A cantilever hoisting and conveying machine is a lifting rig that supports its load on a horizontal boom projecting from a single vertical mast or tower, with the load held entirely by the boom acting as a cantilever beam. It solves the problem of moving heavy materials horizontally and vertically across a worksite without a second support point under the load path. The mast carries the bending moment back to a counterweighted base or anchored foundation, while a trolley or hook block runs along the boom to convey the load. Tower cranes on high-rise sites and pillar jib cranes in steel fabrication shops are everyday examples, with capacities from 250 kg shop hoists up to 20+ tonnes at the tip.
Cantilever Hoisting and Conveying Machine Interactive Calculator
Vary the lifted load and three trolley radii to see the cantilever tipping moments update on the crane diagram.
Equation Used
The calculator applies the article moment balance: a load W at horizontal radius R creates tipping moment M = W x R. Larger radius produces a larger mast and foundation moment for the same lifted load.
- Static vertical load, no wind or dynamic hoist factor included.
- Load W is entered as force in kN.
- Radius R is the horizontal distance from mast pivot to hook load.
- Moment is the tipping moment that the mast, base, and counterweight system must resist.
How the Cantilever Hoisting and Conveying Machine Actually Works
The whole machine is a moment problem. You hang a load at radius R from the mast, and the boom transfers that load × radius back through the mast as a bending moment. The base — whether that's a ballasted slab on a tower crane, a bolted floor flange on a pillar jib, or a wall bracket on a column-mounted unit — has to resist that moment without tipping, sliding, or pulling the anchor bolts. If the rated capacity chart says 2,000 kg at 12 m and 1,000 kg at 24 m, that's not arbitrary — it's the same tipping moment at both points (24,000 kg·m), and the machine is moment-limited, not load-limited.
The hoisting half lifts the load vertically using a wire rope or chain reeved through a hook block. The conveying half moves it horizontally — either by trolleying along the boom (most tower cranes, monorail jibs), by slewing the boom around the mast (pillar jibs, derricks), or by luffing the boom up and down (luffing jib cranes in tight urban sites). A Liebherr 200 EC-B 10 tower crane, for example, slews 360°, trolleys along a 65 m jib, and hoists at 80 m/min on the light hook — three independent motions that combine to put the load anywhere inside a cylindrical work envelope.
Get the geometry wrong and the failure modes are loud. If the counterweight is undersized, the crane tips backwards on a no-load slew or forwards on overload. If the boom is under-designed, you get visible tip deflection — more than L/300 and the trolley starts climbing a grade as it runs out, which loads the trolley motor and chatters the rope. If the slew bearing bolts are torqued unevenly, the bearing races brinell within months and the slew motor draws spike currents on every reversal. The rules are tight because the consequences are public.
Key Components
- Mast or Tower: The vertical column that carries the boom's bending moment down to the foundation. On a tower crane this is a bolted lattice section 1.6–2.1 m square; on a shop pillar jib it's typically a 200–400 mm diameter steel pipe. The mast must be plumb to within 1:500 over its height — more lean than that and the slew bearing wears asymmetrically.
- Cantilever Boom (Jib): The horizontal beam that projects from the mast and carries the trolley or hook. Designed for combined bending and torsion under hook load plus trolley travel inertia. Tip deflection under rated load is typically held to L/300 or better �� a 30 m boom should not deflect more than 100 mm at the tip.
- Counterweight or Ballast: Concrete blocks or cast iron slabs sized to balance the load moment around the mast pivot. On a Potain MDT 219 the counterweight is around 22 tonnes; the rule is that counterweight × counter-radius must equal or exceed maximum load × maximum radius with a safety factor of 1.4 against backward tipping.
- Hoist Winch and Rope: Drum-wound wire rope reeved through a hook block, typically 4-fall or 6-fall on heavier machines. Rope diameter is sized so that rope tension stays below 1/5 of breaking strength. Drum grooving must match rope lay direction or you get fleet-angle wear and birdcaging within a few hundred cycles.
- Trolley or Slew Drive: Moves the load horizontally. The trolley runs on the lower flange of the jib at 25–60 m/min; the slew drive rotates the upper works through a large-diameter slew bearing — typically a 1.2–2.5 m three-row roller bearing. Slew bearing bolts must be torqued to spec in a star pattern; uneven torque brinells the races.
- Foundation or Base Anchor: Either a mass-concrete block (200–500 m³ for a free-standing tower crane), a bolted floor flange (pillar jib in a shop), or a wall bracket (column crane). Must resist the maximum tipping moment plus dynamic factors of 1.25–1.5 for sudden hoist or wind gusts.
Industries That Rely on the Cantilever Hoisting and Conveying Machine
Cantilever hoisting and conveying machines show up wherever you need to move material into a space that has no overhead support — which is most of construction, most of shipyards, and a lot of heavy fabrication. The defining feature is that one end of the load path is unsupported, so you trade structural mass at the base for clear space under the load. That trade is what makes these machines indispensable on tight urban sites where you can't run a gantry, and on shop floors where overhead cranes would block lighting or HVAC.
