Doblhoff WNF 342

[PTKay]

http://www.aviastar.org/helicopters_eng/doblhoff_wnf-342.php

he last machine (V4) had a second propeller mounted co-axially to provide thrust for forward flight when clutched to the compressor motor. Thus, by gradual development, the rotor jets (which had a high fuel consumption) were only used for take-off, hovering and landing, and the rotor blades turned by autorotation for forward flight in the manner of an autogyro.

[PTKay]

It eventually fell into American hands, Doblhoff later accompanying it back to the United States to assist with further tests before joining McDonnell to work on development of the XV-1. Stepan, who had done most of the test flying on the WNF-342, joined Fairey in the United Kingdom after the war, while Laufer went to work for the SNCA du Sud-Ouest in France.

...where Rotodyne and Dijin were born.

Nothing new under the sun.

[C. Beaty]

The Doblhoff machine ended its days at General Electric’s Schenectady, NY Research Center where it was destroyed in a ground resonance accident, severely injuring the pilot, Igor Bensen.

[PTKay]

The Doblhoff machine ended its days at General Electric’s Schenectady, NY Research Center where it was destroyed in a ground resonance accident, severely injuring the pilot, Igor Bensen.

World is small.

Around gyroplanes you hear again and again the same names...

:)

[C. Beaty]

The World is made small by modern communications; those geostationary satellites 22,000 miles above the Equator.

[XXavier]

It eventually fell into American hands, Doblhoff later accompanying it back to the United States to assist with further tests before joining McDonnell to work on development of the XV-1. Stepan, who had done most of the test flying on the WNF-342, joined Fairey in the United Kingdom after the war, while Laufer went to work for the SNCA du Sud-Ouest in France.

...where Rotodyne and Dijin were born.

Nothing new under the sun.

Well, considering the numbers built, the Djinn = جن = genius was unique as the only successful two-place rotor-gas reaction that reached production stage. To my knowledge, no other similar helicopter did ever go beyond test/prototype stage, The جن did...

Regards

Xavier

[C. Beaty]

It’s not that tip jet propulsion doesn’t work, Xavier; it works very well. Pressure jets, pulse jets, ram jets all work. The Russians even mounted small turbojets at blade tips on at least one experimental helicopter.

Tip jet propulsion is so inefficient that it is not economically viable.

[karlbamforth]

I agree Chuck, but then the gyro is not really efficient either but ppl like to fly them.

Do you not think that a 2 place tip jet would have a place in the sport pilot market just like the gyro ?

Cheaper than regular heli to build and maintain.
Easier/safer to fly than a regular heli.

It would never replace the Robinson but for all those gyro guys who want VTOL this would probably work.

[C. Beaty]

I don’t know, Karl, your guess is as good as mine.

Most people don’t like to stray too far from established patterns, with piston and turbine engines being the norm.

Eugene Gluraheff, a former Sikorsky engineer and inventor of a pressure jet that used superheated propane to operate a dynamic compressor (similar principle to a steam jet ejector), sold plans and partial kits for tip jet helicopters for a number of years, but without much success.

http://www.tipjet.com/emg_bio.htm

[Cita]

Eugene Gluraheff, a former Sikorsky engineer and inventor of a pressure jet that used superheated propane to operate a dynamic compressor (similar principle to a steam jet ejector), sold plans and partial kits for tip jet helicopters for a number of years, but without much success.

http://www.tipjet.com/emg_bio.htm

Chuck,

the lack of succes with the Gluhareff G2-8 engines was his own fault.Eugene was so afraid of giving away his secret( which he probably could not protect by patent law) that he left out crucial information in the construction plans package so none of the engines delivered the claimed thrust.
A Canadian firm invested a lot of money to discover the secret that Eugene took with him in his grave.
I once made a G2-8-20 engine per the plans and other than a good propane burner and hand warmer,as a thrust engine it was worthless.

I think it all comes down to what amount of effort and money is "one" prepared to invest in solving a problem.
The billions of dollars invested over the years in piston and turbine engines have made these engines to what they are today,reliable-efficient-"affordable" power packs.
If the same amount of money was invested in the tip jet technology than I'm sure that there would be some breathtaking VTOL's hopping around today.

Just my two cents

Cita

[C. Beaty]

Yes, Gilbert, but there’s no way of making power equal anything except thrust x velocity. A turbine wheel with blade tips traveling 3x as fast as rotor blade tips delivers 3x as much power for the same fuel burn.

On the other hand, fuel economy for a hobby helicopter is not especially relevant.

Perhaps the biggest problem is noise. It’s not very pleasant to be within earshot of a Gluraheff jet running full bore.

Another problem accrues from big lumps attached to blade tips and the effect on autorotation.

