Still not having accurate information, will allow the professional micromotors in the school types of the car, we decided a new “sled” design under MDS-1,5 D of production ON Savelovsky “Progress”. If not today, then tomorrow, the race for the result will be a three-band motors in the world is simple cord snowmobile, and on trainings it is possible not to burn preparirovanie and therefore malaisrie MK-17. As you can see, the reasons for the transition to MDS we had.
Purchased several new motors were given the opportunity to begin the design of the sled. In principle this was a simple task, as we were based on a known design (see “M-K” № 8, 1989, article “speed — through simplicity”). The fact is that, we think, in her scheme of aeromodel brought to its logical perfection with the complete abolition of technical “frills”; she has no equal and adaptability. However, based on a new engine, potentially much higher turnover compared to the MK-17, we had to slightly change the cross section of the housing with simultaneous increase of the wall thickness and raise the surface of the stabilizer. After all, his main goal is to compensate for gyroscopic moments from the rotating propeller, which in turn depends on the speed. Design and materials the new pattern has repeated published in the journal.
The saved and the principle of fixing the “model engine”. Although at first we tried to draw a version with the usual under engine bars (more than usual, which can be recommended only for models beginners), in the end decided to remove the legs from the engine crankcase and cut all the motor mount on the M3 to use for his installation two dural bracket. As our sleigh strut abolished, in the sub boss now are stuck with two fat rods, which are threaded sockets and under the corners of the motor, and cord under the bar. In the manufacture of the site, it is important all work is conducted with maximum precision, so you do not have to eliminate the deviation of the axis of the shaft of the propeller. It is possible to resort to this trick: first, collect all the walk-behind tractor with a tank and only then after trying to glue the tail boom housing. Based on the logic “the model is mounted on the engine” and heavy duty construction of MDS, wire bracket main ridge is screwed directly to the cylinder head (as already mentioned, it is also used M3 screws). Power system is the most modern type, with the nozzle in the tank and pipe supply, Ø 3 mm, 2 mm incoming in the axial hole of the spool (for reference: last size equal to 6 mm). The jet is made from scratch from brass and the Assembly is soldered into the tank. The needle is withdrawn downwards, which increases the ease of adjustment because of the one-way direction with the adjustment screw compression ratio, and racing snowmobiles are not corrupted projecting parts. Of course, the power of the engine the fuel pressure bleed from the crankcase through the nozzle-valve. The deflector hood is in the winter rather for the purpose of protecting the cylinder from hypothermia than the problems of aerodynamics, so the slot for the entrance of air is cut during the selection regime of plant.
The MDS was almost ready when we slipped and began the run-in has not yet converted to the sled motor. Each individual Modeler will understand our impatience! And now…
Fig. 1. Control line racing aeromodel sleds with motor working volume of 1.5 cm3.