Most people, seeing a vertical TMR mixer for the first time, assume the tub is round. From a distance, it looks round. The auger is round. The lid is round. But look closer at how the sidewall meets the floor, and you start to notice the facets. Ten of them. And that number is not arbitrary.
What Happens Inside a True Round Tub
A perfectly cylindrical tub creates a problem that is easy to understand once you think about it. The auger spins. The feed, with nothing to interrupt it, tends to spin with the auger rather than being pulled into it. Material rides the wall in a circular path, and when that happens, mixing action drops off. You get rotation instead of circulation. Those are not the same thing.
Some tub designs compensate with extra knives or higher auger speeds. Both approaches cost horsepower and can compromise ration quality if long-stem material is being torn rather than folded and blended. The geometry of the tub itself is doing nothing to help.
What a Polygon Tub Does Differently
Introduce flat panels to that wall and the physics change. Each panel face presents a slight angle to the rotating material. Instead of continuing its circular path, feed hits a facet at a deflection angle and gets redirected back toward the auger. You get a controlled interruption, repeated ten times per revolution as the auger turns. The result is more material passing through the cutting and mixing zone per unit of time, without needing to increase speed or add mechanical complexity.
The catch with a polygon tub is the corners. A square or hexagonal cross-section creates sharp internal angles where feed packs and stagnates. You trade one dead zone for several.
The Decagonal Floor and Why Ten Sides Solve It
Ten sides is where the geometry starts to work in your favour on both counts. The deflection effect is present. But with ten panels rather than four or six, the internal angles are shallow enough that material does not pack into the corners. The floor profile approaches something close to a radius without actually being one.
LEO Agriculture’s engineering documentation describes the decagonal tub floor as creating “a near perfect radius. The best of both worlds.” That is a precise claim and it holds up mechanically: you get the wall-deflection benefit of a polygon and the smooth-flow benefit of a circle, without the packing risk of sharper corners or the dead-zone spin of a true cylinder.
The design shows up in the tub floor as a ten-sided base panel with a central auger aperture and knife mounting slots positioned to work with, not against, the flow paths the geometry creates.
Ratios, Not Approximations
The shape of the tub is only part of the story. A decagonal cross-section sitting on top of the wrong auger diameter, or the wrong tub height, would not perform the way the geometry promises. Every dimension has to be right in relation to every other dimension.
LEO’s position on this is direct: everything on the machine is designed from calculated, tested, and proven ratios. Nothing is approximated or treated as close enough. That is a quote from the engineering documentation, not marketing copy. The implication is that the 10-sided geometry is not cosmetic. It is structural to the mixing formula, and it only works as designed when the auger diameter, tub depth, and sidewall angles are all derived from the same set of ratios rather than sized independently.
This matters more than it might appear. A tub that is too tall relative to its auger diameter changes the pressure zone distribution. A tub that is too shallow loses mixing residence time. The decagonal wall does its job only when the material arrives at each facet under the right conditions, at the right speed, at the right point in the auger’s travel. Get the ratios wrong and the deflection benefit disappears into dead zones just as quickly as it would with a round tub.
Pressure Zones and Why the Floor Shape Feeds Into Them
Vertical mixer tubs have distinct pressure zones along the auger height. Material near the bottom experiences the most intense pressure from the auger flights and the floor geometry together. The middle zone is where most of the blending action occurs. The top is primarily transfer, moving material back into the descent path.
The decagonal floor directly influences what happens in that bottom high-pressure zone. By keeping material moving back toward the auger rather than packing against a flat wall or spinning freely against a round one, the floor shape helps ensure that bales and coarse roughage keep contacting the cutting zone. Faster contact in the pressure zone means faster processing, and faster processing means less time running the PTO to hit a consistent, homogenous ration.
Five Auger Features Working With the Tub
The tub geometry does not work alone. LEO’s auger incorporates five specific design features that complement what the decagonal walls are doing: a slanted auger top that eliminates dead spots on the cap, angled ripping blades for faster bale processing, a hockey stick kicker that sweeps material from the wall back toward the auger, a V-shaped leading edge that acts like a grader blade to push material toward center, and hay knife relief cuts that let long-stem material fold over the blade before being cut.
Each of those features addresses a specific failure mode. The kicker in particular matters here because it operates at the outer lower edge of the auger, right at the boundary between the auger column and the tub wall. When that kicker is sized correctly and in good condition, it reinforces the deflection work the decagonal wall is already doing. When it is worn or missing, wall dead zones return regardless of the tub shape. LEO offers the kicker as a bolt-on component in four sizes, from small through to an extreme variant with an extended lip for low-density material, so the aggressiveness can be matched to the ration rather than forcing one setting for everything.
Sizing Before Geometry Matters
A correctly designed tub running on a machine that is too small or too large for the herd will still underperform. Getting the mixer volume right is the first decision, and it shapes everything else. LEO Agriculture offers a Vertical TMR Feed Mixer Size Calculator as a practical starting point for matching machine capacity to herd size before any geometry discussion is relevant.
The VT Series covers 6 to 21 cubic meters for dairy, beef, and sheep operations. The HD Series runs from 16 to 45 cubic meters and is built for large-scale feedlot and dairy work, including truck-mount applications. Both series carry the decagonal tub geometry because the fluid-dynamic rationale holds at every scale.
If you are specifying a mixer and the tub shape has never come up in the conversation, it is worth asking. The wall geometry is not a feature that shows up in a spec sheet, but it is doing meaningful work every time the auger turns.
