Masonry Magazine August 2002 Page. 16
Mortar Mixers
It has to be **heavy enough** to **resist vibration** and be **non-steel** or coated to **prevent** rusting.
sales show a preference for Honda engines, followed by Briggs & Stratton, then electric motors," says Faler. Usually, however, the biggest choice is in horse power, not brand of the engine.
Faler's rule of thumb for engines is simple: Get more than you think you'll ever need. "Always pick the highest horsepower engine you can afford. That way, when you're on the job, it will be able to handle whatever comes along. You won't have to check ratings to see if you can use a particular mix or size gravel-up to the size specified for the drum and blades, of course."
He adds, "Also watch for the engine cover or cowling, be sure it allows ample ventilation to reduce engine wear and increase performance while keeping dirt and cement dust off internal parts. It has to be heavy enough to resist vibration and be non-steel or coated to prevent rusting."
Any mechanical device has its upper limits of operation. Usually called ratings, these factors tell the contractor what the equipment can and can't do under given conditions. But while the mixer might be sold to do a certain job, and rated for that job, there is no way for the manufacturer to keep workers from asking more of the equipment. In other words, people sometimes use equipment for tasks it was never designed to do.
"In California, for some reason, it seems most mason contractors use cement mixers for everything," notes Faler. "That's not a good idea when you're mixing mortar-the turning drum type cement mixer won't give you the same thorough consistency as a real mortar mixer which uses blades turning inside the drum."
And regardless of the location, workers tend to try adding just a little more mix to speed up the production and soon overloading occurs. That's when the choice of higher power and hydraulic operation comes in handy. Again, a rule of thumb for mixing capacity, as Faler puts it, is one bag of mix equals three to four cubic feet of mortar mix or, if you are still doing it by hand, 16 shovels of sand and 4 shovels of cement. So an 8-cu. ft. mixer would be rated at 2 to 2.5 bags.
"Our studies show if you have over 10 men on a job, the mixer should be a minimum of a three-bag mixer," claims Lang. "If not, it can't keep up with the men. If your crew is four or five men, you can go to a two-bagger. If you choose a larger hydraulic mixer, you only have to have one mixing station for the whole job site."
Addressing the "one mixer for everything" idea, Lang adds, "The question is, will you be using your mixer to mix grout. If you do, the mixer will need to be larger and it will have to be hydraulic. Hydraulic mixers will mix pea gravel grout, something that many mason contractors are not aware of. They're still using the old drum type mixers that take about three times longer to mix thoroughly. Hydraulic mixers will mix grout and if they happen to get plugged on a rock, you simply reverse it and then run it forward to clear the plug."
Some other concerns surface when you think about the daily use of the mixer. Take the drum for example. Short, deep drums are most efficient because the mortar is carried from end-to-end quicker. That means better mixing faster. And a narrow dump chute is recommended so you can dump into a wheelbarrow from its front or side.
It probably goes without saying, but a thicker drum will take more abuse and wear without failing. Steel, still the most popular drum material, should be lap-welded not butt-welded.
Coming on strong is the "plastic drum" mixer. Polyethylene tubs are easy to clean of dried material, are as abrasion resistant as steel, don't dent like steel, and resist chemical corrosion and rust. Mosher sees these as valuable traits, "Mortar mixers must be easy to clean, both the inside the drum and the paddles that rotate the mortar because they have to be cleaned every day. The easier, the faster, the better it is at the end of a day or end of the job."
Those paddle arms and blades should be pitched at a 30-to-40 degree angle, says Faler. "That will create a fast, uniform mix and reduce material loss due to splashing."
And splashing is a problem, indicates Lang. "There should be more blade where it cuts the mortar so they don't slap it and splash it all over the place. In a good mixer, the blades are more upright, and they cut through the mortar instead of tumbling it."
Lang won't make too many friends with weekend golfers when he relates, "My test is to toss a golf ball inside the mixer when it's running empty. If it's been designed properly, that golf ball will go from one side of the mixer drum clear to the other, and then back. That