Why does Avanti have heavier end panels?  Why do we say the gearbox runs cooler?  Does the area above the discharge door get mixed properly? 

This page answers these questions and others.

Why does Avanti have heavier end panels and look bulkier than others of the same size?  When mixing a heavy load in a twin-shaft mixer, the tremendous torque of the mixer shafts tend to twist the mixer body - it squirms slightly.  50 years of experience has shown that this squirming can twist the shaft seals and bearings out of line, causing excessive wear over time.  The extra-stiff frame and added box-sections along the body of the mixer help Avanti to hold its shape even with full loads of extreme mix designs, such as in concrete for dam applications, resulting in longer life of bearings and shaft seals. 

Longer life with less down-time.

Why do we say the gearbox runs cooler? It's a fact that the Avanti gearbox runs cooler than many others, and as a result does not require an oil cooling unit.  This reduces its complexity and increases reliability while reducing its price.  We say that this is due to its 2-stage design, but this is a simplification.  In fact, it is due to the higher efficiency of this particular gearbox, which in turn is mainly due to the 2-stage design. 

The speed of the motor, 1750 rpm, must be reduced to allow the mixer shaft to turn at 24 to 27 rpm.  This is done with a 2:1 belt reducer followed by a 36:1 gear reducer.  Every pair of gears creates a little friction which results in power loss.  If everything else is equal, each set of gears will add to the total power loss, so the higher the number of stages, the higher the power loss.  Take model AV4500, which uses two 55 HP motors.  Each motor consumes 41 KW (41,000 watts) when running at full load.  If each stage of the gear reducer looses just 0.5% of the power in friction, a 2-stage reducer will dissipate 1% of 41,000 or 410 watts in heat.  A 3-stage reducer will dissipate 50% more, or 615 watts - almost equivalent to the electric heater you might have for warming a cold room!  Luckily the mixer is not fully loaded 100% of the time, so the power dissipated will only be at this level for short periods of time.  The average power dissipation raises the temperature of the gearbox, gears and oil to a proportional amount above ambient;  thus if the 2-stage example gives a temperature rise of, say 60 deg. C above an ambient of 20 deg. C, its temperature will stabilize at  80 deg. C.  The 3-stage example will give a rise of 90 deg. C and its temperature will stabilize at 110 deg. C.  If the oil starts to disintegrate at 100 deg. C, damage will eventually occur unless extra cooling is used.

This example is a simplification and we have neglected some smaller effects such as the different ratio of the reducers in the example, which tends to level the difference somewhat.  Nevertheless, the Avanti's 5-year gearbox guarantee shows that we are very confident in its ability to perform without an oil cooler, even when running non-stop and fully utilized for many hours each day.

Reduced cost and longer life.

Another little story on the gearbox:  when the Avanti was first used in China, where they run them 24 hours a day non-stop at maximum output, one gearbox ran cool and the other ran much hotter.  On investigation it was found that because the two gearboxes run in opposite directions, a small difference in the oil lubrication occurred and was causing the effect.  Once found, it was quickly cured, allowing both gearboxes to run at the same cooler temperature.

Experience eliminates weak points to give a better product.

Does the area above the discharge door get mixed properly?  In a word, YES. The very intense mixing action sweeps the material through this area before it has time to stop, allowing it to mix with the rest of the batch.  There is a step of less than 2" high between the mixer floor and the discharge door, however, and a concern has been raised that a small fillet of unmixed material can lie along the trailing edge.  This is highly unlikely in pratice because the mixing action pushes material across this area from both sides.  To eliminate any possibility for concern, however, the edge of the floor and liner can be chamfered.

Complete mixing and thorough cleanout means no unmixed or stale concrete.

Filling to total capacity and faster mixing time means a lot more throughput for the price, or a smaller mixer, which saves money.

How many Avanti mixers are there in operation?  There are over 1400 in operation worldwide, producing over 1 million cu. meters of concrete per day.  No other twin shaft mixer comes even close to these numbers.  There are 3 plants worldwide manufacturing these rugged workhorses.  In 2004, over 700 have been produced;  more than all other manufacturers combined. 

These statistics show that Avanti is truly what it claims to be - a great mixer for a great price.