In one phase of the studies of the Doblhof helicopter at GE, the rotor was mounted on a dynamometer* to measure cold power consumption. Bensen found that by fairing in the exhaust nozzles with wooden plugs, power consumption was substantially reduced. I don’t recall the amount; I have a copy of the paper that was published in a scientific journal but can’t lay my hands on it in this rat’s nest.

*The dynamometer was a Kellett XR-3 jump takeoff Autogiro that had a 100 hp prerotator and torquemeter.

[Cita]

Hello Chuck,


I agree of course that we cannot beat the laws of nature and that power =thrust X velocity but what I meant was that for example the engine of the Wright brothers was basically the same as a modern Rotax but the efficiency of both engines could not be further apart due to the cycle of developement.

The Doblhoff is a rotorcraft with a 70+ year old history compared to modern standards.

I know from experience that the Gluhareff was a "pain in the ear" to work with and was so bulky that autorotation does not even come into consideration.

The fuel economy of a modern helicopter engine, a piston or turbine, can not be beaten by any form of tip jet power but as you said: for a sporthelicopter fuel economy is not the geatest burden but things as noise probably are in our todays society.

On the other hand,the simplicity of a tip driven rotor is hard to beat !

As we slowly enter the limits of development of our existing enines,maybe the tip jet driven helicopter can start a new life in a not so distant future.

regards,
Cita (Gilbert)

[Bruno]

I don’t know, Karl, your guess is as good as mine.

Most people don’t like to stray too far from established patterns, with piston and turbine engines being the norm.

Eugene Gluraheff, a former Sikorsky engineer and inventor of a pressure jet that used superheated propane to operate a dynamic compressor (similar principle to a steam jet ejector), sold plans and partial kits for tip jet helicopters for a number of years, but without much success.

http://www.tipjet.com/emg_bio.htm

Off-topic perhaps, but the Gluhareff engine has been reverse-engineered (by the Canadian company Gilbert mentions, Conception GLC Inc.) and found to be but a sub-species of valveless pulsejet. In other words, an acoustically-driven intermittent combustion jet. No wonder it's noisy.

If the noise problem could be beaten, a valveless pulsejet (of the Gluhareff or any other persuasion) would be a fantastic powerplant for cheap fun applications. It is the simplest, cheapest and arguably the most reliable engine ever. Not particularly efficient, true, but then, it can run on absolutely any flammable liquid (or gas) you care to mention. If will easily run on used frying oil, for instance. Or anything else. Compressed cow farts.

[XXavier]

It’s not that tip jet propulsion doesn’t work, Xavier; it works very well. Pressure jets, pulse jets, ram jets all work. The Russians even mounted small turbojets at blade tips on at least one experimental helicopter.

Tip jet propulsion is so inefficient that it is not economically viable.

Sure that have been the reason only one tip-propulsion helicopter went beyond prototype stage. And that helicopter was precisely the Djinn, which, as a cold-jet tip propulsion was not typical.

The performance of the Djinn was reasonably good and comparable with contemporary, more conventional (and complex) helicopters of the same size and power:

Crew: Two
Rotor area: 95.03 m²
Empty weight: 360 kg
Gross weight: 800 kg
Powerplant: 1 × Turbomeca turbo-compressor, 240 hp
Maximum speed: 130 km/h (81 mph)
Endurance: 2 hours 15 min

Unique, perhaps, but the fact remains, however, that a machine like the Djinn has never reappeared.


Rgds

Xavier

[C. Beaty]

Xavier, one of the German scientists rounded up by the US Army in Operation Paperclip immediately after WWII to keep the Russians from getting them, Bruno Nagler, was a cold jet proponent.

Mr. Nagler’s last projects were hobby helicopters. I have a video tape of one of his cold jet helicopters powered by a small gas turbine that had impressive performance.

His final project was a cold jet helicopter powered by an OMC V-4 outboard engine driving a centrifugal compressor.

Here’s a link to some pictures:

http://www.rotaryforum.com/forum/showthread.php?t=8677

[karlbamforth]

It looks like Pegasus hlicopters are already working on it.
I believe this is the result of Nagler's work.

http://www.sinocast.com/release-print.jsp?id=23

About the PH-200PJ Helicopter
The PH-200PJ Helicopter is a low-cost, easy and safe to fly, two-seat helicopter that uses pressure jet technology. The helicopter's simplified design significantly reduces the number of parts used compared to a conventional helicopter. Most notably, the PH-200PJ Helicopter has no tail rotor and therefore no tail rotor gear box, tail rotor drive or tail boom. Likewise, it has no main rotor drive system or complex transmission for the main rotor. It will be supplied in both kit and fully assembled forms.