Quick answer: a side flexing flat top chain goes round a bend because its plates have a bevelled underside that lets them fan out on the outside of the curve. The bend has to be a guided curve, with wear strips on the inside and the outside and a hold down on the outer edge, or the chain lifts and jumps out. Minimum turn radius is not one universal number: it rises with plate width and depends on how the curve is built, so it gets confirmed per layout. Every bend adds friction to total chain pull, which is why a long line with several corners often needs a second drive.
What makes a chain side flexing
Two things. The pin and barrel joint has clearance that lets consecutive plates swing sideways relative to each other, and the underside of each plate is bevelled so the plates can fan open on the outer side of the bend without the corners fouling the plate behind.
A straight running chain has neither. The 820 series is a straight running chain and it should never be forced round a bend. It will bind against the outer guide, the plates will ride up over one another, and you will be replacing chain and wear strip together within weeks. If your layout has a corner in it, you need the 880 series side flexing chain from the start.
| Series | Type | Plate widths | Chain plate load | Material |
|---|---|---|---|---|
| 820 | Straight running only | 82.6 / 114.3 / 152.4 mm | 4,300 N | POM / PP |
| 880 | Side flexing | 82.6 / 114.3 / 152.4 mm | 4,420 N | POM / PP |
| 880HD | Heavy duty side flexing | 152.4 mm | 4,420 N | POM / PP |
Note that 880 and 880HD carry the same rated chain plate load of 4,420 N. The heavy duty version is catalogued only at the 152.4 mm plate width, so the difference sits in the construction rather than in the rating. If a heavy duty chain is under consideration for your curve, ask us what it changes before specifying it.
Minimum turn radius and plate width
Here is the relationship, in plain terms. The chain turns by taking a small angular step at each joint. The number of joints in the bend is set by the pitch, and the sideways swing available at each joint is limited by the joint design. Multiply the two and you get how sharply the strand can turn.
Plate width then enters twice. A wider plate sweeps a longer arc at its outer corner for the same angular step, so the gap that has to open between plate corners grows with width. A wider plate also presses harder against the outer guide rail at a tight radius, so it rides up more easily. Both effects point the same way: for a given chain, the wider the plate, the larger the minimum radius.
We do not publish a single minimum radius in millimetres, and you should be sceptical of anyone who gives you one without asking questions. The workable radius depends on plate width, the chain pull at that point in the line, the wear strip material, and how much straight track sits either side of the bend, and none of it converts to the inner radius multiple a modular belt is rated by. Send us the layout and we will confirm a radius against it.
| Factor | Effect on minimum radius |
|---|---|
| Wider plate (152.4 mm against 82.6 mm) | Raises it. The outer corners need more room to fan open. |
| Higher chain pull entering the bend | Raises it in practice. Radial load on the outer rail goes up with tension. |
| Larger wrap angle, for example 180 degrees rather than 45 | Raises the effective demand, because friction accumulates through the wrap. |
| Low friction wear strip, well aligned | Lowers the radial load and lets the published minimum actually work. |
| Curve placed near the drive, on the low tension side | Helps. The same bend is easier where the chain pull is lowest. |
The curve has to be guided on both sides
This is the most common build error we see in customer photographs. A straight track only has to support the chain from underneath. A curve is different, because the chain in a bend is under a radial force that presses it outward continuously.
A working curve needs four things. A wear strip under the chain through the whole arc, so the plates never lose support. An outer wear strip taking the radial thrust, which is the part that wears fastest and should be a replaceable strip rather than bare frame steel. An inner wear strip or guide, keeping the chain on the arc so it cannot cut the corner. And a hold down over the outer edge of the plates, because a chain pressed against an outer rail wants to climb it, and a chain that climbs will eventually sit on top of the rail and stop the line.
Alignment matters as much as the parts. Where the straight track meets the curved track there must be no step and no gap. A joint that is 1 mm out gives the plate corner something to catch on every single link, and the noise tells you long before the chain fails.
Bends add to chain pull
Total chain pull is what it takes to drag the loaded chain along every straight section, plus what each bend adds. A bend is not simply another length of track. Inside a curve the chain presses against the outer rail with a force that grows with the tension already in it, and the friction from that pressure is added on top. The effect compounds: tension leaving bend one is the tension entering bend two, so the second bend costs more than the first.
Two consequences follow. Put the bends as close to the drive end as the layout allows, on the low tension side, because the same corner is cheaper there. And accept that on a long line with several corners one drive may not be enough, at which point the right answer is to split the run into two conveyors with their own drives and a transfer between them. Pushing one drive harder just raises the tension that every bend then multiplies, and the chain plate load rating of 4,420 N is the ceiling that decides it. The 820 and 880 drive and idler wheels are the other half of that calculation, since the teeth in mesh at the drive set how much pull the strand will take.
Entry and exit of a curve
The transfer points either side of a bend are where product falls over, not the bend itself. The chain is changing from straight to fanned, so it settles into the outer rail over the first few links, and the product on top is being pushed sideways by the change in direction.
Give the chain a straight section before and after every curve so it enters the arc already tracking properly, and keep the product guides continuous through the transition rather than starting a new rail at the curve entry. Where product moves from one chain strand to another, a dead plate closes the gap so nothing tips into it. If containers are tall and light, slow the line through the corner rather than adding side pressure with tighter guides.
| Symptom | Likely cause |
|---|---|
| Chain climbing the outer rail in the bend | No hold down, or the radius is tighter than the plate width allows |
| Fast wear on one edge of the plates | Outer wear strip worn through, or a step at the straight to curve joint |
| Chain binds and the drive draws more current | Too many bends on one drive, or a straight running chain in a curve |
| Product tipping at the corner entry | No straight run in, or guides broken at the transition |
| Clicking noise once per link | Misaligned track joint catching the plate corner |
What to send with the enquiry
- A sketch of the line from above with each bend marked: wrap angle in degrees and the radius you have room for.
- Plate width you are running or planning: 82.6, 114.3 or 152.4 mm.
- Total conveyor length, and where the drive sits relative to the bends.
- Product, weight per container, and how many containers per metre of chain.
- Line speed, working temperature, and whether the line is washed down or runs dry.
Our flat top chain guide covers the wider range, the wear strips, wheels and transfer plates around the chain are listed separately, and the full list sits in the flat top chain collection. For a curve, send the layout sketch to us on WhatsApp or through the contact form and we will come back with a chain, a radius we can stand behind for that plate width, and whether one drive covers it.
