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Three Dee RIGID

klick -> Bild im Desktophintergrundformat

 

The Rigid is the first 1.6 meter class production helicopter which is only delivered with a Rigid main rotor for flybarless flying. In my opinion the flybar will not be used any more in future. Due to the technological progress the rise of the electric helicopter in all sizes cannot be prevented any more either. The advantages prevail concerning nearly all points, so that the further development is more or less predictable.

Because of the apparent demand for flybarless electric helicopters the development of a light system without any compromises was the consequent step to apply new standards and to get a compact model especially being adjusted to the 3 axis stabilisation, which perfectly supports the completely new possibilities.

 

Concept:

In general it is not possible to re-invent the wheel. Over the years I have presented innovations and tried various possibilities that have also been adapted in other areas. Some day you approach a constructive solution offering all possible physical features. There are always different possibilities to achieve the aim. However, after some time there is also the danger that only the design is modified not resulting in flight-technical advantages. I am interested in building a system that is determined by a clever assembly of the absolutely necessary components and a minimum number of parts.

In my opinion a straight and clear design is the advantage of this helicopter. For the first time I decided to use a two-stage drive in my helicopters.

Due to the positive experiences using the MP series with the spiral cut gear wheels module 1 concerning the efficiency, robustness and operating noise the different constructive advantages prevail in spite of the small loss caused by the second stage.

In contrast to the predecessor possible savings could be achieved because the production of the smaller gear wheels is less complex and problematic and the one-way drive shaft can be smaller because it is mounted on the intermediate shaft.

The rigidity of the entire mechanics is increased without using additional stiffening elements. The extremely compact assembly of the transmission unit which is the core of the mechanics results in an optimal assembly of the two tail boom mountings that are located far from each other as well as an optimal support of the main rotor shaft. The distance between the upper mount plate and the compact main rotor centre hub is smaller than in any other helicopter of this size, so that the bending stress on the 10mm main rotor shaft does not cause any problems.

The tail gear that has proved its worth in the predecessor was not modified and used again. The only difference is that the tail blade holders now consist of plastic material instead of aluminium. The main reason for this slight modification is that almost only carbon blades are used because of their better performance. These blades often produce slight and aggressive vibrations in connection with the too stiff aluminium blade holders. The plastic blade holders allow a better damping. A horizontal stabiliser was not used any more. This part is not really necessary and it interferes with the flight. Besides it increases the weight as well the vibrations and is difficult to transport (it is amazing how much easier it is to place the helicopters without horizontal stabiliser next to each other and turned by 180° in the car).

Thanks to the remarkably slender and futuristic design of the helicopter you do not miss the horizontal stabiliser. For people who have not much space in their cars it is especially advantageous that the tail boom including the front pinion, the struts and the push rod can be removed from the helicopter within less than a minute. In order to do so, you only have to detach both struts as well as the push rod in the front area of the mechanics, loosen the two lower attachment screws of the tail boom holder and pull out the tail boom to the back. The tail boom is automatically fixed at the correct position in the front holder, so that it is always exactly aligned after having been pushed in.

The carbon chassis structure can be divided into the upper and the lower part, whereas the robust upper part includes all components necessary for the flight and the lower part only contains the battery and my obligatory skid plates. Thus the light mechanics can perfectly be integrated into the fuselages because for this purpose the lower part can be removed completely in order to mount corresponding fastening angles.

The advantage of a mechanics consisting of a flyable upper part where only a stable battery support and the skid plates are attached at the lower area is its great flexibility for different individual uses that can be realised later. All batteries up to dimensions of 60x60x400mm can easily be inserted into the protecting slot of the "Rigid" from the front as well as from the back. The spacers are covered with a silicon tube such that the battery is held in a non-slip and safe position by only two Velcro strips.

The entire mechanics is extremely easy to maintain and can be mounted and dismounted quickly. The gear stages can be assembled and disassembled individually without having to dismount the entire mechanics. It is also possible to assemble and disassemble all servos without dismounting the mechanics.

Without decreasing the strength the weight of the single parts was reduced so that the bare mechanics including the canopy has a weight of only 1.7kg. After adding the recommended equipment of approx. 1.3kg the helicopter ready to fly has a weight of nearly 3kg without the drive battery. Depending on the choice of the drive battery take-off weights of less than 4kg are possible. Using a 12s SLS accumulator of 3700mAh and 1180g a take-off weight of nearly 4.2kg can be reached, which is an amazing value for an all-metal carbon helicopter with this rigidity, stability and life time.

