Comparison Rato R420 vs Lifan 190F-D

The maximum torque developed by the engine during operation. Note that such an indicator is usually achieved only at certain speeds — this nuance can be specified in the characteristics.

Torque can be simplistically described as the force exerted by a motor on a shaft. The higher this effort, the more “high-torque” the motor is, the better it overcomes resistance and handles with high loads. The torque value is directly related to the power. For example, for 5 hp models. and less torque up to 10 Nm is considered quite normal, engines of 4 – 7 hp. give out from 10 to 20 Nm, and values of 20 Nm or more are found in units with a power of at least 8 hp. At the same time, engines of the same power may differ in actual force. So this indicator characterizes the capabilities of the unit well in comparison with analogues.

It is worth saying that many consider torque to be a more reliable and visual parameter than power: the latter can be indicated in different ways (nominal, maximum, etc.), while torque is a completely unambiguous characteristic.

Shaft type, more precisely, the type of fastening for the hub provided on the shaft shank.

Recall that a hub is a part with a hole that is put on the shaft; it is through this part that the rotation is transmitted to the mechanism with which the engine is used. The general rule in this case is this: the type of shaft must match the type of mounting on the hub, otherwise normal operation will not be possible. Nowadays, there are units with shafts under the key, under the spline, under the cone and under the thread. Here is a more detailed description of each option:

— Dowel. Connection using a key — an elongated part placed in a special longitudinal groove. More precisely, there are two grooves: one is located on the shaft, the other is on the hub, and the key is tightly installed in the space formed by the grooves and connects the shaft and the hub. Such connections are simple and at the same time quite functional, due to which they are widespread and found in engines of all price and “weight” categories. On the other hand, a keyed connection is less secure than a splined connection and is less suitable for high RPM and/or heavy loads.

— Slots. Connection based on slots — longitudinal slots. Most often, there are six of them on the shaft, and the seat on the hub has the appropriate shape — in the form of a charac...teristic asterisk. A spline connection is more complicated and more expensive than a keyed connection, and numerous slots reduces the strength of the shaft and it has to be made thicker. However, the connection itself is very reliable, as it evenly distributes the load during rotation. Therefore, splines are recommended for work at high loads.

— Cone. A shaft with a shank in the form of a cone (tapering towards the end), in the centre of which there is a hole with an internal thread. It is used quite rarely, mainly on fairly powerful units — from 7 hp. and higher.

— Carving. Cylindrical shank with external thread. A rather specific option that has not received much distribution — in particular, due to the fact that the thread tends to loosen from vibrations as it is used, and significant efforts may be required to connect and disconnect the shank and hub.

The diameter of the motor shaft, more precisely, the diameter of its outer part, located behind the housing. Data on the diameter of the shaft is needed to clarify the compatibility of the engine with the mechanism for which it is bought.

Now on the market there are shafts with the following diameters: 16 mm, 19 mm, 20 mm, 22 mm, 25 mm.

The compression ratio provided by the engine.

The compression ratio is the ratio of the total volume of each cylinder (above-piston space at the extreme lower position of the piston) to the volume of the combustion chamber (above-piston space at the extreme upper position of the piston). Simply put, this parameter describes how many times the over-piston space decreases when the piston moves from the bottom to the top.

A higher compression ratio, on the one hand, contributes to an increase in engine efficiency and allows you to achieve more power (compared to analogues of the same volume) and lower fuel consumption (compared to analogues of the same power). On the other hand, with an increase in the compression ratio, the likelihood of detonation (“knocking in the engine”) also increases, which puts forward increased demands on the quality of the fuel.

The lowest compression ratio found in modern engines is about 5.6:1, the highest is about 19:1.

The nominal volume of the engine's fuel tank is the maximum amount of fuel that can be safely filled there. Knowing the fuel consumption (see below), it is possible to estimate the operating time of the unit on a single refill by the volume of the tank by dividing the tank capacity by the consumption.

Large fuel tanks, on the one hand, allow you to work for a long time without refueling, on the other hand, they significantly affect the dimensions and weight of the engine. Also note that many models allow refueling "on the go." When choosing a tank volume, manufacturers take into account these points, as well as the “weight category” and the specifics of the engine application.

Regular way to start the engine. To start an internal combustion engine, crankshaft rotation is required, and different types of start differ depending on how this cranking is provided:

— Manual. Starting due to the muscular strength of the operator: usually, to rotate the shaft, you need to pull a special cable, although other options are possible (for example, a starting handle). Manual systems do not require batteries and are generally simple, compact, low cost and reliable; in fact, except for a person, nothing is required to start. On the other hand, the procedure is not very convenient for the user himself: you need to pull the cable quite strongly and sharply, which can be difficult, especially if you are not used to it. Also note that this method is of little use for powerful heavy engines.

- Electric starter. Starting due to a separate electric motor (starter), turning the shaft. Power for the motor is provided by a special battery. This method is much more convenient than manual, because. the user, in fact, just needs to press a button; at the same time, it is suitable even for the most "solid" motors. At the same time, the starter and battery significantly affect the price, weight and dimensions of the engine, and with a dead battery, the entire system becomes useless (however, an “emergency” manual start may be provided for this case).

— Reduction gear. A device that reduces the speed of the shaft at the exit of the engine (relative to the speed at which it rotates directly inside). The meaning of such a decrease is that with a decrease in speed, the torque and tractive effort increase proportionally, which is very useful for hard work — for example, plowing the land on a two-wheel tractor. However you have to pay for this by reducing the speed of work.

— Pulley on the shaft. The presence of a pulley on the shaft is useful if the engine is planned to be used with a belt drive. Usually, the pulley can be removed if necessary.

— Circuit fuse. A device that protects the electrical circuits of the engine (and in some cases, external equipment) from damage during short circuits and other similar problems. In the event of a critical increase in current strength, the fuse operates, opening the circuit. This feature is found mainly in models with electric starters (see "Type of start"). Note that fuses are often made disposable and require replacement after operation.

— Lighting coil. A small generator powered by the rotation of the motor shaft. It is mainly intended for powering headlights and other lighting devices — dimensions, turn signals, etc. The presence of a lighting coil makes it possible to do without external power sources when connecting s...uch devices.