Concrete mixers tend to appeal to contractors located in the southwest and northeast. They're available in a variety of drum capacities ranging from 3 to 9 cubic feet. The most popular tub size for rental is typically the 9-cubic-foot capacity.
These mixers have rotating drums with stationary paddles making them better suited for rocks. It's critical to set the drum angle correctly, at approximately 32 degrees, or it will produce slow, unmixed material proportions. Be sure to advise your customer to never use concrete mixers to mix mortar.
Power options vary from one manufacture to another. As a general rule, larger horsepower engines are favored over low horsepower because of the wide variety of mix designs.
There are three basic power transfers. The conventional V-belt/open gear drive is common on all concrete mixers and mortar mixers up to 9 cubic feet capacity. From a retail standpoint it's also attractive because this drive system provides a low price point for small and medium contractors. High-capacity mortar mixers, typically 12 cubic feet and larger, avoid this type of drive because stiff, dry loads of material can cause belts to slip.
Alternatives to the V-belt drive include the completely enclosed gear box, offered on the 12-cubic-feet mortar mixers. These are used on medium to large jobs. The machines have higher initial costs but offer much lower maintenance, particularly when mixing lower slump material batches. The gears are immersed in oil, offering greater durability. It will also require periodic clutch adjustment or replacements.
The hydraulic-drive mortar mixer is the most reliable mixer on the market. This power transfer offers reversible mixing paddles and typically includes a hydraulic dump option that reduces operator fatigue. Another benefit is greatly reduced maintenance by eliminating V-belts, mechanical gears and clutches.
Apart from the typical small engine service jobs, such as replacing air filters or checking oil levels, maintenance on mixers is kept to a minimum. The most important tip is to maintain safety devices, such as the drum (grate) guard and the emergency and stop switches. All hardware should be inspected for tightness. After each rental, the tow bar, hitch coupler and safety chains should be inspected for damage. The interior of the drum and overall machine should be free of materials.
The amount of maintenance on open gear drive systems is somewhat higher as V-belts can stretch and pulleys will wear over time. Also, if contractors do not close the engine shroud it will allow cement and dust to enter, thus accelerating the wear. Always make certain that the wheel bearings are greased for any towable mixer.
Concrete mixers have a number of grease fittings that require lubrication. Under no circumstance should grease ever be applied to the ring gear of the concrete mixer. It will attract dirt and grit and eventually shorten the life of the gear.
A key maintenance item on mortar mixers are paddle shaft seals. These items, depending on the manufacturer, may require daily greasing or none at all. Always follow the manufacturer's recommendations to maximize the service life of the seals.