Author Topic: Getting started  (Read 5358 times)

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PDM

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Getting started
« on: September 21, 2014, 12:25:34 AM »
Hi,

I just joined up today and my ultimate goal is to make direct drive motors for a telescope (no gearing). I've been doing a lot of reading and it seems axial and radial flux motors are a good possibility but I need to know a hell of a lot more before I even know if I can attempt it. For a telescope drive I'd need very low speeds (less than 1 rev per day - think comets or the moon) but with very smooth movement. Max speed would be perhaps 2 RPM for fast moves between targets.

While looking at all the material I ran across axial flux generators and realized I have a simpler application for axial flux that would be a great starter project - a wind genny for when I'm boon docking and using aforementioned telescope. I have a solar setup (200 watt with PWM controller) that's nearly sufficient (I run a couple laptops, two scopes, astro-video camera, DSLR with battery eliminator (hours of exposures each night) and a handicap scooter. On cloudy days and even some busy sunny days I have to run a gas generator under pretty specific and limiting rules. A quiet wind turbine could run 24 hours a day.

Most of the year I'm just doing a couple of days camping in various places where wind simply won't work. One week each year I attend a star party on top of a plateau at around 4000 feet where there's 10+ MPH wind almost all the time and for about 6-8 hours a day it exceeds 20 MPH. A few times I've seen porta-potties flip and tents go flying.

So I'm thinking if I could build a small genny, say 200-300 watts @15 mph, I'd be swimming in electrons and I'd be a lot further along in understanding enough to build (or know not to build) an axial flux very low speed motor.

So I'm looking for some starting hints helpful to a newb. I do have some mechanical and electrical background (navy marine engineer, presently a power engineer) and I make electronics for a hobby. I've done dataloggers, urinal flushers (not kidding!), HVAC diagnostic dataloggers (dual temp & hum), a talking keyboard for a fellow that was mute, autistic, and had MS (long before tablets), a swimming pool chemistry controller (ORP, PH, Temp), and lots of experimenting with micro controllers (Atmel, Arm, Parallax).

 I also have a small CNC router for wood/plastic and a separate spindle for making circuit boards (using 5  and 10 mil end mills). I was thinking PCB stators since I can make them so easily but I'll save the decision for when I know more.

Anyway, I know generally how much power I want so I'm guessing the first decision is type and size for the turbine/props. What would you folks suggest as a portable, occasional use setup? Most likely I'll be welding a mount to my trailer frame and using a pole to get the blades above the trailer roof and out of range of people's heads/hands (it gets REALLY dark during new moon).

I realize I'll need some way to control the genny speed on those really windy days but thats a topic for later.

Thanks for any feedback.

P.S. I tried reading some of the faqs about building gennys but I keep getting errors and can't view them.

joestue

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Re: Getting started
« Reply #1 on: September 21, 2014, 01:05:26 AM »
you could get a custom linear stepper motor manufactured to do what you are trying to do with the telescope, but it would be a very expensive, also it would need to be a rather large diameter, i just can't see it working out with regard to the positioning accuracy you need.
but there is a chance it could work.. probably 3600 "steps" per revolution at ~1mm per step and 1 meter diameter.
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Frank S

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Re: Getting started
« Reply #2 on: September 21, 2014, 04:03:41 AM »
If you were to go radial  in a more conventional way you could up size a simple 5 phase stepper motor from a standard 50 tooth rotor to a  500 or even a 1000 tooth say at around 300 to 400 mm rotor diameter
for instance a 2 phase 50 tooth motor has 200 steps per revolution and moves 1/4 of a tooth to line up with the next step a 5 phase 50 tooth moves only 1/10 of a tooth to line up to the next phase giving 500 steps per rev.
 a 5 phase with 500 teeth would have 5000 steps. by micro stepping this could be multiplied by 5 giving you 25000 steps or .o144° per step
 Obviously you would want  around 20 coils using 2 per pole 4 per phase .
 a pulse modulated variable frequency  controller  could possibly get you down to 1 rev per  24 hour nominal period
example of a 2ph & 5 ph 50 tooth stepper motor

http://www.orientalmotor.com/technology/articles/2phase-v-5phase.html
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madlabs

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Re: Getting started
« Reply #3 on: September 21, 2014, 11:10:08 AM »
Not to be a wet blanket, but more solar and a larger battery bank would be cheaper and easier. Especially for a once a year trip.

But maybe you're not looking for cheap or easy. It certainly sounds like you have the skills. One issue will be tower height, there is more to it than just missing folks heads. The air at 15-20' is very turbulent and difficult to pull much power from. And 300 watts at 15 MPH isn't THAT small a mill.

But the cool factor would be HUGE!

