A How to select a conventional mortar mixer

How to select a conventional
mortar mixer
Consider capacity, mixing speed and uniformity,
durability, ease of maintenance, and safety features
By Carolyn Schierhorn
mortar mixer that runs
efficiently, never breaks
down, lasts forever, and
glides smoothly over
any terrain when towed: Consider
how this ideal machine would propel productivity and profits.
Though the perfect mortar mixer remains a contractor’s pipe
dream, many mortar mixers today
do offer features that translate into
benefits for the contractor. But
choosing the right mortar mixer
can be a challenge. There are more
than 20 mortar mixer manufacturers, some offering over a dozen
models, each model with an assortment of options.
Before wading into this sea of
choices, masonry contractors
should first look inward and analyze their firm’s specific needs.
Mortar mixers range in price
from about $1,500 for a model with
a 4-cubic-foot, single-bag capacity
to $6,000 for a model with a 16-cubic-foot, 4 1⁄2- to 51⁄2-bag capacity.
Prices increase dramatically at the
upper end of the capacity spectrum because of the heavy-duty
materials and additional power required. Opting for a 16-cubic-foot
instead of a 12-cubic-foot
model, for example, could
easily add more than
$2,000 to the price.
Determining what size
mortar mixer to buy, therefore, is a most critical decision—one that has been
complicated by the persistent construction slump.
Many masonry contractors
have taken on
smaller-than-usual projects,
including repair and rehabilitation jobs, during the
downturn. If this represents a long-term shift in
business for the individual
firm, a smaller 6- or
8-cubic-foot mixer may be
a better investment.
If buying a paddle mixer, examine the
However, if the shift is
paddle configuration and the shape of
seen as temporary, it may
pay to invest in a larger
model. Consider renting a
higher-capacity model.
mortar mixer when unsure of fuAccording to one mixer manuture needs. Remember that the avfacturer, masonry contractors tend
erage life of a properly maintained
to overload their mortar mixers,
mortar mixer is five to 10 years.
which prevents aeration of the
But even on major projects, to remortar and movement of the mix
duce material handling costs,
from one end of the drum to the
some contractors today will use
other. This can cause inconsistency
two smaller mixers where they
of color and structural properties.
previously would have used one
When determining the optimum
mixer size for your operations, realize that the drum size does not
equal the mixing capacity. The
drum should be filled only to a
level three inches above the centerline of the paddle shaft.
Gasoline-powered mortar mixers usually are priced higher than
electric-powered models of comparable capacity, but use, not cost,
should dictate the power source.
Gasoline-powered mixers generally are more convenient because
they don’t have to be plugged in.
In remote areas, lack of electric
power lines may necessitate the
use of gasoline-powered models.
But only electric mortar mixers
can be used indoors, a growing
consideration for masonry contractors accepting more interior remodeling jobs.
Just about every mortar mixer
comes with a variety of engine options—usually one electric engine,
plus two or more powered by
gasoline. Engine choice tends to be
subjective, based on personal experience and preference, with many
masonry contractors swearing by
particular brands.
Engines run constantly and take
a lot of abuse; consequently, even a
masonry contractor who changes
an engine’s oil every three to five
days is lucky to get five years of
life out of that well maintained engine. Typically, two or three engines are needed during the lifetime of a mortar mixer.
Three types of power trains are
available on mixers: open gear and
belt drive, enclosed gearbox drive,
or hydraulic drive. Although they
cost more than the others, hydraulic-drive models are less expensive to maintain because they
have no gears or bolts to shear and
no belts or clutches to wear out.
Quality performance should be
near the top of any masonry contractor’s list of mixer selection criteria. But all too often, performance is taken for granted.
If buying a paddle mixer, examine the paddle configuration and
the shape of the drum. Short, deep
drums are more efficient than long,
shallow drums because the blades
don’t have to move the material as
far. Expect models with long
drums to have as many as eight
paddles for uniform mixing action.
Choose a model that has steel paddle arms with rubber blades,
which keep the drum cleaner and
provide a more uniform mix.
