EDF Afterburner Saturday, February 1st, 2014 posted by RCExplorer - David Ever since my friends Christian, Susan and Peder took me to my very first air show I have been in love jet airplanes. They sound so amazing. I clearly remember the first time I saw a JAS-39 Gripen taking off with full afterburner. It sounded like the rumble of thunder, so loud that I could feel it in my lungs. The tongue of fire licking the runway is a sight I will never forget. Ever since I’ve wanted to have a rc plane like that. But the price, safety issues and space needed to operate a turbine engine is not something that appealed to me. So I tried Electric Ducted Fan models, which can have a pretty cool sound if setup properly, but they don’t make that noise nor can they shoot flames… Or can they? This is my journey to discover if I could add an afterburner to an EDF model. This is the plane I chose. A Durafly De Havilland DH.100 Vampire. Maybe not the most obvious choice for an afterburner. But, there was an experiment to add an afterburner/reheat to a vampire back in the late 40′s.
this article made by david windestal(rcexplorer.se). He is professional on electronics. this article can be literature for someone who love RC airplanes to make something crazy. You can find the video on youtube on flitetest ch or rcexplorer ch. This artcle show how to make a model of afterburner. Afterburner usually work on a military jet aircraft and the function is add more energy for some seconds to make a manuver or increasing speed.
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EDF AfterburnerSaturday, February 1st, 2014 posted by RCExplorer - David
Ever since my friends Christian, Susan and Peder took me to my very first air show I have been in love jet airplanes. They sound so amazing. I clearly remember the first time I saw a JAS-39 Gripen taking off with full afterburner. It sounded like the rumble of thunder, so loud that I could feel it in my lungs. The tongue of fire licking the runway is a sight I will never forget.
Ever since I’ve wanted to have a rc plane like that. But the price, safety issues and space needed to operate a turbine engine is not something that appealed to me.
So I tried Electric Ducted Fan models, which can have a pretty cool sound if setup properly, but they don’t make that noise nor can they shoot flames… Or can they?
This is my journey to discover if I could add an afterburner to an EDF model.
This is the plane I chose. A Durafly De Havilland DH.100 Vampire. Maybe not the most obvious choice for an afterburner. But, there was an experiment to add an afterburner/reheat to a vampire back in the late 40′s.
Unfortunately it never go to take off as the resonance created by firing the afterburner made the booms and fuselage shake so bad that it was deemed too dangerous to fly. I love the vampire and I couldn’t think of a plane more worthy of having a working afterburner.
The stock EDF unit out in the wild. Nothing wrong with it and it seemed quite straight forward to add the flame holder and e-flux ring to the back of it.
To make the flame holder I used 30 gauge (0.3mm) thick galvanized steel I got from Lows.
I chose to use butane for fuel as it’s easy to get, has a great burn but yet is relatively safe. Igniting it is the though bit though. I chose to try a hotwire coil first.
Nicrome wire is almost impossible to solder. So in order to get a good solid connection between the nicrome wire and the the power wires I did this little trick.
IT WORKS! Kind of… I had some real trouble getting the hotwire to work properly. When the EDF is running it cools the hotwire down so much that it’s not hot enough to ignite the butane. But if the hotwire is shortened, which means it gets hotter, it can ignite the fuel but immediately burns up after ignition due to the massive temperature difference inside of the flame holder tube. I’ve seen others use the hotwire method on smaller EDF units with success but I came to the conclusion after a lot of experimentation that it simply doesn’t work on a 70mm fan. So I tried another method…
It works by simply stepping up the voltage from a 4s NiCd battery, which happens to be 5V. As soon as the flyback generator gets the 5V it starts outputting the ~30,000V
As soon as the RC channel the switch is hooked up to goes from low to high it opens up the output. In this case it just lets 5V through to the flyback generator from the stungun.
As soon as the RC channel the switch is hooked up to goes from low to high it opens up the output. In this case it just lets 5V through to the flyback generator from the stungun.
Since there is going to be flames shooting out the tail pipe I though it would be a good idea to add a layer of protection in form of a aluminium foil. This particular one is copper colored on one side, which I think look pretty cool.
To regulate the the flow of butane I added a limiter in the form of a small tube. I simply squished it in the middle until I got the optimum flow of butane.
The Swedish air force had 70 Vampires in service up to 1952 when it was replaced by the J 29 flying barrel. Naturally I just had to repaint this vampire in the Swedish colors to honor my comrades.
One of the servo wires had moved to close to the stungun wire and it arced over to the negative wire, passing through the receiver, which made it freeze up. I panicked and pulled the battery, thinking that the servo would stop pushing on the butane flask. But the servo had moved to far forward and locked on in the on position.
Went out to test fly it, but I ran into some trouble. The cold weather made the butane stay liquid for too long and made the combustion unstable at higher RPMs.
The butane now has to travel a much longer distance before getting to the e-flux ring. That gives it time to heat up and make the transition from liquid to gas form.
To make it work in really cold weather I stole a nicrome wire from a RC car tire heater system and wrapped it around the coil.
Then I insulated the whole thing with foam. Plugged in to the main 4S lipo it gives about 16W of heating power, which is plenty for this application. Now time to fly!