Most operators, when they shop for a vertical mixer, look at capacity, auger count, and price. The shape of the tub floor rarely comes up. That is a shame, because it is one of the details that determines whether your tractor is working harder than it needs to on every single batch.
What a Decagonal Tub Floor Actually Is
A decagonal tub floor has ten sides. That is not a marketing description. It is a geometric fact with real consequences for what happens inside the machine when the auger turns.
Picture a conventional rectangular tub. The auger sweeps a circular path. The corners of the rectangle are outside that path entirely, so material packs into them and sits. Dead zones build up. The flat walls between corners are another problem: a round bale contacting a flat surface spins against it with very little resistance, which means the auger never quite gets a clean grip on the material. You end up adding revolutions to finish what the geometry was fighting from the start.
Now picture a ten-sided polygon. Each flat face is short enough that, collectively, they trace something very close to a circle. The auger’s sweep radius and the tub wall stay in near-constant relationship as material rotates. There are no true corners for feed to pack into and no long flat surfaces for bales to spin against freely.
LEO Agriculture describes this geometry as creating “a near-perfect radius, the best of both worlds” between a fully round tub and a flat-walled rectangular one. The flat sides of the decagon work in your favor: they stop round bales from simply spinning in place, creating pressure against the wall that forces the auger to cut rather than chase the bale around the tub.
Engineered Ratios, Not Approximations
The shape alone does not do much if it is not sized correctly for the auger running inside it. This is where a lot of tub designs go wrong. A machine built by estimating the relationship between auger diameter, tub depth, and floor profile will have regions of the tub where material moves well and regions where it barely moves at all. The result is uneven TMR and longer run times.
On the LEO machines, the company is clear that nothing in the geometry is approximated. The ratios between auger diameter, tub depth, and the decagonal floor profile are calculated, tested, and proven. The stated principle from their design documentation is direct: “It has to be perfect.” That is the reason the decagonal floor works the way it does across their VT Series machines, which run from 6 to 21 cubic meters, rather than only at one specific size.
It also explains why each machine in the range gets an auger matched to its volume rather than a single generic auger design stretched across multiple sizes. A 10-cubic-meter machine and a 20-cubic-meter machine are not running the same auger at different speeds. The geometry of the auger, the floor, and the tub walls are recalculated for each capacity. That is a different engineering commitment than simply scaling sheet metal.
For a closer look at how the auger itself is engineered to work with this geometry, the diamond auger design is worth reading through. The square cutting principle and knife placement described there only function as intended when the tub geometry keeps material in the right pressure zones.
The Practical Result: Fewer Revolutions, Less Fuel
This matters most when you are mixing high-hay rations or processing whole bales. Those are the conditions that expose a poor tub geometry fastest.
With a flat-walled rectangular tub, a round bale dropped in has a decent chance of contacting one of the longer flat walls and spinning. The auger keeps moving, the bale keeps spinning, and tear-down is slow. You add time, you add revolutions, and the tractor is working against a tub that is not helping it. Fuel per batch climbs.
The decagonal floor changes that dynamic. The flat faces create pressure points that grip the bale rather than letting it rotate freely. The bale is forced toward the auger’s cutting zone, tear-down accelerates, and the overall mix reaches homogeneity in fewer revolutions. Less time on the PTO means less diesel burned per batch, and that compounds across a full feeding season.
The auger features built into the LEO design reinforce this. The hockey stick kicker sweeps material away from the wall and back toward the auger center. The V-shaped leading edge pushes material inward rather than letting it pack outward. Hay knife relief cuts let long-stem material fold before it is cut, which reduces the resistance the auger has to overcome. None of those features deliver full value in a tub that puts material in dead corners or lets bales spin against flat walls.
The VT Series mixer range is where these geometry principles are applied across the full 6 to 21 cubic meter lineup, and it is worth reviewing the capacity-specific configurations if you are speccing a new machine for high-roughage rations.
What to Check When Comparing Tub Designs
When you are looking at mixers side by side, the tub floor is not always the easiest thing to inspect. A few practical checks worth making before you commit.
- Ask the manufacturer how the auger diameter relates to the tub depth. If they cannot give you a specific ratio, that is worth noting.
- Drop a tape into the tub corners. A rectangular tub with sharp interior corners will collect material in service. A decagonal or similarly faceted tub should show a short, angled face at each transition rather than a true 90-degree corner.
- Ask whether the auger is sized for that specific tub volume or shared across multiple machine sizes. Generic augers across a full range usually mean a compromise somewhere in that range.
- If you run high-hay or bale-heavy rations, ask what happens to bale contact at the wall. A round tub allows bales to spin; a fully rectangular tub creates dead corners. The decagonal design sits between those two failure modes by design.
Mixing quality ultimately lands at the feed bunk, and how the ration holds together through delivery is a separate problem worth understanding. The article on TMR quality loss after the mixer covers what happens between the tub and the bunk, which is where a good mix can still come apart.
The geometry of the tub floor is one of those details that gets ignored until someone starts counting fuel receipts or noticing variation in the herd. Get it right in the spec stage and it costs nothing. Fix it after the fact and you are either living with the problem or buying a different machine.
