Oh we had that covered too. There's a limit switch with a 4" stick on it positioned right above the mandrel in the infeed area. So if you got tugged in your body would hit it. It had only ever been used once... a female operator was wrapping the paper around the mandrel on setup/startup, her hand got caught. Took the tips of her fingers off before the machine stopped... but that's what happens when you put your hands where they don't belong. Never happened before or since, in 105 years of the company's history...Let it trip when your body gets about halfway around the chuck
That's one reason why I use an indicator for a carriage stop instead of the DRO. I like the feedback of the needle sweeping up to zero.Shawn, you have discovered one of the major drawbacks of using a DRO. While they are convenient to use, they take your attention away from the work. Kind of like texting while driving.
I was also thinking about pneumatic. My 60 gal compressor is always charged. So, there's always air available. I also have a valve solenoid. It has liquid fittings on it, but it's also rated for air and gas. So, all I'd have to sort out is the actual brakeWonder if a solenoid would have enough throw. Fooled around with bikes alot and the caliper brakes don't require much movement to draw tight. Whether they would have enough clamping force to do anything is another matter. Asco Red Hat solenoids are pretty reliable.