The historical Roney mechanical stoker used a hopper pusher to deliver coal onto an inclined grate made from transverse rocking bars. The bars rocked in unison between stepped and inclined positions, disturbing the bed and allowing fuel to progress toward the lower end.
Roney Stoker Ideal Drive-Cycle Calculator
Explore bounded ideal motion for a coupled hopper pusher and rocking grate; no fuel-feed or combustion result is calculated.
Equation Used
- The pusher and grate complete one ideal motion cycle per drive revolution.
- Drive speed is constant and the pusher stroke is symmetric.
- Pusher path is accumulated out-and-back travel, not fuel displacement.
- Bar-tip travel is the chord for a selected radius and rocking excursion.
- Linkage timing, coal behavior, combustion, draught, loads, clearances, wear and safety systems are excluded.
The secondary figure uses the same selected pusher stroke, constant drive speed, grate swing and reference radius.
Measure motion at the load, not at the driver. A stoker crank turning at the right rate proves nothing if the pin is worn and the bar is only travelling 55 mm instead of 65.
How the documented Roney arrangement works
A sliding pusher at the bottom of the hopper moves coal over the dead plate and onto the upper end of the inclined grate. The transverse flat-topped grate bars are carried on inclined supports and rocked together by an external linkage.
Period descriptions say the bars alternately form stepped and inclined surfaces: forward rocking lets the burning bed move down, while return to the stepped position checks that movement and breaks up the bed. The pusher and rocking bars derive motion from the stoker drive, but their detailed timing and linkage dimensions vary by construction.
What this calculator demonstrates
Select a pusher stroke, constant drive speed, grate rocking excursion and reference bar radius. The calculator reports ideal cycle period, cycles per hour, accumulated two-way pusher path and bar-tip chord travel.
These are drive-motion quantities only. They do not determine coal feed, fuel-bed advance, residence time, combustion, draught, heat release, boiler output, emissions, torque, power, wear or a safe setting.
Bounded ideal drive arithmetic
For selected constant drive speed n, cycle period is T=60/n seconds and cycles per hour are 60n. For pusher stroke S, the accumulated out-and-back path is L=2S(60n), with S converted from millimetres to metres.
For a reference point at radius R on a grate bar rocking through selected angle β, the straight-line chord between extreme positions is c=2R sin(β/2). This is not fuel displacement and does not reconstruct the historical linkage.
Selected ideal example
At n=8 cycles/min, S=65 mm, β=30° and R=250 mm, the ideal period is 7.5 seconds, the drive completes 480 cycles/hour, the pusher accumulates 62.4 m/hour of two-way path, and the selected bar-tip chord is about 129.4 mm.
The example describes only selected ideal motion. It is not a historical operating recommendation or a coal-throughput estimate.
Scope and correction boundary
Historical engineering texts and Roney patents describe a hopper pusher plus rocking transverse grate bars. The earlier article instead treated alternate bars as reciprocating sliders and calculated coal feed as a rectangular slice equal to stroke × bed depth × width on every cycle. No cited source establishes that volumetric identity.
The unsupported throughput, density, efficiency, fuel-sizing, temperature, life, cost, fault-diagnosis and boiler-sizing claims have been removed. Real evaluation requires the exact stoker drawings, linkage timing, coal properties, bed behavior, air distribution, furnace and boiler duty.
Questions
Do the Roney grate bars slide back and forth?
The cited Roney descriptions and patents identify transverse bars that rock or oscillate on inclined supports. A separate hopper pusher reciprocates to feed coal onto the grate.
Does pusher path equal coal feed?
No. Coal feed depends on hopper and pusher geometry, fill behavior, fuel properties and actual delivery per stroke.
Is 30° the required grate swing?
No. It is a selectable example value supported only as a period description of one construction, not a universal setting.
Can this calculator commission a boiler stoker?
No. Combustion, draught, emissions, guards, loads and manufacturer-specific limits are excluded.
Primary technical references
- US 409,305, Furnace-grate, William R. Roney — transverse rocking bars on inclined supports and external operating connections.
- US 473,963, Grate, William R. Roney — inclined transverse grate bars, reciprocating operating rod and fuel movement by rocking action.
- William Kent, Steam-Boiler Economy — period description of the Roney hopper pusher and bars rocking between stepped and inclined positions.
- Allen and Bursley, Heat Engines — Roney inclined-grate layout, eccentric-driven agitator, rocking grate and reciprocating pusher.
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