Shaft type
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.Shaft rotation
Direction of rotation of the motor shaft. Usually, it is indicated by the direction in which the shaft rotates, if you look at it from the flywheel side (from the side of the engine from which the power is taken off). The classic option is counterclockwise rotation, but the opposite direction is also found. Anyway, the main selection criterion for this parameter is what direction the car is designed for, under which the engine is bought.
Shaft diameter
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.
Capacity
The working volume of all engine cylinders. Usually, other things being equal, a larger volume allows you to achieve higher power, but increases fuel consumption and affects the dimensions of the unit.
Piston diameter
The engine piston diameter is a reference parameter — in fact, this data is required very rarely, usually, for repairs and other specific tasks that the average user usually does not deal with at all.
Piston stroke
The distance that an engine piston travels from one extreme point to another. In general, it is a rather specific characteristic and is rarely required in fact (for most ordinary users, it is never needed at all in the entire “life” of the engine).
Fuel tank volume
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.
Crankcase oil capacity
The regular volume of oil in the crankcase, in fact, is the amount of oil necessary for the normal operation of the unit (some deviations are allowed, but only within small limits). This parameter allows you to estimate how much oil is required to fill or refill the engine lubrication system.
Specific fuel consumption
Specific consumption in this case can be described as the amount of fuel consumed by the engine per hour per 1 kW of generated power. The lower this figure, the higher the efficiency of the engine and the more economical it is. Specific consumption data is especially useful for comparing units with different capacities.
