For each selected eccentric offset e, ideal peak-to-peak valve travel is 2e. The calculator treats A, B and C as independent selected positions and does not assume they are numerically ordered.
Variable Eccentric Throw · Selected Position Reference
Compare ideal peak-to-peak valve travel at three independently selected eccentric offsets.
Equation Used
- Each selected offset is nonnegative.
- Peak-to-peak ideal travel is twice eccentric offset.
- The animation interpolates offsets for presentation and does not define a physical adjustment path.
- Finite-rod angularity, valve events, loads, wear and tolerances are excluded.
A, B and C are position names, not an enforced low-to-high ordering.
Adjustable eccentric-pin reference
The animation shows a pin moving radially in a finite slot while the eccentric rotates. A dashed projection maps the current radius to an ideal translating valve coordinate. This is a selected-position travel reference, not a design for an adjustment mechanism.
What the calculator determines
Select offsets at positions A, B and C. The calculator reports the exact ideal peak-to-peak travel at each position and the absolute travel difference between A and C.
Selected offset identities
Travel A = 2eA; Travel B = 2eB; Travel C = 2eC; A–C difference = 2|eC − eA|.
Selected-input arithmetic
For offsets 3, 7 and 12 mm, the selected travels are 6, 14 and 24 mm, and the A–C difference is 18 mm.
Geometry reference only
The model excludes the physical adjustment linkage, locking, finite-rod angularity, valve lap and events, loads, balance, wear, speed limits and manufacturing tolerances.
Questions
Must A, B and C be ordered?
No. They are independent selected positions.
Does the animation define a real adjustment path?
No. It interpolates selected offsets only to make the travel change visible.
References & Further Reading
- Wikipedia contributors. Steam engine valve gear. Wikipedia
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