This partial calculator evaluates selected in-line slider-crank obliquity, the corresponding ideal transverse-force factor, transverse reaction per 100 kN selected axial slider load and entered gap-to-diameter ratio. It does not rate a form-3 guide, crosshead clearance, fit, contact, lubrication or safety.
Steam Engine Guides Form 3 - Selected Obliquity Ledger
Explore selected in-line slider-crank obliquity, ideal transverse-force factor and entered gap ratio.
Equation Used
- Rod ratio, crank angle, crosshead diameter and axial gap are entered values.
- The connecting rod is treated as an ideal two-force member in an in-line slider-crank.
- The transverse reaction is normalized to an explicit 100 kN axial slider-load basis.
- Gap ratio is arithmetic only and is not compared with an allowable range.
- Fit, deformation, contact, lubrication, wear and safety are excluded.
The secondary figure is an abstract obliquity and ratio ledger, not a form-3 guide design.
Selected obliquity ledger
For rod ratio n=L/r and selected crank angle theta, connecting-rod obliquity is phi=arcsin(sin(theta)/n). Under an ideal two-force-rod assumption, transverse reaction magnitude divided by selected axial slider load is |tan(phi)|. Entered axial gap divided by entered crosshead diameter is reported only as a dimensionless geometric ratio.
What the calculator determines
Use it to inspect selected in-line slider-crank geometry and ideal force resolution. It cannot determine acceptable clearance, guide loading history, alignment, contact pressure, oil-film behavior or durability.
Selected relationships
phi=arcsin(sin(theta)/n); q=|tan(phi)|; transverse factor=100q%; F_trans at 100 kN=100q kN; gap ratio=100c/D%.
Selected-input example
At rod ratio 4.5, crank angle 32.4 degrees, entered crosshead diameter 200 mm and entered axial gap 0.10 mm, the calculator reports the exact selected obliquity and ideal force factor plus a 0.050% gap-to-diameter ratio.
Not a clearance or guide rating
Load magnitude and history, inertia, friction, gravity, deformation, thermal growth, manufacturing tolerances, alignment, contact distribution, material, surface finish, lubricant, wear and safety are excluded.
Questions
Is transverse-force percentage a guide rating?
No. It is an ideal geometric force factor at the selected angle.
Does the gap ratio say whether clearance is safe?
No. It is only entered gap divided by entered diameter.
Why is the reaction stated per 100 kN?
No actual axial load is entered, so 100 kN is an explicit normalization basis rather than a machine load prediction.
Authoritative reference
- Penn State ME 581 slider-crank equations — gives phi=asin(R sin(theta)/L).
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