A Detachable Link Chain is an open-hook drive chain made of identical malleable-iron links, each formed with a hook on one end and a barred eye on the other so links snap together by hand without pins or tools. Daniel C. Stover patented the form in 1873, and Ewart Manufacturing made it the standard farm chain across North America by the 1890s. Each link transmits tension through the hook-bar contact, letting you break or extend a run anywhere along its length. The outcome is a cheap, field-repairable chain still used on grain elevators, manure spreaders and slow-speed conveyors at speeds under about 350 ft/min.
Detachable Link Chain Interactive Calculator
Vary drive power, chain speed, service factor, pitch, and sprocket teeth to see chain pull, torque, rpm, and speed margin.
Equation Used
The calculator estimates working chain pull from transmitted horsepower and chain speed, then uses chain pitch and tooth count to estimate sprocket pitch diameter, shaft torque, and rpm. The speed margin compares the selected speed with the article's 350 ft/min low-speed guideline.
- Low-speed detachable link chain drive with steady transmitted power.
- Service factor scales chain pull for shock or intermittent loading.
- Sprocket pitch diameter is estimated from ideal polygon geometry.
- 350 ft/min is used as the practical upper speed reference.
Operating Principle of the Detachable Link Chain
A Detachable Link Chain works on a brutally simple idea — every link is the same casting, with an open hook at the front and a closed bar at the back. You rotate one link 90° relative to its neighbour, slip the hook over the bar, rotate it back, and the joint locks under tension. No pins, no bushings, no side plates. When the chain wraps a sprocket the tension keeps each hook seated against its mating bar, and when the chain leaves the sprocket it stays seated because gravity and pull line keep the links roughly coplanar.
The geometry has to be right or the chain throws itself off the sprocket. Pitch on the most common agricultural sizes — 32, 42, 55, 62, 67 — runs from about 1.131 in to 2.308 in, and the sprocket tooth profile is cut to match that pitch within roughly ±0.010 in. If the pitch grows because the hooks have worn (you would be amazed how fast a dusty manure-spreader chain elongates 3% in a single season), the chain rides up the tooth face and skips. If a link gets twisted out of plane — say a stalk of corn jams between hook and bar — the joint can pop open mid-run. That is the classic failure mode. The other one is a fatigue crack at the hook root where the casting is thinnest, usually after years of shock loading.
This is why a Detachable Link Chain is a low-speed, low-shock chain. Above about 350 ft/min the centrifugal lift and the chordal action together get bad enough that the joints start to chatter and the malleable iron work-hardens. Keep it slow, keep the load steady, and an open link chain — sometimes called Ewart link chain or hook and bar chain — will run for decades on a grain elevator with nothing but an annual blast of kerosene to flush out the chaff.
Key Components
- Hook end: The forward portion of each link, cast as an open J-shape that captures the bar of the next link. Hook throat opening is typically 0.25–0.40 in depending on chain size, and the hook root is the highest-stress section — wall thickness here sets the chain's working load, usually 600–2,400 lbf for sizes 32 through 67.
- Bar end: The closed eye opposite the hook, formed as a transverse cylindrical bar inside a closed loop. The bar takes the bearing contact from the mating hook. Bar diameter is held to roughly ±0.005 in on quality castings — slop here directly becomes pitch elongation.
- Link body: The connecting section between hook and bar, cast in malleable iron (typically ASTM A47 grade 32510) for ductility under shock. Body cross-section is sized so the link will deform visibly before it fractures, giving the operator warning before failure.
- Sprocket teeth: Cut to the chain's nominal pitch with a tooth form that captures the bar end, not the hook. Tooth pitch tolerance is ±0.010 in — looser than that and a worn chain skips; tighter than that wastes machining time on a chain meant to be cheap.
- Connector link (optional): An identical link used to close the loop. There is no special master link in a Detachable Link Chain — that is the whole point. You join or break the loop by rotating any link 90° and lifting the hook clear of its mate.
Real-World Applications of the Detachable Link Chain
Detachable Link Chain still earns its keep wherever the load is steady, the speed is low, and somebody in a barn or a quarry needs to fix the chain without a press tool. You will find it on equipment that has been in production since the 1890s and on new builds where field-repairability beats every other consideration. It does not belong on high-speed power transmission — for that you want a roller chain or a silent chain — but for slow conveyors, elevators and ag equipment it is hard to beat on cost.
- Agriculture: Drag-chain feed conveyors on John Deere and New Holland manure spreaders, where the chain runs at 50–150 ft/min through abrasive material and gets repaired with a hammer in the field.
- Grain handling: Bucket elevators on small-scale grain operations and feed mills, particularly the legacy GSI and Brock leg systems built before bushed-roller conveyor chain became standard.
- Mining and quarrying: Slow-speed apron feeders and reclaim conveyors at aggregate operations, where the chain handles 600 lbf working tension on size-67 links at speeds well below 200 ft/min.
- Sugar processing: Cane carrier chains feeding shredders at older sugar mills in Louisiana and the Caribbean — long runs of size-103 chain pulling cane mats into the first crusher.
