Dan - quick questions on 17' - another version

[Dave B]

The photo shows sketch of 16" diameter and 20 1x2 either 1/2 or 3/4 thick mags 15 coils. Limiting the weight and investment 16" diameter 1/2" steel disks are what I will use. I plan to pre-heat water and want to shoot for 48v @ 70-80 rpm with a 17-18' 3 blade. I plan to experiment as I have with my 12' but to be in the ball park I'm asking for suggestions with wire size and winds etc. for this combination. I have 16 and 18 guage wire and figure I'd like to limit the speed and output to maybe 150-180 rpm and possibly 1500-2000 watts ? Dan, if you're out there I know you could let me know quickly if I'm in the game here. Also, if you could let me know where you purchased the 6000lb trailer bearing, spindle and 6 bolt hub unit and what model this is that would be great. (all that I search for appear not to have a flat surface for the rear disk to mount against.) Thank you to anyone with comments)  Dave B.

[Dave B]

I don't know where the photo went. Sorry, I'll try again.  Dave B.

[AbyssUnderground]

This is the image I beleive:

Dont use underscores or spaces in filenames from now on. I think dashes are fine though.

[kurt]

i have been telling people that for a year now no one ever listens scoop does not like spaces in file names it gets things all messed up.

[veewee77]

Starting in comuters when 8.3 filenames are the norm, I never use saces in filenames anyway.  Winders has spoiled people. . .

Doug

[Dave B]

Thank you for getting my photo on board, I've never had trouble before but like you say it must have been in the filename somewhere. Now that's up I am looking forward to a little help and or suggestions with my version of the 16" disks 17 or 18 foot genny. Thank you,  Dave B.  

[Flux]

Dave

Your question is a little vague, not sure if you want 48v ac or dc. For heating the exact voltage is not critical so I have assumed dc at 75rpm and I presume you will be rising to about 100v at full load.

I think you will need the 3/4 thick magnets to meet your spec. 1/2" magnets will not meet your expected power at your top speed limit.

Assuming 3/4" thick magnets and a fairly thick stator ( about 1" total) I suspect you should be trying test coils of about 100turns of about 2 in hand #16 wire.

Flux

[Dave B]

Hi Flux,

  Thank you for your reply. Yes, with the 3 phase I would be running DC volts with a stepped load controller. I had figured probably the 3/4" 1x2 mags would be needed. When you mention a failrly thick stator at 1" total am I correct in assuming this would be just for the thickness of the coils and casting ? I calculate 2 in hand #16 would equal one strand of #13 which should be good to maybe 15-17 Amps or 1700 watts ? I think I have this right but get a little hazy when figuring the total load at each step and the actual current the coils will need to safely handle. Thank you for your help and any other suggestions would be appreciated.  Dave B.

[Flux]

Yes that was the idea, keep the total stator thickness including casting at about 1". You may be able to get your wire into a bit thinner and have a bit more clearance if you are careful.

What you can squeeze out of the wire safely is really an unknown, but if you let full load come up to 100V you will not be pushing things as hard as most of these machines at 2kW. If you are not too concerned about your top speed you can let the volts go higher and get 2kW with safety.

If you hold it down at 48v it will be quite hard going for it at 1500W and the prop will be down towards stall and you loose all round.

Flux

[DanB]

Hi Dave - I think we can extrapolate the power you'll fairly easily from past machines if you use 1" x 2" x 1/2" magnets - Im afraid if its resistively matched to the load you wont have nearly enough there for a 17' machine though.  It makes sense to use longer magnets when the disk diameter gets greater wider/thicker magnets and the airgap gets thicker I think.

From what you're planning now, if you use 40 1/2" thick magnets you'll have 40 cubic inches of magnetic material in the machine.  My 17' machine had 108 for comparison.  While this isn't everything... I think it is an important number to pay attention to.

My 17' machine also really does need to be kept slightly in stall in the higher winds or things get out of hand (as we learned last March) - so the airgap is critical.  For heating  -  as flux said, voltage isn't critical and you may do better than I can since you have a resistive load that you can change over the range of windspeeds so hard to say.  My guess though - looking at the mass of your magnetic material only, is that it will be much less powerful and probably not up to a 17' blade unless it furls very early and even then...

I could be wrong there but those are my thoughts.

[Dave B]

Thanks guys,

  First off I've decided on 3/4 " thick magnets and no smaller than 1x2. Looking at the other design(s) of 12 magnets 9 coils and the power seen of at least 1kw it just seemed like 20 and 15 on a 16" rotor would be cabable of 1500-2000 watts. Heating only seems to be a different animal than shooting for an ideal cut-in to charge batteries and spilling excess to a dump load. I will be controlling the speed with the stepped loads and will dial in on the power curve of the prop and to be able to keep things safe. My goals are to keep a 16" rotor, spin a 17-18 ' 3 blade, keep the speed well below 200 rpm say at 20 mph wind and crank out 200-300 watts in a 10 mph wind. I have experimented with 12,24,48v elements and of course 120v so because voltage is not critical I have plenty of room for design of the controller. I'm running 85' down the tower with 3 wire #8 cord and #6 underground another 120' into the house to the control panel. Any more thoughts or words of advice are much appreciated. Thank you, Dave B.

[Flux]

Yes heating is a different game, you are no longer constrained by a fixed voltage, but you are restricting things somewhat by setting a low limit on your top speed.

Stick with the 120v heaters to keep line losses low and you should be ok. For good heating performance you must not stall, but that does lead to a more noisy and frantic life. If you drag it down at constant volts you can expect about 1/4 the power for a given stator temperature.

Not much point in worrying much about winds much below 10 mph, but you can still match them but you will need more steps,

The tricky area to match is between 7 and 14 mph, above that the curve matches the heater square law fairly well.

Flux