The futuristic canopy with its distinctively surrounding line as well as its concave recesses was modified on the basis of the very popular small MP canopy such that it guarantees a considerably better visibility due to the increased height. It also underlines the very compact appearance.

The low distance between the upper side of the mechanics and the main rotor results in completely new proportions. Thus the actual rotor is located directly above the canopy, which gives the helicopter a very racy design.

People who know me have experienced that I set a high value on 3D performance as well as on fast speeds since I have built my first helicopter, the old, blue Three Dee. In my opinion there is nothing more elegant and fascinating than a helicopter dashing through the air with high speed and blade noises like a pod racer. That is the reason why the Rigid canopy was designed a bit more aerodynamically which is shown by the extreme high speed flight qualities, forwards as well as backwards.

The V-Stabi electronic system offers completely new perspectives regarding the high speed flight, which were not possible when using a flybar. So the advantage of an aerodynamic casing is even more considerable. Try speeding. It is fun, looks elegant and helps to relieve stress and to relax. During the flight events it is a popular alternative to flying within a small area of 10x10 m which is nowadays quite common. For the "aged ones" among us who are older than 25 years old it is still good to cope with because it does not require such quick reactions but more sensitiveness and an eye for spacing. You will also enjoy loopings with a diameter of 150 m or nice slow rolls like being drawn over the entire field on a string. But be careful, slowly approach spacious flying over longer distances, it has to be learnt!

For many years I have known of the problems that layman have during the quite complicated lacquering process. That is why I developed a high-quality, UV resistant decal set with a window and a comet tail to give the helicopter a typical, distinctive design. It can be attached by every reasonably skilful user. The result looks like a high-gloss clean lacquering without frayed edges and is much cheaper and quicker to apply than every kind of lacquering.

In general, it was my aim to keep the costs of replacement parts as low as possible, so that the nice helicopter will not only be used on Sundays. That is why I decided to use again my well-proven blackly anodised 25mm aluminium tail boom. In my opinion the still increasing costs for carbon tail booms because their more precious look are not justified and after a crash they can be a considerable cost factor.

When using a flybarless helicopter the flight properties mostly depend on the used stabilisation electronics to emphasise the quality and performance of the mechanics.

So I recommend the latest Mini V-bar 5.2 express flybarless system from Mikado which gives the TDR a great performance.

The recommended engine using a Pyro 700-52 in connection with the successfully operating Jive controller not requiring any receiver power supply is the optimal configuration for this helicopter at present. Test flights have shown that this setup in 12s operation allows a speed of approx. 1800 rpm at a pitch of up to 14 degrees, if necessary. In general, this light helicopter also allows an 10s operation with brilliant performance values. Because of the low difference in price between the 10s and 12s batteries the decision which battery to use is problably not too difficult. Flight attempts have shown that a slightly higher capacity is needed for the same flight time when using 10s batteries. The reason for this is the higher power consumption at a lower voltage. Thus the balance of weight between the 10s and the 12s is compensated. The advantage of the 12s is that it offers more power during extreme manoeuvres. Apart from that the use of 10s provides more power than every optimally adjusted glow version.

In connection with the development of the Rigid numerous test flights with a logger data capture were carried through, which persuaded me to refrain from the exaggerated present max rotor speed hype. Thanks to light models with flybarless main rotors it is not necessary any more to race with a rotor head speed exceeding the limit of 2000. The properties when flying straight on are even fantastic at 1300 rpm at the main rotor. Every flybar head helicopter would pitch up hopelessly at these manoeuvres. Most of the 3D figures can be flown because of a lower rotor disc load also using a more moderate head speed. So more than 1800 rpm at the main rotor are unnecessary when flying this helicopter. The logger data show that the efficiency of the blades decreases rapidly with increasing head speed, so that most of the energy is wasted. For the same flight condition "Hovering at one position" 570W is required at 1300 rpm at the rotor and at 1850 rpm you already need 1000W. At more than 2100 rpm 1500W are required, i. e. nearly the triple amount, although you do nothing more than hovering.

This result shows clearly that the flight time can be increased considerably, if the rotor does not constantly rotate at full speed. All these results have contributed to and influenced the choice of the speed reduction and the recommended drive of the Rigid.