REPLIKAR IN MODEL PERFORMANCE | MODEL CONSTRUCTION

The Rules on the self-similar sports of the USSR, issued in 1989, a new class: E-5. With the technique permitted by the rules for competition in this class, athletes unfamiliar, and it sharply differs from the known. Try to determine the search paths of optimal solutions racing models-replicas and purpose of this article.

First of all, about the requirements of the rules for the micromachines E-5 (not a secret that in many places the new edition of the rules simply do not get it). So this “racing car model with engine 3.5 cm³“. They are included in the group of cord models drive wheels; competitions are held at maximum speed without determining the copy number of models. On the main technical characteristics of the car E-5 are required to satisfy all the requirements for cordovil racing, and the mass of the model must be in the range of 1.87 kg. Interestingly, the rules do not specify a lower permissible capacity of the engine as in other racing classes, just to mention a maximum 3.5 cm³, it gives the possibility to use motors 2.5 cm³.

Races are held on a filament diameter of 1.0 mm standard length; cord strap on the restrictions of dimensions corresponds to the class E-2 (the minimum width of 9.5 mm, a thickness in the range from 2 to 3.5 mm, material — steel and marking — green). Regarding technology itself, the rules state: “In class E-5 allowed the model muffler are integrally formed with the bearing part of the body. Models need to have the unsprung rear axle. The drive wheel is a cylindrical gear. The model configuration is given a vintage race car.”

Unfortunately, immediately after reading this paragraph of the rules there are many questions. For example, if the variant with a silencer of the resonance type, inscribed in sizes and body milled or cast low body? It’s not that difficult to build and fabricate a model engine, according to the scheme similar to the picture rules, but the “pipe” forward and practically not affecting the external form of the model. Unambiguous language “must-have” regarding the rear axle, put in an uncertain situation, the concept of “allowed.” But without a muffler or with a non-resonant silencer, but is not part of the bearing part? By the way, what models are the most available type with a prefabricated low or even with rod frame? While clear answers to these questions appeared, will focus on the rules given in the figure.

Fig. 1. The model scheme class E-5:

1 — chamber muffler, 2 — spur, preventing rollover, 3 — cylindrical gear, 4 — fuel tank 5 — stopping device.

The scale bar roughly set. Options profile body marked I, II and III.

But he puts his questions on the configuration of the body. Racing real car — that’s understandable. What is old to what time the prototype could be considered vintage? And what General type of proposed rules III body (more clearly it is highlighted for example in figure 2)? There are other problems, however, is a minor character.

Fig. 2. The longitudinal weight balance of the model and the influence of the reactive torque of the drive wheels. Shown unwanted domainservice front of P_σdeteriorating the moment of inertia of the model, and spurs, which, even at low elasticity is able to function as “springs” and to influence the buildup of cars in the vertical plane (in contrast to Fig. 1 terminal spurs should have a maximum size of a section in the horizontal and in the vertical plane and to be absolutely rigid).

And while the rules are yet to be fully established, we will try to design a model class E-5 appears to be the most relevant to the ideas embodied in the technical requirements.

A continuous race for results in sport are inevitably forced to look for solutions exclusively aimed at enhancing the rapidity microcosm. And it is here that the experience of automodelity in a simplified technique not so great — the knowledge gleaned from “adults” racing superclasses, most are not applicable.

Take the weight of the model along the axes. A classic racing machine, judging by the location of cord strap, has a relatively large load on the front axle. The good driving characteristics of the model are provided only with the most careful selection of damping and damping properties of suspensions of both bridges. We have the same rules given in advance the absence of a suspension axle, so the front suspension parts need to be changed. It is very important that the model of the classical type is greatly influenced by the gyroscopic moment from the rapidly spinning gyro-flywheel. This point athletes are forced to work either for raising the nose of the model or compression to the track. In our case, the effect of a flywheel is possible — it rotates in a different plane.

