A feathering paddle wheel carries floats that pivot as the wheel turns. An eccentric linkage changes their orientation through the immersed part of the rotation. Explore a simplified planar angle schedule and calculate the eccentric offset for entered wheel diameter, float entry angle and stroke angle. The model does not calculate thrust or propulsive efficiency.
Feathering Paddle Wheel Interactive Calculator
Explore an ideal eccentric angle schedule with pivoted floats, short cranks and rods to an offset control centre. Compare the required eccentric offset as wheel diameter and selected angles change.
Equation Used
- Planar ideal eccentric geometry.
- Symmetric entered submerged stroke about bottom dead centre.
- Rigid links and frictionless pivots.
- No hydrodynamic, power, load, slip, strength or efficiency prediction.
Ideal planar geometry only. The drawing is not a complete construction of a specific Morgan wheel and does not calculate immersion, thrust, slip, power, bearing loads, member forces, strength or efficiency.
Floats that pivot on the wheel
Each float can rotate relative to its paddle arm. A short crank and connecting rod couple that rotation to an offset control centre. Changing float attitude can reduce unwanted water lifting during entry and exit compared with fixed radial boards.
A complete feathering wheel needs a master rod, the remaining rod and crank dimensions, bearings and axial spacing. The illustration simplifies these details; its angle schedule is not a construction drawing for a particular vessel.
The model controls
Wheel diameter sets the radius R. Entry angle is measured from horizontal, so an 85-degree entry angle corresponds to a 5-degree departure from vertical. Stroke angle specifies the wheel position from bottom dead centre at which that entry angle is required. Speed changes playback timing and does not change the geometry results.
Understanding paddle attitude
The model is useful for comparing an ideal paddle-angle schedule around the bottom of a wheel. It shows how wheel size and a selected entry attitude relate to eccentric offset.
Vessel speed, immersion, float area, water flow and the complete linkage determine propulsion performance. None is calculated here, so the results cannot establish fuel saving, wake height or a suitable wheel for a boat.
Ideal eccentric angle schedule
Let R be wheel radius, e eccentric offset and φ wheel position from bottom dead centre. The selected schedule is θ = atan[e sin(φ)/(R − e cos(φ))], with θ measured from vertical.
The calculator works backward from the entered entry angle A: θ = 90° − A, then e = R tan(θ)/[sin(φ) + tan(θ) cos(φ)]. It reports the symmetric entry and exit angle from horizontal, a 90-degree bottom-dead-centre attitude and total swing 2|θ|.
This equation describes the chosen planar schedule. It does not solve all rod lengths, joint reactions or hydrodynamic forces in a real feathering wheel.
Example: four-metre wheel
Set wheel diameter to 4 m, entry angle to 85 degrees and stroke angle to 35 degrees. Radius R is 2 m and the target departure from vertical is 5 degrees.
The equation gives e = 2 tan(5°)/[sin(35°) + tan(5°) cos(35°)] = 0.27118 m, or about 271.2 mm. The displayed entry and exit angle is 85 degrees, bottom-dead-centre angle is 90 degrees and symmetric float swing is 10 degrees.
Doubling diameter doubles the required offset for the same angles. Changing speed does not change those geometric results. Neither comparison predicts water entry loads or acceptable operating speed.
Geometry and water loads are separate
A fixed radial wheel has fewer moving joints. A feathering wheel adds float pivots and control links to change paddle attitude through the cycle. Those joints introduce additional loads, clearances and maintenance needs that depend on the actual design.
No universal efficiency, bushing clearance, service interval or speed limit follows from this angle model. A working wheel requires full linkage geometry, immersion and vessel data, structural calculations and suitable marine engineering review.
Frequently asked questions
What angle does the entry-angle control use?
It is measured from horizontal. An entry angle of 85 degrees is 5 degrees from vertical.
Why does diameter change the eccentric offset?
For the same selected angles, offset is proportional to wheel radius in this ideal equation.
Why does changing speed leave the angle results unchanged?
Speed sets animation timing. The calculator is geometric and contains no water-force or dynamic-load model.
Does the calculated offset define a complete feathering linkage?
No. Master-rod geometry, float-crank dimensions, bearings and axial supports must also be specified.
Does this calculate thrust or efficiency?
No. It does not model immersion, vessel speed, slip or hydrodynamic forces.
References & Further Reading
- Wikipedia contributors. Paddle steamer. Wikipedia
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