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Old Oct 05, 2012, 02:48 PM
turbonut's Avatar
upland CA
Joined Dec 2004
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It has been done but weight is always a problem..even with a belt drive..if you were to do it as an experement dont use the clutches you dont need them..the other problem is if you dont match the fan design to the power curve of the motor it will never get "on step" and wont make enuff power to fly let alone fly fast
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Old Oct 05, 2012, 03:40 PM
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United States, OH, Fairborn
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Quote:
Originally Posted by turbonut View Post
It has been done but weight is always a problem..even with a belt drive..if you were to do it as an experement dont use the clutches you dont need them..the other problem is if you dont match the fan design to the power curve of the motor it will never get "on step" and wont make enuff power to fly let alone fly fast
yea it all sounds kinda complicated, was kinda thinking by leaving the clutch on the motor that would give me a little safty on trying to figure out how to match the fan size to the motor. i got quite a few size fans and motor types to play with..ive never played around with a belt drive idea....i might consider tryin it also..

just need to figure out how to connect everything and get a parts list made up..

if anyone can point me to a link or anything on the topic id be greatly appreciated.. : )
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Old Oct 05, 2012, 04:14 PM
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United States, MN, Hermantown
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How will you cool motor?
How will you start it?
Exhaust?
Alignment of mutiple shafts? Bearing Blocks?
20%-30% nitro fuel--will it melt foam?
Engine will need to exceed that of both electric motors combined+ extra for lose due to friction in shafts, bearings, belts/gears.
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Old Oct 05, 2012, 05:01 PM
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United States, OH, Fairborn
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Originally Posted by CoolerByTheLake View Post
How will you cool motor?
How will you start it?
Exhaust?
Alignment of mutiple shafts? Bearing Blocks?
20%-30% nitro fuel--will it melt foam?
Engine will need to exceed that of both electric motors combined+ extra for lose due to friction in shafts, bearings, belts/gears.
the motor will be out of an rc truck ( k4.6 out of a savage ss 1/8 scale)
pull star tor roto start i got 1 of each if i need to save the weight..

will be air cooled with the tuned pipe routed somewhere? lol that will be the easy part..

yes fuel would definatly eat some foam..i will be making a mold out of the main body and making a composite hull ect.

getting all the connections figured out is what im working on now....
what would be the litest way to connect the fan blade to the teeth on the cluchbell....
basicly i need to attach 2 spur gears too 2 shafts and line them up on the cluchbell..doing it this way tho the fans could only go directly behind the motor...

i thought about using the flex shafts that are in the rc boats for a wider placement option on the fans......

for me the hardest part will be attaching the spur gears to the driveline..after that just need to fabricate a plate to mount everthing to keep it rock solid for testing.....: )
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Old Oct 05, 2012, 06:38 PM
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whipped it up real quick and dirty not to scale just to show
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Old Oct 05, 2012, 11:22 PM
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Don't you need counter rotating fans for that set-up?
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Old Oct 05, 2012, 11:40 PM
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Originally Posted by CoolerByTheLake View Post
Don't you need counter rotating fans for that set-up?
i was looking at that after i made the sketchup lol

do you think torc roll would be an issue with the edf's?

im new so im not sure..
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Old Oct 05, 2012, 11:56 PM
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United States, MN, Hermantown
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I am really not the one to ask, EDF's are pretty new to me also.

Here's something to think about. Machine work. You are going to need shafts made, keyed, splined, or what ever your method. I had checked last fall on some work, and the machine shop rates were somewhere around $75.00 hr.


What is your reason for considering this new approach? Just battery placement/CG?
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Old Oct 06, 2012, 12:07 AM
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Originally Posted by CoolerByTheLake View Post
I am really not the one to ask, EDF's are pretty new to me also.

Here's something to think about. Machine work. You are going to need shafts made, keyed, splined, or what ever your method. I had checked last fall on some work, and the machine shop rates were somewhere around $75.00 hr.


What is your reason for considering this new approach? Just battery placement/CG?
no reason for doing it other than it was an idea i had...for the 5mm shaft i was thinking about using rc boat 5mm flex shafts that would be braced at points with berrings and suports...i can get 2 shafts for less than 20 bucks...ill keep them short as possible to reduce vibration and weight........

kinda seemed like an easy rig if i had all the little stuff..but trying to get these to counter rotate or feed a belt around would probly melt my brain lol
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Old Oct 06, 2012, 12:22 AM
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United States, MN, Hermantown
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OK , How are your going to separte the shafts far enough apart to be centered in the shroud units and still some how conected to the motor?
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Old Oct 06, 2012, 12:40 AM
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United States, OH, Fairborn
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the boat shafts can bend and still rotate kinda like the shaft in a weed eater has the bend.....basicly the same idea here...

i thought about a belt drive idea but not sure the teeth on the belt would hold up under torc.....or im afraid it would just slip off......

if i was to go with a blet type of idea i would use the sprocket and chain out of a gas rc motorcycle there real small but look like they got some grip lol
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Old Oct 06, 2012, 01:05 AM
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United States, MN, Hermantown
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You have your work cut out for you! Best of luck!
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Old Oct 06, 2012, 05:07 AM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
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The correct spec toothed belt would hold up ok,flanged pulleys would prevent any side slip,but the train needs to be spot on,ie every thing lined up and securely held.Twin pulleys on the drive shaft,belt to each fan.You could use a single double sided belt,even set it up to contra rotate,but that would mean idler pulleys and a complex belt path.Only advantage is it would be easy to install a tensioning device.
I'd advise against flex shafts at these speeds,get every thing lined up and use intermediate bearings.
Regards Stuart
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Old Oct 06, 2012, 06:31 AM
Da' Cajun
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Lake Charles, Louisiana
Joined Jun 2009
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The fans will spin in the same direction if set up like you have them in your drawing. No need for counter rotating rotors.

Right now you have a reduction gear drive train. Fans would never spin fast enough to make any appreciable thrust.

Long drive shafts tend to vibrate. High RPM's would only make it worse. ...and EDF's need high RPM.
Flexable boat shafts would be even worse.


This design would only be a Rube Goldberg exercise in futility. A very heavy exercise in futility.
If there was any advantages to this type of EDF, or any way it would possibly work, someone would have already done it.


I don't mean to sound so discouraging. On the contrary, you've build a really cool jet here. Don't waste that effort chasing a power system that will inevitably end up in failure.
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Old Oct 06, 2012, 06:50 AM
“Do it Right The First Time!”
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United States, MN, Hermantown
Joined Dec 2008
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My mistake on the counter -rotation.
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Last edited by CoolerByTheLake; Oct 06, 2012 at 07:12 AM.
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