Differences Between Crown and Gear Reducer Concrete Mixers

Crown Concrete Mixers

This type of mixing equipment is suitable for infrequent concrete work. Crown concrete mixers consist of two pear-shaped halves containing blades. These halves are connected by a toothed crown (gear). During operation, the motor rotates the driving gear, which in turn rotates the crown with the drum. On the opposite side of the motor in crown concrete mixers is the discharge lever for the concrete mixture, which resembles a steering wheel. Most models are equipped with wheels for easy transportation of the mixer.

Crown concrete mixer Forte with a steering discharge of the mixture.

Crown transmission concrete mixers mix concrete exclusively based on the gravitational principle (while gear reducer mixers can also use forced mixing). The drum rotates at an angle of about 45 degrees; the blades scoop the mixture and drop the solution down upon reaching the highest point. The angle of the concrete mixer can be adjusted depending on the density and quantity of the mixture. Thanks to this design, the device is capable of mixing both standard cement-sand mixtures and blends with large gravel fractions (up to 40 mm).

The most problematic part of such concrete mixers is the crown. During operation, cement, sand, and even small stones from the gravel can get stuck in the grooves between the driving gear and the crown, leading to rapid wear of the teeth. Depending on the material used for the crown (cast iron, plastic, steel, or polyamide), the wear can occur more quickly or slowly. Unfortunately, even polyamide crowns will not last more than three years with active use of the concrete mixer. Additionally, the bearing between the frame and the drum occasionally fails. However, the components are not very expensive, and they can be replaced by yourself without needing to visit a service center. If a durable concrete mixer is required for a construction crew, it is better to pay attention to models with gear reducer drives. However, crown mixers are also considerably noisier than gear reducer models.

Criteria for Choosing Crown Models

When choosing a crown concrete mixer, pay attention to the following parameters:

Cast iron crowns for concrete mixers with 130 teeth.

• Material of the crown. Cast iron and plastic crowns are suitable for home users who do not use the concrete mixer often. Although these crowns are fragile, they are quite inexpensive (approximately one-tenth of the cost of the mixer). For constant concrete work, a steel or polyamide crown is necessary. Both materials have high wear resistance.
• Mixture volume. It should be noted that with the gravitational principle of operation, the concrete mixer can only "mix" 2/3 of the total volume of the drum (with a nominal capacity of 180 L, the mixture volume will be 120 L). Therefore, for a team of up to 4 people, mixers ranging from 180 to 230 L will be comfortable, while for five or more people, it is better to choose 500-liter models, such as BSM 500 500 L .

Gear Reducer Concrete Mixers

Gear reducer concrete mixer with a capacity of 180 L.

Gear reducer units have a similar structure to crown mixers, with the only difference being in the drive mechanism. The concrete mixer operates from a motor that rotates a steel reducer. The reducer, in turn, ensures the rotation of the drum and the mixing of the filler. The reducer itself is enclosed in a housing that provides reliable protection against the ingress of gravel and sand. Unlike crown models, in gear reducer mixers, the handles for transportation (and discharging the mixture) are located at the back rather than the side, which provides more convenient movement of the concrete mixer around the construction site.

It is worth noting that gear reducer concrete mixers can operate on both gravitational and forced principles. The forced type is characterized by a stationary drum and movable blades that mix the solution. This design allows for a homogeneous mixture without lumps. Additionally, such concrete mixers can "mix" around 90% of the total volume of the device.

Compared to crown mixers, gear reducer mixers (forced type) are significantly more productive and durable. The reducer can last more than 7 years without repair or planned maintenance. However, if damaged, it will need to be replaced entirely, which costs about one-third of the price of the entire mixer. The number of transmission links in the gear reducer design is minimized (compared to the crown), achieving a balance between power and electricity consumption. Also, gear reducer mixers are quieter than crown mixers.

Criteria for Choosing Gear Reducer Models

When selecting gear reducer concrete mixers, pay attention to the following characteristics:

• Mixing principle. Gravitational units mix less volume than forced ones, but they are much cheaper, making them suitable for small pouring volumes. Forced ones are very useful when it is necessary to avoid downtime and pour a lot of concrete.
• Thickness of the drum. All drums are made of steel, which deteriorates over time due to the solution. Therefore, choose models with a wall thickness of at least 1 - 1.5 mm.
• Operating voltage. The nominal voltage for most concrete mixers is 220 V. However, some "powerful" models (1 kW and above) operate on a 380 V network, so when choosing a mixer, consider the availability or absence of a three-phase network. Such units are most often used at large construction sites and industrial enterprises.
• Drum (or blade) rotation speed. For most medium-powered models (500 to 1000 W), this indicator is not particularly significant. However, for powerful models (1 kW and above), the drum rotation speed should be at least 30 revolutions per minute. The higher this figure, the faster the mixture is mixed and the less electricity is consumed.