  We write the electromagnetic self-force of a Lorentz-contractible spherical
shell of radius $R$ in arbitrary rectilinear motion as a series expansion in
powers of $R$, and calculate the first two terms of this series. The method we
use, which is based on the description of the particle in terms of a
velocity-dependent volume charge density, avoids some important difficulties of
the previous approaches from the literature. We compare our results with the
results obtained by other authors. The whole calculation is done in the
laboratory frame of reference.
