Ramjet helicopter

[Kakeman]

Well... I bought plans for helicopter like this

colored by myself :P

Check out the plans:
http://kotisivu.dnainternet.net/kaikjuk ... ePlans.zip

Many professionals have said that those plans are crap...
Blades fixing to aluminium tubes is going to fail when blade bends... and many other things are making it deathly :/

But idea is still working? How about those ramjets?
Would it be possible to build helicopter with under 1000euros?

[Anders Troberg]

I wouldn't fly in such a device, there are easier ways to kill yourself.

Some technical considerations:

* The stick, as far as I can see, will be working exactly the opposite as a normal stick, ie push it forwards to go backwards.

* How is the fuel fed to the tip jets?

* How long is that tank going to last?

* Will just a rudder be enough to counter the momentum from the main rotor?

* In the event of a crash, the pilot is completely unprotected under a large spinning mass with nasty edges, in front of a potentially explosive tank and with a hard beam right in front of his crotch. It could hardly be worse.

* There is no seat belt to prevent you from falling out of the chair.

* Is the construction stiff enough to not bend or warp? Will the constant vibrating load on the mast cause it to crack?

If you are going cheap and want something that at least has some helicopter characteristics, go for an autogyro.

[lucky rookie]

hello all
the rudder does not need to counter the rotor as the rotor is not powered through the main shaft in normal helicopters the tail rotor or fin is to counteract the torque from driving the rotors

for every action there is an equal and opposite reation

this is exactly like an auto gyro but instead of the oncoming air turning the prop they are powered by ramjets
and the controls have been used in self build helis for years its just technique
but with the fuel i agree bit worrying because it doesnt matter how much you flap your arms your not going to fly


i would most definatly have a go

[Anders Troberg]

the rudder does not need to counter the rotor as the rotor is not powered through the main shaft in normal helicopters the tail rotor or fin is to counteract the torque from driving the rotors

Even if there is no torque per se, there is still friction in the bearings and a rotating air stream that will create some rotation.

this is exactly like an auto gyro but instead of the oncoming air turning the prop they are powered by ramjets

It's very much different from an autogyro. The biggest difference is that on a helicopter, air is moving down through the rotor disc, while an autogyro has the air moving up through it. The only time they are similar is when the helicopter is doing an autorotation (which is one thing I would not like to try in this contraption).

i would most definatly have a go

I wouldn't mind trying one as a remote controlled model, but it is not fit to carry any live cargo.

[lucky rookie]

risk is assessed by the rewards it will bring

i dont remember what company made it but they created a back pack style copter and this worked well only thing was people never trusted it
if i had the resources i would have a go


anders my concern with the design is the tip ramjet itself the design looks so simple do you think it would actually have enough power to turn the rotors

im not so sure

[jthompso]

"High pressure fuel will be injected into the engine, creating a vacuum and causing air to be sucked in the air intake"

I have a hard time believing that you can start this rotor spinning from a dead stop--as far as you guys know has one of these ever been built? (I don't mean a tipjet helicopter, I mean specifically from these plans. The lack of photos makes me think that the author hasn't built one which diminishes my trust in the plans)

[Irvine.J]

From memory i'm almost sure i've seen pictures or videos of these things flying when searching on the Kilabrie or whatever it was called. I'm only recally from dark, far off memories but I think somewhere I did see a picture of it flying. Still, theres a first time for every nutter out there, just don't get yourself killed. This is exactly the reason aeronautical types keep pet monkeys :)

[Kakeman]

Helicopter with ramjets should have collective pitch controls... that one doesnt have those and making it super deathly :D
Because those engines cant rise RPM fast enaugh and when angle of attack can't be changed... engines fails easily and copter comes down like stone when autorotation is impossible :P

But what kind of effects changeing angle of attack can cause to ramjets? Flame go out?
Can those problems be dissabled with special inlet desing?

[Mr.B]

The fuelsystem in the "Kolibri", the dutch ramjet powered helicopter, had no fuel pump; it was using centrifugal force to force its fuel into the ramjets.......see if this works..

http://portal.omroep.nl/mplayer?mpstrea ... HELICOPTER

[Kakeman]

Is there some kind of ramtip angle changeing things on kolibri? so ramjet angle of attack is allways 0degrees?

[Viv]

On the subject of the engines.

The available heating area of the heat exchanger tubes is insufficient to convert the liquid fuel to gas at any thing near the flow rate required by even as simple an engine as this.

The tubes are threaded and locked to the ribs, differential heating and hence expansion will cause them to be under considerable stress and fail, bending out of shape is the smallest part of the problem, cutting threads in a high pressure tube is a no no!.

The outer skin of the engine (some what hot) fixed to the ribs (also hot) is constrained by the fuel heat exchanger tubes (some cold some warm one allegedly hot), differential expansion and warpage.

Engine is too short for the fuel to mix with air and burn, it takes time to do all that and the engine is just too short for it to happen inside the engine.

Chord length ram jets have been a holy grail for a long time and this is not one of them.

From previous research fuel pressures of over 700 PSI at a tip jet installation are not unusual.

I just noted this

"Make 2 spraybars from the 1/8â€

[Zippiot]

This is how I would approach a tipjet with the ramjet hidden inside

Distance moved is the gain

[Kakeman]

Hmm... it isn't problem to use better and bigger ramjets, works better and thats the main thing.
But can ramjets provide enaugh static trust to get rotor rotating? w/o pressured air?

[Viv]

Hmm... it isn't problem to use better and bigger ramjets, works better and thats the main thing.
But can ramjets provide enaugh static trust to get rotor rotating? w/o pressured air?

If I take your question as its put, then no a ram jet can not provide any thrust when it does not have any forced air flow in to the intake.

There is no such thing as a static ram jet.

Viv

[Zippiot]

A way to start these ramjet helicopters is to place a flaming oily rag in the exhaust and spin the rotor as fast as you can.

Messerschmidt made a linear valvless pj that could sustain ram operation, closest thing to static thrust ramjet.