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Old Aug 04, 2001, 04:21 PM
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Vacaville, CA USA
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homebuilt micro edf

Well...I built a little EDF unit last night using the G9330 (for those of you who don't know it: basically like a light-stick / pico stick motor for $1.25...)
Has a 3-blade rotor (blades at 50 degrees at the root) and a 4-blade stator....all made out of glass fiber.
Diamater of the rotor is 41mm (1.6")...the whole unit weighs about an ounce and that's also the thrust it produces (on 7 110mAh cells)...

50 degrees are most likely too much...maybe I'll try one with a 5-blade rotor at 45 degrees)
I wish I had a battery pack with more cells...that should speed things up. RPMs are just too low...(I haven't measured amp draw but my guestimate is about 1.7-2)

On to the next one...

Bernie
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Old Aug 04, 2001, 04:46 PM
Time wounds all heels.
Phoenix, AZ
Joined Jul 2001
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I am excited to hear that someone else is playing with micro-edf.

I built a test-bed plane for my EDF's

A 4.5' wingspan Wal-Mart toss-glider, bashed to a 2 channel EDF. AUW 272g. Pretty close to what I want to hit with the A-7.

It is a sweet bash, looks really good. 80% complete, I will try to have flying later today, tomorrow for sure.

Oh, and I also tried the KP-44 on my GWS Tiger Moth, hehe.

Not much climb, due to large frontal area, but it worked, and looked very trick. Was odd to hear the Moth screaming like that.
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Old Aug 04, 2001, 05:10 PM
DNA
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Bernie,

So, that's your secret design project.
Sounds interesting.

You designing the plane for it too?

I'd like to see some specs and plans.
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Old Aug 04, 2001, 08:20 PM
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Hi DNA,

Nope -- the thought of building a micro EDF krept into my head just 2 days ago....but the fuselage plug for "the other" project is almost done....

BTW: I don't know if you ever measured but the G9330 with the GWS 4x2.5 delivers about 65 gramms of thrust on 7 110mAh cells (measured after 1 min).... sure gets quite hot though....

Bernie

PS: the "micro edf" is going to go into a (quite small yet-to-be-designed) Mig-15....for that one I'm also going to make a fuselage plug / mold since -- as you might have guessed -- I like my planes to be reproduceable
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Old Aug 04, 2001, 10:57 PM
DNA
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Hi Bernie,

Boy you must really handy with glass fiber.
Which resin do you use? Fiberglass or epoxy?
Your projects sound very interesting.
Keep us informed on how you're doing.

On the G9330, I've been using it and posted
some rpm's and current draws in the 'foamie'
section a while back. It's a neat little
motor, just not the powerhouse I was looking
for. I usually use 6 cells with it.
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Old Aug 04, 2001, 11:22 PM
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Bernie, I and others will be at Lagoon Valley in the morning. Bring it out so we can see it! Around 9 am or ao?
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Old Aug 04, 2001, 11:23 PM
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By the way I have a little twin EDF that I fly out there with 2 KP44's
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Old Aug 04, 2001, 11:28 PM
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Actually I just used CA -- it's plenty strong for such tasks (and extremely quick to boot...)
I'm going to make a new unit now..still with 3 blades but the angle at the root is going to be around 45 degrees...then I'll do one with 5 or 6 blades...
(the first fan assembly only took about 3 hours from design to finish so I can afford a few "failures")

I just wish I wasn't on such a tight budget (on 2-year old and a second baby on the way)...I would get a plasma dash and try an EDF with that one...ah well.


Bernie
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Old Aug 04, 2001, 11:31 PM
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...and Fred: I'll try and be there....
Just don't expect too much...it's just a little fan unit that doesn't produce a lot of power...
I won't be bringing a plane since I still don't have an AMA license

Bernie
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Old Aug 04, 2001, 11:55 PM
DNA
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Bernie,

Now you've really got my interest peeked!
Any chance you could sometime post some
detailed instructions on how you go about
making an EDF from glass fiber?
Do you use a mold?
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Old Aug 05, 2001, 03:12 AM
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Vacaville, CA USA
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Well...I'm going to make a mold for the final blades but for now (since I'm testing viability) I just cheated...I used the innermost part of a CAM 5x5 speed prop, put some packaging tape on it, waxed it up and put 3 layers of 4 ounce cloth on it...soaked it with CA and let it dry...then you pry the pieces off and cut them to size.
The hub is made out of layers of 1/16 balsa (little pieces that are glued on top of each other with the grain always advancing from one piece to the next..then sanded to size with a drill. The stators are also made with the aid of a prop -- this time a CAM Speed 9x5 slowflyer prop. For the shroud I used a bottle of Body wash that happened to have the right diamater...just wrap several layers of ceran wrap around and then the cloth, then soak with CA...this way, when you pull on it it comes right off because if it doesn't want to slide off and you pull hard enough you are unwrapping / pulling the ceran wrap of the bottle....
For the inner part around the motor I used the tube that fine electrical solder comes and wrapped glass around that...it's an almost perfect fit.

For testing purposes this procedure works really well since it doesn't require much time...I can produce a rotor in an hour or so.


I'll keep you posted...


Bernie

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Old Aug 05, 2001, 03:30 AM
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Hmm...3 blades at 45 degrees are not enough -- thrust is quite a bit lower (just finished a test run)...
Since I don't think (actually I'm sure of it) that the little motor can handle 6 blades at the 41mm diamater at a decent pitch I'll try 5 blades next....we'll see what that does.

Bernie
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Old Aug 05, 2001, 11:07 AM
DNA
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Bernie,

Very clever Bern, I may give it a try.
Do you just cut slots in the balsa hub and
glue in the blades?

Which CA are you using?
Does it come in 1/2 gallon sizes?

Would a picture of an impellor made
for gas fans help you any?
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Old Aug 05, 2001, 11:39 AM
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Adding blades will do little for improving thrust. For a given diameter the only way to increase thrust is to increase the velocity through the fan. Adding more blades won't accomplish this but adding more pitch will.

Greg
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Old Aug 05, 2001, 06:40 PM
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DNA,

Yep...I just cut into the hub about 1/12 of an inch or so and glue the blades in...and you don't need a lot of CA (I use the medium thick kind)...I might have used 1/5 of an ounce at the most....


Hi Greg,

Using more than 50 degrees at the root? Hmm...I might try that but I will have to decrease the width of the blades first since the wide blades require a smaller design lift coefficient...

By going to 5 blades the power consumption should increase (I think I need to pull a little more on 7 cells)...if I'm at 10 watts in with the 3 blade I should be around 17 with the 5 blade...

I might have to go to a different motor with a higher KV but first I'll hook the EDF up to my car battery (since I don't have a 10 cell battery)to see what happens


Bernie




[This message has been edited by berniep1 (edited 08-05-2001).]
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