Original plungercam with worn out body cap mounting ring
[Full writeup here.]
1) The mounting mechanism to attach it to the camera uses a plastic body cap, which was never designed to hold much weight. As a result, the teeth on the cap have been slowly disintegrating under the weight (see inset, above). Mounting the lens has now become pretty unreliable.
2) Usage - there is a lot of fun to by forcing the user to tweak the focus by hand, and means that there is zero repeatability - no two plungercam shots will ever be the same. However, this means that it is unusable for time-lapse video applications, where it is important to keep the lens in the same place between shots.
The next few images will go through the construction of the dead simple Plungercam 2, which addresses the above two issues.