cut in speed.

[blueyonder]

  starting again on a new rotor.

  so now i will have two 9" rotors with 8 magnets each. (n42)2x1x1/2"

 the stator will have 6 coils. it will be wound with 14awg as that is the wire i have.

  still got to do a bit work before i can test a coil for cut-in-speed.

   so what i am looking for is a target speed to set out how meny turns i will use.

  the prop is a six foot wooden type as like the hugh piggot 8 footer.

  i have tested coils with a single rotor before . but now i need to try with a new setup.    as others have done with a wood sandwich holding a coil between the two.

   it dosent sound easy .

  i understand how to work out the voltage . 15.9v.

    14.5v +1.4v for rectifier loss = 15.9 v.

 so each coil wants 2.65 v.  

  joined as star.

  i can do that ok but im not good at the maths for getting the prop rpm. needed for cut-in.

  also is there a way to measure amps from a test coil.

 also if i connect up all the coils joining the starts to the finish

 then measure the ohms.  if i am getting less than 1.5 ohms is that a good thing.

or dos it need to be less.

  the multi meter i have the lowest reading for ohms is 200. is this suitable for what im trying to do.

   as im not well up in this type thing before i was using the wrong setting.

  getting the hang of it a bit more now.

  i also have a analogue meter. that looks like the lowest reading is one ohm.

  but i cant make sence of it.  

 if i used a speed of 330rpm on a lathe would that look like a good speed to

  work from.

  any tips or advice would be great . a cut in speed much better.

  im sorry im no good at the maths bit or i wouldn't need to bother anyone here.

   

[Flux]

Cut in for a 6 ft prop of that nature will be in the region of 200 rpm. If you are in a desperately poor area then going to 180 is about as low as I would go. In better wind areas you will get better overall results by going up to 230/240 rpm.

If you aim to make your stator 5/8" thick total so your coils are about 9/16 thick  then you should hit what you want with about 55 turns. You should be able to get thicker than #14 in there but if that is what you have then use it. It will let you run up to 300 to 400W. If you could have used thicker wire it would be bomb proof but you will have no trouble furling at 300 or so watts as it will be somewhat over 20 mph.

Yes you can measure short circuit current by checking your test coil on ac amps on your meter. Don't bother it is pointless and will tell you nothing. If you wind this carefully you will end up with a winding resistance between a pair of output leads of just over .4 ohm. This is way to low to measure on a multimeter but you can do it by measuring volts and amps.

330 rpm on your lathe should give 330/220 x 2.65 = 4 volts on a test coil. When wound it should give you about 18V dc open circuit after rectifying. with a bit of luck you should see somewhere near 10A charging a 12v battery that is not well charged ( 12v ish). If the lathe speed drops or the battery volts rises during the test you will see less current.

Flux

[blueyonder]

 thank you flux.

    i was getting a bit down as i wasent sure as to what i was doing.

  but now you have filled me with incentive.

  what i have been doing was going ok but i was starting to drag my heels.

  the further i was getting into the unknown.

  so your answer was just right. its got all the information i needed  .

   i asked about amps.  so i dont need to go that way on a test coil.good.

  for sum reason i was thinking that the 14awg might be to thick.

   i never thought it could be a bit heavier.

   just a bit doughty. about it all.

  but you have cleared it all up.

   you have also left things a bit open to let me choose for wind speed .

   today the trees are bending.

   but its not every day the wind is so strong.

   spring is in the air and i must go do sum work on my mill.

   but with my new found incentive it will be much more enjoyable.

  it looks like i am on my way to building a little worker.

   thanks again flux and also to the forum.  

[blueyonder]

 hi flux .thanks again for the good advice .

   after much thinking about what you said .the wire could have been a bit more heavy.

  i wound a coil from 14awg .i put 55 turns on it.

  the legs were a bit thin and coil wasent at full size.

  but as it happend i had enough wire to make a new coil using 12awg.

  but first i must explain about the wire .

  its 14swg  flat or maybe can be called oval.

  its to a military spec and the enamel is verry good.

   so its .062thu wide - .048thu thick.

  or 1.68mm wide - and 1.26mm thick.

   one meter will weigh  28 grams.

  i am not trying to confuse you with all this. just trying to help you understand

   about the wire i have.

  so i wanted to try wind a coil to see if it was possible to make one from this flat

   wire.

   also a few pics .

   i dont think you will need the pics as your exppearances  can tell you without them

 but have added them anyway.

  so what i have now is one coil at 40 turns .its 224 grams in weight.

 it comes inside the coil size ok. the legs arent to thick less than 3/4" each.

  with a bit practise i could wind them neater. for the 2x1 mags.

   its possible there's to much wire there .

   now i need to ask you.  can i make six coils from this flat wire.

   i think it will alter the cut in speed. so could you explain what i will be looking

   for as to cut in speed-  number of turns per coil.

  this is new wire . i can make six coils for £15.00 .

   but as i only have one i need to order the rest of it.

   if i said i had a good feeling about this wire. it might just make me happy.

   as to whether it will make for a better mill im not sure.

   in the other reply to you i said spring is in the air.

  now its snowing and i am sneezing . i spoke to soon.

       

[blueyonder]

 i will try to reply to your comment again  flux.

   if you dont read this flux then maybe sum other person can help.

  after all there is 10.000 on here .

   today i tried with a single rotor -8 mags n42 9".

   i tried the 55 turns on two coils 14awg. on test thay put out 1.90volts ac each.

  running speed 330 rpm.

  also tried the 12awg flat wire 40 turns  .but that was only able to make 1.30 volt

  ac.

 looks like the 12 awg  needs sum other winding.

  i only had one rotor running as i havent made the second one yet.

 its still verry cold for mixing fibre glass resin .

  so 1.9 single rotor looks good.  i dont know how it will act with two.

 maybe double the output at the same speed . if so that can be 3.8volts ac.

  not to far out from what was said before. 4.00 volt.

   12awg gives 1.30 volt ac. 40 turns. 330 shaft speed.

   but if that was a five phase stator . ten coils. 24 mags n42. 8 foot prop.

  would that run better with the flat wire.

  its possible i could wind more turns. but not meny more.

   if i can use this wire then its best for me to bye it now.

  rather than wait till i start work on the 12" rotors ( 8 footer  HP)

  anyone out there .