hey guys.. just wanted to know that ... if i can use an engine in place of a motor in a duct fan!!
plzz leave back your comments!

sir check this link:

My answer to your question is NO because its designed for electric motor... talking about engine it has vibrations & definitely not as smooth as electric motor... so you need a duct thats specially designed for engines.

Quote from: sharlock on March 22, 2015, 08:47:54 PM
My answer to your question is NO because its designed for electric motor... talking about engine it has vibrations & definitely not as smooth as electric motor... so you need a duct thats specially designed for engines.

I guess sharlock meant ducted FAN and not just duct!

After seeing the video posted by shijin, you should see an electric EDF.

Only then can you make a meaningful choice.

The video shows you a 'nitro ducted fan unit' they were popular until EDF/turbines became the mainstream . You can still buy one from ebay , though i dont see a point in it (untill you are collecting) . An EDF unit will require alot of modifications which wont be recommended. 

Well.... to put things correctly.  YES nitro / diesel engines can be used for ducted fans.  The only question is that the engine should be able to handle the generally higher RPM of the ducted fan.
Well.... have seen a ducted fan model running of a Glow plug engine (OS Max) a long time ago with a friend of Sharma's who had come visiting him.  It was some 25 years ago.  That time the electrical motors were no where to be heard of. 
You may like to buy a glow plug engine which is capable of reaching RPMs of over 14000 and am sure it will be good for the ducted fan.  As far as the vibrations go.... it is the same for a motor or an engine..... though engines are made very rugged and can handle higher vibe with more ease.

Happy and Safe Flying....