Such a mechanism can easily give the illusion of working when it is 
applied to a vehicle that has even a little static friction.  The 
more intense and shorter duration "pulse" of force as the weight goes 
through the fast part of it's path can overcome static friction 
(aka "stiction") better than the longer duration slow part of the 
cycle.  I'd bet that oiling the wheels of Pawlicki's machine, or 
placing it on an air track, would greatly worsen it's performance, 
thus disolving the illusion.  IMHO, Pawlicki is either suffering from 
a serious case of self delusion, or is a deliberate quack.  I don't 
want to get into speculating about which of these is the case.
---Peace, William Kitchen
bill@iglobal.net