The Bartrum & Powell engine uses a crank carried by a concentric shaft to move a smaller winged cylinder inside the working shell. The wing slides through a rocking joint. Hiscox item 339 shows this orbiting-cylinder arrangement; it is different from a stationary eccentric rotor with a spring-loaded sliding vane.
Bartrum and Powell Rotary Engine Interactive Calculator
Change bore, crank offset, shaft speed and axial end clearance. The section follows the crank and guided wing; the inset enlarges the end clearance.
Equation Used
- The illustrated orbiting cylinder is internally tangent to the circular bore.
- The wing passes through a rocking guide at the lower bore boundary.
- The formula 2e describes crank-centre travel, not a spring-loaded abutment.
- Steam flow, torque, power and packing tolerances are not solved.
The arrangement is illustrated in Gardner D. Hiscox, Mechanical Movements, Powers, Devices and Appliances (1901), item 339, printed page 93. The illustration explains the engine layout; it does not establish an operating-speed range or performance rating.
How the Orbiting Cylinder Works
The fixed inner shell is cylindrical. Its central shaft turns a crank that carries a smaller cylinder. A wing attached to that cylinder passes through a rocking joint in the shell. As the crank turns, the cylinder centre follows a circle and the wing both slides and changes its angle in the guide.
Shell and Packing
Hiscox describes a double shell divided for steam and exhaust, adjustable end packing, and an eccentric sleeve at the crank pin to compensate for rubbing-surface wear. The drawing simplifies the passages and packing so the kinematics remain visible.
Historical Context
This is an example of nineteenth-century rotary steam-engine design documented by Hiscox. The illustration explains its motion; it does not establish performance, service history or a connection to a particular surviving engine.
Crank Geometry and Speed
A crank offset e moves the carried cylinder centre around an orbit of diameter 2e. At N revolutions per minute, shaft frequency is N/60 hertz. Offset as a percentage of the bore is 100e/D.
The clearance output compares the entered axial clearance with 0.05 mm solely as a reference. It is not a leakage prediction or a machining specification.
Worked Geometric Example
For a 150 mm bore, 10 mm crank offset and 400 RPM shaft speed, the orbit diameter is 20 mm, shaft frequency is 6.67 Hz and offset/bore ratio is 6.67%. An axial clearance of 0.04 mm is 80% of the 0.05 mm comparison reference.
What This Model Shows
The moving cylinder, crank and rocking wing guide explain the distinctive mechanism. The calculator covers their simple geometry and speed. Evaluating an engine would additionally require chamber depth, valve timing, pressure, leakage, lubrication and load data.
Questions
Is the shaft eccentric to the fixed chamber?
No. The main shaft is concentric; its crank carries the smaller cylinder off centre.
Does a spring-loaded abutment follow a fixed rotor?
That is a different rotary-engine arrangement. Here the cylinder moves with the crank and its wing slides through a rocking joint.
Does this calculator predict power?
No. It reports crank geometry, shaft frequency and an explicitly labelled clearance comparison.
Further Reading on Other Rotary Engines
- Wikipedia contributors. Rotary engine. Wikipedia
Building or designing a mechanism like this?
Explore the precision-engineered motion control hardware used by mechanical engineers, makers, and product designers.
