Power
The rated power of the engine in horsepower (in fact,
the maximum power that the unit can produce in normal operation, without overloads). Despite the popularity of the designation in watts (see below), horsepower (hp) is still quite widely used to indicate the power of internal combustion engines. 1 HP is approximately 735 watts.
In general, the more powerful the engine, the more speed and tractive effort it is able to develop. On the other hand, this indicator directly affects the weight, dimensions, and most importantly, the cost of the unit, while the real need for high power is relatively rare. Therefore, it is worth choosing according to this indicator, taking into account the features of the planned application; specific recommendations on the selection of an engine for a specific technique and tasks can be found in special sources. We only note that models of the same power can differ in speed and "torque"; see "Shaft speed" for details.
In general, performance up to 8 hp. are considered low, up to 13 hp. — medium, more than 13 hp — high.
Power
The rated power of the engine (the highest power it can deliver in normal operation) in kilowatts. Initially, the power of internal combustion engines (ICE) was usually denoted in horsepower, but now it is also common to record in watts / kilowatts; this, in particular, makes it easier to compare the power of internal combustion engines and electric motors. Some units can be converted to others: 1 hp approximately equal to 0.735 kW.
In general, the more powerful the engine, the more speed and tractive effort it is able to develop. On the other hand, this indicator directly affects the weight, dimensions, and most importantly, the cost of the unit, while the real need for high power is relatively rare. Therefore, it is worth choosing according to this indicator, taking into account the features of the planned application; specific recommendations on choosing an engine for a specific technique and tasks can be found in special sources. We only note that models of the same power can differ in speed and "torque"; see "Shaft speed" for details.
Shaft speed
The highest shaft speed provided by the motor. Before buying, you should make sure that this indicator corresponds to the characteristics of the equipment in which you plan to install the engine — too high a speed can damage the working tool, transmission units, etc.
It is also worth considering that a higher rotational speed (for the same engine power and transmission characteristics) means less torque, and vice versa. Therefore, this parameter allows you to compare engines in terms of the speed / thrust ratio (however, only on the condition that they do not have reduction gears — see "Functions").
Shaft length
It is customary to call the shaft length only the length of its outer part protruding beyond the engine housing. The optimal value of this parameter depends on the characteristics of the machine in which the engine is planned to be installed.
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.
Shaft internal thread
The diameter of the internal thread on the motor shaft (more precisely, on its outer end). This information may be necessary for the successful use of the engine with some mechanisms and devices. It can be indicated both as a real value in millimetres (10 mm) and as a marking (5/16-24UNF, M8, etc.).
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).
