Torque on a stator

[willib]

 48 neos , 24 per rotor ,1 inch long by 7/8 inch dia N40 , 18 coils , when done,

I was charging a 6V battery and measuring torque on the stator

this is the data i collected:

 9 Newtons at 6 inches

 160 RPM

and into the 6V battery was

 8.9V at 1.4A

this is the alt i used , before i put half the coils on

so i have 9 coils , from previous experiments ,installed similar to the mini GenII

Although not optimal .. but needed to charge batteries and keep my excercizing going since i took the mini gen II off of the excercize bike

the stator holder is able to rotate about the central axis quite freely.

so i was able to attach a 0- 20 newton spring scale at a distance of 6 inches from the central axis

i am trying to calculate the power output / power input ...efficiency

i'm sure i could figure it out ? , but if anyone has the formula in the front of their thoughts i would really appreciate it

[Flux]

22.7W in, 12.5W out 55%

[willib]

Thanks Flux, but how did you arrive at that ?

[TomW]

willib;

Not to speak for flux but thats an easy one as far as math goes..

take the # you have divide it by the value you "should" have at 100% take the number from that times 100 it gives percent out.

Cheers.

TomW

[Flux]

The long way round.

9N is 9/9.81 x 2.2 lbs. and at 6" radius gives a torque of 1lb ft.

HP is 2pi x speed x torque/33000. Watts = HP x 746

With your force in N it may have been easier to convert the radius to M and work in metric. This would have got the answer directly in Watts with the speed in rps.

1M is about 39.4" so 6" 6/39.4M   160 rpm =160/60 rps.


Power = 2pi x 9 x (6/39.4) x 160/60   22.9W

Flux

[willib]

Thanks Flux thats what i was looking for..

i would include a picture , but it does not look presentable at the moment , none of the coils are soldered together or otherwise connected properly..

i just have aligator clips making the connections , but it is cool when it starts to charge, the stator holder and stator rotate in the direction of rotation and puts a pulling force on the spring scale.

the angle that the spring scale at, is not quite tangent to the direction of rotation

i think that matters a little ?

i havnt done any calculatons yet but i will ,

 this is the approximate angle