That's correct Tim, it has tin from a can of peas for a washboard effect and that rattles the botle tops, there is 3 screws on the edge of the pedal to rub against the tin. 2 elastic bands for resistance.
Wow -- nice work! I tried something similar, but had trouble with keeping the linkages from blowing up. Do you have anything except the rubber bands holding the pedal to the soundboard along the path of travel (maybe a detail of the "inside" / back would answer my question).
I've got to agree with Michael on this one. Nice attention to detail, a nicely thought out design! Ahhh, the possibilities...CHEERS! (Have you thought out any other variations...like a cajon, perhaps?)
Where the upright part joins the bottom part. It has 2 screws and a strip of foam rubber, the screw holes on the upright are larger than the screws, this alows the it to move back and forward. The rubber bands pull it towards the pedal and pulls the pedal back up. I thought of using springs, but the bands can be adjusted easy. I have a screw at the botom of the tin to stop the pedal damaging the pickup, that also makes a thud.
The bottle tops are in pairs. 24 bottle tops.
I have rubber from an old car mat on the bottom to stop it moving.
I measured my shoe to get the size.
If I make another one, I would make the pedal without the heel part, just 1 long pedal.
Hope this helps.
Here is another pic.