Mike06659

Just a thought fellas. I was wondering if Old School DF technology may get a second chance with the new breed of gas engines coming to market or if a company would possibly develop a fan around these engines. You may ask why, with EDF and turbines? Gasoline DF would be in the middle of the road. Not as fast as turbines or some edfs but would have great flight times and could be fairly well priced if they ever came to market and your still flying a jet!

Example: http://www.towerhobbies.com/products.../osmg1515.html

What are you thoughts? Never, maybe?
Mike

lrb75

My Feedback: (12)

Hmmm. Needs to be rear exhaust. Needs to double max rpm to about 24,000. Needs to make about 5-6hp. Edf is better and more reliable.

dubd

I can't see gas DF becoming popular. They'll sound terrible and be a PITA to tune. EDF is much more flexible with power systems, no tuning, and they sound better.

grbaker

My Feedback: (29)

As Irb75 has pointed out gas engines do not turn nearly enough RPM. I built my grandson a JMP Starfire IIb with an OS .91 VRDF and a Dynamax fan. It's a ball to fly and I don't have to take all of my turbine support stuff with me. Thinking seriously of building my JMP F-4 Phantom with 2 OS .91's and Dynamax fans. Then we can really make some noise.

Mike06659

That was my concern if they could make enough power even if they were purposely build for DF. The idea of 4min EDF flights has always turned me off to bigger EDF jets. I love my turbines but thought maybe this would be somewhere in the middle.

As for tuning, that Evolution SureFire fuel injection technology would have to be incorporated and then we might have something.

dubd

With turbine prices coming down and the ability to use diesel, why would anyone bother with a gas DF? Seems like nearly a wash from a cost perspective.

roger.alli

Nice thought but I doubt if any manufacturer would be bothered to produce a special gasoline engine for DFs.

The old IC DF engines where VERY hi performance motors and ran close to the ragged edge. Methanol based fuel has a lot of benefits for high performance two strokes, and I doubt if you could get the power and reliability out of a gasoline engine..

I am going to start a one man renaissance myself, with a BVM Mavrick and this little gem which I picked up NIB. Unlike Dubd, I just LOVE the sound of these diving wide open out of a split S..

SECRET AGENT

My Feedback: (18)

Bring back glow DF!? I'm all about fond memories and all, but really? Do you not remember the oily mess, the vibration, the blown glow plugs, the tuned pipe o-ring issues and the meager thrust? No thanks. Viva technology!

Mike06659

Yeah I know. I hated glow fuel soaking my planes but that would be another advantage of gas. No mess. I guess I will have to stick to my turbines

SECRET AGENT

My Feedback: (18)

I'm more interested in tiny, affordable, turbines. Very useful and way cool.

roger.alli

I Know, I know. I don't expect it to be a big renaissance.

I just have fond memories, which are probably well and truly misted by the passage of time!! But it will be unique on the flight line.

CafeenMan

I'd look at gas ducted fan because of a couple issues with turbines.

I can't afford to own turbine planes. I don't want to mess with the waiver requirements. I doubt that's a big deal actually - I'm not even sure what they are - so many hours with a 100+ mph plane or something like that and signed off by an AMA designated person?

Mostly it's the costs and then the very short flight times. The flight times are also my issues with electric planes which would be my choice for jets. They're also expensive but nearly the cost of turbines. I've looked at various models and too many of them are foam. But at least there are a lot of composite models that can use electric fan units.

I have to wonder if a gas ducted fan unit will be able to turn the RPMs necessary to get really great performance. What I like about the idea is the reliability of gas engines vs. glow. I never got into glow ducted fan because if there was ever a black art in this hobby that was it. Blown plugs, keeping an engine running, connecting rods punching through crankcases, etc. Once you mastered it you were golden, but getting there for a lot of people just never happened. But back in the day watching a plane flying by a guy who knew his stuff was the greatest.

So yeah, I'd love to see a gas ducted fan setup. That would be perfect for guys like me who can't afford turbines and want longer flight times than electric.

bikecrasher

TO develop a gas/spark ign engine for ducted fan would be more expensive than a turbine. First of all the rpm needed you would need will have to be a two stroke, Then to be reliable probably some flash carb or injection to make it tractable through the whole rpm, massive compression plus crank case pressure to match. with all this power you will need a large cylinder head to provide the cooling what then becomes drag in the thrust tube.
But still I can imagine a direct injected two stroke with 14 to 1 compression short stroke with a supercharged bottom end forcing boosted charge into the combustion chamber then screaming out the back of a un muffled tune pipe at 30,000rpm ..
even sweeter in a high performance pylon style of racer.
It could be done though...with todays cnc technology.. and metals available to Joe public!!!

roger.alli

Cooling would be the main hurdle. As it is with any high performance engine.. High performance Methanol IC engines actually use a lot of fuel simply to cool the piston crown and stop it melting. Gasoline is no where near as effective as a coolant as Methanol. Which is why all the really high power piston engines use alcohol based fuel.

I don't think that there will ever be a resurgence in piston powered fan units. Turbine and brushless motors are so easy and reliable. Plus the cost of a small to mid size turbine is not a lot more than we used to pay for a top of the line DF and motor, such as the BVM 91R/viojet unit. And a turbine is about 1000 times easier to operate..

But I still love the sound.

CafeenMan

I can't see these engines costing as much as turbines. Maybe. I don't know enough about them to have an informed opinion. I seriously doubt they'd use as much fuel as a turbine though. Obviously they're going to use a lot more fuel than a gas engine with a prop that's turning 7K RPM.

wnewbury

this is probably not realistic but could gears or a belt drive be used to get the extreme rpms needed?

LGM Graphix

My Feedback: (22)

I do miss the old Ducted Fan sound and smell. hahaha, for comic relief, here's an old BVM A4 that I bought a few years back with an OS46. This was the first and only flight I had with it, then I sold it LOL. If I could find a good ducted fan jet though I'd still have one haha.
http://www.youtube.com/watch?v=3J03cQmUP70

Jamie C

I still fly a Jim Fox Viggen I picked up second hand, OS 91 with a BVM pipe and a Rantec fan. I love flying it despite many who I fly with thinking I am weird!? I have a few BVM engines and fans that I have collected, a couple are unused and will remain so as they are lovely pieces of engineering. When I turn up to a meet with the Viggen, the first question I get is . . . Why?? I can only fly it at a handful of venues as noise is a problem. Noise is one reason why I don't think they will make a comeback and with EDF as good as it is although quite costly, it is much more reliable and obviously lacks the mess generated by ICDF.

I still want a full house BVM ducted fan such as an Ultra Viper or Aggressor 3 . . . . One day!

hmjets

why not something like this??

https://www.youtube.com/watch?v=ydm5Ap4-S7Y

TimJ

It never worked well 30 years ago, It surly will not do much better now. The engines do not turn enough RPM to have any performance.

popargr

imagine a gas engine mated to a geared fan

ravill

My Feedback: (11)

I do not miss the ducted fan days. Way too much pucker factor for me!

DJH

I still have all my BVM ducted fan stuff and continue to fly them. Turbines are out of my price range. I plan to keep flying them until I run out of parts and then plan to go electric. Gasoline ducted fan just doesnt seem feasible.

dbsonic

My Feedback: (3)

If you want a cheap DF model that is an absolute blast to fly, this is the greatest fun for the money. Decent flight times too:

http://www.horizonhobby.com/umx-habu...ology-eflu4450

ron Sweeney

We still fly icdf at our club occasionally........nothing like it...........currently building a JMP Starfire for Ramtech / os 91. Believe me they are not slow! people have forgotten how fast the good ones flew. Ron.