- High-rise Construction: Liebherr 200 EC-B 10 and Potain MDT series tower cranes on residential and commercial high-rise builds — slewing booms up to 65 m, hoisting forms, rebar bundles, and prefab façade panels onto floor decks 200+ m up.
- Steel Fabrication Shops: Pillar-mounted jib cranes (Gorbel, Abell-Howe) bolted to shop floors at welding bays, slewing 200° and lifting 250–2,000 kg of plate or weldment between the bay and a transfer cart.
- Shipyards and Heavy Marine: Cantilever luffing cranes at fitting-out quays, lifting ship sections, propellers, and engine modules from quay to deck — capacities of 100–200 tonnes at radii of 30–50 m.
- Precast Concrete Yards: Wall-mounted column jib cranes serving casting beds — slewing over a single bed to demould and shift girders or wall panels of 5–15 tonnes without crossing the adjacent bed.
- Warehouse and Logistics: Free-standing workstation jib cranes at offloading stations, handling 500–1,000 kg crates from delivery trucks onto conveyor in-feeds, common in Amazon and Costco regional DCs.
- Bridge and Civil Construction: Derrick cranes mounted on bridge piers during balanced cantilever segmental construction, lifting 80–200 tonne precast segments out over the void as the deck advances.
The Formula Behind the Cantilever Hoisting and Conveying Machine
What you almost always need to size first is the tipping moment — the load multiplied by its radius from the mast centreline. This number tells you the counterweight requirement, the foundation size, and the boom bending design all in one. At the low end of the typical operating range (load close to the mast, short radius), the moment is small and the machine is hoist-limited — meaning the rope and motor capacity decide what you can lift, not the structure. At the high end (load far from the mast, near the boom tip), the moment is at maximum and the machine is moment-limited — every additional kilogram of payload at that radius eats directly into the safety margin against tipping. The sweet spot, where most production picks happen, sits at roughly 50–70% of maximum radius — enough reach to be useful, enough margin to be safe.
Variables
| Symbol | Meaning | Unit (SI) | Unit (Imperial) |
|---|---|---|---|
| Mtip | Tipping moment about the mast base | kN·m | lbf·ft |
| Wload | Hook load including rigging and hook block | kN | lbf |
| R | Horizontal radius from mast centreline to hook | m | ft |
| kdyn | Dynamic factor for hoist acceleration, wind, and swing (typically 1.25–1.5) | — | — |
Worked Example: Cantilever Hoisting and Conveying Machine in a wall-mounted column jib crane in a wind-turbine nacelle assembly bay
Sizing the wall anchor moment for a 5-tonne wall-mounted column jib crane in a Vestas nacelle assembly bay in Brande, Denmark. The crane has a 6 m boom slewing 180° off a tilt-up concrete column, lifting gearbox subassemblies from a transfer cart to the nacelle bedplate. You need the maximum tipping moment so the structural team can size the embedded anchor plate.
Given
- Wload = 5,000 kg (49.05 kN)
- Rmax = 6.0 m
- Rnom = 4.0 m
- Rmin = 1.5 m
- kdyn = 1.35 —
Solution
Step 1 — convert the rated load to a force in kN, including a 200 kg hook block:
Step 2 — compute the nominal tipping moment at the typical working radius of 4.0 m, where most gearbox transfers happen:
Step 3 — at the low end of the operating range, Rmin = 1.5 m (loading directly off the cart parked at the column), the moment drops sharply:
That's 37% of the nominal — the machine is comfortably hoist-limited here, the wall anchor barely notices the lift, and the rigger can swing the load freely without worrying about tipping reactions.
Step 4 — at the high end, Rmax = 6.0 m (the boom fully extended over the nacelle bedplate), the moment maxes out:
This is the design number — every embedded anchor stud, every rebar tie, every weld on the column bracket has to handle 413 kN·m without yielding. In practice, the structural team will design to roughly 1.5× this number to cover the SLS-to-ULS factor, putting the anchor plate design moment near 620 kN·m.
Result
Maximum tipping moment at the wall anchor is 413 kN·m at full 6 m radius with the dynamic factor applied. At 4 m nominal radius the moment is 276 kN·m — comfortable territory where the operator should plan most production picks — and at 1.5 m close-in radius it drops to 103 kN·m, where the structure is loafing. If your strain gauges on the anchor plate read significantly higher than 413 kN·m during commissioning, the three failure modes to check first are: (1) a hoist acceleration ramp set too aggressive on the VFD, which spikes k<sub>dyn</sub> well past 1.35 — slow the start ramp to 2 seconds minimum; (2) load swing from a careless slew start, adding a horizontal component that increases the effective radius — train operators to ramp slew over 3 seconds; and (3) wind on a partially open bay door creating a sail load on a large gearbox cover, which can add 5–15% moment unexpectedly.
