This partial calculator combines selected in-line slider-crank geometry with an ideal static force resolution, entered projected area and exact mean reciprocating path speed. It does not rate a guide, slipper, bearing pressure capability, lubrication regime, wear or engine suitability.
Replacing manual motion in Steam Engine Guides (form 1)
If steam engine guides (form 1) is converted to actuator drive, the actuator is no longer just a replacement for a crank or cam. It becomes part of the timing, force, and limit-control system, so the travel must be checked through the full motion.
For structural members, the actuator load should be applied through brackets that do not introduce unintended bending. Check both static load and the extra load created when the mechanism starts, stops, or binds.
A crank or cam may tolerate continuous rotation through a difficult part of the cycle, while a linear actuator has defined end positions and internal limits. That difference matters when the mechanism needs repeatability or must not drive into a hard stop.
- Map actuator stroke to the actual output travel before choosing a model.
- Check for binding, changing leverage, and peak load near the ends of travel.
- Decide whether timed motion is acceptable or position feedback is required.
For a FIRGELLI design review, calculate the load case with the FIRGELLI actuator force calculator and plan the switching or controller arrangement with the linear actuator wiring diagram generator. If an actuator or cylinder is already installed, the linear actuator replacement finder helps keep the comparison tied to real dimensions.
Steam Engine Guides Form 1 - Selected Ideal Guide Ledger
Explore selected ideal slider-crank transverse reaction, average pressure and mean path speed.
Equation Used
- Axial slider load, rod ratio, projected area, stroke and speed are entered values.
- The connecting rod is treated as an ideal two-force member at maximum obliquity.
- Inertia, friction, gravity and changing axial load are excluded.
- Pressure is an arithmetic average over entered projected area.
- Mean path speed does not predict lubrication or wear.
The secondary figure is an abstract load, area and travel ledger, not a guide or slipper design.
Selected ideal guide ledger
For rod ratio n=L/r, maximum obliquity is arcsin(1/n). Under a selected axial slider load F and an ideal two-force connecting rod with inertia and friction excluded, the maximum transverse reaction magnitude is F tan(phi_max). Dividing by entered projected area gives an arithmetic average pressure. Mean path speed is total travel 2s per revolution times N/60.
What the calculator determines
Use it to inspect selected ideal geometry, force resolution, pressure arithmetic and mean travel rate. It cannot establish actual peak loading, contact distribution, oil-film behavior or guide durability.
Selected relationships
phi_max=arcsin(1/n); F_trans=F tan(phi_max); fraction=100 tan(phi_max); p_avg=F_trans/A; v_mean=2sN/60.
Selected-input example
At selected axial load 1 kN, rod ratio 4, projected area 5 cm2, stroke 150 mm and 255 rpm, maximum transverse reaction is about 0.258 kN, geometric force fraction is about 25.820%, average pressure is about 0.516 MPa and mean path speed is 1.275 m/s.
Not a guide or bearing rating
Load variation through the cycle, inertia, gravity, clearances, alignment, contact distribution, edge loading, material, surface finish, temperature, lubrication, oil supply, wear, impact, structure and safety are excluded.
Questions
Why is the transverse fraction not exactly 1/n?
The exact maximum geometric factor is tan(arcsin(1/n)); 1/n is only its small-angle approximation.
Why is mean speed 2sN/60?
A reciprocating member travels one stroke in each direction per revolution, for total path length 2s.
Does average pressure validate a slipper?
No. Actual contact pressure is generally nonuniform and requires a defined structure and load history.
Authoritative references
- Penn State ME 581 slider-crank equations — gives phi=asin(R sin(theta)/L).
- NIST Guide to the SI, Chapter 4 — identifies pressure in Pa=N/m2.
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