Recent Blogs
Pawl-and-Elbow Lever Feed: Brown Movement 155
Explore Brown’s elbow-lever pawl feed. Calculate ideal angle per stroke, total wheel turns, average speed and elapsed time from whole-tooth indexing inputs.
Parallel Ruler (Form 6): Ideal Alternating Walk Sequence
Explore parallel-ruler motion. Calculate the components of one equal-link transfer and the total perpendicular advance for repeated transfers at a fixed angle.
Parallel Ruler (Form 5): Hiscox Slotted Crossed Bars
Explore Hiscox’s slotted parallel ruler with equal crossed bars. Calculate ruler separation, sliding-end span and center-to-end distance from bar length and angle.
Parallel Ruler (Form 4): Ideal Repeated-Line Transfer
Explore repeated transfers with an equal-link parallel ruler. Calculate perpendicular step size, full placement count, covered distance and final excess.
Parallel Ruler (Form 2): Hiscox Equal-Link Pivot Path
Explore Hiscox’s equal-link parallel ruler. Calculate longitudinal shift, perpendicular separation and circular pivot travel from link length and opening angle.
Parallel Ruler (Form 1): Exact Equal-Arm Translation
Explore an equal-arm parallel ruler. Calculate longitudinal shift, line separation, enclosed area and ideal parallelism from pivot spacing, arm length and angle.
Drawing Pantograph: Exact Homothetic Scale
Explore a rigid-link drawing pantograph. Calculate pencil-to-tracer scale, pencil-path length and ideal area scale from a reduction ratio.
Overconstrained Linkages: Generic Mobility Count Limits
Compare the generic spatial mobility count with an entered observation. Learn why special constraint dependencies allow overconstrained linkages to move.
Metal Expansion Joint: Free Pipe-Growth Worksheet
Explore axial movement in a metal bellows and calculate free pipe thermal growth. The result is a movement estimate, not an expansion-joint rating.
Four-Leg Chair Equalizer: Qualitative Posture Viewer
A qualitative posture viewer for a four-leg chair equalizer, showing how the connected front-leg joint permits opposite rocking directions on an uneven floor.
Kinematic Coupling: Contact-Count Calculator and Limits | FIRGELLI
Compare nominal contact and freedom counts for a coupling. Counts alone do not prove exact constraint, stability, load capacity or positioning repeatability.
Kempe’s Universality Theorem: Working Linkage Example
Explore Kempe’s universality theorem through a rigid-bar Peaucellier linkage. See a circle become a straight line and calculate the illustrated tracing motion.
Jansen’s Linkage: Walking Animation and Foot-Path Calculator
Explore a Jansen walking leg with fixed-length links. Compare foot-path width and vertical excursion, change crank radius, and view two legs at different phases.
Crank and Slotted Lever: Sweep-Time Calculator | FIRGELLI
Calculate slotted-lever sweep angles, unequal timing intervals and cycle time from crank radius, center distance and speed. The attached ram has separate turning points.
Ideal Machine: Force, Travel and Work Calculator | FIRGELLI
Explore lossless force-travel reciprocity and equal input/output work. Real mechanism geometry, losses and load capacity are not calculated.
Hoecken Linkage: Link-Length Scaling and Model Limits | FIRGELLI
Explore approximate straight-line linkage geometry and calculate scaled link lengths. Velocity variation, usable stroke, full-cycle closure and payload are not verified by this tool.
Hoberman Sphere: Folding Animation and Diameter Calculator
Explore a Hoberman-style sphere built from rigid bent scissor links. Watch its joints fold and calculate diameters for the illustrated equal-arm geometry.
Hinge Loads: Ideal Two-Hinge Door Moment Calculator | FIRGELLI
Calculate the ideal horizontal hinge-force couple for a uniform door from mass, width and hinge spacing. Fastener forces, hardware capacity and impact loads are not...
Hart's Inversors: Crossed-Link Motion and Geometry Calculator
Explore a Hart inversor with a crossed four-link cell, circular input and straight tracing point. Calculate the midpoint inversion constant from full bar lengths.
Hart's Exact Straight-Line Inversor: Stroke and Animation
Size an ideal Hart inversor stroke from full bar lengths. See the crank angle, available travel and connected crossed-link motion without a sliding guide.
Grashof Linkage: Four-Bar Assembly and Rotation Calculator | FIRGELLI
Check four link lengths for assembly and Grashof rotation. Compare sorted sums and margin, with a longest-ground four-bar animation and worked example.
Origami Vertex Angle Calculator: Kawasaki Condition | FIRGELLI
Check four sector angles at one origami vertex. See alternating angle sums, total angle and deviation from Kawasaki’s local flat-foldability condition.
Closed Four-Link Chain: Planar Mobility Calculator | FIRGELLI
Explore planar link and joint counts, the Gruebler–Kutzbach equation and a four-bar illustration. Understand connectivity and constraint assumptions.
Four-Bar Linkage: Grashof Margin and Geometry Explorer | FIRGELLI
Explore four-bar lengths, Grashof margin and sampled angles. Learn the limits of branch selection, angle spans and the illustrative index.
Evans Grasshopper Linkage: Coupler-Path Calculator | FIRGELLI
Explore an Evans four-bar linkage with an approximately straight coupler path. Compare link scale, crank sweep, traced stroke and lateral wander.