So what's it going to be, Dynamax, Ramtec? Yes there is a couple of other out there to. Turbax, Byron, Kress, Hurricane, ThorJet that come to mind (along with some electric ducted fans). We will stick to the basics here and concentrate on Dynamax, Ramtec and BVM. Why, because I own 4 Ramtecs, 1 Dynamax and 1 BVM, that's why. Many people will ask wich one is better and to tell you the truth, it depends in the airplane you are going to install it into. Ramtec requires bigger inlets than a Dymanax (required to suck in more air)BVM requires precise inlet design in order to get the max RPM. out of all the best one has been proven to be the BVM. I didn't say it was the cheapest, but the best. A BVM Engine, Fan and Pipe will set you back $1000.00. In the other hand a Dynamx/Ramtec with an O.S. .91 and Pipe will come out to $600.00.
Mounting instructions come with every Fan unit and they are not a big deal, but how to hook up your throtle should be. Here is where many have a hard time at first while trying to figure this out. I have have not done them all, but I will list the ones I have. like installing the servo two feet away from the engine or gluing the servo directly on the Fan or shroud.
So what exactly powers our planes? Well they are basically two stroke, internal combustion engines mounted to a fan inside the fuselage. You can't really see the engine from outside the plane so it gives it a realistic Jet Look. The sound of course is a lot different but hey it does the Job.
First is the most popular Ducted Fan work horse in the world. O.S.91 Rear Intake, Rear exhaust.Picture two is the O.S. 91 with the Ramtec Fan Housing next to it. Picture #3, Yep it does have a propeller, well sort of. It is called and Impeller. Picture #4 is the Ramtec Fan Housing again. Those things you see going from the outside into the middle are called Stators and they serve to "Guide" the air the impeller sucks in. The air will form a circle through the thrust tube. That little pipe nipple you see at the top of the Fan is for Impeller pressure. You can have pipe pressure (goes into the fuel tanks just like any other two stroke engine) or Pitot pressure as it is called. Picture #5 is a Ramtec Fan next to a Dynamax fan. THey are both the same size but the pitch of the impellers are different. The other difference is the number of stators, Ramtec has 10 stators while Dynamax has 16.
Next Couple of shot's show you how I installed the Engine to a Dynamax Fan used for my Byron MIG 15. Note the metal tab used to mount the Fan to the Airframe. The engine is mounted into the fan with four bolts. wholes are pre-drilled on the engine and also on the fan. The fans already come with blind nuts installed to mount the engines. One of the hardest things about installing a Ducted fan and engine is the Throttle. Note the Golden Rod method I used. Remember the Carburator is on the back of the engine and you got a impeller spinning at least 15K rpm. Throttle cables must be drilled trhough the fans or find other creative ways to install linkage. Picture #2 also shows the Throttle cable again. If you look closely you can see that I disconnect the Throttle servo control horn to remove the engine. This will allow me to keep the same Throttle settings without having to paly with it once I mount it back into the Jet.The Purple thing you see installed on the top is a BVM In-Flight Needle mixture valve. Set on a seperate channel you can control how rich or lean your engine runs in the air. Picture#3 is just another view of the same, but it also shows you the fuel tubbing from the In-Flight Mixture to the Carburator
Pictures of a BVM Engine and Fan coming soon. (yep I got to remove it from the Plane just to take the pictures.)
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Ralphs@pcmagic.net.