Quick answer: a radius belt turns flat, inside one level, because slotted rod holes let the inside edge of the belt collapse while the outside edge stays extended. A spiral is a different product family: the belt climbs while it wraps around a drum, so it is a tower, not a bend. If your line has 90 degree corners, S curves or an accumulation table, a radius belt is the answer. If you need vertical rise in a small footprint, you need a spiral, and no radius belt substitutes for one.
What actually happens inside a radius belt
A straight running modular belt has round rod holes. Every module sits at a fixed pitch from its neighbour, so the belt can only travel in a straight line. A radius belt changes one detail: the rod holes are slots, not circles.
When the belt enters a bend, the modules on the inside of the curve slide along their slots and close up. Pitch on the inside edge shortens. On the outside of the curve the modules stay pushed out to the full slot length, so the outside edge keeps its full pitch. The belt fans out across its width and follows the bend without slipping, because the sprockets are still engaging the same drive bars they engage on the straight sections.
That is the whole trick, and it has three consequences you feel in the field. The belt stays positively driven through the corner, so no transfer plate and no second motor are needed at the bend. The inside edge takes a disproportionate share of the tension, because it is the shorter path. And the collapse has a limit, which is what the inner turning radius specification describes.
Inner turning radius, expressed as a multiple of belt width
Radius belts are not rated in millimetres. They are rated as a multiple of belt width, measured from the centre of the curve to the inside edge of the belt. A belt rated at 2.5 x running at 600 mm wide needs an inner radius of at least 1,500 mm. The same belt at 300 mm wide only needs 750 mm.
This is the number that decides your floor plan, so it is worth doing the arithmetic before you pick a series rather than after.
| Belt width | Inner radius at 1.7 x | Inner radius at 2.3 x | Inner radius at 2.5 x |
|---|---|---|---|
| 400 mm | 680 mm | 920 mm | 1,000 mm |
| 600 mm | 1,020 mm | 1,380 mm | 1,500 mm |
| 900 mm | 1,530 mm | 2,070 mm | 2,250 mm |
The floor space you actually lose is the inner radius plus the belt width, because the outside edge sweeps that far out. A 600 mm belt at 2.5 x sweeps 2,100 mm from the centre of the curve. The same belt at 1.7 x sweeps 1,620 mm. That 480 mm is often the difference between a corner that fits and a corner that eats an aisle.
What a tighter multiple costs you
A tighter turn is not free. To let the inside edge collapse further, the module needs longer slots and more clearance around the rod, and both of those take material out of the part exactly where the tension runs. Then the geometry itself works against you: the tighter the bend, the larger the share of total belt pull that concentrates on the inside edge.
The Veybelt range shows this clearly. The 916 series turns tightest at 1.7 x and carries the most open grid in the group at 60%, and it also has the lowest belt strength of the four at 14,200 N/m in PP. The 7100 series gives up some turn tightness at 2.3 x and gets 24,200 N/m in PP back for it. That is the trade in one line.
So the design order matters. Work out the tightest corner your building forces on you, then check whether a belt that can turn that tight still has the strength for your longest run. If it does not, the fix is a wider corner or a shorter conveyor, not a stronger radius belt.
The four Veybelt radius series side by side
| Series | Pitch | Inner turning radius | Belt strength | Open area | Thickness |
|---|---|---|---|---|---|
| 300 | 46 mm | 2.5 x belt width | 18,200 N/m (PP) | 41.5% | 14.5 mm |
| 916 | 25.4 mm | 1.7 x belt width | 14,200 N/m (PP) / 14,700 N/m (POM) | 60% | 13 mm |
| 2400 | 25.4 mm | 2.5 x belt width | 17,000 N/m (PP) / 31,800 N/m (POM) | 44.2% | 13 mm |
| 7100 | 25.4 mm | 2.3 x belt width | 24,200 N/m (PP) / 30,900 N/m (POM) | 44.2% | 12.8 mm |
Read it as three positions rather than four. The 916 is the tight turn and high drainage choice, and you accept the lowest strength for it. The 7100 is the strong one that still turns reasonably tight. The 2400 in POM is the strength option when the corner is generous, at 31,800 N/m. The 300 sits apart on a 46 mm pitch with a coarse open grid, which suits larger and heavier packs rather than small items.
If you want the product level detail on each of these four, our radius and spiral belt buyer's guide goes through them series by series. This article is the layer above that: which family, what radius, what it costs.
Why a spiral tower is a different product
A spiral conveyor does something a radius belt cannot do at all. The belt wraps around a rotating drum in a helix and gains height on every turn, so a long dwell time for cooling, proofing or freezing fits into a footprint the size of the drum, and what the cold does to the belt material becomes the next question. The belt is in contact with the drum through the whole wrap, and that contact is typically what carries the belt up, with the head drive taking only part of the load. Tension is fed in along the wrap instead of arriving all at one shaft.
None of that is a bend. A radius belt bends in one plane, at a fixed elevation, over one corner at a time, as does a side flexing flat top chain in a guided curve. Stacking corners does not produce a spiral, because a spiral needs continuous drum contact, a helical cage or track, and a tension model built around wrap. This is why a spiral tower is bought as a system, with the spiral conveyor chain plate as the running surface inside it, and why you cannot quote a spiral as so many square metres of radius belt.
| Your requirement | What to specify |
|---|---|
| 90 or 180 degree corner, same level | Radius belt. Check the inner radius multiple against the corner you have. |
| S curve to dodge a column or a machine | Radius belt, and count both bends into the total belt pull. |
| Accumulation table feeding a filler | Radius belt, high open area if the line is washed down. |
| Vertical rise with a long dwell time | Spiral system with a spiral chain plate. A radius belt does not apply. |
| Corner that is tighter than 1.7 x the belt width | Neither. Split the line and use a transfer, or narrow the belt. |
That last row catches more enquiries than people expect. Below the tightest published multiple there is no belt to buy, and forcing a belt round a corner it is not rated for shows up as edge wear, rod hole elongation and eventually a belt that jumps the sprockets.
What to send with the enquiry
For a curve or a spiral we can give you two workable options and the trade between them if you send these five things. You can browse the range first on the radius and spiral belt collection, but the numbers below matter more than the series you start from.
- Belt width, and the inner radius your building allows at each corner, measured from the centre of the curve to the inside edge.
- How many bends on the run, and the total conveyor length including straight sections.
- What you are carrying: product, weight per metre of belt, and whether it is stable standing up.
- Line speed and working temperature, plus whether the line is washed down.
- For a spiral: the rise in millimetres and the dwell time you need, not just the throughput.
Send that to us through the contact form or on WhatsApp and we will come back with the series, the radius it needs and where the strength margin sits.
