Then these empty slots are used with each succissive phase of windings.
I cut off the orig rotor fingers but left the base field assembly on the shaft. With the fingers cut off just at the height the original field coil starts it was just enough space to put in 1-7/8 X 7/8 X 3/8 ceramics , 8 ea. The start up torque to overcome cogging on this unit is 15 inch oz. It will start with a 5 ft prop direct drive in a 4 to 5 mph wind, but with the cutin RPM sitting at 480 RPM direct drive is not an option if I want any measureable charging at less than 10 or 12 mph. So I opted to gear it up with a belt and pully system. Side note here, my measurements have not demonstrated that gear up systems are such inefficient power wasters as is typically spoke of. I think my numbers showed I get about 93% power thruput through a typical 2 or 3 to 1 belt drive system. The big down side is probably more maintenence.
I also converted a Delco (14 pole) rewinding it with 11 turns per coil, 14 coils per phase arranged with a coil within a a given phase such that there is a coil over every N and S pole, with the coils in a phase sharing a slot with the next coil. As for the rotor, I just ground off enough of the face of the original finger face to be able to mount 1 X 1/2 X 1/8 inch neos. At first I mounted them aligned down the finger but the cogging was really bad ( around 325 inch oz) so then I remounted them diagonally with about a 30 degree tilt and got the cogging down to 108 inch oz. This alternator puts out considerably more power than the Prestolite as the cutin V is around 310 RPM and the impedance of the alternator is less than 1/2 of the Prestolite. Ive tested it on the mill described above with a 2.2 to 1 gear up ratio and typical numbers for it would be (using your reporting method)
5 mph 0A; 8 mph 4A; 10mph 7A ; 15 mph 16A. It turns out that this alt is just on the edge of being (as Dan B calls it) too stiff for the 8 ft prop at a 2.2:1 gear up ratio. It really should be only geared up about 1.8:1 to keep the blade power curve greater than the alternator power curve so the blades dont start stalling due to being loaded too heavily.
If your testing on your delco was done with your 58 inch blades that is the reason you dont get any output or even startup below 15 mph as the alternator is too much of a load for that small of blade set. Do you get these types of numbers from mounting the unit on a vehicle and driving at these speeds?? I dont have relaible 25, 30 or 35 mph winds often enough to depend on building units with smaller bladesets that get useable power out of these windspeeds. We do have wind like this along the front range of Colorado but they are called Chinook winds and they sometimes get gusts as high as 50 to 80 mph in places, at which time you really dont want your mill to be running. I think the Dans discovered this and that is why they are going to larger 14 and 15 ft models, to get some useable power out of those 6 to 15 mph winds. That is why Im now building a mechanical tail vane turn it out of the wind 90 degrees manually shutoff mechanism on my larger gravity furl mill. I had one of these gusts break the shaft this 8 ft prop was attached to and the entire blade set went flying off in one piece landing about 50 ft from the tower. Luckily it landed belly flat on the dirt so it was not severly damaged, but it did totally destroy a 14 inch alum pully mounted to the back of the blade hub that hit the steel mount structure as it broke off.
Ill take a pic of the delco, and prestolite and post it here later.
Regards
John
