Most modular rail systems for cameras use the standard 15mm tubing 6cm spacing measured from the heart of the tubes. If I wanted anything modular and compatible with off-the-shelf stuff like matte-boxes or follow focus rings, that should be the foundation, I thought.
This turned out to be mostly true. The standards were quite important, but the basis of a modular system is that one concept that ties everything together. Following the standards turned out to be frighteningly easy.
One of the most used systems for central heating in my part of Europe just happens to use 15mm tubing with 6cm of separation between the pipes. So all the attachment hardware have the very same dimensions as the pro-rigs use. This makes me suspect that the industry standard for rail systems perhaps has it's origins in this very same isle of the hardware store.
So the compatibility with other systems could not be that much of an issue. The problem with a DIY modular system is the part that is universally suitable to attach stuff to.
I chose the mounting system with the rubber inlays to dampen short sudden motions in he rig and for attaching various components I made several aluminium shaped blocks that would house the body of the clamp, the bolt and any mounting hole that was necessary.A wingnut will hold the module fairly tight on the rail. The blocks make it possible to mount stuff on the top and bottom side of the system.
I made various modules to plat around with like a shoulder piece, mounting brackets for audio gear, handles, grips, camera off-set plates, straight plates, a matte-box fixture and a failed version of a follow focus system.
Not only does the modularity help in figuring out what works best for me, it can be adapted with minor changes as the dependencies and the types of gear change .
I went through various iterations and adapted on the basis of each working experience I got with it. The foam shoulder pad was replaced by a shoulder piece from an old VHC shoulder camera and I redid the offset mount to include an Arca Swiss type mounting clamp. The unit has attachments for a Zoom hd recorder, a front facing condenser mic and wireless mic receiver.
The red bike light on the grip is attached to the IR module that starts and stops filming. For some odd reason, the wired shutter port will not let you start and stop shooting video.
In the future I'd like to add a big battery to the back for a big more balance and A mounting option to quickly put this think in the video tripod would be nice, but with Arca styled mounting systems everywhere, this isn't critical at this point.