Kinetic energy to be absorbed | ![]() |
Energy due to drive force | ![]() |
Total energy to be absorbed | ET = Ek + Ed |
Maximum impact force | ![]() |
Design mass for buffer | ![]() |
To avoid confusing conventions within calculations always use SI units in formulae then convert to more appropriate units if required.
Notation | Quantity | SI Unit |
M | Mass of body | kg |
Me | Buffer design mass | kg |
S | Buffer stroke | m |
K | Radius of gyration | m |
Ek | Kinetic energy | J |
Ed | Energy due to drive force | J |
Et | Total energy | J |
ω | Angular velocity | rad/s |
I | Moment of inertiaa | kg.m2 |
T | Torque | Nm |
F | Impact force | N |
N | Number of buffers in parallel | – |
ξ | Efficiency | - |
Eg. Consider a swing bridge, having a moment of inertia (I) of 7500000 kgm2, buffer arm radius (r) 8m, angular velocity (ω) of 0.174 rad/sec and a driving torque (T) of 1500000 Nm. Using 2 buffers.
To find the energy to be absorbed:
Let us select a Type 4 with 114mm stroke:
Total energy to be absorbed:
Therefore ET = Ek + Ed = 113535 + 21375 = 134910 J = 134.91 kJ
To find the maximum impact force:
§To find the equivalent mass for metering pin selection:
Therefore select metering pin code 08 for masses up to 80000kg (80 tonnes).