Also, look at spiral mixers for
added speed and more efficient
mixing action. A spiral mixing
blade works like a spiral conveyor,
rapidly moving material across the
drum. But spiral mixers cost $200
to $300 more than comparable
paddle mixers and are more expensive to repair. If one paddle
mixer blade is damaged, the individual blade can be replaced; but if
a spiral blade is damaged, the entire mixing blade must be replaced.
When shopping for a mortar
mixer, Guy Michel of Alsip, ILbased Michel Masonry Co. values
ease of maintenance above all other considerations. The first component of a mortar mixer to give out,
he notes, is usually the packing,
which helps form the seal where
the paddle shaft is attached to the
drum. Mortar seeping through the
packing will eventually cause the
blade to freeze.
With certain mixer models, it is
very difficult to replace the packing, and some models require daily packing adjustment. Michel
prefers to buy mixers with packing
that is easy to replace and requires
little or no adjustment.
Examine the drum: The hub
should be bolted, not welded,
which makes shaft-bearing replacement easier and much less
expensive. According to one manufacturer, a polyethylene drum can
save cleanup time because mortar
can be quickly and easily freed
from this surface with minimum
effort and without dents or rust.
Always ask the dealer how
quickly various parts can be replaced. Some manufacturers tout
readily available, off-the shelf industrial components that allow replacement with minimal downtime.
Though the blades and shaft
bearing need considerable maintenance, the drum should last
throughout the life of the mixer.
Make sure that a metal drum is
constructed of heavy-duty steel
since thick drums withstand more
abuse and wear than thin ones. In
addition, the drum sections should
be precision-cut to size. Lap welds
are stronger than butt welds.
One clue to an engine’s durability is the cowl. If this protective
cover is spacious and well-ventilated, more air will pass through the
engine. A cool engine lasts longer.
Even heavy-duty steel won’t
withstand the bouncing, caroming,
and capsizing that may occur in a
troublesome tow. A mortar mixer
should have a low tow pole to
minimize the possibility of jackknifing. For clearance over rough
ground and curbs, the tow pole
should have a downward pitch.
Check to see that the tow pole
has a second safety bolt to prevent
it from coming out of the frame.
Also, insist on a heavy-duty, steelreinforced foot, designed to reduce
stress on the leg and tow bar and
help prevent bending, twisting,
and excessive vibration. And
high-speed tires are a must if you
intend to tow the unit faster than
45 miles per hour.
In these tough times, masonry
contractors are traveling farther
and more frequently, as projects
tend to be smaller and not necessarily close to home. As a result,
ease of towing is especially important today.
Whether out of genuine concern
for worker safety, fear of OSHA
fines, or the desire to reduce workers’ compensation premiums, masonry contractors are paying more
and more attention to safety features.
Mortar mixers should have safety guards that combine operator
protection with easy access for
cleaning. In addition, a mixer
should have a clutch handle that
disengages the paddles while the
machine is still running.
A well-ventilated cowl or engine
cover affects safety, as well as performance and durability. If too little air is reaching the engine, masons may be tempted to open the
cover, thus exposing themselves to
safety hazards.
The cowl keeps dust and foreign
objects from entering the engine
and being spewed out at the workers.
Additional features can help
boost worker productivity. Notice
where the drum latch is located.
According to one manufacture r’ s
literature, the latch should be
placed so that if the operator uses
his hands in dumping, he can release the drum latch with his knee.
Another time-saving feature is a
guard lifter, which automatically
moves the guard out of the way as
the mix is being discharged.
Consider buying a mixer with
an attached measuring sandbox to
ensure that the same amount of
sand is used in every mix. This
counteracts any tendency to use
too little sand. Properly measured
sand should make the mortar go
farther, saving time and money.
Because masonry contractors today have widely varying job requirements, mixer versatility can
be a crucial issue. Some mixers, for
example, have adjustable axles
that contract to fit through narrow
Also available are versatile
two-in-one paddle-blade designs,
which sandwich long-lasting rubber blades between strong steel
blades. With highly abrasive mixes, the rubber blades can be removed and the steel blades extended.
Assigning priorities to the benefits that various features provide
will help you answer that critical
question: Which mortar mixer or
combination of mixers will best
meet both my current and projected needs?
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