Walschaerts Mechanism

This is a simulation of the Walschaerts valve gear used on most 19th and 20th century steam locomotives. The number of free parameters might be a little overwhelming. I need to build a cleaner version with fewer adjustments and with a better explanation of the outputs/graphs.

Adjust the Rs Radius Rod Set Angle (center left), and then click Start to get things moving. Positive for reverse and negative for forward.

M1 Main Rod Pin

M2 Main Rod

M3 Piston Axis Offset Y

L1 Valve Piston Center Y

L2 Reverse Link Center X

LE Eccentric Throw

AE Eccentric Offset Angle

L4 Lower Reverse Pin

L5 Eccentric Rod

T3 Radius Rod

T4 Combining Lever

TY Combining Lever DY

T5 Crosshead Link

T6 Crosshead Link Drop

T7 Crosshead Link X

RR Reverse Link Radius

RA Reverse Link Angle

AY Reverse Link Offset Y

PX Steam Tube Offset

PT Steam Tube Diameter

VW Valve Width

PW Piston Width

RS Radius Rod Set Angle 0 deg

N 0 RPM

Effective Inertia 1000 X 10-6 kg-m2

Load Factor 300 X 10-6 x ω

Steam Pressure 1000 Pa

PD Piston Diameter 20 mm

VR Valve Rod Length

VS Valve Face Separation

Drawing