Jonathan


Frank S

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Re: Getting started
« Reply #4 on: September 21, 2014, 04:23:49 PM »
If you were to set your sights on a 30 to 50 watt wind generator it would be more realistic for a weekend wind power station the turbine would be between 4 to 6 ft in diameter I think.
 you could construct a ridged enough 30 ft telescopic coupling tower that could remain mounted to a trailer providing the trailer were heavy enough not to blow over but even at that it could be guy wired to the ground .
 the genny could be made out of many different types of motors or alternators if it were in the 30 to 50 watt range.
 But like Madlabs said another 200 watts worth of solar and perhaps a larger storage battery and you'd be all set
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Mary B

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Re: Getting started
« Reply #5 on: September 21, 2014, 05:28:18 PM »
Frank is right, plus your next door neighbors are not going t be happy with wind generator noise all day long when they want sleep. This is a case of solar panels make the most sense and would be far cheaper.

As far as using an axial flux as a telescope drive I don't see it. The tolerances required are going to be way to hard to do with home machine tools.

PDM

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Re: Getting started
« Reply #6 on: September 21, 2014, 10:54:00 PM »
Actually the comments about hundreds of watts being unrealistic are spot on. I realized that even 200 watts would be around 16 amps and even if the battery were 50% discharged and the panels were putting out zero then the charge time would only be just over 3 hours which is massive overkill.

Something more like 30-50 watts would be more reasonable and allow me to not run the gas genny most days.

Flux

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Re: Getting started
« Reply #7 on: September 22, 2014, 03:36:00 AM »
In view of the consistent wind and the fact that you can let it down if the wind was excessive your modest figures of about 50 watts are probably possible. I think you would do well to look at Hugh Piggot's 4ft machine as something to base it on.

It is not silent, but is very quiet, and a bit of attention to the blade tips could make it even quieter. Certainly quieter than a gas engine.

If your wind is as described I think you will average 50W and see double that at times. I only think this is possible in view of your predictable wind speed. Normally solar is the only way to go for portable supplies but you have obviously thought about this.

Flux

PDM

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Re: Getting started
« Reply #8 on: September 22, 2014, 05:57:25 AM »
Here's a picture showing what the site it like. wind comes out of the south the majority of the time and there's nothing in the way of obstructions within a half mile in that direction or hundreds of feet east and west. There are some trees to the north but they are on a down slope making the tops of the closest ones (perhaps 200 feet away) about 10 feet high.

http://www.fvas.net/gallery/details.php?image_id=819

SparWeb

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Re: Getting started
« Reply #9 on: September 23, 2014, 07:00:39 PM »
I've always wanted to check out the Mt. Kobau star party.  Knowing there's going to be a WT around is just even more incentive!
(Oh now that I checked your link, I see you mean Merritt...  not much further)

The power requirements for 'scopes is pretty low.  If it was me lugging all of this around, the batteries wouldn't get the kindest treatment, and to keep them portable, probably be undersized.  You may be doing better than I would be.  Solar power and astronomy kind-of go well together - clear skies, and all, while wind power implies that astronomy isn't going to be happening either.  Anyway!  You've already been put on the scent of Hugh Piggott's website, the best place to start.

Have you been able to read the FAQ pages yet?
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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PDM

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Re: Getting started
« Reply #10 on: September 24, 2014, 08:47:13 PM »
THis is the Merritt Star Quest, not Kobau. I almost went to Kobau but the road up is horrendous and I'm not willing to risk my trailer axles. My girlfriend is wheelchair bound and it doesn't look like the best terrain for her either.

The MSQ is later (new moon around labour day) so its darker and dark longer though the weather is riskier. Kobau's normal problem is forest fires & smoke while the MSQ is clouds.

P.S. No on the faqs but it's being looked into by the admin(s)

Mary B

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Re: Getting started
« Reply #11 on: September 24, 2014, 10:07:06 PM »
I would put enough solar on the roof of the trailer to charge the bats and call it good. With panels as cheap as 68 cents a watt it is hard to build a wind genny.

gww

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Re: Getting started
« Reply #12 on: September 25, 2014, 08:35:01 AM »
maryalana
I know you have done so in the past but rather then trying to do a search of this site could you post a link or two of the place to buy solar panels.  If I could match closely my 24 current panels I could add 9 more without having to add a cc or more wire from the combiner box.  At .68 cents a watt I may still not do it but I have been sort of checking the prices "just in case"  Thanks
gww

Bruce S

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Re: Getting started
« Reply #13 on: September 25, 2014, 09:25:14 AM »
http://www.solarblvd.com/
IS my go to these days.
Cheers
Bruce S
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gww

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Re: Getting started
« Reply #14 on: September 25, 2014, 12:20:03 PM »
Bruce
Thank you.  Do you know where this company is located?  I have mx 235 panels 29.8 volt 7.88 amp.
How close do I have to match this to put both panels on the same mppt cc?  30.2 volt and 8 amp as an example.  Either way thanks for the link it will go in my favorites so I don;t have to ask again.
gww

gww

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Re: Getting started
« Reply #15 on: September 25, 2014, 12:49:51 PM »
My mistake, thread hyjack.
gww

Mary B

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Re: Getting started
« Reply #16 on: September 25, 2014, 07:49:13 PM »
yup www.solarblvd.com is my main source too. gww they are in CA, get the voltage to match as close as possible and the amperage if going in series with something else.

gww

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Re: Getting started
« Reply #17 on: September 25, 2014, 10:16:23 PM »
maryalana
Thanks
gww