- Lumber and pulp: Log-deck and slasher conveyors at small sawmills, where chain replacement happens with a cold chisel and a punch rather than a chain breaker.
- Cement and bulk material: Drag conveyors moving clinker and raw mix in older cement plants, particularly retrofits where the original 1920s-1950s chain layout is preserved.
The Formula Behind the Detachable Link Chain
The number you actually need before specifying a Detachable Link Chain is the chain pull — the working tension the chain sees while moving its load. Chain pull tells you what working load rating to buy and what sprocket shaft torque to design for. At the low end of the typical operating range (slow conveyor, light load, level run) the pull might be 100–200 lbf and any size-32 chain is fine. At the high end (heavy material, inclined run, dynamic shock) the pull climbs into the thousands of pounds and you need size-67 or bigger plus a 2× shock factor. The sweet spot for an open link chain is the middle band — a few hundred pounds of steady pull at under 200 ft/min — where the chain runs cool, wear is gradual, and you can replace a damaged link in 30 seconds with no special tool.
Variables
| Symbol | Meaning | Unit (SI) | Unit (Imperial) |
|---|---|---|---|
| Fchain | Required chain working pull | N | lbf |
| W | Combined weight of conveyed load plus moving chain and flights | N | lbf |
| μ | Coefficient of friction between chain/flights and trough | dimensionless | dimensionless |
| θ | Incline angle of the conveyor run from horizontal | degrees | degrees |
| Fmaterial | Drag force from material being pushed against trough or sidewalls | N | lbf |
| Kshock | Shock/service factor — 1.0 steady, 1.5 moderate, 2.0+ heavy shock | dimensionless | dimensionless |
Worked Example: Detachable Link Chain in a maple sugar shack firewood drag conveyor
Your maple sugar operation in Beauce, Quebec needs a drag conveyor to feed split firewood from an outdoor crib into the evaporator shed. The run is 12 m long, inclined 15° up to the shed floor, and you want to size a Detachable Link Chain to pull a steady stream of 18 inch firewood splits up the trough. Estimated total moving weight (chain + flights + wood on conveyor at any moment) is 800 lbf. Friction coefficient of dry hardwood on a galvanized steel trough is roughly 0.45. Material drag past the loading point is around 60 lbf. The drive runs continuously during boil-down, so call shock factor 1.5 — steady but with the occasional jammed split.
Given
- W = 800 lbf
- μ = 0.45 dimensionless
- θ = 15 degrees
- Fmaterial = 60 lbf
- Kshock = 1.5 dimensionless
Solution
Step 1 — compute the friction-plus-grade term at the nominal 15° incline:
Step 2 — at nominal load, calculate the chain pull before the shock factor:
Step 3 — apply the 1.5 shock factor for nominal continuous operation:
That sits comfortably inside the working load of a size-55 Detachable Link Chain (typically rated around 1,400 lbf working). At the low end of the operating range — say a half-loaded conveyor at 400 lbf moving weight on the same incline — the pull drops to roughly:
That is light duty. The chain barely notices the load, wear rate is gradual, and a size-42 chain would even cover it. At the high end — a fully packed trough during a hard boil with wet wood, weight climbing to 1,200 lbf and shock spiking to 2.0 from the occasional jam:
Now you are right at the working limit of the size-55 and you should step up to size-62 or 67. This is the practical reason these chains come in five common sizes — you pick the one that puts your nominal pull at roughly 50–60% of working load so the chain has headroom for the bad days.
Result
Nominal chain pull works out to 923 lbf, which lands a size-55 Detachable Link Chain squarely in its sweet spot at about 65% of working load. In practice that means the chain will sit quietly in its trough, hooks fully seated, with no clicking or skip — a healthy size-55 on this duty should deliver 8–12 seasons before pitch elongation passes the 3% replacement threshold. The range from 461 lbf at light duty to 1,846 lbf at peak shock is exactly the band the chain has to survive, and it tells you why sizing on nominal alone is a mistake. If your measured pull comes back 30% higher than predicted, check for a dragging idler bearing first (galled bushing on the tail shaft is the usual culprit), then check trough alignment — a 5 mm side-to-side offset between head and tail sprockets puts the chain in bending and adds substantial drag. Third on the list is wet or icy material increasing the effective μ from 0.45 to 0.7 or worse, which alone can blow your pull number past the chain's working rating.
