Fan unit with drive shaft? - RCCanada - Canada Radio Controlled Hobby Forum
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Old 04-03-2009, 06:40 PM   #1
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Fan unit with drive shaft?

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Has anyone experimented with a fan unit that has a short drive shaft? I was thinking that if you could move the engine a little way from the fan and stator, you could cowl it in and make it more streamlined. The real Jets tail pipe exit hole size is very critical, many use segmented strips to tune the jet. Is there some kind of formula for fan size and tail pipe exit size.

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Old 04-03-2009, 06:52 PM   #2
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Re: Fan unit with drive shaft?

Well, considering glow ducted fan is all but dead, and you can't really get more streamlined than the EDF units are getting, I can't imagine what additional gain you might get by doing this. With all the testing that both Jet Model Products and BVM did with fan units and glow engines, I'm sure if there was a better method they'd have found it. BVM had a piece that was designed to fit behind the cylinder head of the engine to streamline the airflow and also perfected (or as close as anyone ever got) the idea of area ruled ducting.
The EDF stuff has the motor with a nice fairing all directly behind the center of the fan, can't see moving it back with a drive shaft being any more efficient for sure.

Just my thoughts though
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Old 04-03-2009, 08:25 PM   #3
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Re: Fan unit with drive shaft?

Hi Kip

Like Jeremy said, BVM has pretty much got the system tuned to the max. BVM had a fellow do aerodynamic studies on the design. He used something called the Area Rule to keep the air moving smoothly around the engine. As you said, exhaust exit diameter is critical to the system performance, even more so than the turbines. Unfortunately, except for EDF, ducted fans are all but dead.

Ed Miedzybrocki
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Your Canadian Jet Source for BVM, Festo, Fei Bao, Robart, JetCat, Jersey Modeler, Skymaster, Graupner Modelbau and more coming...!!!
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