Simplex vs Duplex vs Triplex Roller Chain: Load Chart | CTS

A triplex roller chain is three simplex chains assembled on common pins. Same pitch, same roller, same plate thickness — roughly three times the tensile strength of the single-strand chain, and about three times the wear life at the same pull. What it is not is a drop-in swap: the sprocket, the transverse pitch and the shaft width all have to change with the strand count. The load data and the matching rules are below.

Simplex, duplex and triplex chain: what actually changes

All three share a chain number, so pitch, roller diameter, inner width and plate thickness are identical. The only difference is how many plate stacks sit on each pin. A simplex chain has one row of inner plates between two outer plates, a duplex chain has two rows with a shared centre plate, and a triplex chain has three. The tooth form doesn't change, which is why a #80 simplex sprocket and a #80 triplex sprocket have the same tooth profile—and why they still cannot be used interchangeably.

The ISO naming runs the same way: ANSI #80 is ISO 16B, and the -1 / -2 / -3 suffix counts strands in both systems. Compare pin diameter and inner width before trusting a cross-reference, because the two standards are close but not identical at every size.

Load capacity: the numbers, and the trap behind them

The table is our catalogue minimum ultimate tensile, the figure that goes on the test report. Because every strand rides on the same pins and uses the same plates, the value scales almost exactly with strand count: duplex sits at 2.0 times the simplex figure and triplex at 3.0 times.

The ratio holds across the range because plate thickness and pin diameter do not change with strand count; only the pins get longer. #41 is the exception worth knowing: it is catalogued as simplex and duplex but not as a standard triplex, so a request for 41-3 normally means a move to #40-3 or a different pitch.

Ultimate tensile is a breaking figure, not a working load. Drive selection usually runs a factor of roughly 6 to 8 against it for smooth duties, and higher where there is shock, reversing, or frequent starting — confirm the figure the applicable standard or the machine builder requires rather than assuming it.

The trap is that 3.0 times is arithmetic, not field performance. Three strands share the load evenly only when both sprockets are aligned, unworn, and cut to the same transverse pitch. A hooked sprocket or half a degree of shaft misalignment loads one strand harder than the other two, and the chain breaks at the load you thought you had margin on. Until the alignment and tooth wear are verified, treat triplex as something below its catalogue 3.0 times.

One thing does not change with strand count: the pull on the shaft. Chain pull works out as twice the torque divided by pitch diameter, so at the same sprocket and the same torque, a triplex chain pulls exactly as hard as a simplex chain. What triplex changes is the stress inside each plate and each pin, and the wear life at a given load. It does not reduce the radial load your bearings see. If anything, the heavier chain and the wider hub make the shaft and bearing check more important, not less.

Sprocket matching: four dimensions that have to agree

A multi-strand sprocket is a single part with several rows of teeth. It is not three simplex sprockets bolted together and it cannot be assembled from them, because each tooth row is narrower than a simplex sprocket and the spacing between rows is fixed by the chain standard. These are the numbers to match against.

1. Strand count. The sprocket needs exactly as many tooth rows as the chain has strands. A -3 chain on a -2 sprocket runs off-centre, and the middle row takes the punishment because it has no tooth to sit in.
2. Transverse pitch. Fixed by the chain number, for example 29.29 mm on #80, 35.76 mm on #100 and 45.44 mm on #120. It cannot be adjusted in the field, and a sprocket cut to a different spacing pulls the chain sideways one strand at a time.
3. Axial room. Triplex adds two transverse pitches to the pin length: on #80 that is 91.7 mm of pin against 32.70 mm for simplex, before any clearance. Check the gap between hub face and bearing housing, and check that no washer, circlip or guard now sits where the third row runs.
4. Bore, key and hub. The wider hub needs a longer keyway and often a longer shaft extension. Verify key length and shaft shoulder, not only bore diameter, before accepting a stock sprocket.

What a triplex drive needs that a simplex drive does not

• Mass and sag. A triplex chain weighs about three times its simplex equivalent per metre, so re-check the tensioner and the sag figure. A setting copied from a simplex drive leaves the triplex chain too loose and it whips on the slack side.
• Alignment. Keep shaft parallelism within roughly 0.5 degrees, about 0.9 mm over 100 mm of span, and both sprockets coplanar. Multi-strand chain is less forgiving than single strand because load transfer between strands depends on that alignment.
• Teeth on the small sprocket. 17 is the conventional floor for a drive; on triplex we recommend 19 or more, because fewer teeth concentrate the uneven strand loading on a smaller number of contacts.
• Hidden wear. The middle strand sits behind the outer two. A hooked tooth row in the centre cannot be seen from the guard side, so measure tooth width across all rows instead of eyeballing the visible one.
• Change as a set. A new triplex chain on worn sprockets runs on the outer rows and frets the middle. Chain and both sprockets should go in together.

What CTS supplies

We build ANSI simplex, duplex and triplex roller chain from #35 to #240, the ISO 05B to 72B range, and the ANSI sprockets to match them. The three chain families are listed separately: simplex, duplex and triplex roller chain, all to ANSI B29.1 and interchangeable with other certified chains of the same number.

If you are replacing an existing triplex drive, send the chain number stamped on the plates, the pitch count and the tooth counts on both sprockets. If the chain is unmarked, send pitch, roller diameter, pin diameter and pin length across the outer plates — pin length is what separates a -2 from a -3 once the plates have worn and the markings are gone. The full dimension set for every number is in our roller chain size chart, and the tooth and wear rules are in the chain and sprocket matching guide.

We confirm strand count against the sprocket before quoting, because that is the mismatch that shows up most often: a triplex chain ordered for a duplex sprocket, or a stock sprocket whose transverse pitch does not match the chain. Documents on request: dimensional inspection report, tensile test report, and material certificate.

Request a triplex chain quotation