Choosing the Detachable Link Chain: Pros and Cons
Detachable Link Chain is the cheapest and most field-repairable drive chain you can buy, and it has real limits. Here is how it stacks up against the two chains you would most likely consider instead — pintle chain (the obvious upgrade for ag and conveyor work) and roller chain (the standard for power transmission).
| Property | Detachable Link Chain | Pintle Chain | Roller Chain (ANSI) |
|---|---|---|---|
| Maximum operating speed | ~350 ft/min | ~450 ft/min | 3,000+ ft/min |
| Working load (typical mid-size) | 600–1,400 lbf | 1,500–4,400 lbf | 2,000–10,000+ lbf |
| Pitch accuracy / smoothness | ±0.010 in, chordal action obvious | ±0.005 in, smoother | ±0.003 in, runs near silent |
| Field repair without tools | Yes — twist and unhook by hand | No — pin must be driven out | No — chain breaker required |
| Cost per foot (size-55 equivalent) | $3–6 | $8–14 | $12–25 |
| Service life on dirty ag duty | 3–10 seasons | 8–15 seasons | Often <3 seasons (grit kills bushings) |
| Best application fit | Slow ag/conveyor, dirty service | Medium-duty conveyor, mining feeders | Power transmission, packaged goods conveyors |
Frequently Asked Questions About Detachable Link Chain
Pull a 12-link section taut and measure end-to-end. Compare to 12 × nominal pitch. Up to about 2% growth is normal wear and the chain will keep running fine. Between 2% and 3% you are on borrowed time — the chain will start climbing the sprocket teeth on heavy loads. Past 3% you replace it.
Failure-imminent links look different from worn ones. Look for hairline cracks at the hook root (where the J meets the link body) and for hooks that have visibly opened up — the throat gap will be 15–20% wider than a new link sitting next to it. A link that has started to open never goes back; pull it out now or it pops off the next time the chain shock-loads.
Almost always sprocket-side, not chain-side. Three usual causes, in order of likelihood. First, that sprocket's teeth are worn into hooks themselves — the bar end rides up the worn tooth face and pops out. Pull the sprocket and check tooth profile against a new one; if the leading face is curled, replace it. Second, the sprocket has slipped on its shaft and is no longer coplanar with its mate at the other end of the conveyor. A 3–5° misalignment is enough to lever links open at the wrap point. Third, you have a few links installed backwards — hook facing the wrong direction of travel. The hooks must all face away from the pulling direction so tension seats them; reversed links unseat under load.
You can, but only within tight limits. A new link has nominal pitch — a used link is 1–2% longer. If you splice a single new link into an old chain, that link sees the highest tooth-engagement load on every sprocket pass because it is the shortest pitch in the loop, and it will wear out about three times faster than the rest. The opposite is worse: a single old, stretched link in an otherwise new chain will be the one that skips on the sprocket and pops off.
Rule of thumb — replace links in groups of at least 6–8, or just replace the whole chain if more than 10% of links are bad. Detachable chain is cheap enough that piecemeal repair past that point is false economy.
Depends on the original equipment and the duty cycle. If the spreader is a vintage New Idea or Massey-Harris built around 32 or 42 detachable chain, stay with detachable — the sprockets are cut for that pitch and converting to pintle means new sprockets, new attachment links and new flights. Cost will run 4–6× a chain replacement.
If you are rebuilding heavily, the spreader sees daily commercial duty, or you are losing chain mid-field more than once a season, pintle is worth it. Pintle's pinned joint cannot pop open the way a hook joint can when a frozen clump jams the trough, and the working load is roughly 2–3× higher for the same pitch class. The break-even point is roughly 200 hours per year of run time.
The pull calculation assumes steady drag. Real wear comes from abrasion at the hook-bar contact, and abrasion scales with how dirty your material is, not how heavy it is. Grain dust, sand, lime, manure solids — they all act as lapping compound at the joint. A size-55 running 600 lbf in clean sawdust might last 10 seasons; the same chain running 600 lbf in wet sand can be worn out in 18 months.
Two practical fixes. Flush the chain weekly with kerosene or diesel during the run season — it floats grit out of the joints. And check whether your trough has a return-side scraper; if abrasive material rides on top of the return strand it grinds into every joint on every revolution. Adding a simple wiper bar usually doubles chain life.
Short answer — no, not reliably. The 350 ft/min limit is not arbitrary. Above that speed three things stack up against you: chordal action gets violent (the chain literally rises and falls each tooth pass because the wrap is polygonal, not circular), centrifugal lift starts pulling hooks off bars on the slack side, and the malleable iron's fatigue limit comes into play because each joint is now seeing tens of thousands more load reversals per shift.
If you need higher speed, you switch chain types. A 60-pitch ANSI roller chain will do 1,500 ft/min without complaint. Trying to push detachable chain past its design envelope ends with a hook letting go at speed, and a flying cast-iron link is genuinely dangerous — there are reasons OSHA-era guarding standards on grain elevators went up around exactly this kind of failure.
Because the old worn chain had stretched into a pitch that matched the sprocket's worn tooth profile. New chain on old sprockets is a mismatch — the tight new pitch climbs slightly on each worn tooth, and you hear it as a click or chatter on every revolution.
The fix is sprocket replacement, not chain adjustment. There is no break-in period that will quiet a new chain on worn sprockets; the chain just wears out fast trying to mate with a profile it does not fit. As a rule, replace the sprockets every second chain replacement, or any time the tooth tip-to-root depth has shrunk more than about 10% from new.
References & Further Reading
- Wikipedia contributors. Chain drive. Wikipedia
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