A couple of comments...
First, this design places an object directly in contact with the bearing edge of the drum. Although I have found no damage, I'm using a very inexpensive kit that I never intend to play acoustically. Always remember to be very careful with the bearing edge of your drums.
Second, this drop-in is an alternative to the tried-and-true crossbar method, not a replacement. In fact, I use one of Jman's 14" trigger kits on my snare and its my favorite drum!
Finally, the process of collaborating with JmanWord on the project has been a blast. The people on this site are an incredible resource and its been great fun sharing the build process. Thanks to everyone here and elsewhere who graciously share their DIY efforts. You guys rock!
I started playing around with the idea of a drop-in trigger in December. Version 1 was simply a 9" x 2" deep cake pan with a foam column in the center... 4 layers of 1/2" Poron about 1.5" in diameter stuck onto a piezo, which was stuck to the bottom of the pan with some foam tape. Fast and simple.
I found that the pan fit into a 10" tom, resting on the bearing edge. I attached some 1/4" thick foam weather stripping from the home store around the outside of the pan to keep it snug and provide some isolation. I don't have any pics of it, but it worked nicely. However, it got me thinking about a dual-zone option.
Using some sheets of 3mm thick hobby foam, I created a foam "donut" that could support a head trigger on top and surround a rim trigger which would be stuck directly to the bottom of the pan. It was all stuck together using KRT. I switched from a simple column of foam to a cone made from 3 pieces of 1/2" Poron.
The build process was pretty simply. It produced perfect head response using the PD105 preset on my TD-20. It also produced 360 degree rim triggering with a single piezo. Very cool.
It worked well enough that I ordered cake pans to fit the rest of my kit. Each pan is 1" smaller than the diameter of the drum. They all fit fine, although I found that the larger the pan, the tighter the fit. For the 14" drums, I switched to 1/8" thick weather stripping. I'm currently using 9", 11" and 13" drop-ins in my 10", 12" and 14" toms and they work great! I don't own a 16" floor tom, but I suspect a 15" pan would fit nicely inside the shell.
Because there are no restaurant supply stores near me, I had to order the pans online. My guess is that those of you in bigger cities can find the pans locally. Jman recently found a site that had every size he wanted and the price was really reasonable. I'm sure he'll link to it if anyone is interested.
I had been talking to JmanWord about the build process and he offered to help me test the design. So, I shipped him a 10" drop-in. After some initial testing, he redesigned the head trigger platform. I'll let Jman explain it from here but needless to say, Jman's Version 3 worked so well, I abandoned the foam "donut" and started rebuilding my triggers using his re-design.
OK Jman, you're up...