Choosing the Cantilever Hoisting and Conveying Machine: Pros and Cons
The cantilever layout is one of three main ways to hoist and convey a load horizontally. The other two are overhead bridge cranes (load supported on two parallel runways) and gantry cranes (load on a portal frame with legs to the floor on both sides). Each choice has consequences for floor space, load capacity at radius, and capital cost. Here's how they line up on the dimensions that actually drive selection.
| Property | Cantilever Hoisting Machine | Overhead Bridge Crane | Gantry Crane |
|---|---|---|---|
| Typical load capacity range | 0.25–250 t at tip | 1–500 t (uniform) | 1–1,500 t (uniform) |
| Floor footprint required | Single column or wall mount — minimal | Zero floor footprint (runways on building columns) | Two leg paths consume floor lanes |
| Load capacity vs radius | Drops linearly with radius (moment-limited) | Constant across the bay | Constant across the gantry span |
| Hoist + travel speed (typical) | Hoist 8–80 m/min, slew 0.5–1 rpm | Hoist 5–60 m/min, bridge 20–100 m/min | Hoist 3–30 m/min, gantry 20–60 m/min |
| Capital cost (relative) | Low — 1× | Medium — 2–4× (needs runway structure) | High — 3–6× (full portal + rails) |
| Best application fit | Workstation pick-and-place, tower crane site lift, dockside ship loading | Production bays, machine shops, paper mills | Outdoor yards, container terminals, shipyards |
| Coverage geometry | Sector or full circle (slew) — donut work envelope | Rectangular bay coverage | Rectangular yard coverage |
Frequently Asked Questions About Cantilever Hoisting and Conveying Machine
Almost always slew bearing preload or brinelling, not the load. When the bolts that fasten the slew bearing inner race to the column flange are torqued unevenly — even just a few bolts under-torqued — the bearing races flex elliptically under load and the rollers wedge at one quadrant. Startup current spikes because the motor is fighting friction in that wedged sector.
Quick diagnostic: jack the boom slightly with no load and rotate by hand. If you feel notchy resistance every 90° or so, you have brinelling and the bearing needs replacement. If it rotates smoothly by hand but spikes under power, re-torque all bearing bolts in a star pattern to manufacturer spec — usually 250–600 N·m for an M24 grade 10.9 bolt.
Probably not bent — more likely the tie-rod or pendant cable that pre-tensions the boom has gone slack. Many cantilever booms aren't pure cantilevers; they're partially supported by a top tie running from the mast cap down to the boom mid-span. If that tie loses pre-tension (thermal cycling, anchor creep, or someone adjusted it during transport), the boom reverts to a pure cantilever and deflection roughly doubles.
Check the tie tension with a strain gauge or by frequency-tapping the cable — published natural frequency for the cable at rated tension is in the manufacturer's manual. If it's flat-sounding and low frequency, retension to spec.
Luffing jib, almost always, when neighbouring buildings or property lines are within the swing radius. A trolley jib has a fixed horizontal boom that sweeps the full radius whenever you slew — so if your maximum reach is 50 m and the property line is 35 m away, you can't legally slew that direction even with no load. A luffing jib raises its boom on demand, so you can park the boom near vertical when slewing past the property line and only luff out when you're over your own footprint.
The trade is roughly 15–25% higher capital cost and slower cycle times for the luffing machine. On open suburban sites with no neighbour issues, the flat-top trolley jib wins on cost and productivity.
Linearly interpolate the moment, not the load. The chart is built around constant tipping moment, so if 2,000 kg is allowed at 12 m and 1,000 kg at 24 m, the moment is 24,000 kg·m at both. At 18 m the allowable load is 24,000 / 18 = 1,333 kg, not the simple average of 1,500 kg.
Always round down to the nearest 100 kg and apply your site's working load limit factor on top. Rigging crews who average instead of moment-interpolating routinely overload by 10–15% in the mid-radius zone, and that's exactly where load moment indicators are calibrated tightest — you'll trip the LMI before you tip, but you'll also stop production cold.
Fleet angle, almost certainly. The fleet angle is the angle between the rope as it leaves the drum and the line perpendicular to the drum axis. Spec limit is typically 1.5° for grooved drums and 2.5° for plain — exceed that and the rope tries to climb the groove flank on every wrap, which works the strands against each other and pops them outward as a birdcage.
Measure it: at the drum end-of-travel positions, sight from the drum centreline to the lead sheave on the boom tip. If the angle is over 1.5°, you need either a rope guide (a roller assembly that re-aligns the rope as the trolley moves) or a longer boom-tip sheave block to push the lead point further from the drum. This is most common on retrofit installations where someone shortened the boom without recalculating the fleet geometry.
Slew bearing grease has stiffened in the cold and the rollers are skidding instead of rolling for the first quarter-turn. Standard EP-2 lithium grease loses pumpability below about –10°C, and the rollers in a three-row roller slew bearing rely on a thin grease film to hydroplane at low speed. With no load, there isn't enough Hertzian contact pressure to push the grease aside, so the rollers stick-slip and you get the creak.
Switch to a low-temperature synthetic grease (NLGI 1 with PAO base oil) rated to –30°C if your site sees real winter. The fact that it lifts fine under load confirms the bearing geometry is healthy — load pressure squeezes through the grease film, no-load slew doesn't.
References & Further Reading
- Wikipedia contributors. Crane (machine). Wikipedia
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