HELPS HYBRID | MODEL CONSTRUCTION

Considering the number of characterizing a working volume of cylinders of internal combustion motors produced by our industry, necessarily pay attention to the typical “failure”. Unfortunately, the motors of the class from 2.5 to 5.0 cm3 we did not exist. However, these engines required for flight training, high-speed radio-controlled model airplanes, scale airplanes. They can also be set on auto and advanced.

What to do in this case? Not to develop the same motor from beginning to end on their own? Because the design of the new engine and its debugging process difficult and long, it’s only Modeler “very high qualification. It would be more appropriate to create new designs based on already existing and proven in long-term operation?

As it turned out, this path is real. You can, for example, to make an engine whose stroke is like a “Rhythm” (16 mm) and the diameter of the cylinder — like MK-12V (15.5 mm). In this case, the amount of “hybrid” will be a few more than 3 cm3. These considerations formed the basis for the development of the engine, the design of which is shown in figure 1. The crankcase of this engine from the “Rhythm” of the crank mechanism and the slide valve device, a piston and a pair of MK-12V.

Completion of the Carter — most complex operation. If you are going to follow our recommendations, we note that alteration can only be “Rhythms” of the first releases. First of all it is necessary to choose well-preserved case and to muffle mounting holes shirt dural cylinder plugs on glue BF-2 or epoxy resin. Then the seat under the sleeve rastaquouere to Ø 21 mm to a depth of 15 mm and it tapped M22X1 mm. Heed carefully to this operation strictly observe the perpendicularity of the axes of the cylinder and the crankshaft. This is best done on a faceplate on a lathe or jig-boring machine.

Seats for bearings in the crankcase is cut scan or lapped. The outer rings of the bearings it should be chrome-plate to preserve the guaranteed tightness of the fit. To do this, bearing cages filled with paraffin, the bearings are clamped in a holder and placed in a plating bath.

Fig. 1. Design compression engine with a working volume of 3.0 cm3

Fig. 1. Design compression engine with a displacement of 3.0 cm³:

1 — crankshaft 2 — bearings, 3 — Carter 4 — rod, 5 — cooling, 6 . — screw kontrpartiya, 7 — controlling, 8 — thumb, 9 — piston, 10 — casing, 11 — a carburetor.

To remove the paraffin after covering you in hot engine oil. The outer surface of the crankcase for improved heat transfer process it is desirable to sandblast.

Try to find a couple of broken piston from the engine. If this is not possible, then used the sleeve must rassledovat to Ø 15,8—16 mm and re-grind. The volume of the new engine will be 3.2 cm3. I do not advise thus to further increase the working volume — it will not increase capacity as it may seem at first glance.

The fact that sharply reduced the cross section of the overflow channels.

The piston of large diameter may be carved from cast iron brand of SCH 21-40. Controlling should be cut at 4 mm. Note that the area of the fins should be increased — this can be achieved by installation of additional ribs, cut from the “shirt” of a different engine, or to make new fins (Fig. 2).

Fig. 2. Shirt cylinder engine.

Engine Assembly is simple. To obtain the necessary phases of the exhaust and bypass under the flange of the sleeve, you need to install strips of aluminum foil. The position of the sleeve, or rather, passageways and Windows, you can define but the formula F. Brix:

where α is the position of the piston relative to the dead point,

φ is the rotation angle of the crankshaft relative to TDC

L — length of connecting rod,

R is the radius of the crank.

We regulate the motor phase exhaust MK-12V, not tinkering in this slide the node “Rhythm”.

The engine is easy enough to run on standard fuel for compression engines with screw Ø developed 250X100 mm 14,5—14,6 thousand rpm the power Gain in comparison with the MC-12B is obvious: with the same screw the latter has a rotational speed of the crankshaft 11-12 thousand Rev/min., Wins new engine when comparing it with the “Rhythm” — that develops with the similar screw not more than 13.5 thousand rpm the New engine consumes up to 10 ml of fuel per minute.

We do not consider our work finished. The power and frequency of rotation of the crankshaft of the hybrid can be increased through the installation of the slide node from the engine KMD-2,5 and also the selection and expansion phases, purge and bypass.

A. PIKELNY, head of the aeromodelling circle Dnepropetrovsk

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