Tom,
Here is a bit of real time video of the clam loading some concrete blocks into a hopper barge at the north sea wall. I am going to try and find some material that loads well and shoot another video of loose material. The sand was a bit wet tonight and the clam is real tricky on loose material. I have tossed around the idea of making a new clamshell, making it just a bit narrower and maybe a bigger mouth and taller for more leverage in the close.
https://youtu.be/CfcPLkml37A
Jim