? ??????? ???????? ????? ??? ????? ?????? ???????, ??? ??????? ??? ???? ?? ????? ??????? ?? ???????? ??????? ?? ??????????:??? ???? ???????? ?????? ????????? ????????? ?????? ???????????? ? ??????????? ?? ???? ?????? ? ???????????? ????????.A comparatively recent enhancement could be the substitution of wheels or steel crawler-form tracks with flex