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Nov 20, 2003, 06:13 PM
Scratch fly,Scratch crash

EDF unit from scratch??


Has any one tried to build an EDF unit from scratch??
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Nov 20, 2003, 06:30 PM
Carbon fiber is our friend
Steve C's Avatar
Yes.

There were even articles in EFI on how to DIY.

What size are you most interested in?

Steve C
Nov 20, 2003, 06:34 PM
Scratch fly,Scratch crash
I tried a 540 motor and hand built aluminum fan. about 3.5" diameter. good thrust but plane was too little and too heavy. used 8x600AA (9.6V) pack. Using existing R/C car Electrics with a GWS-400E ESC. Any suggestions??
Nov 21, 2003, 05:05 AM
Registered User
Hy there, how much trust did you get out of it??
I build one myself too, but trust wast that good and current too high.
Look on the forum, you'll find a picture of it.
Nov 22, 2003, 03:31 AM
smug in granny panties
monkamarm2000's Avatar
yeah stay away from dangerous aluminum blades! and if you make them beefy enough to suit your purpose they will be too big and heavy. And those cells wont be enough to power that motor for a good prop even. But hey thats how we learn. A good fun cheap way to start is do a ducted prop. find a good 2blade prop that would suit the motor and cut 2 of them up, cut each blade off the center in a pie section, so four blades make the pie whole again, make sense? epoxy it together balance it and give it a whirl. loook up 540 motor prop selections on the net for good prop choice and account for the fact that you may have to compensate for 4 blades instead of two. This is long shot math but if 8x6 is the right prop, try 2 4x3 props cut up, or maybe the same prop works fine since it has four blades that equal the length of the 2 full size blades.

Barry
Nov 22, 2003, 10:41 AM
Scratch fly,Scratch crash
I tried the cup prop method. BAAAAD! results! I had a severe vibration that I couldn't fix. I even tried a Cox 3 blade at about 3" dia. Lots of rpm's, not enough thrust. The aluminum one worked well since it was cut from one piece. NO GLUING! Needs more R&D.

Ivan, Where about on the forum for that pic?
Last edited by scratchbildr; Nov 22, 2003 at 10:43 AM.
Nov 22, 2003, 11:14 AM
Registered User
https://www.rcgroups.com/forums/show...hreadid=160301
Here it is .
Have fun reading.
Nov 22, 2003, 01:01 PM
Carbon fiber is our friend
Steve C's Avatar
540 motor? I haven't heard that in a long time. You should really start with something better. I'm not trying to tell you to spend a lot of money, but you probably wont have much luck with a 540, even with a regular prop.

You can get a good ball bearing car motor for $19 and I've sold most of mine for half that. Keep an eye on the sale forum. Motors between 16 and 22 turns are quite usable. They're probably the biggest bang for the buck in electric motors.

There have been some planes flown with clipped props as mentioned. They need to be good thin props to start with. Those flexable Cox three blade props are not too good for anything. The two blade grey (stiff) props are much better. Look at electric props in small sizes too.

Oh, as far as vibration goes....No matter how you make it, you gotta balance it.

Dave Morris has had good luck making wood fans for small motors. This is how I started. You can make the whole thing with ply wood and my first ones didn't even use a lathe. I used a drill press.

Now I make most of the parts molded, but the hub is still ply wood.

Here's an old one powered by an AP29. It worked pretty well.

Steve C
Last edited by Steve C; Nov 22, 2003 at 09:08 PM.
Nov 22, 2003, 01:58 PM
smug in granny panties
monkamarm2000's Avatar
Steve is right, not only that but even put a regualr little prop thats too small for a 540 motor and see how little it puts out even at full size. I remember experimenting with even a hot car motor and a actual wemotec impeller along time ago, the wemo impeller even though it was a proper impeller just didnt have enough pitch to drag the motor into the power range that it wanted to be in. I think it pulled 50 wattts and just spun fast for a prop, which makes you think it should work, but for a fan you need some real RPM. And as a a good indicator, if you didnt seem to think it needed balancing you weren't spinning enough pitch at enough RPM. Thats why I like Steve's idea with a AP29, it will bwe much easier to find a sweet spot for it. And if I remember rightly, Steve has done some pretty cool homebuilt impeller stuff too

Barry
Nov 22, 2003, 08:16 PM
Scratch fly,Scratch crash
Thanx Monkawarm, and Steve. Good Imput!! Here is a pic of that jet and fan I created. (Front half of jet os no more!)
Nov 22, 2003, 08:32 PM
smug in granny panties
monkamarm2000's Avatar
oh yeah thats not gonna do anything, I think my wattage fan has more blades and pitch than that does, and it's for a speed 400. for starters dont bother with gas prop's there just not goona cut it. look at the APC electrics

Barry
Nov 22, 2003, 08:34 PM
Scratch fly,Scratch crash
Well the pitch is more than it appears, but i understand your advice.
Nov 23, 2003, 12:04 AM
smug in granny panties
monkamarm2000's Avatar
exactly, cause as it is that was a pitch for a full size prop not half of it. And for reference purposes my Wattage Fan rotor on a 400 acts exactly like a 4x4 prop on a 6V 400.

Barry
Nov 23, 2003, 01:04 PM
Scratch fly,Scratch crash
Nice scratch fan Steve. Is there a template? How heavy is it? Good thrust?


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