The Lancaster hoisting machine carries two opposed trussed booms on a revolving frame mounted on a rail truck. Suspended buckets turn with the booms to convey material between loading and discharge locations.
Cantilever Hoisting and Conveying Machine Interactive Calculator
Compare the moment from one suspended load at three alternative horizontal reaches. The animation shows the opposed-boom arrangement using R2, with a stationary rail truck and a revolving upper structure.
Equation Used
- Static suspended force W acts vertically at the selected horizontal radius.
- R1, R2 and R3 represent alternatives; they are not three concurrent hooks.
- The drawing uses R2. Booms and standing frame rotate together, and their proportions are illustrative rather than measured historical dimensions.
- Bucket ropes are schematic. Hoisting and slewing timing are illustrative, with no acceleration or rope-tension calculation.
- Opposite-side load, structural weight, rail reactions, ballast and allowable capacity are outside the calculation.
The Lancaster machine has opposed booms on a revolving rail-mounted frame. The animation uses R2; R1 and R3 compare the same suspended load at two other reaches. Each result is a separate load case.
Opposed booms on a revolving frame
Hiscox’s Lancaster machine has two trussed booms carried by a standing frame. That upper assembly revolves on rollers above a truck, while the truck itself can travel along rails. Buckets hanging from the booms move around with the frame.
The animation keeps the rail truck stationary so the revolving structure is easy to see. The booms remain rigid, and both bucket ropes stay connected as the upper assembly turns. A small illustrative hoisting motion raises and lowers the selected bucket.
Hoisting and conveying material
The reference drawing shows bucket loading on one side and discharge on the other. Rotating the opposed booms moves the suspended containers between locations without a separate traveling trolley along a single jib.
The calculator compares the bending-moment contribution of a selected suspended force at alternative horizontal reaches. It does not reproduce the complete machine’s balance or establish lifting capacity.
Force multiplied by horizontal reach
A vertical force W applied at horizontal radius R creates a bending-moment magnitude WR about a point on the slewing axis. With force in kN and radius in metres, the result is in kN·m.
The moment vector is horizontal. A stationary vertical load therefore does not, by itself, create a torque about the vertical slewing axis. Turning the machine requires a different analysis of friction, inertia and operating conditions.
The three displayed results use the same W and each entered radius separately. Hoisting height does not change WR while horizontal reach remains fixed. Slewing changes the direction of this moment, while its magnitude remains constant for the same force and radius.
Compare three reaches
With a selected load of 2 kN, reaches of 3 m, 8 m and 12 m produce moment magnitudes of 6, 16 and 24 kN·m. The middle case is the one illustrated in the animation.
Doubling the selected force doubles all three results. Doubling only R1 changes only the first comparison. These are alternatives, so their moments should not be added together.
Load moment is not a stability rating
The selected force is only one contribution to the complete machine. The opposite bucket, booms, machinery and supporting truck also contribute forces and moments. The relevant tipping edge depends on the rail and wheel geometry.
No support width, ballast or structural capacity is entered here. The calculator therefore does not report a restoring moment, safety margin or safe working load. Those cannot be inferred from WR alone.
Questions about the hoist comparison
How are the two booms carried?
The opposed booms are carried by a standing frame that revolves above the rail truck. Suspended buckets turn with the booms between loading and discharge locations.
Are the three radii simultaneous loads?
No. They compare the same selected force at three alternative reaches. The animation uses R2.
Why does the moment stay constant while the bucket rises?
The calculation uses horizontal reach. Changing height alone does not change the moment magnitude of a vertical force.
Does this result give the slewing motor torque?
No. WR is a horizontal bending-moment magnitude. Motor torque for rotation about the vertical axis requires a separate model.
Primary drawing and description
Gardner D. Hiscox, Mechanical Movements, Powers, Devices and Appliances (1901), figure 1472, page 355: Lancaster cantilever hoisting and conveying machine, with opposed trussed booms, revolving frame, rail truck and suspended buckets.
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