100 watts per cubic inch mag ???????

[coldspot]

100 watts per cubic inch mag

for round magnets

And rectangular ones

getting 1.4-1.5 as much

??

OK

How about the #29's

rectangular in shape I guess

1. 75"
   
1. 25"
   
   

.25"

8. each
   
4. 38" cubic
   
   

maybe about 650 watts

[zubbly]

hi coldspot,

the estimates i gave for figuring out the potential of magnets, round and rectangular, are that only (estimates). it is just a guide line.

much also depends on your airgap, mag grade, winding, prop selection and wind.

TomW is currently flying a test unit (joint project). it is a 6 pole machine with 6 of the curved/skewed #29's in it. with those mags, it calculates out to 492 watts. tom has seen 500 watts from it.

again, it is just an estimating tool and you may see less or more from them.

my  current project is a 7.5hp conversion. it will have 24 of the 2x1x1/2 mags. that calculates out to approx 3600 watt.  we will see how close it comes

zubbly

[Stonebrain]

Hi coldspot

Think about some parameters:

-how much flux leakage between magnets

-How well the magnet fits the coil

The major one:

-at what rpm?

cheers,

stonebrain

[dinges]

I like that rule of thumb, if only it gives a very rough estimate.

2 small questions:

• is the goal to always keep the airgap as small as possible (in a conversion)?
  
• if I had a motor of 130W and I would convert; how much power should I expect as output (roughly)? 50%; 80%; 99%; 120% ? (I know it depends on windings too, but, any rough estimates possible?)
  
  

Peter.

(who has his eyes set on a 130W fluidproof 3phase 4pole motor for conversion).

[zubbly]

hi again coldspot,

your post prompted me to do some more calculating.

i did a little figuring on my 1.5hp conversion that i have had up for some time. it has 48 3/4 round by 3/8 long mags in it. that is 7.9467 cubic inch. 7.9467 cubic inch times 150 watts equals 1192 watt. i have very often seen this unit doing 1kw plus, in 12 volt batt bank. a few times i did have it doing 2kw at 24 volt connection (but in a severe wind storm).

the original hp rating is 1.5hp, which is 1119 watts. so the output rating of the conversion seems to regularly equal the original rating and a bit more.this is connected to a 24 volt battery bank.

i had to do some figures on my first 7.5hp conversion. it was from a 7.5hp 3 phase motor. i sold it to Jacquesm before i ever got to fly it. it had 48 1 inch by 1/2 inch round mags (18.84 cubic inch) which works out to 2826 watt assuming 150 watts per cubic inch.

when i tested it, it was driven with a 5 hp dc motor at 600 rpm connected to a bank of heating elements. no load volts was 242 volt. loaded it dropped to 205 volt. it worked out to 4700 watt, and ran it for 20 minutes without any signs of the unit heating up. the elements were connected in 3 phase and the genny was connected for 1 star output.

the 150 watt rule seems to apply to battery charging. when connected to a load that allows the unit to come up considerably in voltage (like heating elements), that 150 watt rule seems to get blown out of the water.

so for now,(and just observations) it seems that the 150 watt rule can be further increased by times 1.66.  so the 150 watts per cubic inch would now be 249 watts per cubic inch of mag material.

observations seem to tell me that the higher a genny is allowed to run in voltage-12/24 volt batt banks or 200 plus volt heating elements, the wattage seems to significantly increase.

again guys, this is just all observations and i think we will all get a better understanding of what to expect from conversions from all of us as time goes by and we build more of the units.

if this rule holds true or at least close, the 3600 watt i expect from the new 7.5hp conversion with the 24 2x1x1/2 mags, and now times a further 1.66, would work out to 5976 watts output running in the 200 volt bracket and using heating elements. ( it now tells me my prop is no wheres going to be big enough) but then again, i don't need 6kw.

what beasts are we creating?  

lol, its all about fun to me guys and sure beats spending time blowin money in the casinos.

have fun,

zubbly

[Nando]

Zubbly:

You said:

>would work out to 5976 watts output running in the 200 volt bracket and using heating elements

Raise the voltage to around 380 volts for 5976 to get around 6800 watts (?).

Nando