It would seem that we can specify only stiffness and degree of damping suspension on the front wheels. But wait! The most important thing, which will depend on the evenness of the stroke along the path of the track, not in this. More importantly, how much would be pinned nose model her weight, and what are inertial forces. And last, depending on the mass linearly in the “square” changes with the increase or reduction of the shoulder (in this case the shoulder will be calculated from the center of rotation axis of the rear wheels)! The calculation of the pressure due to the weight of the model taking into account the influence of the reactive torque of the driving wheels M_{of reakt.} it is easy to spend according to figure 2. Also need to consider that M_react. by lowering the engine speed in the gear accordingly. And the moment of inertia of the bow will be able to influence her relief, and reduction of the length of the model. Compared to the classic race car class E-5 can be shortened.

Now — about the choice of engine. In spite of the tolerance of engines working volume of 3.5 cm³, today more advantageous is the variant with uprated engine 2.5 cm³. Are higher power with less torque, and the relation to the maximum mass of the machine more profitable. The last factor in terms of unsprung rear axle is able to be decisive. Because our model vibration from operation of the plant will not be extinguished in the suspension bridge, and, from the point of view of adhesion with the track, it will be somewhat like a shaker! And every effort aimed at reducing the level of vibration and the gain of the clamp to the track with minimum torque, will benefit the rapidity.

A few words about the degree of balance of the engine. If we’re talking about a special type of aviation motor timing or fighting with power up to 1 HP at 30 000 rpm, then somehow it is well balanced — otherwise it is impossible to obtain such high characteristics. On industrial designs, which are clearly not up to such a high data on virtually all motors and piston group neoborocillina counterweight of the crankshaft. To implement the uploading of the cheeks the shaft is not so easy, so when using industrial engines can be recommended to put the engine head into the horizon. This solution is known from the practice of constructing “school” of micromachines. With a very light piston, you can even go for the lack of balancing, providing only the mass compensation of the finger crank shaft and the lower half of the connecting rod. Unexpected technique allows for horizontal cylinder to eliminate vibrations in the vertical direction, dramatically increasing the grip when the unsprung axle. A massive part of the body that is attached to the crankcase of the engine, will allow an unbalanced motor with a light (of course, made of aluminum alloy) piston to operate at the highest rpm.

Fig. 3. Model class E-5 in the first stage of the design process.

Fig. 3. Model class E-5 at the first stage of design. Compared with Fig. 1 maximum compressed size of its housing, respecting the traditional value of the base wheels. To increase the number of copies you can shift the cutout of the cab back. In the engine it is necessary to provide protection of the rod from slipping on the piston finger through the installation of light spacer bushings.

Fig. 4. Comparative vibration in a circle:

A heavy piston, crankshaft neobetonirovannymi; — lightweight piston, the balancing is close to perfect; — lightweight piston, the engine deliberately newbalancewomen.

Fig. 5. Model class E-5 in the second stage of the design process.

Optimal force diagram of the frame shown in figures 3 and 5. In both cases, she represented a massive base with the lightest tubular I-beam, carrying the front suspension. By the way, this kind of model frame much more affordable known, based on the one-piece milled or cast frame-low. With a light bow you can try to limit a simple wheel suspension on the leaf “springs” increased elasticity, and the body shell to keep the decorative function of the fairing. By the way, when you freely open the front “radiator” and the flow of air inside the body the resistance is little different from the slicked-closed front aerodynamic housings.

Reducer with cylindrical gear wheels, of course, better placed inside the body for protection against dirt. When you calculate the gears you can benefit from the experience of radioautomation or, more precisely, modelers. The fact that the choice of the size of the parts, it’s helpful to look carefully: the maximum transmission efficiency is provided only on the calculated loads, and pereraspredelenie gears leads to greater mechanical losses. Perhaps the experience of the modelers will help in determining the size of the flywheel because they limit the spacing of the gearbox.

The images show two stages of a design model class E-5: the original, with a track, selected from the statistics of the racing of this class (Fig. 3), updated, which introduced adjustments to the moment of inertia of the bow and the binding nezaboravnog engine (Fig. 5). In the latter case slightly increased the track as close to the wall of the body can cause aerodynamic losses in the flow of air in narrow gaps. On both models the majority is concentrated in the area of the plant for the increased load on the driving axle and to reduce the vibration transmitted to the wheels.

Yuri PAVLENKO, engineer

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