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Dec 12, 2009, 08:14 PM
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Discussion

leaf blower fan for tip controls?


In another post somewhere the idea of using a leaf blower fan came up. I'm not really familiar with what/how the fan differs from EDF, but I do know it creates pressure not pure airspeed. That sounds like a centifigul pump to me.

The big question is can we use a small "pressure" fan to feed wingtip control jets? With pressure there aren't huge penalties for moving the air around like a EDF with a duct. Anyone have any thoughts?
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Dec 13, 2009, 01:02 AM
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RCvertt's Avatar
Quote:
Originally Posted by davidgp
...The big question is can we use a small "pressure" fan to feed wingtip control jets?...
For a Harrier I doubt you can get a centrifugal fan small enough to fit in a wing tip and still be effective. The only other place I can think of would be above the main engine. This would need an unsightly hole in the top of the model and the weight of the extra motor and fan may outweigh any benefit.

I'd like to see it tried though.

Quote:
Originally Posted by Googleplex
A lot of the toy RC hovercraft have a 1/2" tall centrifugal fan...
Nice idea. Would be interesting to see if this would create more pressure than straight bleed air.
Last edited by RCvertt; Dec 13, 2009 at 10:27 PM.
Dec 13, 2009, 08:35 PM
It's a really big number.
A lot of the toy RC hovercraft have a 1/2" tall centrifugal fan (about 2.5" in diam) that pumps a lot of air when attached to a speed 300 class motor. You could perhaps sqeeze one of them into the wing and have the spun air squeeze down to a small outlet.
Dec 14, 2009, 01:33 AM
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I have been thinking about this setup in the past and believe it could work. Ideally, I'd use a large box spar doubling as air conduit, and run the fan with a cdrom type outrunner driving the fan from the intake side, with the intake facing downwards to pick air from the scale intakes. This should keep things looking close to scale, and keep the outrunner cool as a bonus. Also, another conduit could be run to the tail to act as a pitch control. Naturally, you'd have to use valves on the tips or at the base of the conduits to control the jet, since the same fan would control all the tip jets
Dec 14, 2009, 11:20 PM
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motorhead's Avatar
I had thought about the hollow spar for my F_35 project but had not thought about a fan from a hover craft. Do you know of any place that would have parts?
Mike
Dec 14, 2009, 11:48 PM
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fish tank air compressors looks tempting !! Hard to find a lighter one with a useful psi rating though...
Last edited by numb_thumb; Dec 14, 2009 at 11:53 PM.
Dec 15, 2009, 01:55 AM
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larger disk = higher pressure. Also, angling the fins backward relative to the flow increases pressure and decreases volume. Small handheld vacuum cleaners could be a source, but you really want to look for a largish disk. you could probably build one out of balsa and plywood, like they used to do for the early homemade turbines. the fishtank pumps are way too inefficient to even consider, IMO


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