Stefang,
Congradulations on a very well thought out and very well built design. I sure hope you don't mind a few thoughts though. Before today's common commercial quality and accuracy DRO's were even invented companies such as Moore Tools used the exact same idea on there more than very very very accurate Jig Borers and Jig Grinders. They even cast openings in there castings that after precision machining it then allowed the dial indicators to be dropped down into 'wells' that helped to protect them from most bumps, dropped tools, etc. Usually they added a hinged clear heavy glass or plastic door above the indicator to provide further protection. Also there was a side cut out that allowed the operator to spin the indicators dial like you can on most of them to zero it wherever you'd like without opening that top door.
But the indicators also used a very thin rubber set of bellows I'd guess you'd call them. One end was fixed to the round part on the indicators housing and the other end was a tight fit on the indicators plunger shaft. That kept any metal dust, swarf, or even cutting fluids from being sooner or later dragged up inside the indicators insides and ruining or at least partially ruining the indicators precision.The last time I checked Mitutoyo at least still sold those rubber bellows for indicators. Starrett might too, but I can't say for sure. The last time I did notice them they were very cheap.
But that Moore Jig boring equipment also used a set of machined U shaped holders, one dead in line and just in front of the indicators tip, and another aligned so it was dead straight at the fixed end. At that end there was also a pin that got screwed into the casting so it had a flat precision end much like an elephants foot that get's screwed onto an indicator's tip.So with an indicator with only 1" of travel, you could add what they called 'setting rods'. Those were basically the exact same thing as what are supplied with today's micrometers from the 2" range and up. So you can then just drop those micrometer gauges into those U shaped holders, butt one end up against that fixed pin and then end up with a very precise system at 1" increments. With the 1" travel on the indicator, you end up with a system that can accurately measure to the length of your machines travels and the range of micrometer gauges you have. I hope I've made this a bit clear for you.
Mosey,
The D.I.'s work exactly the same as what any add on DRO does. They don't rely on the dial or feed screws lead/lag inaccuracies at any point. Plus there's no need to compensate for any backlash. When it's set up right it's a direct reading system. If a slide moves? Then the system will show it. It does take a bit of time with it to get fast, but it's an excellent setup and was very well proven by at least Moore tools as I mentioned. Very high end digital indicators and quality gauge blocks would give you at least the movement accuracies of the best DRO's made. But you wouldn't have all those nice to have added in canned programs the average DRO has. And it's a lot slower to use with much more chance of making a mistake than a standard DRO. Personally I think it's a far better system that should be much more accurate than any of those Chinese bar type scales that aren't any better than a cheap digital caliper. YMMV.
Pete