Autogyro Rotor Tip Rockets
An autogyro - also called gyroplane - looks very much like a helicopter, but the rotor is not driven. It rotates freely. The autogyro is instead driven forward with the help of a propeller, like an airplane.
An autogyro needs to roll faster and faster on the field before the rotor spins fast enough in the wind for the autogyro to lift off. 100 meters or so of runway is needed for take-off. Many autogyros have a link shaft from the propeller engine and a cogwheel drive so the rotor can be pre-rotated before take-off. The take-off distance required is then shorter.
If the rotor is pre-rotated with tip rockets it can take-off vertically like a helicopter! So far, tip rockets have been tested on very few autogyros. The best known project is Fairey Rotodyne. Fairey Rotodyne could carry about 50 passangers and the first flight took place in 1957. Vertical helicopter style take-offs and landings were made, using the tip rockets. Rotodyne was cruising at 310 km/h (!) with help of the thrust from propellers and with the rotor spinning free. As the tip rockets do not give a torque force that want to twist the autogyro in the opposite direction, there was no need of a tail rotor as is the case for a helicopter. Despite the project was a tremendous technical success it was still finally cancelled, because the noise was said to be too high when starting and landing in heavily populated city centers. A movie presentation of the Fairey Rotodyne project is found here
I presented the idea to install and test hydrogen peroxide tip rockets on an autogyro, at the Swedish Rotorcraft Flyingclub's annual meeting at Gävle-Sandvikens Airport on May 30, 2003. The members found it very interesting. In September 2003 we started the project. The first prototype system was installed on a gyro glider during the summer of 2004.
The system was a great success! We COULD really make vertical take offs!
Two examples are shown on these movies:
Vertical Takeoff 1
Vertical Takeoff 2
As you can see, the VTO:s were not very stable, but when pulling the glider forward, right after it started to lift we could make very nice and stable 0-roll take-offs, as shown on this movie:
Zero Runway Takeoff
This first system was damaged and had to be scrapped, later in the summer of 2004, after a demonstration when the rotor struck the long grass at take-off and the glider fell over on the side. Goodbye, rotor!
To be able to make further development and testing, I repaired the rotor head and got hold of a pair of old rotor blades and installed a new rotor tip rocket system during year 2005. The main difference compared to the first system was that the H2O2 tank pressure was much lower this time; -2 to 3 bars, compared to 50 bars in the original system. The pressure at the rotor tips was still high, thanks to the centrifugal force. The rotor works as a big centrifugal pump at rotation!
Another change was that the catalyst chambers, were the H2O2 is decomposed, were embedded in the rotor blades. Only the rocket nozzles were outside the rotor tips.
This system was tested and evaluated on a static test stand, which happened to be my flag pole foundation!
The system worked fine. I offered the components on my website, for people to be able to install rotor tip rockets on their own autogyros. A few systems were sold, but no one is flying so far. It seems to be a too complicated project for an average gyroplane user to install the components and get off the ground with it, so I stopped selling it.
I have now built a new complete prototype system. It is quite similar to the previous system, but with a few important upgrades and quality improvements. The idea is to offer the complete system with tank, rotor and rotor head, rather than components only, to gyroplane users, after the first prototype system has been successfully tested.
Ivan Tuelstrup, Denmark, has offered to test the prototype system on his gyro. I delivered it to him on November 22, 2006
(Remark March 2008:Unfortunately Ivan never came up in the air with his autogyro in the summer of 2007, because of health and other reasons.)
The different parts of the system at different phases of the construction are seen on the below thumbnails -N.B. Click to enlarge!:
Hans Krugloff is working with the rotor blades in the workshop at his company Allteck. Hans is making most of the equipment, like the rotor connections to the hub bar, the hub bar and the rotor head. Hans and his employees are very profesional mechanics and Hans has come up with several brilliant mechanical solutions!
Rotor blades before installing the tip rockets
The catalyst chamber is enbedded inside the rotor blade and covered with an aluminium plate. Only the flange connected rocket nozzle itself is sticking out outside the rotor tip.
Hub connections and H2O2 pipe/hose connections.
The hub bar seen from two diffrent directions.
The coning angle is 2 degrees andd the pitch angle is 1.5 degrees.
This picture is showing the complete rotor head, with H2O2 hose connections.
These pictures are intended to show how the H2O2 flow is directed through the rotor head.
I will publish a drawing later on, because it is difficult to explain only with the help of pictures and my poor english how this is done.
For you that want more details, there is an archive with all project reports, starting Year 2003 and up to now, in the bar on the left side of this page
Update March 2008
Very little happened with the project since November 2006. The system was never used on an autogyro during the 2007 season as originally planned for. Tests on ground revealed that the maximum speed was only 190 rpm when using the low pressure plastic fuel tank.
To make the system more powerful I have replaced the low pressure plastic tank with a 12.5 bar, 10 liter aluminum tank. I have now tested the rotor pre-rotation with the new tank in my test stand and it was a great success! The system is so much more powerful than before! The speed easily reached 330 rpm and the rotor was still accelerating when I closed the control valve. The pressure was only 8.5 bar at this test while the system can be run at 12,5 bar if necessary (1 bar = 14.5 psi). See pictures and movie below:
Filling hydrogen peroxide in the tank.
A relief valve is used as a plug after filling the peroxide.
The tank was pressurized with CO2 from a CO2 bottle.
This was a practical procedure for me because I happen to have this CO2 bottle available since before, but next time I plan to use a small 12 Volt compressor for pressurizing the tank. The compressor can be driven with the battery on a normal gyroplane propeller engine.
As before I used my flag pole foundation as a test stand.
Test movie:
Tip Rocket Test Movie, 330 rpm
Some performance data:
* It took less than 30 seconds from the rotor standing still to rotor speed 330 rpm.
* My calculation is the rotor with diameter 7,5 meter (24.6 feet) is giving 2200 N lifting thrust at 330 rpm. (2200 N = 224 kp = 498 lbf). With other words: -VTO with a gyrocopter with total weight 498 lbs will take place at 330 rpm
* 1.1 liter H2O2 (=1.5 kg = 3.3 lbs) was consumed at each start.
We are now very satisfied with the quality of the system.
We sold the prototype system in April 2008 to a customer that wants to be anonymous. He plans to install the system on a new design gyroplane with VTO/L capabilities.
This article was updated on July 14th, 2008