some may find the following link helpful for clearing up the basics on gravity motor-type designs.
http://www.nathancoppedge.com/Perpetual_Motion_Gravity_Motor.html (http://www.nathancoppedge.com/Perpetual_Motion_Gravity_Motor.html)
It is not a skeptic site, but does try to look at the devices with the eye of an 'engineer'.
Included are my own diagrams, and some interesting links to various sites on the web.
There is also a sort of introductory description on gravity-motor-type devices.
As a warning, though, some of my examples rely on a kind of nano-rope that is not commonly thought to work for this application. I thought perhaps through some sort of tension-heat conversion motion would not be necessary. It might be a case of viable energy within a very specific set of conditions, such as a hot room, or extreme force. The workability depends on the non-maleability of the material, however, even in ideal cases. Ultimately, however, the links I provide may be more interesting, such as a lamp that is designed to recharge based on a counterweight, etc.
I have limited patience to reply to this topic, but I think the link will be well-worthwhile visiting for those interested in the topic.