Leading the world in
energy absorption


Horizontal Impact

Horizontal Impact
Kinetic energy to be absorbed
Energy due to drive force to be absorbed Ed = FdS
Total energy to be absorbed ET = Ek + Ed
Maximum impact force due to inertia
Total maximum impact force Design mass for buffer FT = Fi + Fd
Design mass for buffer

Summary of notation

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
Ek Kinetic energy J
Ed Energy due to drive force Total energy J
ET Total energy J
v Velocity m/s
Fi Inertial force N
Fd Drive force N
FT Total force N
n Number of buffers in parallel -
ξ Efficiency -

Worked example

Eg. Consider a body of mass M = 20000kg (20 tonnes), moving at a velocity (v) of 1.5m/s with a drive force (Fd) of 20kN (20000N).

To find energy absorbed:
Ek = 1/2 Mv2 = ((20000kg)x(1.5m/s)2)/2 = 22500J = 22.5kJ

Let us therefore select a Type21-150
Ed = Fd.S = 20000N x 0.15m = 3000J = 3kJ

Total energy to be absorbed

To find the maximum impact force:
Fi max = Ek / (S. ξ) = 22500J / (0.15m)x(0.8) = 187500N = 187.5kN

Fd max = 20000N = 20kN

F T max = F i max + F d max = 187500N + 20000N = 207500N = 207.5kN

To find buffer design mass for metering pin selection:
Me = 2.ET / (n.v2) = 2 x 25500J / (1 x (1.5m/s)2 = 22667kg = 22.667 tonnes

Select a Type 21-150 buffer with a dynamic capacity of 30kJ and a maximum permissible load of 250kN, to meet these requirements.Therefore select metering pin code 155, for masses up to 25000kg (25 tonnes).